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Retrospective Theses and Dissertations
Summer 1979
Isomerization and Dehydrocyclization of 1,3-Pentadiene Isomerization and Dehydrocyclization of 1,3-Pentadiene
Thomas E. Marcinkowski University of Central Florida
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STARS Citation STARS Citation Marcinkowski, Thomas E., "Isomerization and Dehydrocyclization of 1,3-Pentadiene" (1979). Retrospective Theses and Dissertations. 433. https://stars.library.ucf.edu/rtd/433
IS0~1ERIZATION AND DEHYDROCYCLIZATION OF 1,3-PENTADIENE
BY
TH0~·1AS E. MARCINKOWSKI B.S., St. Leo College, 1977
RESEARCH REPORT
Submitted in partial fulfillment of the requirements for the degree of Master of Science: Industrial Chemistry
1n the Graduate Studies Program of the College of Natural Sciences at the University of Central Florida; Orlando, Florida
Sununer Quarter 1979
ABSTRACT
Pipcrylene concentrate is ~ complex mixture of 5-carbon
unsatur.1tcd hydrocarbons obtained as a by-product when naphtha
or gas oils are cracked. The major component in this mixture is
1,3-pentadiene.
During the course of this study, a number of trials, utilizing
liquid phase reaction conditions, were made to investigate the
geometric isomeri:ation of 1,3-pentadiene and its separation from
the piperylene concentrate.
Isoiaeri:ation \\·as accomplished employing catalytic amounts of
iodine at temperatures ranging from 0°C to reflux. Using this
method. tl1e maximum amount of trans-1,3-pentadiene obtained was
70~ as compared to 51% in the piperylene concentrate. Recovery of
the proJuct \\·as 909o, \vi th the remainder being diiodo compounds and
polymer. Isomerizations employing catalytic amounts of potassium
tcrt-butoxide were also investigated. Using this anionic isomeriza
tion, the theoretical amount of trans-1, 3-pentadiene (84~6 @ 20°C)
\..;as obt~ined in the product. The greatest dra\-.rback with this
technique \vas the low recovery (50°a), Jue to the extensive polymer
format .ion.
Successful separation of 1,3-pentadiene from the mixture was
accomplishct.l through cuprous chloride complexing. Utili:ing this
technique, SL~~o of the 1, 3-pentadiene was recovered from the mixture,
with the separated product being 99.9% pure 1,3-pentadiene.
Separ~tion of trans-1,3-pcntadienc from the mixture was accomplished
through a Diels-:\lJer reaction \oJith maleic anhydride. Since this
dienophilc will react readily with trans-1,3-pentadiene but not
ci.s-1,,:)-pent:ldiene:, this method offered an easy and efficient means
of removing the former isomer from the mixture. In attempting to
reverse this Diels-Alder, via pyrolysis, many products were obtained;
incluJing those present in the original mixture.
The ·~~s phase dehydrocyclizati_on of l, 3-pentadiene \\'as
investigated in a 316 stainless steel tubular flow reactor utilizing
various heterogeneous and homogeneous catalysts. The selectivity
to cyclopentadiene was greatest (60%) in the presence of a hydrogen
sulfide promoter. For all other catalysts, the selectivity remained
relatively constant L30~). This constant selectivity over a wide
range of par~meters indicates that a significant amount of competing
side reactions are prevailing within the preheater section of the
apparatus.
ACKNOIVLEDGE~·IENTS
TI1e author wishes to express his appreciation to Dr. Guy
~·Iattson for his personal quidance and profound patience which he
exibited during the course of this project; Dr. Chris A. Clausen
and Dr. John T. Gupton for their suggestions and encouragement
leading to the completion of this work; and Dow Chemical USA,
Louisiana Division, for making this research possible through
indirect support.
The author \vould also like to extend his thanks to his father
for his support throughout the authors lmdergraduate and graciuate
years.
iii
CONTENTS
Introduction 1
Uses and Outlook for Various Components in the Piperylene Concentrate 4
1,3-Pentadiene 4
Cyclopentene 5
Cyclopentadiene and Dicyclopentadiene 6
Chemical Separation of 1,3-Pentadiene From Piperylene Concentrate Using Sulfur Dioxide 9
Separation of 1,3-Pentadiene From Pipery1ene Concen-trate By Cuprous Ammonium Chloride Cornplexing 11
Separation of Trans-1,3-Pentadiene From Piperylene Concentrate Via Dicls-Alder Reaction With ~·laleic Anhydride 13
Thermodynamics 16
Isomerization of 1,3-Pentadiene 17
Dehydrocycli:ation of 1,3-Pentadiene 19
Experimental 23
Analysis 23
Analytical Standards 25
Liquid Phase Reactions of 1,3-Pentadiene 26
Halogen Catalyzed Isornerizations 26
Base Cataly::ed Isomerization 26
Separation of 1,3-Pentadiene From The Piperylene i'·lixturc By Cuprous Ammonium Chloride Treatment 27
Synthesis of 3-~Iethyl-1,2,3,6-Tetrahydrophthalic Anhydride Via Die ls-Alder Reaction With ~laleic Anhydride 29
Pyrolysis of 3-Nethyl-1,2,3,6-Tetrahydrophthalic Anhydride 30
Pyrolysis Procedure 32
Vapor Phase Isomerization and Dehydrocyclization of 1,3-Pentadiene 32
lV
CONTENTS (cont.)
Paae b
Catalyst Preparation 36
Operating Procedure 38
Results and Discussion 40
Separation of 1,3-Pentadiene From Piperylene Concen-trate Using Cuprous Ammonium Chloride 40
Iodine Isomerization of 1,3-Pentadiene 40
Potassium tert-Butoxide Isomerization of 1,3-Pentadiene 45
The Synthesis and Pyrolysis of 3-Methyl-1J2,3,6-Tetra-hydropht!1alic Anhydride Sl
Thermal and Catalytic Dehydrocyclization of 1,3-Penta-diene 53
Conclusions 92
References 94
v
Table
l
II
III
IV
VI
VII
VIII
IX
X
XI
XII
XIII
XIV
LIST Or TABLES
Title
Typical Composition of Piperylene Concentrate
Some Properties of Tne Common Sulfones
Rate Constants For Various Diels-Alder Reactlons of Several Dienes With Maleic A.nhvdride
.;
nesu1ts of A Dehydrocyclization Experiment Performed Bv Hutchincrs75
b
Composition By Weight of Chemical Sample Co~pany Piperylene
Data For The Separation of 1,3-Pentadiene From Piperylene Concentrate Through Cuprous Chloride Complexing
Data For The Iodine Catalyzed Isomerization of 1,3-Pentadiene
Data For The Potassium tert-Butoxide Isomerization of 1~3-Pentadiene
Products Obtained From The Pyrolysis of 3-~lethyl-1, 2, 3, 6-Tetrahydrophthalic Anhydride
Constant Dehydrocyclization Reaction Parameters
Composition By Weight of The ';Pure'; Component Feeds
Dehydrocycli::J.tion Products Obtained From TI1e ''Pure" Component Feeds
Retention Time And Identity of Products Found In Effluent Strean
Results of 1be Thermally Initiated Dehydrocycli:ation of Piperylene In A Packed ru1d Unpacked Reactor
Vl
Pacre __ b_
2
10
15
21
27
41
44
47
52
55
57
58
60
61
\\'
X\' I
XVII
X\'TII
LIST OF TABLCS (cont.)
Title
Cracking Data Obtained In A Clean And Coked Reactor
Results of The Hydrogen Sulfide Pro~oted Dehydrocyclization of Piperylene
Results of The Dehydrocyclization of Piperylene Over A Sulfided Stainless Steel Bed In The Presence and Abscence of Sulfur Dioxide
Results of The Dehydrocyclization of Piperylene Over Silica Gel And Alumina Catalyst Beds
vii
Pacre __ .:>_
66
69
80
85
f igtlTC
l
3
4
5
-I
8
9
10
11
1.2
13
LIST OF FIGURES
Title
The ~·1orc Comr:1on Chiaro Cor1pounds of Cyclopentadiene
Pyrolysis Apparatus
Vapor Phase Isomerization-Dehydrocyclization Apparatus
Proposed ~1echanism For The Iodine Catalyzed fsomeri:ation of 1,3-Pentadiene
Possible Side Reactions During Iodine Catalyzed Isomerization of 1,3-Pentadiene
Proposed ~·Iechnnism For The Potassium tertButoxide Catalyzed Isomerization of 1,3-Pentadiene
Effect of Temperature On The Conversion of Piperylene And Selectivity To Cyclopentadiene In A Packed And Unpacked Reactor
Effect of Temperatur-e On The Conversion of Piperylcnc And Selectivity To Cyclopentadiene In The Presence of Nitrogen And Steam Dilutents
Effect of Contact Time On TI1e Conversion of Piperylene And Selectivity To Cyclopentaciiene Over A Stainless Steel Bed
Effect of Hydrogen Sulfide And ~itrogen On The Conversion of Piperylene And Selectivity To Cyclopentadiene At Various Temperatures
Effect of Hydrogen Sulfide And Steam On The Conversion of Piperylene And Selectivity To Cyclopentadiene At Various Temperatures
~lcchanism For The Hydrogen Sulfide Promoted Dehydrocycli:ation of 1,3-Pentadiene
~lcchanism For The Thermally Initiated Dehydrocycli:ation of 1,3-Pentadiene
viii
Paae __ o_
8
31
33
43
46
so
63
65
67
71
7'2
74
75
15
16
17
18
19
20
LIST OF FIGURES (co~t.)
Title
Effect of Hydrogen Sulfide Concentration On TI1e Conversion of Piperylene ~nd Selectivity To Cyclopentadiene
Effect of Contact Tioe On The Conversion of Piperylene And Selectivity To Cyclopentadiene In The Presence of Hydrogen Sulfide
Effect of A Stainless Steel A~d-A Sulfided St~inless Steel Bed On The Conversion of Piperylene And Selectivity To Cyclopentadiene
76
78
In Relation To Contact Time 82
Effect of Te~perature On The Conversion of Piperylene And The Selectivity To Cyclopentadiene In The Presence of Sulfur Dioxide
Effect of Contact Time On The Conversion of Piperylene And The Selectivity To CyclopentaJiene Over Silica Gel
Effect of CoTJtact Time On Tne Conversion of Piperylene And TI1c Selectivity To Cyclopentadiene Over Aluoina
Proposed Carbonium Ion Mechanism For The Cyclization of 1,3-Pentadiene Over Alumina
ix
83
87
88
so
INTRODUCTIO)J
Tremendous quantities of ethylene and propylene are produced
eacn year .for use as starting materials for a Hide variety of petro-
che:nicals. These were, and still are, produced by the thermal
cracking of condensate from natural and refinery gases. But due to
the decreasing production of natural gas and the increasing raw
material restrictions ln the United States, there is a trend towards
1 the usc of heavier naphthas and gas oils as cracking stock .
Due to the large amounts of ethane present in the lighter
gases, relatively small amounts of by-products are formed on the
pyrolysis. But when the heavier naphthas and gas oils are cracked,
large amounts of by-products are produced. Of particular interest
to this project is a by-product stream consisting of a mixture of
5-carbon unsaturated hydrocarbons. The major component in this
distillation fraction is 1,3-pentadiene, known commonly as pipeT)'-
lene; hence, the name "piperylene concentrate" has been given to
this mixture. A typical composition of piperylene concentrate is
shown in Table I.
The amount of piperylene concentrate produced 1s dependent
? on the feed employed-. In general, the heavier the naphtha or gas
oils, the greater the amount of piperylene formed. Also, the more
severe the cracking conditions are, the greater the diene content.
The total production of the 5-carbon stream from cracking of
naphtha and gas oils has been estimated to be approximately five
TABLE I
Trpi.cal Composition By \\'eight Of Piperylene Concentrate
Component Percent
2-mcthyl-2-butene 2.7
2-rnethyl-1-butene 5.2
isoprene 14.4
cyclopentcnc 24.9
trans-1,3-pentadiene 22.5
cis-1,3-pcntadicne 16.1
Remainder* 14.2
* consists mainly of c4 to c6 unsaturated hydrocarbons, benzene,
dic;:c1opcntadiene and other heavy materials in varying amounts.
2
3
I million tons per year-. With this amount being produced, it is
incvit3blc that the piperylene concentrate fraction will become an
imnort~nt tJ.ctor in the economics of the petrochemical industry.
Despite the large volume of piperylene concentrate available,
3 relatively few commercial uses have been developed . At present,
the pipcrylene concentrate is used to produce resins which find
end usc as tackifiers for various adhesives.
A co~~crcial epoxy hardener is obtained through a Diels-
Alder reaction with maleic anhydride. The acids and esters of this
adduct can be used as plastisizers and softening agents for resins,
plastics, gums, and lacquer films 4 . ~·Ialeic anhydride can also be
copolymeri:ed \vi th piperylene to encorporate the very reactive
5 anhyJride groups into the polymer . The excess amounts are being
used ~s fuel for combustion furnaces and as a gasoline blend feed-
stock. These uses are not economically desirable, since the fuel
value of the piperylene c~ 6.~¢/#) is much less than its resin
value c~ 9.1¢/~).
The main drawback of the piperylcne concentrate is the large
amount of impurities it contains. These impurities have a depre-
ciating affect on the quality of the hydrocarbon resin products.
It is therefore desirable that these be removed in order to nroduce
superior products.
It has then been the main objective of this project to
improve the quality of the piperylene concentrate. Emphasis was
placed on removal of the alkenes and the isomerization of cis-1,3-
4
pentaJicnc to trans-1~3-pentadicne. Both of these changes will
subst:antially upgrade the hydrocarbon resins produced from the
conccntr:J.te. Another quality improvement sought was the cycliza-
tion anJ Jcllydrocycli:ation of tl1e 1~3-pentadiene to produce
cyclopentene and cyclopentadiene respectively. Both of which
have a hig!1er value than the piperylene concentrate.
Presently, few industrialized schemes are being utilized
to produce ?urer 1,3-pentadicne from the piperylene concentrate.
lioh·cvcr, it is widely known that the Japanese are using the GPB
and GPI process to produce high quality 1,3-butadiene and isoprene6 .
~ippon Zcon Company is employing this technology to produce highly
pure cyclopentadiene and 1,3-pentadiene in high yields 2
Uses and Outlook for Various Components 1n the Piperylene Concentrate
The c!1cmistry and the applications of the major components in
? 6-26 the piperylene concentrate have been reviewed-' . These reports
indicJ.te the importance of separating the components of the p1pery-
lene concentrate.
1,3-Pcntadiene
Polymers of 1, 3-pentadiene \vere first prepared by J. TI1iele ?'J
in 1901 using hydrogen chloride and heat._.:.. Currently, polymers
and co-polymers with 1, 3-butadiene are prepared \vi th transition
metal catalysts to produce elastomers. Two resins now produced ....
from pure 1,3-pentadiene are Quintone and QuintolL.
Quintone is a resin used as a tackifier for pressure sensitive
adhesives, hot melt adhesives, and in rubber compounding. This
material has been Jescribcd as "synthetic polyterpenerr since it
has .:haractcristics sirnil::1r to polyterpenes with regard to color,
odor, stJ.bility, creep strength!' etc. Quintal, which is a liquid
po lyr::8 r o i 1, 3-pcnt ::1diene is \'ery similar to linseed oil. Due to
its quick drying properties, it can be used in paints, coatings,
sealants, and caulking COQpounds.
Cyclopcntene
Cyclopentenc has promising \:ormnercial potential for use in
the rubber industry. This is due to the similar properties that
the vulcani:ed polymer of cyclopentene has to cis-polybutadiene ,
and cis-polyisoprene- 1•
These unsaturated polymers of cyclopentene are known as
pol)~cntenamers and are produced using transition metal catalysts
, 1 . . 1 . 21' 27 tnroug1 a r1ng open1ng mec1an1sm . Originally, it was thought
to proceed through the typical sigma bond rupture, but this was
?Q proven false by Calderon- . He and his co\vorkers showed that the
polymers h·ere formed by a double bond interchange, or olefin
metathesis, typified by the follo\·Jing28
,CII .~ ..
( CI L,) -- ~ W - n~CH
--,;..--~ ---
CH-----HC---.__ ( CH
2) :::::-- ~ \\T I / ( CH2) n --.............' '/' n CH-----HC
5
6
The most LOQmon catalysts presently used are tungsten and ~olybdenum
comt)lexes such as tungsten hexachloride with a trialky1 aluminum.
T!1es e c~t alysts arc stereospeci fie. Tnngsten yields the trans -1,5-
polypen~cnamer and molybdenum, the cis-1,5-polypen~enamer.
Cyclopentadiene and Dicyclopentadiene
Dicyclopentadiene is the dimer obtained from cyclopentadiene
on standing or heating. It deconposes to cyclopentadiene when
heated to 1G0°C. In terms of general chemical reactions, cyclo-
pentadicne IS a very versatile compotul.d. It owes its chemical
reactivitv to three structural characteristics: the double bonds,
their conjugation, and the activated methylene group. Although
very versatile, cyclopentadiene still has few industrialized
applications.
The chemistry of cyclopentadiene has been reviewed exhaus-
. 7-16 17-21 t1 vely . Its uses have been surveyed , and lvill be reviewed
J.n the follo\ving paragraphs.
In general, it is used as a raw material for all types of
res ins~ ~1eat resistant polymers, insecti cidcs, flame- retardants,
anJ as a precursor to cyclopentcne which is used as an elastomer
monomer.
Streams which contain 75% dicyclopentadiene can be thermally
polymerized to produce a low grade resin used as a tackifier for
. . 23-25 rubber and as a coat1ng varnlsh The resin made from higher
purity dicyclopcntadicnc resembles natural rosin in terms of
physical properties. Since some of these resins contain double
7
bonds, their properties can be improved through l7lodification.
These J1odi.fiablc res1ns find use as rubber tackifiers, pressure
sensitive tapes, :1ot-melt adhesives, coatings, .inks, and paints 2' 25
~·n1cn Jrying oils, such as soybean, linseed, marine, and
vegetable oils, are reacted with dicyclopentadiene they dry more
rapidly and have increased \vater and alkali resistance 22.
The halogen derivatives of cyclopentadiene are used as fire-
. - . . .. 2, 7,8,11,18-20 s f 1 rc::.1ruJ.nts and lnscctlCll1es . ome o tne more conunon
chloro compounds of cyclopentadiene are illustrated in Figure 1.
All of the compounds shown are potent insecticides or pesticides.
Dcchlor311 (~lire:x) and Het acid are also used to impart fire-retard-
2 ancy properties into polyester resins and polyurethane foams .
Dicyclopcntadiene finds use as a vulcanizing agent for
? ethylene anJ propylene copolymers-. A superior vulcanizing agent,
\..rhi ch acts more quickly than dicyclopentadiene is ethylidene
no rbornene. It is synthesized from cyclopentadiene and 1, 3-buta-
dicne.
+
Propenyl norbornene, produced from cyclopentadiene and 1,3-penta-
dienc, also has good vulcanizing properties. It should also be
chcapeT to produce than ethylidene norbornene since its synthesis
0 +
0 1C
12 110
1 --~
' C
l C
l ,.,..
H
et A
cid
Cl
~ .,
Cl 0
/ c
cr c
1 ~1
le»
I c
Cl
Cl
Jl
J
c( / J
c
\:2 Cl
· C
u/E
tOH
1 Ald
rin C
l /
/ K
epon
e H
202
Cl
Cl
Cl
c~\1 ?;
tl
:~cr
,o
Cl -{:
a' ~ ·Cl
Pen
tac®
D
ield
rin
Fig
ure
1.
The
Mor
e Co
mm
on C
hlor
o C
ompo
unds
o
f C
yclo
pent
adie
ne.
Cl
0 0
I C
l
Chl
orda
ne \ S
+O
End
osul
fan
Hep
tach
lor
00
involves one less step .
. \s mentioned earlier, cyclopentadiene is a precursor for
eye lopentenc ~·;hich is used to produce the 1,5-polypentenaners.
Cyclopentadiene is also used to produce norbornene resins through
polymerization \vj th a vinyl rnonorner2
These find use in various
molding applications. Norbornene rubbers are finding application
as sound-shielding and soundproofing materials.
C!1emical Separation of 1, 3-Pentadiene From Pipei}',.lene Concentrate
Using Sulfur Dioxide
:.tany conjugated dienes form crystalline monomeric sulfones
\~hen heated with sulfur dioxide under pressure27
. One exception
to this general statement is cyclopentadiene, which reacts with
sulfur dioxide to form t~e polysulfone resin 7 shown below.
0 502 0 0
11-0-11 s s II II 0 0 n
The reaction of dienes with sulfur dioxide is reversible. At high
temperatures, usually above 100°C, the sulfone dissociates.
Since most dienes form crystalline sulfones, which can be
9
decomposed easily to yield the original dienes, they can be conven-
,., . 27 f iently separated from alkene hydrocarbons. 1ne propert1es o
some conunon sulfones are illustrated in Table I I. These sulfones,
especially that of 1,3-butadiene, have some commercial usefulness.
The hydrogenated sulfone of butadiene is sold under the generic
name "Sulfolane" 27 . It has a melting point of 28°C, boiling point
TABLE II
?7 Some Properties of the Common Sulfones-
Oicnc
1, 3-butadicne
1,3-pcntadiene
isoprene:
cyclopcntaJiene
Melting Point oc
65
oil
63
Sulfone
Decomposition Temperature °C
125
100
125
125
10
of 285°C, is chemically inert, non-corrosive, and 1s very miscible
with \vater.
Due to its high selectivity toward aromatic compounds, it
1s used in extractive distillation and solvent extraction processes.
Two examples in which sulfolane has been successfully used are:
1 d t • 29 1 . . . t 1c U ex tcc.1n1que , w 1ere 1t 1s an al ternat1 ve sol vent to aqueous
diethylcncglycol in the solvent extraction of aromatics; and in
h .. 1". 27 1 . b b. d . h h 1 t e Su r1nol process , \\flere 1t can e com 1ne \~lt monoet ano
amine t:o remove hydrogen sulfide, mercaptans, carbonyl sulfide,
and carbon dioxide from hydrogen, natural or synthesis gas.
The sulfone formation technology has been applied by
C . 30-32 1 3 d. f . t d ra1g , to separate , -penta 1ene rom var1ous unsatura e
hydrocarbons and for the isomerization of cis-1,3-pentadiene to
trans-1,3-pcntadiene.
Separation of 1,3-Pentadiene From Piperylene Concentrate By
Cunrous .\nunonium Chloride Complexing
fhc formation of unscn:urated hydrocarbon complexes with
.salts of heavy metals of group IB and IIB of the periodic
sys tern have been knoVv11 for some time. 33 In 1898, Chavastelon
reported the reaction between acetylene and cuprous chloride.
34-41 ~.]ore recent work , involves using the complexing ability of
the ;;1ctal salts, usually cuprous chloride, to separate various
alkcncs, cyclic alkenes, and dienes from one another.
The stoichiometry of these stable complexes formed involves
33 38 one group IB metal atom for each pi bond of the hydrocarbon '
The stability of the complex is dependent on the type of hydro-
carbon involved. In general, the order of increasingly stable
complex formation is: alkenes, acetylenes, cycloalkenes, dienes,
. 33 37 and cyc1olllenes ' . The type of anion present in the salt is
11
also important in complex formation, for CuCl and CuBr will complex
\vith unsaturated hydrocarbons, whereas CuO, CuCN, Cui, and Cu2s .).)
\vi 11 not .
One advantage to the pi complexes between the metal salt
~md the double bond is that it does not convert to a sigma complex.
The normal chemical reactivity of the cornplexed double bond is
effectively inhibited33 . Evidence of this is the lack of isomer-
ization and polyrneri:ation of the tmsaturated hydrocarbon during
complex formation and decomposition of the complex to recover the
pur .i fied hydrocarbon.
Complex formation has been achieved in the gas phase, where
the ~ctal salt is Jispersed on a carrier38
or in a 50/50 mixture
\oJi th .::lass beads for use in a fluid bed lll1i t 33 More generally
12
ho\·;evcl', ::he rc3.ction is ~arried out in the liquid phase, Hith the
34-38 metal salt in an aqueous solution or slurry The aqueous
solutions of the copper salts are prepared by·using various
1 . . 34' 35' 39 1 . h 1 . d so ut1z1ng agents , suc1 as anunon1um c or1 e. As shown
3.+ 35 by Lur' c ' , the amount of soluti:ing agent in the solution has
a marked affect on the rate and extent of complex formation.
At the higher concentrations, t\venty five weight percent or more,
the complcxing is sJo\.; and incomplete. This seems likely, since
these agents and other alkali salts or bases, can be used to
. 3-+ 35 decomuose the complexes to regenerate the purified hyarocarbon ' .
Decomposition of the complex can also be accomplished by heating
. 33-35 or rcJuc1ng the pressure .
. \ny alkene present in the hydrocarbon mixture will also have
a marked aifect on the rate of complex formation 33
. In the gas
phase, the al kenes wi 11 dis sol \·e large arnotmts of cuprous chloride
by '.'t·eakly complcxing wi t.h it. This enables the dienes to react
more quickly throu~1 a liquid-solid reaction rather than a gas-
solid reaction.
Separation of 1,3-pentadiene from other hydrocarbons, includ-
1ng cyclopcntene, has been accomplished through the use of cuprous
chloride complexes 33 ' 36 , 40 '41 It was first found by Ward and
"f k. 36 Fa ·1n , that the complex involved two moles of cuprous chloride
13
per r:-1olc of 1, 3-pentadicnc and had the following formula:
The separation of l, 3-pentadicne from aliphatic alkenes
pro\·ccl to be a simple chore, since its complex \vas an insoluble
solid which could be recovered from the solution and soluble
complexes easily. The cyclopentene present in the mixture would
also precipitate, but its complex formation was prevented by the
3.Jdition oi JliUTionium chloride and increasing the temperature to
35°C. The cyclopentene cuprous chloride complex is unstable at
these conditions. This allows only the more stable 1,3-pentadiene
cuprous chloride complex to form.
Using this method, 54 9o of the 1, 3-pentadiene was recovered
from the pipcrylene concentrate in 99. 9go purity. The contaminant
being a trace of cyclopentene.
Separation of Trans-1,3-Pentadiene From Piperylene Concentrate By
Dicls-.\ldcr Reaction With r.taleic Anhydride
The Diels-AlJer adduct of trans-1,3-pentadiene and maleic
anhydriJe is used cor.unercially as 311 epoxy hardener3
. Its acid
and esters arc used as plastisi:ers and softening agents for
d f. 4
resins, plastics, gums, an lacquer 1lms .
The Dicls-Alder reaction of trans-1,3-pentadiene and maleic
anhydride to form 3-methyl-1,2,3,6-tetrahydrophthalic anhydride
has been used as an cffecti ve means to separate trans-1, 3-penta-
d ' , d b 42-..J. 7 dicne from cis-1,3-pentadicne ::m otner ny rocar ons . This
can be accomplished since trans-1,3-pentadiene reacts readily with
14
maleic ~nh,:Jride, while the cis-isomer ~vill not react at an
4 3 ' -+ 4 ' -+ 6 ' ·+ 7 apprcci3.blc rate . Cis-1, 3-pentadiene t-1ill react slo~vly
\•:i. t~1 ;:1.1lcic anhydride, but only ~..1ndcr ',rigorous conditions 43
In order for a 1,3-diene to react with maleic anhydride,
. . . l . . d f . 44' 4 7 1t must ex1st 1n tae ClSOl con ormat1on . 1nis conformation
is necessary in order for the 1,3-diene to exist as a coplanar
system \vi th one of its sides completely exposed to the dienophile.
By vbs\Jrvin~ a scale model of cis-1,3-pentadiene, it can be seen
that the cisoid conformation is sterically hindered by the
protrudin~ methyl group, ho\..:e\·er, a scale model of its adduct
shows no stcric hindrance. Since the planar cisoid conformation
is required to expedite the transition state, the slow rate of
this reaction must be due to the hindrance of the planar cisoid
conformation and not a sterically hindered product.
The reaction rates of various 1,3-dienes with maleic anhydride
47 have been studied . It was found that trans-1, 3-pentadiene
reactcJ much faster than either 1,3-butadiene or isoprene, but much
slower than cyclopentadiene. This is depicted in the rate constants
listed in Table III-l 7. The increase in reaction rate as proceeding
from 1,.3-butadicne to trans-1,3-pentadiene is due to the methyl
groups ability to release electrons into the system. The rapid
rate at which cyclopentadiene reacts is attributed to the low
activation energy of 8.5 kcal as compared to 11.7 kcal for butadiene.
This lo\v activation energy \-.ras expected, since no change in confor-
mation 1s necessary to form the required planar transition state.
TABLE III
Rate Constants for Various Diels-Alder Reactions of Several Dienes with Maleic Anhydride
Reaction Rate Constant Diene Temperature oc 1/mol/h
butadiene 25 0.19
isoprene 25 0.57
trans-1,3-pentadiene 25 0.92
cyclopentadiene 25 -200.00
cyclopentadiene -40 4.00
cyclopentadiene -60 0.72
15
47
16
Thcrr.:ouvnJ.mics
TI1crmodynarnic values for various hydrocarbons, including the
d . t d b K ·1 . k l 48 . D 1 · 49 pent;1 lcncs, \vere repor e y 1 patr1c ~, et a . and. ous ln .
fhc values produced through these studies proved to be inaccurate.
The data implied that the stability of cis-1,3-pentadiene was
greater than trans-1,3-pentadiene at all temperatures above 298°K,
\vhcreas the reverse has been shown to be true. Therefore, the
thermod~·naf.lic llatet of the pentadienes and the other components of
50 the piperylenc concentrate reported by Messerly, et al. and
Stull, et a1. 51 have been used.
The equilibrium constants for the geometrical isomerization
of 1,3-pentaJiene were calculated using the linear equation given
5? by Egger and Beason -. They studied the geometric isomerization
of 1,3-pentadicne with nitric oxide over the temperature range of
400 to 670°1\. Their data was fitted by least squares using a
rcS_;ular rc~rl!ssion program to yield the following linear equation,
2.303Rlo0: K = --- t/c
with R in cal/molc °K.
-(.14±.05) + (1037±28)
T
Thermodynamic data for cyclopcntadiene at low temperatures
53 was given by Kistiakowsky et al. . The free energy of cyclopenta-
dicne at the higher temperatures \'Jas estimated by neglecting the
effects of the conjugation and assuming the following to be true.
17
The equilibrium constant for the conversion of the piperylene into
cyclopentadicne could then be calculated by:
6G = -RT ln K T) ..L
with R in cal/mole °K.
Isomerization of 1,3-Pentadiene
The isomerization of simple alkenes with small amounts of a
. . 53-57 h~lo0;en has been knohn for qu1te some t1me Benson, et al.ss,sg
sho\.;ed that small catalytic amounts of iodine vapor at 200-300°C
\-:as capable of not only positional but geometrical isomerization
of alkenes. Rate studies of these isomerizations have been made
60 and concluded the following general rate formula :
rate a (I ) ~ (alkene) 2
Interpretation of this half-order dependance on the iodine indicates
that rart of the mechanism entails the addition of an iodine atom
to the carbon-carbon double bond60 . If this is true, the rate
detcrr:1ining step must be either the internal rotation in the inter-
mediate raJical or the addition or removal of the iodine atom.
. 60 61 The general proposed mechan1srn ' for any atom or radical
cataly:cd cis-trans isomeri:ation has been shown to be consistent
with a consecutive step mechanism. This involves the formation of
an intermediate radical followed by internal rotation in this
radical.
If A 1s allowed to represent the radical catalyst, then this
18
mechanism :n~y be de pi cteJ 8.5 follo\vS:
R R" a R R_.. \ u \ + A ~
b . \ ·A
c' 1l c
R_.. b"" R"" A + pd RriA a
R
The rate determining step for this general mechanism has been shown,
for some simple alkenes, to be the internal rotation in the inter-
d . d. 152,60,61 me late ra lea . But, if the Carbon-A bond strength and
the rcsonanl:~ energy introduced by the alkyl group(s) totals to
more than the strength of a carbon-carbon double bond (approximately
58 kc~l) then the rotation in the intermediate radical will occur
faster th:tn either the addition or removal of the radical catalyst
and h·i 11 not L:ontrol the rate of isomerization.
(someri:ation using radical catalysts, mainly nitric oxide
and iodine, l1ave been applied to 1,3-pentadiene by several research-
4 2 , 5: , G 1 - 6 3 Tl F k l 4 2 _1 4
ers . 1us. ~ran' et a . ref uxed pure trans- or pure
cis-1,3-pentadiene with traces of iodine to obtain, after 18 hours,
869o trans- and 14(lo cis-1, 3-pentadiene in both cases. They also
passed separately, pure trans- or pure cis-1,3-pentadiene through
a vertical glass tube at 600°C to obtain 45~ and 40~ cis-1,3-penta-
diene in the liquid products respectively. 52,61
Egger and Benson
19
isomeri.:2J l, 3-pcnt~dicn<.: l,.;ith nitric oxide over the temperature
ranee Jt -l00°K to 598.S°K and obt~ined 73~ to 69% trans-1,3-penta-
Jicnc in the product. SimilJ.r results \\·ere obtained using an iodine
1 • I J S. . 1 62 d . ~·atJ ... :·~t. ~\o lr(;r J.n , 1nt~ t use a mlcroreactor to study the
effects of alumina on 1,3-pentadiene at 760°K. They reported a
proJuct \~hich contained 63.lgo trans-1,3-pentadiene. Wells and
\ .. 1 63 \' 1 son , using cabal t po\,'der and cabal t supported on alumina,
t~) nhtJ. in ab0ut ~5~) trans-l, 3-pentadiene at -+33°K using
either of these c~talysts.
D c hydro c ~· c I i : :1 t ion of 1 , 3- Pent ad i en e
The Jchydrocycli:~tion of 1,3-pentadiene has been attempted
h\· various researchers. It should be noted, ho\,·ever, that most of
these researchers used pure 1,3-pentadiene as their starting
matcri:1l ~ \,·hcrc~s, in this study, the piperylene concentrate \\ras
useJ.
The thermally induced transformations of 1,3-pentadiene has
1 J . 1 1 ~ l . k . b--l • b 5 d l . . Jcen ;-;tu ICl t)y ~1u1 ·1n an 11s coworKers. They passed pure
1,.)-pcntaJicnc through a quart: tube reactor at ~50-550°C and
atmospheric pressure to obt:1in less than 1.0 9o cyclopentadiene at
RO~, pcntaJ icne conversion. \\1lcn the pressure h·as dropped to
20 mm llg, thP yield of cyclopcntadiene \vas less than 1. S9o at 13°o
p c n tad i c n e con v e r s ion . At 15 atmospheres , 9 ..J. 0a of the pentad i en e
was converted into r.S to c10
aromatics and high boiling polymeric
residual hYdrocarbons.
KenncJv ()b, \vas u b le to obtain 7. 3l~ eye lopentadiene by passing
20
1,3-pcntadienc through a stainless steel tubular reactor at 600°C
and .)0 !'lm II~ ,..·ith a contact time of ~.4 seconds. Under identical
conJi tions, he produced 3. 9 9a and 9. 2~.5 cyclopentadiene over silicon
.. J () 7' (J ~ d . k l . 6 7' 69 . ~arDt 0 an JaC c1a1n respcct1vely.
Timashev70
and Gregorovich71 produced 12.4 mole percent buta-
dicne and 7 mole percent cyclopentadiene in a quartz tube reactor
at 700°C and SO mm Hg. The contact time was 1.2 seconds.
l3oJn3rvuk 7 .., -,-1
_,,.) 0
ct a . produced 30~ cyclopentadiene and ~0%
butadiene at a pcntadiene conversion of 25%. Their quartz reactor
\,•as heated to 700°C at 50 nun Hg. The space time was reported as
-1 800 l.sec.mole . They concluded that the overall yields of cyclo-
pcntadicne and butadiene were not only dependent on the pressure,
but also ho~ the partial pressure of the diene was obtained. Thus,
h'hcn water \•;as used as the dilutent, it promoted dimer and polymer
formation, h·hcreas nitrogen did not.
Hutchings ct al. 74,
75 used hydrogen sulfide as a promoter to
produce cyclopcntene and cyclopentadiene from 1,3-pentadiene while
reducing cracking. Table IV briefly illustrates their results.
Other promoters, such as hydrogen bromide, hydrogen fluoride,
and carbon tetrachloride, have been found to promote the dehydro
. 76 77 cycli:ation reaction while reducing crack1ng '
Bencsi 78 cracked n-pentane in the presence of hydrogen over a
Pt/Siu, catalyst at s:s °C and atmospheric pressure to obtain 2.1 ~o
cyclopentaJicne, 2.S<~ cyclopentene and 6.S?o cyclopentane \vith a
selectivity of 34%. Witl1out hydrogen present, he obtained 5.3%,
21
TABLE IV
Results of a Dehydrocycli:3.tion Experiment
P ~ d ' H h. 75 ertorme oy utc~ 1ngs
Reactor Temperature 650 650
Mole Percent H2S 0 100
Conversion 21.8 15.2
Components
methane 6.24 1.97
c'"' 4.62 1.01
c_ 1.96 1.40 .)
butcnes 2.55 2.85
hutaJicne 28. 80 4.30
pentane 0. 4 7 1.18
1-pcntene 0.59 4.00
2-pentcne 2.04 10.20
cyclopcntcne 6.16 49. so
cyclopentadienc 26.70 20.40
22
2.lc~' ~d ~. -f~ of these products respectively with a selectivity of
Various cracking catalysts have also been utilized to produce
1 d . t- 1 ~ d. Th ~1 . k. 79 b eye cpcnta 1cnc rom ,~-penta 1ene. us, S1u1·1n was ale to
obtain 18~ cyclopentadiene at 600°C and 20 mm Hg over a Al2o
3-cr
2o
3-
K,O catalyst (42-7-1 mole % respectively) with a space velocity of
-1 1.0 hour . Under identical conditions, over a 5% Pt/C catalyst
th~\· oht;Jj ned 1 :-' 0) cyclopenta.diene.
80 Shuikin and Tulupov produced 9. 7?o cyclopentadiene over a
AL,O~-Cr_,O_ (1: 1 by \veight) at 600°C and 10 rnm Hg \vith a space - .) - .)
-1 velocity of 0. 5 hour . TI1e conversion of 1, 3-pentadiene was 35.2%.
At atmospheric pressure the yield of cyclopentadiene dropped to 0. 4'1o
at 71.9~ 1,3-pentadiene conversion.
Kennedy and Hct:e167
obtained up to 9% cyclopentadiene over
various heterogeneous catalysts at 600°C and 20 nun Hg with a contact
time of 0.1 seconds. Thus, over fused alumina81
, they produced 8.69o
cyclopcntaJicne ~t 69.1 o., 1, .3-pentadiene conversion. At 600°C and
200 nun ilg over activated alumina 82
they obtained 4 . .3 96 cyc1opentadiene
at 43(1o 1, 3-pentadiene conveTsion. At 600°C and atmospheric pressure
83 over a chromic oxide supported on alumina catalyst , they obtained
2.8~ cyclopentadicne at 70% diene conversion and 8.3% cyclopentadiene
cyclopcntadiene over silica ge184
at 62.7~ conversion.
85 0 Gi. tis 3.nd Rozengart produced 7°~ cyclopentadiene and ~. 0 5
cyclopcntcne with a selectivity of 35 and l0°o respectively at 615oC.
The Jienc conversion was 20~.
EX PER I:.IENTAL
Pip::;ry lene is a cormnon name for 1_, 3-pentadiene. In this
report, 1,3-pentaJlene will be referred to by IUPAC nomenclature.
"Piperylene Concentrate" is the name given to a mixture of
unsaturated hydrocarbons obtained as a by-product distillation
fraction from a naptha cracking process. The term piperylene
concentrate will be used to designate this mixture. A typical
composition of this material was presented in Table I.
Analysjs
The components of the starting materials and products were
separated and analyzed on a Perkin-Elmer Sigma I Gas Chromatographic
system equipped with flame ionization and thermal conductivity
detectors. This system integrates the area under each peak,
compares each peak area to the total peak area, and calculates the
\-:eight percent of each component using a response factor.
The response factors employed were taken from literature
86 values . The values given were all approximately 1.0. The two
exceptions were benzene 1.1~, and toluene 1.07. The response
factors for the hydrocarbons not listed in the literature were
calculated using standard samples. All 1vere found to be approxi-
mately 1.0.
The colwnn consisted of a ten foot section of one-eighth inch
thin \vall stainless steel, packed with 20 weight percent sebaconitrile
(Pfal tz and Bauer, Inc.) on 80-90 mesh acid washed Anakrom C22
24
(Ana labs Inc.) follo\ved by a 20 foot section of one-eighth inch
thin Hall stainless steel, packed \<Jith 15 weight percent bis
(2-r::ethoxyethyl) adip::tte (Supelco Inc.) on 60-80 mesh Chromsorb W
l~1alabs Inc.) non-acid washed. With only the injector end
connected, the column was conditioned with a helium flow of 25 ml
per minute at 100°C for ten hours. The exit end was then connected
in parallel to the flame ionization and thermal conductivity
detectors via a one-eighth inch stainless steel tee which had been
packed \vi th the Chromsorb W to decrease dead volume.
The starting materials and products were analyzed isothermally
at 60°C with a helium flo\v of 25 ml per minute. The injector
temperature \oJas set at 75°C and the flame ionization detector at
250°C. These conditions were held until all major peaks eluted,
usually about 22 minutes. Heavies (residues after distillation of
liquid product) \vere analy:ed on the sebaconitrile column. This
proceeded isothermally at 100°C with a helium flo\~ of 30 ml per
minute. The injector was set at 100°C and the flame ionization
detector at 250°C. Under these conditions, all peaks eluted within
90 minutes. Hydrogen \vas analy:ed on a ten foot by one-eighth inch
stainless steel column packed \vith 80-100 mesh Carbosieve B and
operated at 70°C with a helium flow of 15 ml per minute. The
injector temperature was set at 75°C and the thermal conductivity
detector at 150°C.
Since the analyzer was not equipped with a backflush accessory,
the column tended to load up with heavies after prolonged use. To
25
minimi~c this load up, the colunm was purged for one hour at 100°C
with a helium flow of 45 ml per minute '.·:henever the retention times
of the components Jecreased more than 2°o from their set points.
This analytical procedure has a precision \\jhich indicates a
relative standard deviation less than or equal to 0.02% for all
components except butadiene, cyclopentene, and isoprene which are
less than or equal to 0. 03go, and cyclopentadiene and trans-1, 3-
pcntJ.diene \vhich are less than or equal to 0.08%87
. It is also
indicated that the values obtained will not vary more than 2o from
the averages, (i.e., trans-1,3-pentadiene will be ±0.16% relative
at the 95~6 confidence level).
Analytical Standards
The pure samples of cyclopentadiene required for gas chroma
tograph peak identification and response factor calculations, were
obtained by depolymerizing dicyclopentadiene (technical grade) using
the r.1cthod of :.loffctt 88 . Using this method, a product which \vas
approximately 94'?6 pure cyclopentadiene was obtained. This was
increased to 99.5+% by fractionating the product through a nine-inch
glass column packed with Penn State extruded packing and collecting
the fraction which distilled bet\veen 39 and 42\JC. This fraction \vas
then used immediately for the response factor calculations.
Standard samples of trans-1,3-pentadiene (Aldrich) were used
without further purification; while the samples of cyclopentene
(.J. T. Baker), cyclopentane (J. T. Baker), pentenes (Pfal tz and
Bauer, Inc.), 2-methyl-1-butene (Pfalt: and Bauer, Inc.), and
:-methy 1-:-butene (East.man) were all fractionated before using.
Liquid rh2SC Reac"tions of 1,3-Pentadiene
26
A number of trials, utilizing liquid phase reaction conditions,
·~-;ere m:tdc to investigate the geomet.ric isomerization of the penta-
diencs and their separation from the mixture.
Halogen Catalyzed Isornerizations42
A mixture of 100 grams of piperylene concentrate and 0.6 to
1. 3 6rar:1s iodine (or bromine) \oJas refllLxed with a trace of hydro
quinone for :..t to 72 hours. The piperylene was then removed by
distillation through a twelve inch Vigreux column and analyzed.
A similar mixture of piperylene concentrate and iodine was placed
inside a stoppered flask and stored at 0°C. Small portions,
approximately 25 rnl, of this mixture \-Jere removed periodically,
distilled as before, and analyzed.
Base C~taly:cd Isornerization89
These isomerizations were performed in a 100 ml three-necked
round bottom flask equipped \oJith a thermometer, condenser, and
stirrer.
To the apparatus \vas added 50 ml (0. 2 mole pentadiene) of
pipcrylcnc concentrate and l gram (. 01 mole) of potassiu..rn tert
butoxide. This was carried out both with and without a nitTogen
blanket. This \vas repeated using 20 ml (0. 08 mole pentadiene)
pipcrylenc concentrate, and 5.0 grams (.045 mole) potassiwn tert
butoxidc i.n SO ml of dimethyl sulfoxide. This mixture was stirred
for 24 hours under nitrogen, both at ambient temperature and reflux.
27
Tltis was repeated us1ng ~0 ml (0.08 mole pentadiene) piperylene
conccntr~te and 10.0 grams (0.9 mole) potassium tert-butoxide in
50 :.11 of dimethyl sulfoxide. Similar mixtures Here stirred tu1der
ni tTogcn for: :.~ hours at l5°C, 12 hours at 35°C, and 12 hours at
reflux.
At the end of the reaction period, the mixture was quenched
with 250 rnl of ice-water containing 25 rnl cyclohexane. The organic
l:Jyer ,\.3.5 ,..;asncd once \'/ith 100 ml of ice-l-.rat:er, dried over molecular
sle\·e (1~:\), distilled, and analyzed.
Separation of 1,3-Pentadiene from the Piperylene Mixture by
. h 'd 30 Cuprous Ammon1urn C lor1 e Treatment
For all of the following work, piperylene obtained from the
Chemical Sample Company was used. Its composition is presented in
Table V.
TABLE V
Composition By Weight of Chemical Sample Company Piperyler.e
Component Percent
lights 1.0
2-methyl-2-butene 2.0
cyclopentene 17.7
trans-1,3-pentadiene 67.8
cis-1,3-pentadiene 11.5
28
Into ~ 500 ml three-necked flask equipped with a mechanical
stirrer md thermometer, ~-.ras placed 64 grams (0.65 mole) cuprous
chloride, 32 :.;rams (0.6 mole) ar.llllonium chloride, 80 ml \vater, 4 ml
concentrated hydrochloric acid, and 2 grams copper turnings. The
flask was stoppered and stirring was started. On stirring, the
temperature decreased rapidly to approximately l0°C with the
formation of a deep bro\vn slurry. After one-half hour, stirring
h·as discontinued and the mixture was allo\ved to set overnight.
The flask was then placed in a 25°C water bath and 40 ml
(0. 31 mole diene) of piperylene was added. The stirrer was started
and the reaction proceeded \vi th a slight evolution of heat and the
formation of a greenish-yellow precipitate. After stirring for one
hour, the \vater temperature \vas increased to 35°C and the stirring
was continued for an additional five to six hours. The mixture was
then fi 1 tcred and \vashed with warm water to remove any residual
~mmonium chloride. The prouuct h·as allowed to stand open, \vith
occasional stirring, to allow any unreacted hydrocarbon to evaporate.
This procedure gave 60 grams, or 70% yield of complexed product
based on the dicnc.
The complexcd product and 175 ml of water was then placed into
a 250 ml ~lorton flask \vhich was equipped with a thermometer,
mechanical stirrer, and an unpacked factionating distillation
apparatus. The stirrer was started and the temperature of the pot
\-.ras increased very slowly (approximately l0°C per hour). The
decomposition proceeded rapidly at a pot temperature of 63 to 72oC,
giving ll. 75 grams (54~)) of pure 1, 3-pentadiene.
S~rnthesis of 3-01ethyl-l, 2, 3,1}-Tetrahydrophthalic Anhydride Via
Diels-,\lder R0action h'ith 0Ialcic Anhydride 42
To a 250 ml round bottom flask equipped with a mechanical
stirrer and condenser, was added 28 grams (0.3 mole) of maleic
29
anhydride, 110 ml piperylene (0. 7 mole trans-1,3-pentadiene), 100 ml
benzene, and 0.1 gram of picric acid. The flask was then fitted
\•;ith :1 thermometer 311d stirring was started. Heat \~as applied to
st~rt the reaction which continued with the evolution of a consider-
able amount of heat. After stirring for 24 hours, the benzene and
unrcacted piperylene was removed by simple distillation tmder a
reduced pressure (about 380 Torr). The residue which was left, was
allo~ed to crystallize and then heated with a 20 volume percent
solution of benzene in pet ether. The solution was then treated
with :\'orit-A, filtered, and cooled. The crystals formed were
\vashed with cold benzene-pet ether solution to remove unreacted
maleic anhydride, giving 21.5 grams, or 45~o yield (based on maleic
anhydride) of product with a melting point of 62°C. (lit.43
= 63°C)
l11e above procedure was repeated with refluxing the mixture
for 1-l hours. The yield dropped to 25°o, apparently due to the loss
of piperylcne through the condenser. With acetone as the solvent,
the reaction was carried out at l0°C for 48 hours. After workup,
and on cooling, 9. 5 grams of crystalline product \'las obtained. The
mother liquor from this crystallization was then cooled to approxi-
mately -45°C in an acetone-dry ice mixture to give an additional
7.0 grams of product. The total yield using this method was 35%
of theory.
Pyrol\·sis of 3-C.lethyl-1,~,3,6-Tetrahydrophthalic Anhydride42
30
The :1pparatus used for this pyrolysis is shown in Figure 2.
The pyrolysis tube consisted of a 12 inch long, one-half inch 316
stainless steel pipe filled with glass beads (4 mm diameter). This
was heated to, and maintained at, 575 to 600°C by means of a
Lindbcr.; single :one tubular furnace. The temperature \vas monitored
through thermocouples attached at various points around the tube
and connected in parallel to give an average temperature reading.
The reactant hopper consisted of a 250 ml pressure equilized
dropping funnel which was connected to the pyrolysis tube by a
24/40 to 10/30 reducing union which was inserted into a drilled out
one-quarter inch stainless steel S\vagelok union. The 10/30 portion
of the reducer was \vrapped with Teflon pipe tape before being
inserted. Once joined, the entire joint \vas \vrapped tightly with
glass cloth tape to obtain a gas tight seal.
The exit end of the pyrolysis tube \vas connected to a three
necked round bottom blask containing an excess sodium carbonate
solution \vhid1 \vas maintained at 60 to 70°C. The purpose of this
solution was to dissolve the maleic anhydride, preventing recombina
tion with the diene. The 1,3-pentadiene was then distilled off and
collected in a receiving flask and a hydrocarbon trap, both of which
were cooled by Jry icc.
To
Hoo
d
Fig
ure
2.
Py
roly
sis
Ap
par
atu
s
-A
dduc
t H
oppe
r
Rec
eive
r w
ith
Na 2co
3 S
olu
tio
n
Pvrolysis Procedure
One hundred sixty-six grams (1.0 mole) of 3-methyl-1,2,3,6-
tetrJ.hyJrophthalic anhydride \vas placed into the dropping funnel
and h~atcd to 100°C to insure complete melting of the adduct.
32
Once mel ted, and with a nitrogen flow of approximately 400 ml per
minute, the adduct was slowly dropped (20 drops per minute) through
the pyrolysis tube and into the sodium carbonate solution. The
\'Ol:Itilc portion \.;as distilled out of the flask and collected to
give 26 grams or 38°o crude product. The crude product was then
distilled and analyzed.
Vapor Phase I someri :ation and Oehydrocyclization of 1, 3-Pentadiene
The apparatus utili:.ed in this portion of this study is
illustrated in Figure 3. In general, this system consists of a
dilutcnt inlet, a two-stage steam generator, a hydrocarbon inlet
and prcheater, a tubular reactor, a \vater scrubber, and water and
hydrocarbon traps.
Stage I of the steam generator consisted of a 3/8-inch 316
stainless steel pipe tee \vhile Stage II was a twelve-inch length
of 1/4-inch stainless steel tubing. The entire steam generator
h1as wrapped \vith two layers of asbestos heating tape and insulated
\-lith one-half inch of asbestos cloth. Water was pumped, via two
30 ml disposable syringes and a Stage Instrwnent model 355 variable
flow syringe pump, through a 1/ 16-inch stainless steel tube into
the steam generator (Stage I). Flash vaporization effects \vere
minimized by the use of this small inlet. The relatively large
To
Hoo
d 1
I ~'
I _
_j
l l Hyd
roca
rbon
T
rap
I W
ater
T
rap
Sam
ple
Po
rts [-
Wat
er
1/ S
cru
bb
er
Fig
ure
3
.
_J
Pip
ery
len
e
1 -
L
Rea
cto
r
!l_ 1~
,1 I I~
Fur
nace
\Vap
oriz
er
Vap
or P
hase
Is
om
eriz
atio
n
Deh
yd
rocy
cliz
atio
n A
ppar
atus
H20 I ,I
I 1
N2/A
ir
1 Ste
am
Gen
erat
or
34
volume (10 ml) oi Stage I of the steam generator and a dilutent
stream of nitrogen entering from the rear of the steam generator
(St.1.gc T), 3.lso helped to vaporize the water, minimizing flash
1.·apor1:ation. The exit end of the steam generator (Stage II) \~as
attached to a 1/4-inch stainless steel Swagelok tee. One end of
this tee \vas attached to a pressure gauge (Master gauge Type 100-f\1-
moncl, ~1arsh Instrument Company) and the other to the hydrocarbon
\·a pori :cr.
The hydrocarbon vaporizer consisted of a five-inch length of
1/-l-inch stainless steel tubing \vi th a Swagelok stainless steel tee
connection at its entrance, which served as the hydrocarbon inlet.
A 1/8-inch hole was drilled through one side of the vaporizer
section. A 12-inch length of 1/8-inch stainless steel tubing was
fitted into this hole and welded into place. This served as the
inlet for gaseous promoters. TI1e entire vaporizer section was
heated by means of t\vo layers of ~0 gauge Nichrome wire which had
been insulated from the vaporizer and each other with asbestos
paper. The vapori:er was then wrapped in glass cloth tape and
insulated with one-inch of asbestos cloth.
Piperylene was pwnped, in the same manner as the water, through
a one-inch hypodermic needle (gauge 25) into the vaporizer. TI1e
liquid hydrocarbon feed thus mixed with the preheated dilutent
(usually steam and nitrogen) \vhich completely vapori:ed it before
entering the prcheater.
The preheater consisted of a six-inch piece of 1/4-inch 316
stainless steel tubing i-Jhich connected the vaporizer to the
re:1cror inlet. TI1e function of the preheater \vas to heat the
g:1scous hydrocarbon-Jilutent mixture to a temperature Hhich was
approximately l00°C below that of the reactor.
The reactor consisted of a 3/8-inch 304 stainless steel
threaded pipe having a volume of 7.1 ml. It was placed in the
center of a Lindberg Single-Zone tube furnace (~1odel 54031)
equipped h·i th a solid state temperature controller (type 2200,
~lodel 59344). Its temperature was monitored with thermocouples
positioned at various points around the reactor and connected in
parallel in order to obtain an average temperature reading. The
exit was attached to a 12-inch piece of 1/4-inch 316 stainless
steel tubing \~hich '"as heated by a means similar to that of the
inlet vapori:er. To the end of this exit tube was attached a
316 stainless steel Swagelok tee. A stream of diluting nitrogen
flo\-.rco through this tee and met the effluent stream, cooling it
and insuring its complete vapori:ation.
35
\Vater vapor \vas removed from the effluent by means of a \vater
scrubber \vhich \vas made up from an eight-inch length of 3/4-inch
pyrex tubing closed at one end and attached to a ~ 19/22 Claisen
adaptor at the other. The water scrubber was wrapped \vith heating
tape, insulated, heated to, and maintained at 45 to 50°C to insure
none of the c5
hydrocarbons \vould condense. TI1e exit end of the
adaptor was fitted \vith a West-type condenser, through which heated
(50°C) \vater was pumped. The exit end of the condenser was
36
connected, via Tygon tubing, to the water trap \1/hich consisted of
a 12S ill Erlenmeyer flask filled \vith 4 mm diameter glass beads.
Its purpose \vas to condense any remaining Nater vapor from the
·..:-fflucnt hefcrc entering the hydrocarbon trap.
The hydrocarbon trap consisted of two 25 ml test tubes which
were filled \vi th 4 ml diameter glass beads and immersed in
isopropyl alcohol cooled to -65°C.
S:.unplc ports were located at the reactor exit, after the
h'ater scrubber, and after the hydrocarbon trap. The two former
ports \'iere used in obtaining hydrocarbon samples, \-Jhi le the latter
\-:as used in obtaining hydrogen samples.
All temperature measurements were made with Chromel-Alumel
thermocouples and read with an Omega model 200 digital thermometer,
except the hydrocarbon trap temperature, which employed an iron
constantan type J thermocouple and was read with a Fluke 2100A
digital thermometer.
Catalyst Preparation
TI1e activated al urnina, 8-14 mesh (~1athes on, Co 1 ernan and Be 11) ,
and silica gel, 6-16 mesh, grade 03 (~Iatheson, Coleman and Bell),
\-Jere Jried overnight at 120°C prior to use. The stainless steel
packing was the 316 stainless steel Penn State extruded packing.
Hydrogen sulfide (Air Products) and sulfur dioxide (Matheson) were
supplied from a lecture bottle.
The sulfidcd 316 stainless steel surface was prepared by
passing air through the reactor (500 ml/rnin) which was packed \vith
37
Penn St.:1tc extruded pack:.ng for approximately six hours at 600°C to
oxidi:e the surface. The temperature was then dropped to 300°C with
~i.r rlO\ving. Once the reactor equilibrated at this temperature, the
a1r \vas .r·lushcd ~·•ith nitrog~n. After a thorough flushing, a mixture
of 10 to 25 volume percent hydrogen sulfide in nitrogen was passed
through the reactor at a feed flow rate of about 100 rnl per minute.
·n1e sul fiding of the metal was very exothermic as indicated by an
1ncrease in reactor temncrature. This temperature was kept below
3S0°C by controlling the hydrogen sulfide flo\v rate. After the
reaction \vas completed, as indicated by a stabilizing temperature,
the reactor \vas flushed with nitrogen and brought to the desired
conditions. The composition of sulfides on the metal was not
determined. It is assumed that the bulk of the sulfide was iron
sulfide \-:ith some chromium and nickel sulfides also being present.
~lolybdcnum does not oxidi:e or sulfide readily under the conditions
. d90 ment1one .
The :11 urn ina s upporte<.l cat al ys t \vas prepared by the incipient
\vctncss ted1nique. In this technique, deionized water was added
drop\-:ise to a measured amount of support material until the first
sign of free water. The volwne of water added at this point was
the water pore volume of the support. The desired amount of metal
salt was then dissolved in that amolillt of water and added dropwise
to the dry support as before. The \vater was then removed by gently
heating the material leaving the metal salt behind. The heat was
38
applied s lo'.vly JS not to fracTure the pore structure and decrease
its __;urface area. The salt can then be reduced '\'lith hydrogen,
le:1vin~ the wetal deposited in the pores of the support. 'lliis
method Insures that the metal was dispersed over the entire surface
of the support and not deposited in the bulk.
The alumina supported platinum catalyst was prepared as
follo\·.'S. A solution of 1.1266 grams of chloroplatinic acid in
39.5 rnl of deioni:cd \o;ater \vas slo\vly added to 51.13 grams of
alumina \vith rapid stirring. This \.Jas then dried overnight at
120°C prior to calcination and reduction. This gave a catalyst
h'hich contained 0. 82 weight percent platinum on alumina. Unfortu
nately, time did not permit this catalyst to be fully evaluated.
Operating Procedure
l'.·ith nitrogen flo\ving through the system, all the components
\vere brought up to temperature. Once the desired temperatures
\~·ere obtained. water was pumped into the steam generator. The flow
of nitrogen and steam was then adjusted to their desired rates.
The system was then allowed to equilibrate for one-half hour ~'V'ith
minor adjustments JS required. Once equilibrated, the desired
feed flow of piperylcne was introduced and the timer started. At
a time of approximately two minutes into the reaction, a 0.5 ml
sample of the effluent was taken and analyzed. Subsequent samples
were taken every 20 minutes and analyzed until the reaction
equilibrated and them for one hour longer. After the gaseous
hydrocarbon was analyzed, a wet test meter was positioned after
the hyJrocarbon trap and 0. 5 ml samples of hydrogen were taken
(gencr~lly six) at five minute intervals and analyzed.
39
Run tiQes ran~ed from approximately one and one-half to seven
hours, JepenJing on the catalyst employed and the conditions. After
each run, the catalyst \vas cleaned \vi th a 1:1 weight ratio of steam
and air for one hour to remove coke which was deposited during the
reaction period.
Scpara~ion of 1,3-Pentadicne from Piperylene Concentrate Using
Cunrous c:tl~.1 r i.dc ComnlexinB
Since the cuprous chloride complexes of simple aliphatic
alkcnes are soluble in the salt solutions in which they are formed,
they arc easily separated from the insoluble pentadiene and cyclo-
34-38 pentene complexes . Through the addition of ammonium chloride,
the Jlh.cne anJ cyclopentene complexes will decompose leaving the
. 34 35 39 more stable and insoluble pentadiene complex behlnd ' ' This
.:1J.Kcs :he :.Jcparation of 1, 3-pentadiene from the piperylene concen-
tratc a relatively easy chore.
The d~t:1 for this separation lS shown in Table VI. The
rcco\·cry \oJas above fifty percent, with the product being 99. 99o
pure 1,3-pcntadiene. It was interesting to note the increase in
the relative amount of trans to the cis lsomer. This can be
cxplain~d, not by isomeri:ation, but by the stability of the
corilplcxes. .).)
The cis isomer forms a more stable complex . Since
the Jccomposi tion temperature \vas not taken much above the decorn-
position temperature of the cis-1,3-pentadiene complex, some was
left undccomposed in the pot, \'Jhile all of the trans-1, 3-pentadiene
complex was completely decomposed.
Iodine isomerization of 1,3-Pentadiene
The isomeri::ation of 1,3-pentadicne by small amount.s of
halogens, mainly iodine and bromine, is believed to proceed through
TAGLE 'JI
D:1t;1 For The Separation of 1,3-Pcntadiene From Piperylene L:unccntTate fhrou~h Cuprous Chloride Cornplexing
Reactor Temperature (°C)
Contact Time (hr)
~CC0\'Crv ( '',)
f-EED CO~iPOS IT I 0:\' ( wt 0o)
trJns-1,.3-pentadiene
cis-1,3-pentadiene
cyclopcntenc
trans-1,.3-pentadiene
cis-1,.3-pent3diene
cyclopentene
DEC0~11'0S1TIO:-\ TE~!PERATURES (° C)
trans-1,3-pentadiene
cis-1.3-pentadiene
Pot De composition Temperature
25
7
54
67.7
11.8
17.7
90.9
9.0
0.1
66 "":''") I-
63-75
41
42
the frec-r~dic~l reaction path exem~lificd in Figure 460 , 61 . As
shohTI in the first step, the halogen may either abstract an allylic
hydrogen or ~dd to the double bond. The simultaneous addition of
the r1alo~en to form a dihalo compound should not occur to any
appreciable extent since the concentration of the halogen is low.
The low halogen concentration decreases the probability that the
adduct radical will react with molecular halogen. It should
instc~d, Jissociatc aga1n to yield the 1,3-pentadiene with or
1~ithout isomerization. This is not to say that no side reactions
\vill transpire, since during these isomerizations, two important
side reactions did indeed take place: polymerization and diiodide
formation.
These side reactions are explained through the energies
· 1 d E 5 ~' 60 , 61 ·f· d the d · · · 1nvo vc . ggar , ver1 1e rate eternun1ng step 1n
iodine isomeri:ation of simple alkenes is the internal rotation of
the intermediate radical. This is not the case with 1,3-pentadiene,
due to the additional resonance energy (-12.6 kcal) involved. TI1e
secondary carbon-iodine bond energy (-53 kcal) plus this resonance
energy, add up to more than the strength of a carbon-carbon double
bond (58 kcal). Therefore, in the iodine isomerization of 1,3-
pcntadiene, the addition or removal of the iodine is the rate
determining step rather than the internal rotation of the inter-
mediate adduct radical.
The rcsul ts for the iodine isomeri zations of 1, 3-pentadiene
are sho\vn in Table VI I. These results are not consistant \vith the
r ":/ X
I
/\
v X
t
I I i
~ + HX
~G~98 = ~\I
~H298 = RXN
""' I
I
i I I
I v
-1.2 kcal
-1.7 kcal
Figure 4. Proposed i\lechanism for the Iodine Catalyzed Isomerization of 1,3-Pentadiene.
43
TAB
LE
VI
I
Dat
a fo
r th
e
IoJi
ne C
atal
yze
d
Iso
meri
zati
on
o
f 1
,3-P
cn
tad
icn
e
(I
0 o.
T
emp
erat
ure
C
on
tact
~1ole
'o
·o
Tra
ns
Lso
mcr
'o
T
ran
s Is
om
er
(oC
) T
ime
(hr)
Io
din
er.
11
1 F
eed
**
lll
Pro
du
ct
**
42
20
O
.lo
5
1.2
6~.7
42
20
0
.51
5
1.2
6
9.7
42
72
0.2
6
51
.2
61
.8
0 22
0
.40
5
1.2
60
.(>
0 72
0
.40
5
1.2
6
0.6
0 14
4 0
. 40
5
1.2
6
2.4
0 6
48
0
.40
5
1.2
6
2.9
0 72
75
0.4
0
51
.2
57
.3
* B
ased
on
th
e to
tal
pip
ery
len
e
feed
.
*·k
Bas
ed o
n th
e
amou
nt
of
1, 3
-pen
tad
ien
e in
th
e p
ipery
len
e
feed
.
**
·k
Basi
s:
2.3
03
R
log
K
t/c
= -
(0.1
4±
0.0
5)
wit
h R
in
ca
l/m
ole
°K
+
(103
7± 2
8)
T
Kt/
c
2.3
0
2.3
0
1.6
2
1.5
4
1.5
4
1.6
6
1.7
0
1.3
4
K
·A·
·k *
t/c
5,
Calc
ula
ted
....
-------
4.
o8
-~.
B8
4.o
8
6.2
9
6.2
9
6.:.
?9
6.2
9
6.
29
45
. l Th 1 1 d . 1 . b · 52 exp~ctcu resu t3. J c ca cu ate equ1 1 r1um constant shows
that i:hc mixture should contain 83°u trans-1, 3- pentadiene relative
to the tot~1l open chain 1, 3-pentadiene present, but after refluxing
.2or .20 l1ours, 69. -;--'~ tr~ns-1, 3-pcntadiene was detected and on
reflu.xing for three days, only 60.996 trans-1, 3-pentadiene was
detected.
The decrease in the trans-isomer on additional refluxing is
Jul: to the i_:1crcascd amount of polyrneri:ation and diiodide forma-
ti.on. It has been sho\'.'11 that trans-1,3-pentadiene will dimerize
anJ polymeri:e much more rapidly than its cis-isomer42
This
indicates that on longer refluxing, the amount of trans-1,3-penta-
dicne may increase, however, the polymerization reaction increases
more rapidly. That is, the rate of polymerization and diiodide
formation are faster than the addition or elimination of an iodine
radi ca 1 from the adduct. Some of the possible but improbable side
reactions are .sho\·Jn in Figure 5. As sho\vn by the thermodynamics,
these siJe reactions should only occur to a small extent as compared
to the cis- to trans-isomeri:ation of 1,3-pentadiene.
Potassium tert-8utoxidc fsomcri:ation of 1,3-Pentadiene
The tabuL1tcJ results for the potassium tert-butoxide isomer-
i:ation of 1,3-pentadiene, both neat and in dimethylsulfoxide, are
shown in Table VIII.
The effect of dimethylsulfoxide on the isomerization is appar-
ent through a comparison of runs A and B. There \vas little, if any,
isomcri:ation in run A, perhaps due to the insolubility of potassium
l1H298 = 10.7
l1G298 = 8.6
-H:!gs = 13.0
G298 = 7.41
I
(
I ~I
I·1l
)
46
I
I
J, 11
~~ ~<~)~ •
1' RH .,..
~8H298 = 5.6
8G298 = 4. 8
F· gure 5. Possible Side Reactions During Iodine Catalyzed Isomerization of 1,3-Pentadiene.
TA
BLE
V
III
Dat
a fo
r th
e
Po
tass
ium
Tcr
t-1
3u
tox
idc
Tem
p.
Co
nta
ct
D~lSO
+
-K
t-
BuO
R
un
(oC
) T
ime
(hr)
V
ol u
n1e
0 ~lol e
?o
·k
~D
A
B c 0 E
25
18
nea
t
25
24
so
20
24
70
20
24
90
35
6 70
·x B
ased
on
1, 3
-pen
tad
ien
e in
fe
ed
.
** B
ased
on
1,3
-pcn
tad
ien
e co
nte
nt.
5.9
5.9
44
.0
36.
7
44
.0
2.30
3R
log
K
t/c
=
-( 0
. 14
± 0
. OS)
wit
h R
in
ca
l/m
ole
°K
+
Cat
aly
zed
Is
om
eriz
atio
n o
f 1
,3-P
cn
taJi
cn
e
0 ·u
Tra
ns
l$om
cr
in
Fee
d
51
.2
51
.2
57
.6
57
.6
57
.6
(1 0
37±
28)
T
·x*
0 o T
ran
s Is
om
er
K
Pro
du
ct
**
lll
t/c
54
.0
1 .
l -;
79
.8
3.9
5
83
.6
5.1
0
82
.8
4.8
1
82
.3
4.6
5
Calc
ula
teJ52
K
* ·.1;
·)
c
tIc
5.3
7
5.3
7
5.6
3
5.6
3
5.0
7
48
tert-butoxide in the piperylene. In contrast, in the presence of
dimethylsulfoxide, the isomerization approaches the thermodynamic
equilibrium value.
Dimethylsulfoxide enhances the rate of isomerization reaction
through its ability to: solvate the potassium ion91 , and activate
the weakly acidic allylic carbon-hydrogen bond92. These abilities
f "1" h f . f h b . . d" 92-95 ac1 1tate t e ormat1on o t e car an1on 1nterme 1ate . It
92 94 has been postulated ' , that the carbanion transition state,
formed b~~ the abstraction of an allylic hydrogen by the base, is
the rate determining step. If this is true, then any factor which
will decrease the energy of the transition state will increase the
rate of its formation. The ability of dimethylsulfoxide to activate
the acidity of the allylic hydrogen, must then increase the rate of
intermediate formation enabling the thermodynamic equilibrium to be
established sooner. This is supported by the data collected for
runs C and Also seen, is the lack of substantial difference in
the extent of isomerization in the presence of excess solvent or
base.
Another factor which effects the ease of allylic hydrogen
abstraction is the coplanarity of the alkene or diene system. As
seen in the illustration below, a coplanar system must exist to
+ B H
" ~r~/ ~ j::U,,'"~
• . • • H- B
49
insure the max.1mum overlap bet1veen the TI bond and the rehybridizing
p-bonJ oi the ~llylic carbon. This situation should not present
Jifficulties \·lith open-chain molecules such as 1,3-pentadiene, but
has been sho\vn to play an important role in the isomerization of
96 ring systems
Through several base catalyzed isomerization studies of
simple alkenes, the intramolecular cyclic transition state shown
97 bela~ .. · hJ.s been suggested . This suggestion is based on the
strongly negative entropy of activation and observation that the
isomeri:ation reaction takes place about sixteen times faster than
the hydrogen-deuterium exchange reaction.
fhe proposed mechanism for the potassium tert-butoxide isomer-
ization of 1,3-pentadiene is shown in Figure 6. This mechanism 1s
a modi.fication of the olefin isomerization mechanisms given by
S , · I · ~ 1 2 ' 9 ..t. p · 9 S d B kg 3 h 1 d th th c.nr1es 1c1m , r1ce , an an~ , w o postu ate at 1 e
intermediates \vere allylic carbanions. The proposed mechanism also
shows ho\v small amounts of 1, 4-pentadiene and cyclopentene could
form.
The major drawback found during this isomerization was the low
so
9 .. I ~ KB + ~ + KBH +
I \ e
.~1 ~ . ()
~
I \ !
'V r::::- HBK BKH ® ~ ~~ " ..;
7 • / e· /1 , """
y
I \
BKH (£)
~ Ve e
BKH@ I
. ~
BKH ® 0 ~ ~ 9
B = t-butoxide
Figure 6. Proposed Mechanism for the Potassium tert-Butoxide Catalyzed Isomerization of 1,3-Pentadiene.
51
recoveries of the pipcrylenc ( <SO?o) due to the extensive amount of
::'olymcri:ation.
The Svnt:1csis and !1vrol·.rsis of 3-i·.Iethyl-1,~,3,6-Tetr::lhydrophthalic
.\nhyJri Jc
The Diels-Alder reaction of trans-1,3-pentadiene and maleic
anhydride to form 3-methyl-1, 2, 3, 6-tetrahydrophthalic anhydride was
used to separate trans-1,3-pentadiene from cis-1,3-pentadiene and
:::12 other hydrocarbons present in the piperylene concentrate. The
aJduct proJuced was then decomposed by pyrolysis. The first step
\~as easily accomplished since trans-1, 3-pentadiene reacts readily
\\'ith maleic anhydride \oJhile cis-1,3-pentadiene does not react at
. ll 43,44,46,47 d . d" h 1 an\· apprec1a J c rate ue to 1ts protru 1ng met y group.
As indicated earlier (Experimental section), long contact times
(.:~l to 48 hours) were employed during this adduct formation. Tnese
. d d" c . 47 h long contact times arc not requ1re . Accor 1ng to ra1g , t e
rcJction \oJi 11 be compl cted in twelve hours. This was confirmed in
l:.1tcr experiments in which similar yields were obtained 1n twelve
hours -.)r less.
The adduct produced was then pyrolyzed in an attempt to produce
pure tr~:ns-1,3-pentadicnc. TI1is pyrolysis was carried out in the
apparatus depicted in Figure 1. On pyrolysis of the adduct, trans-
1,3-pcntadiene was obtained in fair yields. However, once freed
from the adduct it was able to undergo· side reactions as it passed
Jo\._.n the heatcJ pyrolysis tube. The products obtained along with
reaction conditions are sho\vn in Table IX.
TABLE IX
Products Obtained from the Pyrolysis of 3-~lcthyl-1, 2, 3, 6-Tet rahydrophthalic Anhydride
Reactor Temperature:
Contact Time: 5-6 sec
Recovery (as liquid): 38 wt %
ComT'u~i::ion of Liauid Products lTI
Boiling Point oc 38-50
trans-1,3-pentadiene 25.3
cis-1,3-pcntadiene 14.8
1,3-butadiene 16.3
cyclopcntcne 1.~
cyclopentadienc 34.6
Remainder * 7.6
.:.: C ~nd hea\·ier hydrocarbons 6
Wei.ght Percent
50-85
30.8
20.8
2.2
2.1
38.9
5.2
52
53
Th\..!rm~ l and C~ttalyt ic DehyJ.roc~.-cl i zat ion of 1, 3- Pentadiene
The ~~tuiument utili:ed in these runs \·.ras illustrated in
Fi:;urc .). The objective in constructing this apparatus was to
..:cvi_;..; .1 systcl!l \·:hich ~\·oulJ produce and reproduce consistant
data. The system also had to be easy to operate and maintain.
The largest maintenance problem encountered '~as the clogging of
the system due to polymer and coke formation. The two major
fa~tors responsible for the excessive polymeri:ation Here found
to be: 1) the presence of heavy material in the piperylene feed
.:1nd 2) the temperature of the hydrocarbon vaporizer. Distillation
of the feed through a nine inch glass colunm packed with Penn
State Extruded Packing \~as sufficient to remove all of the heavy
m3tcrials.
The extent of cracking and polymerization was also decreased
by decreasing the temperature of the hydrocarbon vaporizer. It
,,.a~; oh:~crvr2d that if the dilutent gases were heated to a high
b f · · 1il~'droc,.,rbon feed, the amount of ... tenpcraturc e ore contact1ng the ! u
crJ.cking wi.thin the reactor decreased. The extent of thermal
cracking ~as also reduced considerably in the presence of steam.
The ste:1111 can bcnefi t the reaction in several ways:
1) Lowering the partial pressure of the piperylene allows the
conditions to become more favorable toward the isomerization and
cycli=ation reactions.
~) Removing carbon deposits by a "Water Gas r~eaction" during the
JchyJrocycli:ation, and Juring regeneration of the catalytic system.
c (SJ
+ IL>O l. ~ ... g)
54
co (g) +
3) The: l "'.c~t ~apacity or· the super-he~ted steam can provide some of
the :1c-:.1t :1ccdcd for the Jehydrocycli::ation l'Caction.
The cracking, isomerization, and polymerization reactions of
piperylene \.;ere found to be sensitive to the reactor surface. Due
to this surface sensitivity, a small reactor was utilized. In
cat31Yst evaluation, this small reactor insured that the principle
reaction ·,,·as occurring on the catalyst surface rather than the walls
of the reactor. To further decrease surface reactions, a greater
... L::o~nt vi .i.i1ert gas \'.'as used to reduce the diffusion of the piper-
ylcnc molecules to the reactor walls.
The reaction conditions which were kept constant for all runs
arc shoh·n in Table X. These conditions represent a compromise
bcth·ccn optimum :1nd feasible conditions related to the equipment
limitations. For example, less cracking and higher selectivities
we rc obscrvcu when the hydroc~rbon contributed S~o rather than 15?.5
to tile total vo 1 umetric feeJ. flO\'¥; ho'''ever, the latter was chosen
clue to the inaccuracy of the syringe pump at the lo\ver settings
rcqui.rcJ for the former.
The data presented in this report are best understood if the
fcllo\ving uefini tions are recogni:ed.
1) Key L:o1.1ponents - cyclopcntenc, trans-1, 3-pentadiene, and
cis-1,3-pentadienc.
~) Cant act Time - TI1e vo l wne of the reactor or unexpanded catalyst
55
TABLE \
Constant Dehydrocyclization Reaction Parameters
Steam Generator - Stage 1 125°C
Steam Generator - Stage 2
liyJroc:lrbon rapori:cr
Prchcater reactor temp. - 125°C
Sample Port
Hydrocarbon Trap
\"o 1 umc ~o Di 1utent 85% (75% H 0/10% N ) 2 2
Volume (~ Hydrocarbon
bed JiviJeJ b\r the volumetric feed flo~..,· rate at reaction
conditions.
56
3) Convcrs ion - The difference ln the ~.:eights of the key components
entering and leaving the reactor divided by the former, all
multiplied by 100.
4) Yield of Cyclopentn.diene - Weight of cyclopentadiene 1n the
effluent divided by the Neight of the key components in the
fccJ. all multiplied by 100.
5) Selectivity - Yield divided by the conversion, all multiplied
by 100.
To obtain an indication of the relative reactivities of the
components in the piperylene concentrate, several runs utilizing
"pure" component feeds were made. The composition of these feeds
arc shotvn in Table XI.
The relative reactivities based on conversion are:
tr~lns-1,3-pcntadlenc > ~-methyl-1-butcne > cyclopentene >>
2-methyl-2-butcne >>> cis-1,3-pentadiene
however. relative selectivities to cyclopcntadiene formation are:
eye lupentcnc > cis-1, 3-pentadlene ~ trans-1, 3-pentadiene >>>>
2-methvl-1-butene > ~-methyl-2-butenc.
The Jat~ sho\vn in Table XI I was obtained by passing the above
individual feeds through the packed (316 SS) reactor in a diluting
stream of steam and nitrogen for one seconJ at 650°C.
·nH~ major reactions for l, 3-pentaJiene were isomerization and
cyclization. TI1c isomerization of trans-1,3-pentadiene to the cis
Ti\B
LL
X
I
Col
llpo
siti
on b
y
\\'e
ight
o
f L
he
"Pu
rc11
C
ompo
nent
F
eeds
\Vei
gt1t
P
erce
nt
tran
s-1
,3-
cis
-1,3
-cy
c1op
L;n
tene
2
-met
hy
1-
2-m
cth
yl-
iso
pre
ne
Fee
d p
enta
J.ie
nc
pen
tad
icn
e
1-b
utc
nc
2-b
ute
Hc
tran
s-1
,3-p
cn
tad
ien
c
91
.0
7.0
2
.0
cyc1
op
ente
ne
99
.5
2-m
eth
yl-
1-b
ute
ne
99
.6
2-m
eth
y1
-2-b
ute
ne
98
.1
] . 3
pip
ery
len
e 6
9.5
1
2.6
1
6.1
1
.8
TABLE XII
Dehydrocycli:ation Products Obtained from the ''Pure:' Component: Feeds
Feed ComE anent trans -1,3- cyclo- 2-methyl-
\\'t 0 Composition pentadiene pentene 1-butene ·v
1,3-butadiene 10.7 0.4 0.2
2-methyl-1-butene 61.7
~- ;nethy l- :-butene 9.~
3-methyl-1-butenc 9.7
isoprene 0.5 7.1
trans-1,3-pcntadiene 45.4 0.6 0.6
cis-1,3-pentadiene 26.5 0.4
cyclopentcne 1.8 65.5
cyclopentaJicne 5.1 26.5 0.6
58
2-methyl-2-butene
0.6
13.6
66.:
4.3
8.2
0.3
0.1
<0.1
<0.1
59
. b , . I . 98 1somcr ecomes more preaomln~t as t 1e temperature 1s 1ncreased .
Th i.s J.ccotmts for the relatively lo\v conversion of the cis 1somer.
1t also indicates higher temperatures will be required to accomplish
the c~·cli:~tion, since the reactive intermediate must. be in the cis
configuration.
As sho\m, the dehydrogenation is the most prominant reaction
for cyclopentene, \oJhi le the methylbutenes both isomerize (H-Shift)
;tnJ JchyJro~cnate readily. The products 3.re tabulated according
to retention times and identity in Table XIII.
The results for the thermal conversions of piperylene within
bot}1 packed and unpacked reactors are presented in Table XIV. The
conversions are lower in the absence of any packing, however, the
sclccti\'ities are greater. The maximum once through yields of
cyclopentadiene were obtained at 700°C in both the packed and
unpackcJ reactors. In the unpacked reactor the reaction was 38~o
selective toward producing 18 weight percent cyclopentadiene, while
only .:::s l~ selective to yield an equivalent amount of product in the
prcs0nce of the packing.
The effect of surface on the convers1on of piperylene is
illustratcJ in Figure 7. The conversions in the reactor packed with
stainless steel are greater, indicating a surface reaction. TI1e
maximum selectivity is less, and shifted to the lower temperatures
for the pa.ckcd versus the tmpa.cked reactor. This indicates the
optimum temperature for the reaction ls lower in the presence of
the stainless steel packing, but a more efficient conversion takes
Peak ~umber
1 /
3
' -t
5
6
-I
8
9
10
11
1~
13
14
15
16
17
18
19
~0
TABLE XIII
Retention Time and Identity of Products Found jn Effluent Stream
Retention Time* (min) Identity
3.26 methane
3.45 ethane/ethylene
3. 76 propane
-L 01 propylene
4.55 1-butene
5.06
5.46 trans-.2-butene
5.80 cis-2-butene
6.24
6.58 1,3-butadiene
7.29
7.85 ~-methvl-1-butene .;
8.35
8.89 2-methyl-2-butene
10.~2
11.53 isoprene
12.14 cyclopentene
60
13.73 trans-1,3-pentadiene
14.77 cis-1,3-pentadiene
16.~2 cyclopentadiene
* Retention time decreases as column ages.
Tem
p.
Run
jc
C)
Al
600
A2
650
A3
700
A4
750
AS
550
A6
600
A7
650
A8
700
A9
550
AlO
60
0
All
6
50
TABL
E X
IV
Resu
lts
of
the Th
erJo
~LJl
ly
Init
iatc
J
Dch
yJr
ocy
cli
:ati
on
o
f P
ipcry
lcn
e
j n
a P
ack
ed
and
U
np
acke
d I~cactor
To
tal
Co
nta
ct
I Iy
dro
cu rh
on
Sele
cti
vit
y t
o
Tim
e (s
ec)
Dil
ute
nt
Pac
kin
g
Co
nv
ersi
on
C
ycl
op
cnta
die
ne
1.0
st
eam
s.
u 3
4.0
l.U
st
eam
--
. 1
4.3
4
2.7
1.0
st
eam
4
3.
<-l 3
7.8
1.0
st
eam
8
8.2
1
.9
1.0
st
eam
31
6SS
2
c •
J 3
0.8
1.0
st
eam
31
6SS
1
0.5
3
3.3
1.0
st
eam
31
6SS
27
.3
33
.3
1.0
st
eam
31
6SS
6
4.3
2
7.5
1.0
n
itro
gen
31
6SS
2
.0
41
.1
1.0
n
itro
a en
5
316S
S
9.8
2
8.7
1.0
n
itro
gen
31
6SS
7
3.4
2
0.3
K
}\
t/c
t/c
Cal
c.
---
1. 7·
~ 1
.69
1.6
b
1. 6
·l
1. 6
3 1
.59
1.4
2
1.5
5
2.0
8
1.7
3
1.7
9
1.6
9
1 . 7
.3 1
.64
1.7
1
1.5
9
2.2
8
1.7
3
1.7
4
1.6
9
1.6
7
1.6
4
0\
1--l
Run
Al
A2
A3
A4
AS
A6 A7 AS
A9 AlO
All
1ABL
E X
IV
(co
nt.
)
Resu
lts
of
the
Th
erm
all
y
Init
iate
d
Dch
yd
rocy
cli
zatl
on
o
f P
ipery
lcn
e
]n
a P
ack
cJ
and
Unp
acke
d R
eacto
r
\\'e
igh
t P
erc
en
t in
P
rod
uct
T
ran
s-1
,3-
Cis
-1,3
-C
yclo
-C
ycl
op
ente
ne
Pen
tad
icn
e
Pen
tad
ien
e
Pen
tad
icn
e
1,3
-Bu
tad
icn
e
15
.4
45
.9
26
.4
] . 7
1
.5
13
.2
41
.4
25
.0
G.1
4
.8
5.0
2
5.2
1
5.5
lb
.4
15
.9
3.2
4.
7
3.3
1
. 7
2.1
17
.6
53
.0
25
.5
0.8
0
.5
15
.6
46
.1
25
. 7
3.5
3
.1
11
.2
37
.6
21
.7
9.1
9
.0
4.6
2
2.9
1
3.4
1
7.7
1
7.9
17
.1
54
.2
23
.8
0.7
0
.3
16
.0
45
.7
26
.2
2.8
3
.0
3.1
1
4.9
8
.9
15
.3
20
.1
2-~.Icthy-f~ 1
-til
ltL
·ne
and
J-
Pcn
tC11
e
6.o
5.0
3.7
1.7
0.5
0.6
0.7
0.8
0.6
0.7
Q\
N
Figure '· Effect of Temperature on the Conversion of Piperylene and Selectivity to Cyclopentadiene in a Packed and Unpacked Reactor.
64
place i.n its absence. The stainless steel is apparently acting as
a catalyst for the desired Jehydrocycli:ation reaction, however,
it is :1lso .Lctin.s, to a greater extent, to adsorb and crac1: the
pipcrylene.
The presence of steam increases the selectivity of the
reaction by reducing cracking. This is shown in Figure 8. The
ste3m may exert this effect by maintaining a clean metallic surface
free r~ro;n carbon or met31 carbide. ~Ji trogen used alone as the
dilutcnt does not have this effect. To support this assumption,
the metal surfaces \"·ere coked by passing the gaseous feed through
the reactor at a very slow rate in order to crack it severely.
Some condensed data obtained for the reaction over both a "clean"
(Runs 1:\ and~:\), and coked (Runs lB and 2B) surface are in Table XV.
As ii1JicateJ by the higher conversions and lower selectivities
(Runs lB and ~B), the coke effects the type of reaction occurring
\-Ji thin the reactor. Since the undesirable cracking reaction occurred
more extensively in the presence of excess coke, steam was routinely
employcJ as the Jilutent to help remove the carbon deposits during
operation.
Figure 9 depicts the effect of contact time on the conversion
and selectivity of the reaction. As the contact time increases,
so docs the conversion. This is expected, since at the longer
contact times the true thermodynamic equilibrium for the primary
reactions arc being approached. But the lonoer contact times also ~
enables the undesired secondary reactions of the pr1mary products
(l)
s:: (l)
·~ "'0 ("j
~ c::
Co.. I
t") .. ..... c 0
•P'f .,. ,..... (l)
> c 0 u Q~
100
90 60
80
0 so o\o
70 (/) (1) ...... ro • n rt
60 :J .....
40 <: ~·
+ + rt '<
so n .. "< n 1-'
30 0 ""0
0 ~ 0 ,_j
rt ~ 0.. ..... ro
30 20 ::l I CD
/, ' 20 ;·
10 '/
10 ~= ~/
550 600 650 700
Temperature (oC)
Legend:
Stearn
..., Nitrogen ~ J ~
F·gure 8. Effect of Temperature on the Conversion of Piperylene and Selectivity to Cyclopentadiene in the Presence of Nitrogen and Steam Dilutents.
65
Temperatur~
Run
(o
C)
lA
600
1!3
600
2A
650
213
650
TA
BLE
XV
Cra
ckin
g
Dat
a O
bta
ined
in
a
Cle
an
anu
C
oked
l~vactor
Co
nta
ct
Co
nv
ersi
on
o
f S
ele
cti
vit
y t
o
Tj
lltC
(s
ec)
~ i
pcr
ylc
nt!
C
ycl
op
cnta
die
nc
1.2
3
8.7
3
5.1
1.2
7
5.8
2
7.3
1.0
7
3.4
2
0.3
1.0
7
6.2
1
.8
Co
le
no
ye
s
nu
yes
Q\
0\
n> c: Q)
•M
-o '"' ._.;
= '.)
I
t'i ... ~
c c ·~ •r
;... CJ ~ c c u ~":)
100
-f I
90 j_
I 60
l I
80 •
so 70
/
/ 60 /
/ 40
/
t I 50
I , -----·---- 30 ' ~
. ! () ""T'"
t +- ' -+
30 1J 20
I
20
10
10
• ••
0.~ 0.5 1.0 1.5 2.0
Contact Time (sec I
Figure 9. Effect of Contact Time on the Conversion of Piperylene and Selectivity to Cyclopentadiene Over a Stainless Steel Bed.
67
o\o
(f)
ro ~
ro (')
rt ....... < ....... rt '<
n '< (') ,...._. 0 ~ (i)
=' r+ p.l 0.. 1-'.
(i)
::l (i)
68
to occur. The _;cl ecti \"i ty incrcn.ses tvi th increasing contact time,
rc~chcd J. max1rnum at about 0.8 seconds, and then decreases. This
inJi~atcs a cont~ct time of 0.8 seconds as the ontimum under the ..I.
spec~ fi cd conJi tions. .-\bove 3.nd below this point, the secondary
reactions are predominant.
Both the conversion of the piperylene and the selectivity
toward cyclopentadiene are increased in the presence of hydrogen
sulfiJ~}. :\ sum.rnarv or the results obtained using hydrogen sulfide
as a promoter are shown in Table XVI. The increase 1n conversion
and selectivity 1n the presence of hydrogen sulfide at various
temperatures 1s compared to that 1n the presence of nitrogen as
the dilutent in Figure 10, and to that in the presence of steam as
the dilutcnt 1n Figure 11. In the presence of hydrogen sulfide,
the con\'crsion increases linearly with increasing temperature,
\\"hcrcas in the presence of nitrogen, it increases slo\vly to ~10 9s
~t 600°C and then abruptly to 70~; at 650°C. In the presence of
steam, this increase in conversion is less abrupt, being about 11 qo
at o00°C and ~hS~, at 700°C. TI1e selectivity for the unpromoted
rcJction tends to decline over the s1:.ated temperature range.
llo,.,·cvcr, 111 the hydrogen sulfide promoted reaction_, the selectivity
increases \vi th the temperature. This indicates that \vithout the
promoter, the secondary reactions are occurring to a greater extent
\vi th increasing temperature.
The superior conversions and selectivities observed when
hydrogen sulfide is used as a promoter are thought to be due to its
TABL
E XV
I
Res
ult
s o
f th
e
lly
Jro
gL
:n S
ulf
ide
Pro
mo
ted
D
ch
yd
rocy
cli
z.;
ltju
n o
f P
ipcry
lcn
L:
To
tal
K
Tem
p.
Coi
l tact
~lo lc
~o
or
lly
dro
carb
on
S
ele
cti
vit
y t
o
h t/
..:.
Run
(a
C)
T:i
mc
( S
0C
) P
rom
ote
r P
I\)m
otcr
C
on
ver
sio
n
Cy
clo
pcn
tad
icn
e t/
c
Cal
c.
---
--
B1
50
0
2.0
11
s 2
200
1 :~.
6 3
6.0
1.8~
1.7
3
B2
600
2.0
II
2S 20
0 4
0.0
3
9.4
1
.83
l.
b9
B3
650
1.0
H
S
2 50
4
3.0
4
1.0
1
. 72
1.6
4
B4
65
0
1.0
II
2S
10
0 5
9.6
5
8.6
1
.72
1
.64
BS
650
1.0
ll s 2
200
50
.6
53
.8
1.6
o
1.6
4
B6
65
0
2.0
H
S
2 20
0 6
6.0
4
7. 9
1
.77
1
.64
B7
650
3.0
11
2s 20
0 6
6.9
4
1.1
1
.80
1
.64
B8
70
0 2
.0
li s 2
200
91
.8
53
.2
2.0
7
1.5
9
Resu
lts
of
thC
:: H
yd
rog
en
S
1tl
fid
e
Pro
mo
tcJ
Dch
yJr
o'"
·ycli
zati
un
o
f P
ipcry
1cn
c
\~ejght
Perc
en
t lT
I P
roth
Jct
Tra
ns-
1,3
-C
is-1
,3-
Cy
clo
---
~-_ ~
I c th
y 1
-l
-B
ut c
n e
R
un
Cy
clo
pen
ten
c
Pcn
taJi
ene:
P
cnta
dic
nc
Pen
t ;1 J
icn
c
1,3
-Bu
tad
ien
e
~uHI
]
-r\ ... '1
1 t
CJl
L'
-----
B1
16
.2
~~ 3
. 9
24
.1
·1. 9
0
.4
3 . (
)
B2
12
.2
24
.2
13
.2
10
.3
4.7
7
.9
B3
9.9
2
8.9
1
6.8
1
7.6
8
.0
B4
10
.5
18
. 1
10
.5
3-'1
. 9
6.8
3
.3
BS
13
.9
21
.2
12
.6
27
.2
5.7
B6
10
.3
14
.6
8.2
3
1.6
8
.5
B7
10
.9
13
.7
7.6
2
7.5
9
.8
BB
3.4
3
.1
1.5
4
8.8
7
.5
100 + 90 90
80 /0
/ 75 o\o
70 • (/) (1) . CD c I , ~
Q) /cf CD •P"'4 n ~ rt ("j
60 ......
+J 60 < c: ......
rt 0.. '<
I t'} n
... so ~ "< ~
c 0
$-4 Q)
> c 0 u o·!=J
n ~
45 0 "'d
0 + ~ .,.I
~~ rt Pl ~ !-'•
CD 30 30 ==' ('!)
20
0 15
+ 10
/ " -----
550 600 650 700
Temperature (oC)
Legend:
J Nitrogen
._, J ~ Hydrogen Sulfide
Figure 10. Effect of Hydrogen Sulfide and Nitrogen on the Conversion of Piperylene and Selectivity to Cyclopentadiene at Various Temperatures.
71
! 1 ou ...
so
70
60
~0 l 10
550
Legend:
.) ~ Steam
I I
/
,.
I
600 650
T t ( OC) empera ure
IIydrogen Sulfide
90
75
60
45
30
15
I
700
Figure 11. Effect of Hydrogen Sulfide and Steam on the Conversion of Piperylene and Selectivity to Cyclopentadiene at Various Temperatures.
72
73
abilitY to act as a chain carrier. The proposed mechanism for the
' ..... . . . ,. . . f I_j t h. 74 ~ . . promottJll reaCL.lon, :1 moa1rlcat1on o 1U c lngs mecnan1sm, 1s
dep.i.c:cd i.n Fi~urc 12. The mechanism for the thermal decomposition
of l, .3-pentadiene is sho\vn in Figure 13. In both mechanisms, the
initiating step is the homolysis of 1,3-pentadiene to form the
pentadienyl free-radical and a hydrogen atom. For the promoted
reaction, the hydrogen atom reacts with hydrogen sulfide to produce
r1olcculJr ~1ydro~en and a sulfhydryl free-radical (the chain carrier).
The chain carrier can then abstract an allylic hydrogen from
1,3-pent:ldiene to 11roduce the intennediate pentadienyl radical.
In order to produce cyclopentadiene, this radical must isomerize
to the cis configuration, transform to the boat conformation,
cycli:~ to the cyclopentadienyl radical which then can eliminate a
hyJro.:;cn :1tom to fonn cyclopentadiene. For the unpromoted reaction,
the chain carrier may be a methyl free-radical produced by the
crackin~ of 1,.3-pentadiene to butadiene.
rhc effect \vhich various amounts of hydrogen sulfide has on
the con\·crsion and selectivity is illustrated in Figure 14. As the
pcrccnta~e of hydrogen sulfide Ll00~~ = 1:1 mole ratio of piperylene ..,
c.onccntratc/ll...,S) is increased, both the conversion and selectivity
increase, pass through a maximum, and decrease in parallel. This
decrease at higher hydrogen sulfide concentrations might be explained
by the follow:i.n.g scheme which invol vcs the formation and consumption
of sulfhydryl radicals.
I n i t i :it i on ,
-/
rJropagation H· +
I I
Tcrmin3tion • SH + H·
• SH + • SH
H7 S,., ~
Ovcr:1ll
----..:; H2 + • SH
~--
~ H2S
~
H2S2 ...:---
H") + s_.,
-
------. \'
'\ I
.\ +
+ H•
Fi gurc 12. ~lechanism for the Hydrogen Sulfide Promoted Dchydrocycllzation of 1,3-Pentadiene.
74
75
Initiation
Propagation H· + )
> ~ + • CH3
> ~. +CH4
~ ~ ~ • ~
~ ~ 111 + H· JV ~
Termination
Overall 2
Figure 13. Mechanism for the Thermally Initiated Dehydrocyclization of 1,3-Pentadiene.
<lJ c:: <lJ
•rl
-::; r: +-J -.... ~..)
-I
tl"'}
~
c c ...... ,,.. ;..... () ;... ,....
G u ~;)
100 (_
l I
~0 I
+ 90
~0
75 o\o
70 en (D ~
(D (')
rt
60 ~~~' ,, 1--1•
60 < ,_. . rt
I / --~ , ·e
~ / ~
so
I / n
!'' '< n
+-; -;.. .,._... I 0 •• 45 ~
·l 0 J: Q :::! rt
t PJ 0.. !-J•
~0 ("!)
30 :::l (D
20 )
15
10
so 100 150 200
~ Hydrogen Sulfide
Fi.~;urc 14. Effect of Hydrogen Sulfide Concentration on the Conversion of Piperylene and Selectivity to Cyclopentadiene.
76
77
l I • + Ii.,S ----}- H2 + HS •
~' ' --../';/-......,'-..... H S ~''-~"-.. ./ . + -----? + HS • 2
HS • + HS •
/ H.., +
The hydrogen sulfide can react \vith any free radical present, or
"'i th the re~ctor \-walls to form a sulfhydryl radical. With large
excesses oi hydrogen suliide, greater amounts of the sulfhyciryl
radical form. With increasing concentration of these radicals,
l:hc prooaoi 1 i ty th:1t they \\·ill react \"Vi th each other lS greater
than the prob:1bility of reacting with 1,3-pentadiene to form the
pcntadicnyl radical. \\"hen t\\'O sulfhydryl radicals react, they
can either dissociate back to the radicals or decompose to elemental
hydrogen and sulfur. If this decomposition is significant:~ the
reaction uf the pentadiene will tend to follow the thermal reaction
patiHvay rather than the promoted patln.;ay.
The effect \lihich contact time has on the convers1on and
selectivity is illest:rated in Figure 15. As expected, the conver-
sion of piperylene increases with increasing time spent inside the
reactor. The relatively small slope of the conversion curve
illustrates the Jbility of the hydrogen sulfide to suppress the
secondary reactions (c.f. Figure 9). The decrease 1n selectivity
100 l I
90 I + 90 I
80
75 o\.o
Q) 70 (/) (1)
c:: ~
C) ro • r-1 ()
""'0 rt ,... ........ +-J 60 ~
60 < ::: / ........ ".) rt
'-": I .B--__
tr. • ---------- n "' so "< - ()
--& ~
r- 0 ..... I 45 ,.... '"0 ._. .......
..J.
s.... C)
> c 0 u e,.':l
. ~ L)
f 30 30
~0 l I 15
10 t I
1. 0 1.5 2.0 2.5 3.0
Contact Time (sec)
Fl~urc 15. Effect of Contact Time on the Conversion of Piperylene and Selectivity to Cyclopentadiene in the Presence of Hydrogen Sulfide.
ro rt ~ n. ........ (i)
::s ro
78
79
as the ~outact time 1s increased indicates that the secondary
reactions ·.·ierc not ~:ompletcly suppressed. Also, over the range
of contact t L1:1es observed, the selectivity \vas constantly decreasing
...1nd J.iJ not p3.Ss through a maximum as in the tmpromoted reaction
(c.f. Figure 9). This indicates the maximum selectivity might be
at a contact time of less than one second at these reaction
conditions.
The J~ta obtained for the reaction over the sulfided 316
stainless steel packing, both in a diluting stream of nitrogen
and in sulfur dioxide, are shoh'Tl in Table XVII. The effect which
the sulfided 316 stainless steel packing had on the conversion and
selccti\·ity is compared to that of the metal itself in Figure 16.
'l11is comparison indicates the sulfided stainless steel causes less
cracking or other side reactions than the unsulfided stainless
st~el. The conversions of the piperylene are also more selective
to cyclopcntadicne over the sulfided metal.
The conversion and selectivity with respect to temperature in
the presence oi sulfur dioxide is sho\m in Figure 17. No firm
conclusions can be made \vith regard to the pTesence of sulfur
JioxlJe Juc to the small nwnber of runs. Experimentation was
terminated a short time after it began due to mechanical problems
associated with it, i.e., rapid corrosion of brass needle valves.
In 11encral sulfur uioxic.le seems to increase the selectivity of .._"'0 '
the reaction ~t the lower temperatures but offers no assistance at
the elevated temperatures employed.
Run
Cl
C2
C3 C4
cs
C6
TA
ilLl:
XV I
I
Hesu
lts
of
the
Och
yd
rocy
l:li
zati
on
o
f P
ii1
0ry
lcn
c O
ver
a
Su
lfid
e S
tain
less S
teel
BeJ
in
th
e
Pre
sen
ce
and
A
bse
nce
or
~;t
llfu
r D
juA
iJe
Pro
mo
ter
To
tal
Tem
p.
Co
nta
ct
or
~lole
0 o ll
yd
rocarb
on
S
ele
cti
vit
y to
K
( O
C)
Tim
e (s
ec)
Pac
k:i
ng
D
ilu
ten
t P
rom
ote
r C
on
ver
s:io
n
Cy
clo
pen
t3Ji
cn
c
-t/~
65
0
0.5
S
ul
fid
cd
n
itro
gen
1
0.0
3
1.0
1
.71
31
6SS
650
1.0
II
n
itro
gen
2
9.4
3
5.7
1
.70
65
0
2.0
II
n
itro
gen
4
5.6
2
8.9
1
.73
550
2.0
II
so
2 20
0 2
1.6
4
2.1
1
.86
650
2.0
"
so2
200
59
.9
33
.9
1.
85
700
2.0
"
so2
200
85
.3
24
.4
1.4
5
K t/
c
Cal
c.
---
1.6
4
1.6
4
1.6
4
1.7
3
1.6
4
1.5
9 00
0
Run
Cl
C2
C3 C4
cs
C6
TA
bL
E
X\'
1(
(co
nt.
)
Res
ult
s o
f th
e
Uch
yd
rocy
cliz
atio
n o
f P
ipcr
ylc
nc
(J~,
•cr
a S
ulf
ide S
tain
less
S
teel
BL.:J
in
th
e
Pre
sen
ce
and
A
bse
nce
o
f ~~
tllf
ur
Dio
.\.i
dc
\vci
gh
t Pcr~ent
in
11 ro
du
ct
Tra
ns-
1,3
-C
is..:
-1
3- ' C
ycl
o-
2-~Jcthyl-l-
Bu
ten
e C
ycl
op
ente
ne
Pen
tad
j enc
: P
cnta
d:i
cne
Pcn
tad
icn
c 1
,3-B
uta
die
ne
Jnd
1-P
cntc
nc
----
----~ --
----------
15
.4
45
.7
26
.7
5.1
3
.6
0.8
11
.6
36
.1
21
.2
10
.5
8.4
1
.7
7.9
2
8.6
1
6.5
1
3. 2
1
3.5
2
.2
10
.6
42
.8
23
.0
~.1
1.3
4
.3
4.7
2
2.3
1
2.0
2
0.3
1
1.5
3
.9
1.3
7.
7
5.3
2
0.8
1
8.6
1
. 2
100
90 90
80
75 o\o
Q) 70 Ul C1)
c:: ..._. Q) C1) ..... n
"U rt ("j
+-J 60 .......
c 60 < ..... ~ rt
Q. / "< t") + n .. so / "< ........
c:: 0 ..... VI
<!)
> c 0 u oP
(') ..._. 0
p /~ 45 "'0
40 /
30 /lo-r- 30
20 rf' I /
I + ~ 15
10 • \
0 b
0.1 0.5 1.0 1.5 2.0
Contact Time (sec)
Legend:
, Sulfided 316 Stainless Steel
, 316 Stainless Steel
Figure 16. Effect of a Stainless Steel and a Sulfided Stainless Steel Bed on the Conversion of Piperylene and Selectivity to Cyclopentadiene in Relation to Contact Time.
(1) ::::3 r1' ~ 0.. ....... (t) ::s (i)
82
C)
c:: ()
•1""'1
.... '~ ~
:: :,;
-I
r'l
~
c 0
:...... r:; ;.....
= c L,
'='::>
83
lUO l I
90 + 90 I
'~
80 I I 75 o\o
70 (f) (1) ...._. ro
I n rt
60 .. I ,_.. < 60 ,_.. rt ·~
/ n so " '< n ..._.
I' 0
3t----___-----I 45 -:J
/
.; [) / ()
~ ~ -- --- rt
---~- PJ
~ 0..
/ .......
30 ()
+/ 30 :::::1
/ {,)
1-
'-.J
20 e
I 15
10
550 600 650 700
Figure 17. Effect of Temperature on the Conversion of Piperylene and the Selectivity to Cyclopentadiene in the Presence of Sulfur Dioxide.
84
The Jat:.1 for the silica gel and alumina catalysts are shown
in TJ.blc XVIII. The conversion and selectivity for the reaction
un sili.c:.1 ~el \·w"ith respect to contact -rime are shown ln Figure 18.
The reaction on silica gel follows the same general trend as on the
stainless steel packing (c.f. Figure 9), however, its surface is
more inert in regard to cracking reactions. It does provide some
cracking surface ho~ever, since the conversions are unselectively
incr'~3scJ in its presence as compared to an empty reactor (c. f.
Figure 7). Due to the lack of acidity of the silica gel surface,
the reaction should involve free-radicals and proceed by the
mechJnism:-.f depicted in Figure 13. The alumina was found to be very
acti \'C in converting the piperylene. This is shown in Figure 19.
The high Jctivity of the alumina is due to its acidity. The
selecti\·ity of the reaction over the alumina follows an interesting
path. At the short contact times, it is relatively high; however,
JS the contact time is increased, the selectivity decreases, passes
throu~h a minimum and then slowly starts to increase. It may be,
that J.s the cont.:1ct time increases from :ero to 1.5 seconds the
amount of cracking \vill increase. At the longer contact times
however, carbon is being deposited at a faster rate than it can be
removed by the \vater gas reaction. TI1ese carbon deposits may block
the acid sites of the alumina, thus decreasing cracking and increas-
1ng the selectivity of the primary reaction.
Olefin isomcri:ations, both double bond and skeletal, over
alumina have been interpreted to involve carbonium ion mechanisms.
Tem
p.
Run
( O
C)
Dl
600
02
600
03
600
04
650
DS
650
D6
650
07
650
08
65
0
09
55
0
D10
5
50
011
600
012
600
013
600
Co
nta
ct
TAB
LE
\VI
I I
l{cs
u1ts
o
f th
e
Dch
yd
rocy
c1iz
atio
n
o!"
P.ip
cry]
t.;Jl
C
Ove
r S
il]c
a G
el
and
A
lu11
1ina
C
ata
lyst
B
eds
To
tal
Hy
dro
carb
on
S
ele
cti
vit
y
to
Tim
e (s
ec)
Cata
lyst
D
ilu
ten
t C
on
ver
sio
n
<:yc
l op
enta
die
ne
0.5
Si
O.J
st
eam
5
.9
16
.9
.... 1
.0
5]0
2
stea
m
8.3
1
9.2
2.0
S
i02
stea
m
20
.2
11
.4
0.5
S
i02
stea
m
27
.0
30
.7
1.0
S
i02
stea
m
30
.3
32
.3
2.0
S
]02
st
eam
5
6.2
2
2.6
3.0
S
i02
stea
m
82
.8
16
.1
5.0
S
i02
stea
m
97
.1
0.5
1.0
A1
203
stea
m
10
.5
10
.0
2.0
A1
2o 3 st
eam
1
2.3
9
.8
0.5
A
l 2o 3 st
eam
2
9.1
2
5.4
1.0
A
l 2o 3 st
eam
4
3.5
1
8.4
2.0
A
l ')0
'"?
st
eam
54
.1
1
8.3
....
.)
Kt/
c K
t/c
Cal
c..
2.
3l)
1
.69
2.2
4
1.6
9
2.1
7
1.6
9
1.7
0
1.6
4
1.7
0
1.6
4
1. 7
1 1
.64
1.4:
-1
1.6
4
1. 7
5 1
.64
2.0
1
1.7
3
1.9
5
1.7
3
1. 7
7 1
.69
1. 8
0 1
.69
1. 7
9 1
.69
00
t.
n
Run
C
yc1
op
ente
nc
01
17
.6
02
17
.5
03
17
.0
04
13
.1
DS
11
.6
D6
7.3
07
2
.9
08
0.6
D9
16
.6
010
16
.8
011
11
.7
012
9.1
01
3
6.7
T A~ . E
XV
1 I
I ( c
on
t .
)
Resu
lts
of
the
Deh
yd r
ocy
c 1
i z at
jon
o
f P
i pcry
L ~.-
·nc
Ov
er
S i
1 i c
a G
c 1
~u1<
J i\
1 u
mi n
a
Cat
; 11
y s
t B
e J s
\1/ej
gh
t P
erc
en
t ]_
Jl
1>ro
duct
T
ran
s-1
, 3
-C
is-1
,3-
Cy
clo
-P
enta
dic
ne
Pen
tad
i.cn
c P
cnta
dic
nc
1,3
-Bu
tad
icn
c
---------
51
.8
21
.9
1.0
0
.3
49
.7
22
.2
1.6
0
.5
41
.6
19
.2
2.3
1
.2
36
.5
21
.5
8.3
5
.8
34
. 8
20
.5
9.8
7
.5
22
.2
13
.0
12
.7
9.3
8.0
5
.6
13
.3
12
.1
1.4
0
.8
0.5
0
.3
46
.4
23
.0
1.0
0
.6
45
.1
23
.1
1.2
0
.7
36
.4
20
.6
7.4
1
.6
29
.4
16
.3
8.0
2
.0
24
.3
13
.5
10
.0
2.6
2-~lethyl-1-Butene
:llld
1
-Pcn
tcn
e
----
----
----
--..
....
....
...-
---
1. 6
')
~·
.... ,.)
-~.
9
1.8
1.8
3.0
6.6
0.2
1.9
1. 6
8.0
10
.8
11
.9
87
I I
.30 T 30
I
o\O
~ (/)
s:: (t)
u ....... 20 + • 20 CD
n --' I r+ ·~ ------- p....J•
._J < c .......... () c ""
)o-1•
r+ I " ' '<
t.r: " n \,
" '< ()
,- _,.. ~
l 0 c \ '"d
Cf'. +- ro s... • ;:::j
/ r+ () 10
/ PJ > /
/ 10 I
~ ' c.. = !-"· ...... /
c._; ~ e· ;::::1
:lo ~/ (D
----~----
0.5 1.0 1.5 2.0
Contact Time (sec)
Fi~ure lS. Effect of Contact Time on the Conversion of ''
Piperylene and the Selectivity to Cyclopentadiene Over Silica Gel.
Q)
c ~
•.-1
v ~ +-l c ':.)
-I
rr:
~
:::: c
• .-1
•r. :... (, ;..... c 0 u ::. ::.
88
10() l l
YO t l
80
75 o\O
70 (f) (1)
~
ro n rt 1-'·
60 60 < 1-'• rt
I -~ '...-: ----so
I ~_.,--
n '-<
/ n ,/ ""
~
45 0 .:t' .__.
-..J
, / (D
40 ~ ...,J
rt
t /
~ /' 0..
/ I-'•
30 (D
• 30 ~ (i)
U,.
~()
+ 15
o.s 1. 0 1.5 2.0
Contact Time (sec)
Figure 19. Effect of Contact Time on the Conversion of Piperylene and the Selectivity to Cyclopentadiene Over Alumina.
89
The results obtained in this study, including cyclization reactions
of pipcrylcnc, ~auld ln\·o l ve the carbonium ion mechanism proposed
1n Fi6ure 20. The presence of the 1-pentene and 2-methyl-1-butene
found ln ~he effluent ~an be explained via this mechanism along
\vi th the isomeri: at ion ability of alumina. That is, the 3-methyl-
!-butene sho\.;n, can isomerize to 2-methyl-1-butene readily. The
cycli:ation reaction should occur only to a limited extent, since
it in\·ol vcs an .intermediate first degree carbonium ion. TI1e
cyclopentadicne found, may be produced by the thermal dehydrogena-
tion of the cyclopentene formed as sho\vTI by the mechanism below:
0 0 I
' • ) 0 or Jircctly from 1,3-pentadiene adsorbed on the metal ('M).
Durj ng all runs, heavy material \.;as obtained. The heavies
\vhich ,,ere identified arc: JicyclopenTadiene, m-xylene, benzene,
toluene, cyclohcxane, and cyclohexene. These products, except
Jicyclopentadiene, are formed through the dimerization of 1,3-
pent aJicnc \1/hich has been sho\vn to proceed as follows, to form
l)l)
3-mcthyl-5-propenylcyclohexene-·.
_, /
r. . 'I("' 1·1 guro - '.
.,.
--.±.
\
"/
'/
"7' ~
//-.._ ',/ ......... , ...... ,
/
R-H
~-[ i· '
R-H I I
'! ~
Proposed Carbonium Ion 0Iechanism for the Cycli:~tion of 1,3-Pentadiene Over Alwnina.
90
91
+
,r;---:. I ' I . \
.I ', \..__
These dimerizations are then followed by dealkylation, dehydrogen-
ation, and isomerization, to yield the above mentioned products.
CONCLUSIONS
Surveying the results obtained 1n this study lead to the
iollo\.:ing conclusions:
92
1. The isomers of 1,3-pentadiene can be separated from the
other components in piperylene concentrate through cuprous ammonium
chloride complexing and subsequent decomposition of the complex.
2. Trans-1,3-pentadiene can be removed from piperylene
concentrate via a Diels-Alder reaction with maleic anhydride. The
reverse Diels-Alder (pyrolysis), to free the trans-1,3-pentadiene,
\\as found to produce many of the components of piperylene concentrate
due to t!1e thermal cracking of the freed trans-1, 3-pentadiene.
~). The concentration of trans-1, 3-pentadiene in piperylene
concentrate can be increased by refluxing with traces of iodine or
catalytic a~ounts of potassiun tert-butoxide dissolved in dimethyl
sulfoxide.
~- The isomers of 1,3-pentadiene can undergo dehydrocycli:
ation tn a catalytic and non-catalytic reaction, for which a free
radicJi mechanism is indicated.
5. The highest selectivity for the dehydrocyclization of
1,3-pentadienc was 60 %. This was achieved using 100 Tiole %
hyJrogcn sulfide promotor, at 650°C and atmospheric pressure with
a contact time of 1.0 seconds.
6. !'fatcT reduced cracking and prolonged catalyst life by
reducing the carbonization of the catalytic surface through the
93
water ~as reaction.
7. The net!1od er.1ployed in vaporizing and preheating the
hvJrocarbon feed ~.:as critical in controlling the extent of cracking
·~,.ri t:J.in the reJ.ctOl'. It Has found, if the dilutent (most desirably
steam) \\as superheated before contacting the hydrocarbon feed the
extent of cracking lvithin t!1e reactor was oinimized.
8. The relatively constant selectivities for the dehydro
cycli:a:i:Jn uf 1,3-pcntac.licne under thermal and heterogeneous
catalytic conditions indicates that a substantial amount of competing
side reactions arc taking place wit!1in the preheater section of the
apparatus.
9. If this project is to be continued, it is suggested that
var 1ous horJogencous free-radical prol!lotors be enployed \~i th
cmpl1asis on lower temperature operation. These may include ~Br,
(\H4)S, various mercaptans, and the like.
10. It would also be desirable to purify the piperyleue
concentrate to ~ain information on the side reactions before
ernbarl,ing in ~ simular project. The most likely method seems to
be an extractive distillation using various nitrogenous bases.
REFERENCES
(1) Stinson, S. C. Chern. Eng. (fe,vs 1979, 57 (22), 32.
(2) ~·oshiaki. ~\'. Chern. Econ. En?". P\ev. 1 074 6 lr8) ~6 _, • ..!... ...... ' - ' oJ •
(3) ~Jattson, G., University of Central Florida, Personal Communication, 1977.
(4) Soday, F. J. U.S. Patent 2 384 855, 1946.
(5) Gaylord, N. G. U.S. Patent 3 491 068, 1970.
( 6) :\i.e lly, T. ln "Encyclopedia of Chemical Processing and Desi.sni'; ~·lcKctta, J. J., Ed.; ~larcell Dekker: New York, 1977; \'ol. 5, pp 110-157.
(7) \':irth, ~·1. ~1. Chern. Prod. 1956, 19, 352.
(8) \\'irth, ~I. ~1. Chern. Prod. 1956, 19, 400.
(9) Chandrasckaran, S.; ~.iark, H. F. In "Kirk-Othmer Encyclopedia of Chemical Technology", 2nd ed.; Standen, A., Ed.; John Wiley and Sons: ~ew York, 1964; Vol. 7, p 77.
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(11) ~·;ells, T. H.; :\'ilson, P. T. Chern. Rev. 1944,34, 1.
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(1.3) Kunt:, I. rn "Encyclopedia of Polymer Science and Technology", Bikalcs, 1\. ~1., Ed.; John ~'!ilcy and Sons: New York, 1966; Vol. ~, pp 563-567.
(14) Ferguson, L. N.; Paulson, D. R. '!Alicyclic Chemistry II"; FJ.anKlin Publishing Cornpa;1y: New Jersey, 1977, pp 47-85.
( 15) Lloyd~ 0. ''Alicyclic Compounds"; American Elsevier Publishing Company: New York, 1963; pp 91-93.
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,
(17) ~letcalf, R. L. In ''Kir~\:-Othmer Encyclopedia of Chemical Technology':, 2nd ed.; Standen, A. Ed.; John Wiley and Sons: New York, 1964; Vol. 11, pp 696-698.
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95
(19) Brooks, G. T. "Chlorinated Insecticides~'; CRC Press: Cleveland, 1974; Vol. 1, Chapter 3.
(20) Morton, 01. "Science and Technology of Rubbern; Eirich, F. R. Ed.; Academic Press: New York, 1978; Chapter 2.
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. ...., ...., ) l-- Taketa, A. Chern. Econ. Eng. Rev. 1976, ~ (3), 26.
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(: ~) Lear~·. R. F. U.S. Patent 2 773 051, 1956.
(~5) Hamner, G. P.; Jones, T. G. U.S. Patent 2 750 359, 1956.
(26) Kudo, K.; et al. U.S. Patent 3 929 747, 1975.
(~7) Goldstein, R. F.; \Vaddams, A. L. "The Petroleum Chemical Industry", 3rd cd.; E. & F.N. Span: London, 1967; Chapter 12.
(~8) Hughes, W. B. In "Homogeneous Catalysis - II"; Forster, D.; Roth, J. F., Eds.; American Chemical Society: Washington, D.C., 1974; Chapter 14.
(29) "Sulfolane Finds ;.Jew Uses In Extraction"; Chem. Eng. News 1964, 4~ r:o), so.
(30) Cr~ig, D. J. Am. Che~. Soc. 1946, 65, 1006.
l31) Craig, D. U.S. Patent 7 347 667, 1944.
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