catalytic hydrotreating of middle distillates blends in a fixed-bed reactor
TRANSCRIPT
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Applied Catalysis A: General 207 (2001) 407420
Catalytic hydrotreating of middle distillates blends in afixed-bed pilot reactor
Gustavo Marroqun-Snchez a, Jorge Ancheyta-Jurez a,b,
a Instituto Mexicano del Petrleo, Eje Central Lzaro Crdenas 152, Mxico 07730 DF, Mexicob Instituto Politcnico Nacional, ESIQIE, Mxico 07738 DF, Mexico
Received 24 March 2000; received in revised form 12 June 2000; accepted 18 June 2000
Abstract
An experimental study was conducted in a fixed-bed pilot reactor in order to evaluate the effect of catalytic hydrotreating
on diesel quality by using feedstocks prepared with different amounts of straight run gas oil, kerosene and jet fuel streams. Ex-periments were carried out at constant reaction pressure and hydrogen-to-oil ratio of 5.3MPa and 356.2 ml ml1, respectively.
The effect of reaction temperature and liquid hourly space velocity were studied in the range of 613633 K and 1.52.0 h1,
over a commercial Ni-Mo/-Al2O3 catalyst. The experimental information showed that diesel specifications could be reached
through single stage hydrotreating of these blends at moderate hydrotreating operating conditions. 2001 Elsevier Science
B.V. All rights reserved.
Keywords: Middle distillates; Hydrodesulfurization; Hydrotreating
1. Introduction
Catalytic hydrotreating (HDT) plays an important
role in the modern oil refining industry. The HDTprocess ranks in importance with other petroleum
refining processes, such as catalytic cracking and
reforming. The uses of the HDT process include pre-
dominantly the desulfurization of middle distillates
(kerosene, diesel fuel and jet fuel).
HDT is a catalytic process in which a number of
reactions are involved, i.e. hydrogenolysis, by which
CS, CN or CC bonds are cleaved and hydro-
genation of unsaturated compounds. The reacting
conditions of the HDT process vary with the type of
feedstock; whereas light oils are easy to desulfurize,
the desulfurization of heavy oils is very difficult.
Corresponding author. Fax: +52-5-587-3967.
E-mail address: [email protected] (J. Ancheyta-Juarez).
In view of the new diesel specifications introduced
around the world (Table 1) [15], the demand for
high-quality middle distillates has grown significantly
over the past decade [6]. Gas oils deep hydrodesulfur-ization has achieved much attention since the tolerated
sulfur content in diesel fuel is being lowered more and
more.
It becomes necessary to remove sulfur from the
compounds that are the most difficult to desulfurize,
which are higher molecular weight dibenziothiopenes
(DBT) that contain side chains in positions that limit
the access of the molecule to the active sites on the
catalyst, such as 4-methyl DBT and 4,6-dimethyl DBT
[7].
Straight run gas oil (SRGO) obtained from atmo-
spheric distillation units remains the main source
of diesel fuels, and in some cases, the light cycleoil (LCO) produced in fluid catalytic cracking units
(FCC) is frequently used as HDT feedstock. The
0926-860X/01/$ see front matter 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 6 - 8 6 0 X ( 0 0 ) 0 0 6 8 3 - 9
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408 G. Marroqun-S anchez, J. Ancheyta-Juarez / Applied Catalysis A: General 207 (2001) 407420
Table 1
Specifications for diesel fuels in different countriesa
Property Mexico
PEMEX (a)
US EPA
(a)
US CARB
(a)
Sweden
class I (b)
UK
(c)
Germany
(d)
Europe
(e)
Europe
(f)
Worldwide
fuels charter
API gravity >32 >30 3339 41.145.4 3841.1 >37 >36 >36 3741.1
Flash point, K >318 >327
Viscosity @ 313K, cSt 1.94.1 1.94.1 2.04.1 1.24.0
Nitrogen, wppm 10
Sulfur, wppm 500 500 500 10 50 50 (10)b
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Table 2
Middle distillates and blends properties
Properties SRGO Ka JFb B-1 B-2 B-3 B-4 B-5
API gravity 33.38 40.16 47.12 41.84 39.75 38.57 37.15 36.51
Flash point, K 333 331 317 321 323 328 328 335
Viscosity @ 313 K, cSt 4.10 1.76 0.99 1.71 2.02 2.21 2.73 3.01
Nitrogen, wppm 317 47 9 103 142 179 207 227
Sulfur, wt.% 1.21 0.67 0.21 0.58 0.71 0.81 0.92 0.97Aromatics (FIA), vol.% 26.4 21.8 19.0 21.4 22.3 23.2 23.9 24.2
Aromatics (SFC), wt.% 31.70 24.60 21.04 24.36 25.90 26.85 28.29 28.37
Mono-, wt.% 14.82 17.09 20.04 18.04 17.25 16.36 16.20 15.72
Di-, wt.% 13.42 7.51 1.00 5.59 7.47 8.72 10.21 10.52
Tri-, wt.% 3.46 0.00 0.00 0.73 1.18 1.77 1.88 2.13
Cetane number 54.1 48.0 42.8 47.5 48.9 50.7 50.9 51.9
ASTM distillation, K
IBP 429 409 417 409 414 427 429 418
10 vol.% 543 474 442 452 459 471 475 497
50 vol.% 586 507 461 491 516 532 548 555
90 vol.% 619 536 483 578 599 600 606 609
FBP 637 554 504 616 624 626 630 631
a Kerosene.b
Jet fuel.
These middle distillates were derived from a
crude oil with the following properties: 29.42 API,
2.16 wt.% sulfur, 1848 wppm nitrogen, 6.25 wt.%
Ramsbottom carbon, 4.9 wt.% asphaltenes in C7, and
22 and 111 wppm of Ni and V, respectively.
It can be observed from Table 2 that the three
streams are representative middle distillates (API grav-
ity: 33.38 SRGO, 40.16 kerosene, 47.12 jet fuel).
Kerosene and jet fuel do not present aromatics with
three rings, inclusive the jet fuel has a very low content
of di-aromatics (1.0 wt.%). However, they exhibit a
higher mono-aromatics content compared to SRGO.The total aromatic content is high in SRGO because
it increases with the boiling point of the fraction.
The following blends were prepared with SRGO,
kerosene and jet fuel streams:
B-1: 20vol.% SRGO, 30vol.% kerosene and
50 vol.% jet fuel.
B-2: 33.33 vol.% SRGO, 33.33 vol.% kerosene and
33.33 vol.% jet fuel.
B-3: 40vol.% SRGO, 40vol.% kerosene and
20 vol.% jet fuel.
B-4: 60vol.% SRGO, 20vol.% kerosene and
20 vol.% jet fuel. B-5: 50vol.% SRGO, 50vol.% kerosene and
0 vol.% jet fuel.
The physical and chemical properties of these
blends are also shown in Table 2. They are clas-
sified in an increasing amount of heteroatoms (i.e.
0.580.97 wt.% sulfur for B-1 and B-5, respectively).
Fig. 1 shows the variation of sulfur and nitrogen
contents as a function of API gravity for the different
blends. It can be seen that the higher jet fuel content
(B-1) the higher the API gravity and hence the lower
the heteroatoms content.
2.2. HDT catalyst and presulfiding conditions
The hydrotreating catalyst used in the present study
was a Ni-Mo/-Al2O3 commercial available sample
and its properties are presented in Table 3. This cata-
lyst showed a MoO3/NiO ratio of 4.47.
After loading the catalyst, the reactor pressure was
increased from atmospheric to 6.9 MPa (30% higher
than typical reactor pressure) in order to be sure of
the airtightness of the system. This condition was kept
during 2.5 h. Once the reactor was verify to be her-
metic, the reactor pressure was decreased to 5.3 MPa.
The temperature of the reactor was increased from
ambient to 503 K at a heating rate of 30 K h1 in thepresence of hydrogen (99.8% purity) at a flow rate of
150lh1.
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Fig. 1. Sulfur and nitrogen contents as a function of API gravity.
The catalyst was in-situ presulfided with a desulfu-
rized naphtha (specific gravity of 0.752,
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Fig. 3. Isothermal reactor.
small inert particles, whereas the catalytic conversion
behavior is that of the catalyst in the actual size [9].
The reactor temperature was maintained at the de-
sired level (613, 623 or 633 K) by using a three-zone
electric furnace, which provided an isothermal tem-
perature along the active reactor section.The catalytic bed temperature was measured dur-
ing the experiments by three thermocouples lo-
cated in a thermowell mounted at the center of the
reactor.
The temperature profile was measured at the middle
of each experiment by a movable axial thermocouple
located inside the reactor. The greatest deviation from
the desired temperature value was about 34 K. Threetypical temperature profiles at 613, 623 and 633 K are
shown in Fig. 3. It can be observed that an increase
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in the reaction temperature increased the temperature
differential along the reactor due to the exothermicity
of the reactions.
2.4. Operating conditions in the pilot reactor
Once the catalyst sulfiding was completed, the tem-
perature of the reactor was increased to the desired
reaction temperature and the feedstock and hydrogen
were passed at the required rates.
The hydrodesulfurization of the five blends was car-
ried out at the following operating conditions: reaction
temperature of 613, 623, and 633 K, and LHSV of 1.5
and 2.0 h1.
Reaction pressure and hydrogen-to-oil ratio for all
runs were 5.3 MPa and 356.2ml ml1, respectively. It
was used pure hydrogen in a once-through mode.
Product samples were collected at 48 h intervals
after allowing a 2 h stabilization period under each set
of conditions and mass balances for each run were inthe range 1005% [10].
2.5. Analysis of products
Physical and chemical properties were determined
with the following methods:
API gravity: ASTM D-287.
Total sulfur: ASTM D-4294.
Total nitrogen: ASTM D-4629.
Flash point: ASTM D-93.
Cinematic viscosity: ASTM D-445.
Distillation curve: ASTM D-86.
Cetane number: ASTM D-613.
Aromatics content in feed and products was measured
by fluorescent indicator adsorption (FIA) (ASTM
D-1319), and by supercritical fluid chromatography
(SFC) (ASTM D-5186), which determines aromatics
distribution (mono-, di-, tri- and poly-) in wt.%.
The FIA method has been prescribed by the Envi-
ronmental Protection Agency as a standard method for
specifying aromatics in diesel fuel, which gives the
total aromatics content in vol.%, however, it does not
give breakdown of aromatics distribution.
On the other hand, the environmental legislation
about the aromatics content in diesel fuels has led to anincreased fundamental interest in the detailed nature
of aromatic fractions. In this sense, the SFC method
has been chosen by ASTM to replace the FIA method
for determination of aromatic hydrocarbons content in
diesel fuels. Besides the FIA method does not give
the aromatics distribution, it is applied only for fuels
with final boiling point (FBP) less than 588 K, and
SFC method is valid for fuels in the boiling range of
473673 K [11].
3. Results and discussion
3.1. Effect of reaction temperature and
space-velocity on diesel quality
The effect of reaction temperature on product qua-
lity at LHSV of 2.0h1, 5.3 MPa total pressure and
356.2ml ml1 hydrogen-to-oil ratio is presented in
Fig. 4 for the five HDT feedstocks.
The product quality shown the classical behav-
ior when the temperature is increased in the range613633 K, that is a decrease in sulfur, nitrogen and
aromatics, and hence an increase in cetane number.
It should be mentioned that the reversibility of the
aromatics saturation reaction was not observed in this
study, which has been reported in the literature [12]
to be at higher temperatures (>633 K at 5.3 MPa).
The effect of space velocity (LHSV) on product
quality at 633 K reaction temperature, 5.3 MPa total
pressure and 356.2ml ml1 H2/oil ratio is presented
in Fig. 5 for the five feedstocks.
A decrease in LHSV from 2.0 to 1.5 h1 resulted in
improved product quality (a reduction in sulfur, nitro-
gen and aromatics contents, and an increase in cetanenumber).
It can be observed from Figs. 4 and 5 that the five
feedstocks reach less than 380 wppm sulfur, 53 wppm
nitrogen and 21.2 vol.% aromatics, in the range of tem-
perature 613633 K and LHSV of 1.52.0 h1. Cetane
numbers were higher than 49 for all feedstocks.
Very low sulfur, nitrogen and aromatics contents
were obtained with feedstock B-1 (
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Fig. 4. Effect of reaction temperature on product sulfur, nitrogen, aromatics and cetane number at 2.0h1 LHSV, 5.3MPa total pressure
and H2/oil ratio of 356.2 ml ml1. () B-1; () B-2; () B-3; () B-4; () B-5.
increase of 3.1 units in cetane number. This behavior at
high temperature and low space-velocity is because the
aromatics saturation and cetane number improvement
require high severity for CC bond scission to take
place from naphthenes to mono-aromatic molecules.
Feedstocks B-4 and B-5 presented aromatics higher
than 20 vol.% at low temperature and high space veloc-
ity (613K and 2.0 h1). This result was expected since
B-4 and B-5 feeds contain high content of SRGO,
60 and 50 vol.%, respectively, which is the higher
aromatic concentration stream used for preparing the
HDT feedstocks (26.4 vol.%).The flash point and viscosity of the hydrotreated
product decreased, while API gravity increased as the
reaction temperature was increased and the LHSV was
decreased.
The values of these diesel properties changed in the
following ranges: flash point, 338365 K; viscosity,
1.932.86 cSt, and API gravity, 3842.9.
The boiling range of the hydrotreated products
presented the following ranges: IBP, 448483 K;
10 vol.%, 460506 K; 30 vol.%, 474525 K; 50 vol.%,
491544 K; 70 vol.%, 519567 K; 90 vol.%, 571600 K,
and FBP: 610625 K.
The results of the present studies reveal that hy-
drodesulfurization is considerable influenced by reac-tion temperature and space velocity, and for a given
feedstock, low-sulfur diesel fuel (500 wppm max) can
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Fig. 5. Space-velocity effect on product sulfur, nitrogen, aromatics and cetane number at 633K, 5.3MPa and H2/oil of 356.2 ml ml1. ()
B-1; () B-2; () B-3; () B-4; () B-5.
be achieved by varying one of these process para-
meters.
3.2. Aromatics distribution in diesel fuels
3.2.1. FIA and SFC methods
A plot of total aromatics as measured by FIA and
SFC methods is presented in Fig. 6. It can be observed
that aromatics calculated by SFC (in wt.%) are always
greater than those evaluated by FIA method (in vol.%).
This difference becomes higher at high aromatic
contents.A lineal relationship, which is also shown in Fig. 6,
was found between the aromatic contents evaluated
with these two methods with correlation coefficient
R2=0.97.
3.2.2. Aromatics distribution
Aromatic compounds can be divided into four cat-
egories [13]: (1) mono-aromatics, (2) di-aromatics,
(3) tri-aromatics, and (4) polycyclic aromatics or
poly-nuclear aromatics (PNA) with four or more
condensed benzene rings.
Mono-, di- and tri-aromatics are more common in
middle distillates, whereas PNA are found in the heavy
fractions [13,14]. This was confirmed in this worksince all the HDT feedstocks showed very low contents
of aromatics with three rings (Table 2).
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Fig. 6. Comparison of methods for determining percent of aromatics. () Feedstock; () hydrotreated products.
Aromatics saturation in HDT process begins with
the partial saturation of multiple-ring aromatics
as can be observed in Fig. 7 [15]. However, the
mono-aromatics content showed an increase as the
multiring compounds are saturated as can be seen in
Fig. 8, where the mono-aromatics for B-4 feedstock
had increased from 15.72 wt.% to values higher than
19 wt.%, which is mainly due to the hydrogenation of
di- and tri-aromatics, since mono-aromatics are much
less reactive than di- or tri-aromatics.
Di- and tri-aromatics presented a reduction from
10.21 and 1.88 wt.% to values smaller than 3.0 and
0.45 wt.%, respectively.This behavior confirms that mono-aromatics are sig-
nificantly more difficult to saturate, which agrees with
experiments reported in the literature with model com-
pounds that suggest that naphthalene and substituted
naphthalenes are an order of magnitude more reactive
than benzene and substituted benzenes [16].
Aromatics density in feeds and hydrotreated prod-
ucts can be calculated with aromatics content in
Fig. 7. Aromatics saturation model.
wt.% (SFC method), aromatics content in vol.% (FIA
method) and feedstock density by means of the fol-
lowing equations:
Aromaticsin wt.% (SFC)
Aromatics in vol.% (FIA)=
garomatics/goil
mlaromatics/mloil
=
garomatics
mlaromatics
mloil
goil
=
aromatics
oil(1)
aromatics = oil
Aromaticsin wt.%
Aromatics in vol.%
(2)
It should be mentioned that the evaluation of aroma-tics density with Eq. (2) depends on the accuracy of
experimental determination of total aromatics by FIA
and SFC methods. SFC method has shown good ac-
curacy and FIA method presents poor accuracy for
determining aromatics in diesel fuels. The accuracy
of FIA method for diesels having end boiling point
(EBP) higher than 588 K has not been yet determined
[11].
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Fig. 8. Effect of reaction temperature and LHSV on aro-
matic distribution for B-4 feedstock. () LHSV=1.5 h1; ()
LHSV=2.0h1.
Most of the hydrotreated products in this work have
EBP higher than 588 K, specially those obtained fromfeedstocks with high SRGO content. This means that
not too much faith should be put on aromatics deter-
mination by FIA method. In spite of this, FIA numbers
were used together with aromatics by SFC method and
Eq. (2) to have an idea of aromatics density. These
results are discussed in the following paragraph.
Fig. 9 shows the variation of aromatics density in
the hydrotreated products, calculated with Eq. (2), as
a function of reaction temperature and LHSV for B-1
and B-4 feedstocks. It can be observed that the den-
sity of aromatic compounds decreases as the tempera-
ture increases and the LHSV is reduced. This confirms
that part of heavy aromatics (mostly tri- and di-) arehydrogenated into lower aromatics (mono) and their
densities and hence their molecular weights are re-
duced as the severity of the hydrotreating reactions is
increased.
3.3. Comparison of hydrotreated product properties
with diesel specifications
All the hydrotreated products obtained in the pilot
plant experiments using the five feedstocks reached
the required sulfur content (500 wppm max), cetane
number (48 min), and viscosity @ 313 K (1.94.1 cSt
for Mexico and 2.04.1 for US CARB legislation),
inclusive at the less severe operating conditions (613 K
and 2.0 h1 LHSV), as can be seen in Figs. 4 and 5.
Aromatics via FIA method presented values smaller
than 21.5 vol.% for B-4 and B-5 feedstocks, and
smaller than 19.4 vol.% for B-1, B-2 and B-3 feed-
stocks.
The experimental results indicate that at identical
operating temperatures very similar sulfur, nitrogen
and aromatics contents can be obtained with differentfeedstocks by adjusting the LHSV (first two columns
of Table 4).
The same result could be obtained by operations at
the same LHSV but with an increase of the operating
temperature, of course, at the expense of catalyst cycle
length (third and fourth columns of Table 4).
In Table 4 is also shown a comparison of three
hydrotreated products (columns 4, 5 and 6) with the
CARB diesel specification. It can be observed that all
properties reached the required CARB values, except
nitrogen and aromatics contents. It should be men-
tioned that CARB is one of the strictest specifications
for diesel fuels.The Mexican and US EPA legislations (Table 1) can
be easily reached with any of the diesel products ob-
tained by using the five feedstocks reported in Table 2,
within the operating conditions of the present study.
In addition, in some cases, the space-velocity may be
increased in order to expand the plant capacity. The
possibility of increasing the reaction temperature be-
yond 633 K and of increasing hydrogenation rate is
usually limited due to thermodynamic limitations of
aromatics hydrogenation.
3.4. Effects of type of feedstock on diesel quality
The composition of the feedstock to be treated in
a HDT plant will have a significant impact on the
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Fig. 9. Effect of reaction temperature and LHSV on aromatics density. () LHSV=1.5h1; () LHSV=2.0h1; () B-1 feedstock;
( ) B-4 feedstock.
unit performance. SRGO obtained from atmospheric
distillation remains the main source of diesel fuels.
Sometimes, the LCO obtained in FCC or coker gas
oils (CGO) are fed to the hydrotreater together with
SRGO. Each feed component contains thousands of
different molecules, making each unique in its pro-
cessability. For instance, SRGO is usually the easiest
feed to process, and LCO is difficult to treat because of
its high sulfur, nitrogen and aromatics contents. These
LCO properties adversely affect the quality of the re-
sulting diesel fuel [8].
Table 4
Comparison of operating condition to reach similar heteroatoms contents with different feedstocks
Feedstock B-1 B-2 B-3 B-4 B-4 B-5 CARB
Operating conditions
Temperature, K 633 633 623 633 623 633
LHSV, h1 2.0 1.5 2.0 2.0 1.5 1.5
Product properties
API gravity 42.61 40.96 39.66 38.71 38.72 38.45 3339
Flash point, K 340 345 348 348 354 363 327 min
Viscosity @ 313 K, cSt 1.85 2.17 2.45 2.57 2.51 2.65 2.04.1
Nitrogen, wppm 3 5 14 24 26 21 10 max
Sulfur, wppm 82 90 210 207 230 190 500 maxAromatics, vol.% 16.5 16.8 18.8 19.6 19.1 18.8 10 max
Cetane number 50.0 52.6 52.0 54.8 54.6 55.6 48 min
As the end point of blending components for diesel
production increases, the complexity of the het-
eroatoms increases and hence the hydrodesulfurization
rate decrease. Thiophenes are the lightest and most
reactive molecules with an unsaturated ring. Benzoth-
iophenes are relatively easy to desulfurize. DBT are
harder to desulfurize, but the difficulty varies greatly
according to their alkyl substitution, for instance DBT
substitued at the 4- and 4,6-positions, in particular,
are among the most refractory molecules. All of these
sulfur compounds can be found in diesel fuels.
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Fig. 10. ASTM D-86 distillation curves for SRGO, kerosene and jet fuel.
The concentration of the most difficult to desulfu-
rize species is high in the higher boiling fractions of
diesel materials. The level of HDS difficulty increasesto the point where ring saturation reactions begin to
compete with direct sulfur removal as the preferred
mechanism for HDS. Tailoring feed components, or
diesel feed boiling range can be an effective means of
controlling the difficulty of diesel HDS [4].
Another option to achieve a high-quality diesel is
to use lighter streams, such as kerosene and jet fuel,
together with the SRGO in the feedstock to the HDT
process in order to have more easier to desulfuize sul-
fur compounds.
With respect to this latter alternative, when the
kerosene and jet fuel are blended with SRGO, a
considerable reduction in the heteroatoms contentin the HDT feedstock is observed. SRGO sulfur
and nitrogen contents are 1.21 wt.% and 317 wppm,
respectively, and, for instance, for the feedstock
having the highest amount of jet fuel (B-1), sulfur
and nitrogen contents are 0.58 wt.% and 103 wppm,
respectively.
Unfortunately, the type and concentration of the dif-
ferent sulfur compounds in the feeds used in this work
were not determined, however, as it was stated before,
easier to desulfurize compounds are found in lighter
fractions, and hence, the rate of hydrodesulfurization
increases when these streams are used together with
SRGO as HDT feedstock.In spite of this, a good idea about the complexity
of sulfur compounds can be obtained by using the
ASTM D-86 distillation curve. Fig. 10 shows the boil-
ing point curves for SRGO, kerosene and jet fuel. The
boiling ranges for each stream are: 429637 K SRGO,409554 K kerosene, and 417504 K jet fuel. Accord-
ing to this figure, jet fuel will exhibit sulfur compounds
easier to desulfurize compared to other streams, and
its blend with SRGO will also provide a HDT feed-
stock with less complex and more reactive sulfur
compounds.
3.5. Basic approaches to produce low sulfur diesel
At present, most of the world refiners are either cur-
rently producing diesel fuels with 500 wppm sulfur or
are investing aggressively to reach this level. However,
some countries require a reduction to 50 wppm or to
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unit producing 500 wppm sulfur diesel, an increase
of 2035 K will be required depending of the feed
quality [4,5]. This increase in temperature will limit
the unit cycle life to an unacceptably short time pe-
riod. This means that temperature is not an effective
solution. Hence, the long term solution will certainly
need the addition of reactor volume and quench ca-
pability or even the investment in new hydrotreating
plants.
In addition to sulfur content, future diesel will re-
quire significant reductions in aromatics, density and
boiling range together with an increase in cetane num-
ber. The optimal reaction pathways to achieve the up-
grade objectives will be feedstock dependent and will
also need to consider the best utilization of existing
refinery resources.
4. Conclusions
The effect of hydrotreating of SRGOkerosenejet
fuel blends on diesel fuel quality has been studied
in a pilot reactor over a commercial Ni-Mo/-Al2O3catalyst under typical operating conditions.
The experimental results showed that the specifica-
tions in diesel quality can be achieved through single
stage hydrotreating of these blends. The maximum sul-
fur content in diesel fuels (500 wppm) and minimum
cetane number (48) can be easily reached at moderate
hydrotreating operating conditions.
Similar heteroatom contents in the products were
observed using the five feedstocks by adjusting the
LHSV or reaction temperatures.A lineal relationship was found between SFC and
FIA methods for determining aromatic distribution.
This information was used for evaluating the aro-
matic density, which was employed to show the
partial hydrogenation of heavy aromatics into lower
aromatics.
Acknowledgements
The authors thank Instituto Mexicano del Petrleo
for its financial support.
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