ppt_petrochem 10 - sem 1 12-13
TRANSCRIPT
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PETROCHEMISTRYBSK3513
Dr. Mohd Hasbi Ab. Rahim
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Reactions and Chemicals of BenzeneOxidation, , Hydrogenation, Alkylation, Chlorination, Nitration
Reactions and Chemicals of TolueneOxidation, Chlorination, Nitration, Carbonylation, Dealkylation, Dispropornation
Chemicals from XyleneTerepthalic acid, Phthalic Anhydride, Isophthalic Acid
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AROMATIC HYDROCARBONS
•Benzene, toluene, xylenes (BTX), and ethylbenzene are the aromatic hydrocarbons with a widespread use as petrochemicals.
•They are important precursors for many commercial chemicals and polymers such as phenol, trinitrotoluene (TNT), nylons, and plastics.
•Aromatic compounds are characterized by having a stable ring structure due to the overlap of the π-orbitals (resonance).
•Accordingly, they do not easily add to reagents such as halogens and acids as do alkenes.
•Aromatic hydrocarbons are susceptible, however, to electrophilic substitution reactions in presence of a catalyst.
•Aromatic hydrocarbons are generally nonpolar. They are not soluble in water, but they dissolve in organic solvents such as hexane, diethyl ether, and carbon tetrachloride.
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Catalytic reforming for aromatics production
Desired reactions in Catalytic reforming
60-90°C cut for benzene90-110°C cut for toluene110-140°C for xylenes
The reactions are:
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Uses of benzene
• Benzene (C6H6) is the most important aromatic hydrocarbon.• Almost all compounds derived from benzene are converted to other chemicals and polymers.• Benzene is not easy to polymerize due to the resonance stabilization of benzene ring.
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Oxidation of Benzene
+ 9/2 O2 + 2 CO2 + 2 H2O
Oxidation of benzene to maleic anhydride, 380 oC, atm. Pressure with V2O5/MO3 cat.90% Conversion with 50 – 60% selectivity.
The main route is oxidation of n-butane
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Hydrogenation of Benzene (production of cyclohexane)
OH
+
O
O2
-H2
H2
HNO3
COOH
COOH+N2O
Hydrogenation which involved an addition of H2 into benzene ring to produce cyclohexane.Ni/Al, Ni/Pd cat. , 160 – 220 oC, 25 – 30 atm.The pressure of H2 play an important role in controlling the catalytic activity and selectivity.
Cyclohexane is oxidized in a liquid-phase process to a mixture of cyclohexanol and Cyclohexanone. (Cobalt acetate & orthoboric acid as cat., 95 – 120 oC, 10 atm).
With similar catalyst at lower temperature and longer residence time produces adipic acid.
Cyclohexane
Adipic acid
2.5 O2
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COOHCOOH COOH
COOH O
OH
OH
OH
OHOH
(current route)
(Noyori's route)
adipic acid muconic acid
D-glucose
(Biocatalysis; Frost's route)
Enviro-friendly routes for adipic acid
O2 COOH
COOH
O2
R. Noyori, Science 281 (1998) 1646 K.M. Draths & J.W. Frost, JACS 120 (1998)10545
J. M. Thomas & R. Raja, Chem. Commun. Feature Article, 675 ( 2001)
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• Alkylation is the introduction of an alkyl group into a molecule • It may involve a new C-C, O-C, N-C bond formation• Alkylation is catalyzed by acidic or basic catalysts
Acid catalysts are used mainly in aromatics alkylation at ring-C
Basic catalysts are used in alkylation at side-chain-C
CH3
+ MeOH
CH3
CH2CH3
CH3
Acid Catalyst
Basic Catalyst
(p-Xylene)
(Ethylbenzene)
Alkylation
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Some important industrial alkylation reactions
Reactants Product Catalyst Process licensors
Benzene + ethylene /EtOH EB ZSM-5 Mobil-Badger /NCL etc
Benzene + propylene Cumene H-Y; H-M; H- DOW, UOP etc
Benzene + C11 – C13 olefins LAB Solid acid/ RE-Y UOP / NCL
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kg
Alkylation of Benzene1. Production of ethyl benzene (EB), C6H5CH2CH3
Colorless liquid with boiling point of 136 oC.
C6H6 + CH2=CH2 C6H5CH2CH3 (AlCl3-HCl, 40-100 oC, 2 – 8 atm)
(Diethylbenzene and higher alkylated also form which later recycled and dealkylated to EB)
Main use of EB: Manufacture of styrene (C6H5CH=CH2)
Dehydrogenation of EB produce styrene
C6H5CH2CH3 C6H5CH=CH2 + H2
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ReactorsTemp. (ºC)WHSV (h-1)PressureBenzene / alc. (mole)Alcohol sel. (%)EB + DEB (%)EB (%)Cycle length (days)No. of cycles
3 beds in series380 – 420 ºC5 – 10 (6)1 - 44 – 15 (5)98958545>25
+ + H2O
CH2 CH3
CH2CH3 OH
Mobil-Badger process is based on ethylene and uses ZSM-5;Other licensors are UOP, CDTECH etc; use other zeolitesCDTECH process uses reactive distillation
Mobil-Badger process
Catalyst is Encilite – pentasil (ZSM-5) type
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Mobil-Badger process
Uses ethylene as the alkylating agentT = 370 - 420°C; P = 7 – 27 bars;
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[Degnan et al. Appl. Catal. A 221 (2001) 283]
Kg
> 40 SPA units have been licensed (UOP
Main use of cumene: in the production of phenol
2. Production of Cumene or isopropylbenzene, C6H5CH(CH3)2
Benzene + propylene Cumene
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Comparison of NCL (H-beta) and SPA catalysts
CATALYST N.C.L. S.P.A.
Mole Ratio (benz./C3) 6.0 8.0
Temperature (°C) 150 210
Pressure (bar) 30 30
WHSV (h-1) 3.5 2.5
Products (wt. %)
Aliphatics 0.003 0.67
Toluene + Ethylbenzene 0.01 0.01
Cumene 22.03 17.18
Di-isopropylbenzene 1.70 1.11
Conversion of propylene 99.99 99.90
Prop. Sel. To Cumene 92.80 89.70
Bromine index <0.1 1-2
CUMENE
NCL processes for alkylation and transalkylation are available
Benzene + propylene Cumene
Process licensors: UOP, CDTECH, Enichem, Mobil-Badger, DOW
Zeolite processes involve a transalkylation (with benzene)step to convert >10 % di i-pr-Bz into cumene
Yield of cumene in zeolite processes is more as transalkylation is not possible with SPA catalysts
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CDcumene process (CDTECH)
Reaction is done in catalytic distillation reactor The catalyst is held in distillation traysA transalkylation reactor converts the di-iprBz.
Features
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H3PO4/zeolite
[O]
N2O
FeZSM-5
TS1
O
OOH
OH
H2O2/
+
(Benzene) (Cumene) (Cumene hydroperoxide)
(phenol)
Phenol production
Phenol is a white crystalline material with a distinctive odor, highly soluble in water andSoluble in weakly acidic solution.Important monomer for phenolic resins, reaction with acetone produce bis-phenol A whichIs important monomer for epoxy resin and polycatbonates., Aspirin, salicyclic acid
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3. Production of linear alkylbenzene (LAB), C6H5CH(CH3)
R
C6H6 + RCH=CH2 C6H5CH(CH3) R
The alkylating agents are either linear C12 – C14 mono olefins or monochloroalkanes.Alkylating with olefin is industrially preferred
Normally to produce biodegradable anionic detergents.
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UOP
Evolution ofLAB processes;BecomingGREENER
Benefits in product quality - use of solid acid
Green
Catalyst
AlCl3
AlCl3
HFSolid acid
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Production of LAB Alkylation of benzene with C11 – C13 olefins
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Heavy alkylates
H2 rich off gas
Distillation
N-paraffin recycle
ParaffinRecovery
BenzeneRecovery
Alkylation Solid-acidCATALYST
Make up H2
PACOL
DehydrogenationPt/Al2O3
SelectiveHydrogenation
DEFINE
Fresh n-paraffin
H2 recycle Fresh benzene
Ben
zene recycle
LAB
Linear alkyl benzene (LAB) using a solid-acid catalystLinear alkyl benzene (LAB) using a solid-acid catalyst
Detal process for Linear Alkyl Benzene production
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Industrial alkylation Processes
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Chlorination of Benzene
Electrophilic substitution reaction in which Cl serve as electrophile.
Lewis acid i.e. FeCl3 as catalyst, 80 100 oC, atm. Pressure.
The products are a mixture of mono- and dichlorobenzenes. The ortho- and the para-Dichlorobenzene are more common than meta-
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Nitration of Benzene
Electrophilic substitution reaction in which (nitronium ion) NO2 serve as electrophile.
Concentrated nitric and sulfuric acids as catalysts at 50 oC.
HNO3 + 2H2SO4 2HSO4- + H3O+ + NO2
+
C6H6 + NO2+ C6H5NO2 + H+
Nitrobenzene use to produced aniline, C6H5NH2 (hydrogenation of nitrobenzene), quinoline, benzidine and as a solvent for cellulose ethers.
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Reactions and Chemicals of Toluene
Toluene (methylbenzene) is similar to benzene as mononuclear aromatic, but it is more activedue to the presence of the electron-donating methyl group.
Could produced more polysubstituted products compared to benzene.
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DeAlkylation of Toluene (produce benzene)
DeAlkylation of toluene produce benzene
C6H5CH3 + H2 C6H6 + CH4
(La, Ce, Pr, Nd, Sm, Th or Ni-Cr2O3 as catalyst, 600 – 800 oC or Ni-Al2O3 catalyst at 320-630 oC)
Disproportionation of Toluene (produce benzene & xylene mixture)
Disproportionation of toluene produce benzene and xylene mixture
2C6H5CH3 + H2 C6H6 + C6H5(CH3)2
(450 – 530 oC, 20 atm, CoO-MoO3 on aluminosilicates/alumina catalyst, ZSM5)
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Some important industrial alkylation reactions
Reactants Product Catalyst Process licensors
Toluene + methanol P-Xylene Modified ZSM-5 Mobil
Naphthalene + propylene 2,6-DIPN H-mordenite Chiyoda
Naphthalene + methanol 2,6-DMN Zeolite Rütgerswerke
Biphenyl + propylene 4,4’-DIPB H-mordenite DOW
Alkylation of Toluene
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Oxidation of Toluene (produce benzyl alcohol, benzaldehyde, benzoic acid)
1. Production of benzoic acidC6H5CH3 + 1.5O2 C6H5COOH + H2O
(cobalt acetate, 165 oC, 10 atm)
Benzoic acid is a white crystalline solid, soluble in water and most common organic solvents.
Use to season tobacco, preserve food, make dentifrices, precursor for caprolactam, phenol,Terepthalic acid
Phenol from benzoic acid:
C6H5COOH + 1/2O2 C6H5OH + CO2
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2. Production of benzaldehyde and benzyl alcohol
C6H5CH3 + 1.5O2 C6H5COH + 1.5O2 C6H5CHO + H2O
1.5O2
+ C6H5COOH Esterification
Benzyl benzoate
How to limit over oxidation?
Selective catalyst, short residence time, high toluene-to-oxygen ratio, low reaction temperature
Benzaldehyde use as a solvent for oils, resin, cellulose esters, ethers,As flavoring compound and synthetic perfumes.
O
O
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Chlorination of Toluene
Free radical reaction with Cl resulting benzyl chloride, benzal chloride, benzotrichloride
Benzyl chloride can produce benzyl alcohol by hydrolysis:
C6H5CH2Cl + H2O C6H5CH2OH + HCl
Benzyl alcohol use as precursor for butylbenzyl phtalate, a vinyl chloride plasticizer,Precursor for phenylatic acid which later produced phenobarbital (sedative)
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Carbonylation of Toluene (produced p-Tolualdehyde)
Carbonylation with CO in the presence of HF/BF3 catalyst
C6H5CH3 + CO C6H4(CH3)CHO
C6H4(COOH)2
P-Tolualdehyde use as intermediate in perfume synthesis, dye and in pharmaceutical.
?
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Chemicals from toluene
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(bp, 110 - 140°C)
Reforming(Pt-Re-Sn/Alumina)
Fraction-ation
Xylene iso-merizatrion(Pt-ZSM-5; Pt-Mord.;Pt-MAPO)
Fraction-ation
Arom. Extraction
TransalkylationPt/Mordenite
Mol. SieveSeparation
(PAREX)
Benzene
Toluene
Xylenes + EB
C9+Arom.
DisproportionationPt/Mordenite
Naphtha
o-Xylene
p-Xylene
m- + EB
Raffinate
Production of xylenes
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Xylene isomerization
Catalysts are usually bifunctional typesTypical examples: Pt-ZSM-5, Pt-mordenite& Pt-(silica)-alumina
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Xylene isomerizationXylene isomerization
CH3
CH3
CH3
CH3+
CH3
CH3
+
CH3
CH3
Zeolite
Catalyst: ZSM-5, Mordenite; MAPO; SiO2-Al2O3 loaded with Pt
XYLOFINING developed by NCL-ACC-IPCL in 1986
Mechanism
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Production of Terephthalic Acid (HOOCC6H4COOH)
Oxidation of p-Xylene with cobalt acetate/NaBr or HBr as catalyst in an acetic acid medium,200 oC, 15 atm pressure.
p-Xylene + 3/2O2 HOOCC6H4CH3 (p-Toluic acid) + H2O
HOOCC6H4COOH
Has an annual capacity of approximately 610,000 tonnes and employs over 170 full-time employees. PTA is the key raw material for the manufacture of polyester for fabric, as well as audio and videotapes, and in making plastic drink bottles.
*With 1 tonne of PTA , can make approximately 3,500 car tyres
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Production of Phtalic anhydride ( )
Oxidation of o-Xylene with metal oxides catalyst i.e. V2O5 + TiO2/Sb2O3
Vapor phase, 375 – 435 oC, 0.7 atm, yield about 85%
Liquid phase, 150 oC, Cobalt or manganese acetate in acetic acid medium as catalyst.
C6H4(CH3)2 + 3O2 + 3H2O
Use for producing plasticizer.
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Production of Isopthalic Acid (HOOCC6H4COOH)
Liquid phase Oxidation of m-Xylene with ammonium sulfite
m-Xylene + 2(NH4)2SO3 HOOCC6H4COOH + 2H2S + 4NH3 + 2H2O
Main use for producing polyesters
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