r&d on hydrodesulfurization (hds) of atmospheric residue ... · r&d on hydrodesulfurization...
TRANSCRIPT
1
[M2.1.6]
R&D on Hydrodesulfurization (HDS) of Atmospheric Residue
Long-Run Technology
(Hydrodesulfurization (HDS) of atmospheric residue long-run group)
� Kazuo Idei, Takeshi Ebihara, Hitoshi Shibata, Yoshinori Kato,
Hiroshi Mizutani, Hideki Godo, Kazuyuki Kiriyama, Motoki Yoshinari
1. Contents of Empirical Research
In an effort to construct internationally competitive hydroprocessing which can supply oil
products stably in line with demand, the present R&D aims to establish long-run technology that
can stably produce low sulfur heavy oil over long time periods with extant heavy-oil,
hydrodesulfurization (HDS) of atmospheric residue equipment. For this purpose, the following
catalysts and processes are being developed.
(1) Development of new preprocessing (demetalization) catalyst as primary treatment
(2) Development of new desulfurization catalyst as secondary treatment
(3) Construction of long-run catalyst process through development of technology for the
optimal combination of new preprocessing (demetalization) catalyst and desulfurization
catalyst.
A schematic illustration of the developed technology at completion is presented in Figure 1-1.
Crude oil
Hydrogen
Hydrodesulfurization (HDS) of atmospheric residue long-run catalytic process
Hydrodesulfuri
-zation (HDS) of
atmospheric
residue unit
Preprocessing
unit
Atm
osph
eri
c d
istilla
tio
n
FCC unit (cracking)
or LS-C heavy oil
Figure 1-1: Schematic Illustration of the Developed Technology at
Completion
The following specific target values have been established with respect to the conventional
hydrodesulfurization (HDS) of atmospheric residue unit.
(1) Development of catalyst that enables long-run over a time period 1.5 times longer than that
of current catalyst under low-pressure conditions.
2
(2) Achievement of a long-run period of 2 times greater duration through a combined catalytic
processing system in which the aforesaid catalyst is combined with extant equipment to
which preprocessing unit has been added.
In order to make further progress with the results of research conducted last year, the following
investigations were conducted this fiscal year.
(1) Catalyst development
Pretreatment catalyst and desulfurization catalyst were designed and test manufactured.
Trial-produced catalyst underwent primary screening in relation to initial HDS activity test and
accelerating test for metal capacity, using micro-reactor.
Industrial scale trial production of promising desulfurization catalyst was also carried out and
industrial scale production methods were investigated.
(2) Process examination
The performance of catalyst combinations was evaluated, using extant bench plant, under
industrial HDS condition of atmospheric residue, long run process was examined. Evaluations
were also made of the water-addition process, and its industrialization was investigated.
(3) Examination of estimation technology
For the purpose of constructing a long-run simulation method, the impacts of coke deposit, a
factor in catalyst deactivation, and of metal deposition were analyzed quantitatively, and the
results served as basic data for determining catalyst service life and the ratio of catalyst
combination. In addition, a catalyst pore structure meter and a cumulative carbon combustion
unit were introduced, and the mechanism of catalyst deactivation was analyzed.
(4) Analytical investigation
The properties of trial-produced catalyst and of used catalyst were analyzed, and catalyst itself
was analyzed in detail by the instrumental analysis method. In addition, characterization of
heavy oil was completed in order to analyze the difficult-to-remove sulfur compounds such as
asphalten contained in feedstock or product oil.
2. Results of Empirical Research and Analysis Thereof
2.1 Catalyst Development
In the current fiscal year, preprocessing catalyst and desulfurization catalyst were trial-produced
and/or improved to serve as catalyst for long-run hydrodesulfurization (HDS) of atmospheric
residue. Primary screening was carried out by means of a microreactor, catalytic activity tester,
catalyst accelerated deactivation test, etc.
With respect to catalyst trial production, pretreatment catalyst (4 points) and desulfurization
catalyst (16 points) were designed and trial produced in consideration of low-pressure,
hydrodesulfurization (HDS) of atmospheric residue unit. Table 2-1 lists the catalyst for which
trial production was requested.
3
Table 2-1: Trial Produced Catalyst
Catalyst Trial production points
Pretreatment catalyst Novel additive attached
Investigation for high performance by catalyst with
weak base added
Investigation of differential pressure countermeasures
1 point
2 points
1 point
Desulfurization catalyst Investigation of low-pressure, low-deactivation catalyst
Control of calcination conditions
Pore distribution control
Investigation of carrier improvements
7 points
4 points
3 points
2 points
(1) Development of desulfurization catalyst
Figure 2-1 give the results of primary screening by microreactor for desulfurization catalyst trial
produced this fiscal year. Using Boscan crude oil, desulfurization activity was evaluated with
respect to normal pressure residual oil and permissible metal content. As shown in Figure 2-1,
low-deterioration catalyst and catalyst for which calcination conditions have been optimized
have metal capacity equal to or greater than that of standard catalyst, and it became evident
that desulfurization activity is improved by a wide margin. In the case of catalyst to which 3rd
ingredient was added and in which the pore structure was finely controlled, although
desulfurization activity was somewhat low in comparison to standard catalyst, it was confirmed
that metal capacity can be greatly increased.
The present investigation confirmed that the developed catalysts are all very promising as
desulfurization catalyst for long-run hydrodesulfurization (HDS) of atmospheric residue. In the
future, trial production of these catalysts, using industrial equipment, will be investigated, and
bench evaluations will be made by combining industrial trial-produced products.
Low deactivation catalyst
Optimization of calcination conditions
3rd ingredient added+pore control
Metal capacity
Desulfurization
activity
Relative value (%)
Standard catalyst
Figure 2-1: Primary Screening of Trial-Produced Catalyst
(2) Development of low-pressure, low-deactivation catalyst
In the previous fiscal year, it was discovered that in catalyst in which additive A is retained by
means of the impregnation method, the amount of coke deposit is reduced in comparison to
conventional catalyst and desulfurization activity is improved over a period of stability. In the
current fiscal year, optimization of the amounts of additive A included was investigated.
4
Firstly, the relationship between the amount of additive A included and the amount of coke
deposit was examined. An autoclave was used as the evaluation unit, and Middle Eastern
atmospheric residual oil was evaluated. Upon completion of tests, catalyst was removed,
Soxhlet was extracted from benzene, and the volume of coke deposited on catalyst was
measured.
Evaluation results are shown in Figure 2-2. It was confirmed that the volume of coke deposit
decreases as the volume of additive A included is increased.
Coke d
eposit (
%)
Relative addition of additive A
Figure 2-2: Additive A Volume vs Deposited Coke Volume
Next, using a fixed-bed, flow-type microreactor, the desulfurization activity of catalyst including
different amounts of additive A was evaluated. The desulfurization activity of each catalyst over
a period of stability is presented in Figure 2-3. Here relative desulfurization activity is shown,
taking as standard the desulfurization activity of catalyst in which additive has not been added.
Figure 2-3 shows that there is an optimum value for the amount of additive A included in
catalyst. It was thus confirmed that in comparison to base catalyst, desulfurization activity in
catalyst with optimal additive A is improved by about 20%.
Relative addition of additive A
Re
lative
de
su
lfu
riza
tio
n a
ctivity (
%)
Figure 2-3: Additive A Volume vs Desulfurization Activity
5
The degree of catalyst deactivation with optimal additive, as compared to that in base catalyst,
is presented in Figure 2-4. Here the reaction rate constant (k) on the first day of reaction is
taken as ko, and the deactivation rate is the value obtained by dividing each k by ko (kt/ ko).
Figure 2-4 indicates that in comparison to base catalyst, the catalyst deactivation with additive A
is curtailed. Moreover, upon completion of the test, analysis of the amounts of coke deposited
on catalyst revealed that the amount on catalyst with optimal additive A was about 90% of the
amount deposited on base catalyst.
Given these findings, it is conjectured that in catalyst with optimal additive A included, catalyst
deactivation is curtailed by virtue of the fact that the volume coke deposit is reduced, and
desulfurization activity over a stable period is improved by about 20%.
De
activa
tion
Le
ve
l (k
t/k0
)
No. days on stream
Base
Optimization of additive A
Figure 2-4: Pattern of Deactivation in Each Catalyst
(3) Development of catalyst with controlled pore structure and 3rd ingredient
The present investigation was carried out for the purpose of developing a desulfurization
catalyst having a high metal capacity. Generally speaking, metal capacity can be increased by
increasing the cubic capacity of catalyst pores, but in such cases, the specific surface area is
reduced and desulfurization activity declines. Accordingly, 3rd ingredient was added and an
investigation was made in order to reduce to a minimum the drop in desulfurization activity by
controlling catalyst pore structure more finely, and in order to develop catalyst in which
demetalization activity and metal capacity are increased.
6
Catalysts were trial produced in which physical properties and the amounts of active metal
retention are the same but pore structures are different. Desulfurization and demetalization by
these catalysts were then evaluated using a microreactor. Desulfurization and demetalization as
opposed to the pore distribution index of each catalyst are represented in Figure 2-5. Here, a
certain pore diameter is taken as the base, and the pore distribution index is taken as the
percentage of pore capacity with pores of base diameter or greater and the percentage of pore
capacity with pores lower than the base in diameter. In the investigation, it was demonstrated
that as the pore distribution index becomes larger, the pore distribution of the catalyst is
unimodal, and as the index becomes smaller, the pore distribution becomes bimodal. Figure 2-5
confirms that as the pore distribution index increases, demetalization increases but
desulfurization drops sharply after a certain value has been reached. When the pore structure
was finely controlled, based on these findings, the aforesaid catalyst in which metal capacity
could be drastically increased was successfully developed.
Pore distribution index
De
su
lfuri
za
tio
n a
ctivity k
De
me
taliz
atio
n r
ate
(%
)
Figure 2-5: Pore Distribution vs Demetalization and Desulfurization
2.2 Process Examination
(1) Test of long-term service life of hydrodesulfurization (HDS) of atmospheric residue long-run
process
In order to design a catalyst system aimed at long-run hydrodesulfurization (HDS) of
atmospheric residue, consideration must be given to the metal capacity, catalytic deactivation
and desulfurization activity matching the system’s operation time period. Moreover, in the case
of a low-pressure, hydrodesulfurization (HDS) of atmospheric residue unit, ample attention must
be paid to the types of combined catalysts and catalyst ratio because the impact of coke
deactibation will be manifested in large measure. Already in research conducted up to the last
fiscal year, the impact of catalyst combination ratio on reactivity and on catalyst deactivation
pattern were investigated, and findings were obtained on the optimum catalyst combination
ratio.
In the present study, long-term service life tests were performed with combinations of catalysts
as described in Section 2.1 on catalyst development, for the purpose of industrialization of the
hydrodesulfurization (HDS) of atmospheric residue long-run process. The properties of
feedstocks used in the investigation are listed in Table 2-2 and evaluation conditions appear in
Table 2-3.
7
Feedstock
Middle Eastern
atmospheric
pressure residual oil
Midget plant
Density g/ml
Sulfur content mass%
Conradson carbon residue mass%
Metal content massppm
Asphaltene content mass%
Nitrogen content mass%
0.9640
2.80
10.3
46
2.30
0.23
Reaction temperature ℃
Hydrogen partial
pressure MPa
LHSV h-1
Hydrogen/oil ratio m3/m
3
Sulfur content in product
oil
Constant
Constant
Constant
Constant
Table 2-2: Feedstock Properties Table 2-3: Evaluation Conditions
Three types of catalyst were used in combination. Catalyst with weak salt base was used as
early-stage catalyst; catalyst with 3rd ingredient added plus pore control was used as the
middle-stage catalyst, and catalyst with optimal calcination conditions was used as the
final-stage catalyst. For each catalyst, laboratory trial-produced products were combined into a
catalyst system (hereinafter, laboratory trial-produced products) and industrial trial-produced
products were combined into another catalyst system (hereinafter, industrial trial-produced
products). Long-term service life tests were then conducted on these systems.
Systems were operated under conditions such that the reaction temperature was increased in
accordance with the catalytic deactivation so that the sulfur content in produced oil becomes
fixed. In addition, hydrogen partial pressure was low in comparison to regular
hydrodesulfurization (HDS) of atmospheric residue unit.
The trend in required temperature for long-term service life tests and the trend in estimation
result are represented in Figure 2-6.
Re
qu
ire
d t
em
pe
ratu
re
No. of operation days
Laboratory trial
-produced product
Industrial trial
-produced product
Estimated value
Figure 2-6: Trend in Required Temperature vs Performance
Assessments
Figure 2-6 shows that the trends for laboratory trial products and for industrial trial products are
similar. We confirmed that combinations of industrial products exhibited trends in activity as
estimated, as did laboratory trial products.
8
(2) Process investigation using water
In the present study, investigations were undertaken from a process-type standpoint concerning
improvement of reactivity in the conventional hydrotreating process. Already in R&D conducted
up to last year, it was found that by adding water to the hydrodesulfurization (HDS) of
atmospheric residue unit, reactivity is improved and catalyst deactivation is suppressed. Again
in the present fiscal year, investigations were made concerning the reaction mechanism in the
hydrogenation desulfurization process with water added.
An evaluation was made by adding water from on the bench plant. The conditions of evaluation
are presented in Table 2-3. Furthermore, spent catalyst was used for evaluation. And the Middle
Eastern atmospheric pressure residual oil given in Table 2-2 was used for the properties of
feedstock under evaluation. Operations were carried out with produced oil of constant sulfur
content.
In an evaluation of activity by means of bench plant, base data were collected on the trend in
activity when water was not added for the first two months and on deactivation. Thereafter,
water was first added and data were collected on activity and deterioration the same as before
the addition of water. The trend in required temperatures in investigation of water addition
appears in Figure 2-7. After the start of operation, the required temperature stabilized over
about 10 days, then stable deactivation was exhibited. From about 50 days after the start of
operation, water was added from the top of the reactor, and thereafter, evaluations were made
continuously for about 100 days. Following the addition of water, the required temperature for
manifesting catalytic activity began to gradually diminish, and it was noted that activity is
improved by adding water. From 70 days after the start of operation, the temperature-increasing
rate (TIR) per day, which indicates catalyst deactivation, dropped to about half the rate prior to
the addition of water, and it was recognized that the addition of water has a suppressive effect
on deactivation. Furthermore, in order to confirm the effect of adding water, from 150 days after
the start of operation, the addition of water was stopped, and reactivity and deactivation pattern
were checked. Since it was confirmed that activity returns to its level prior to the addition of
water and that the pattern of deterioration thereafter continues to be gentle in slope, it is
suspected that the addition of water has a reversible action.
Days on stream
No water added No water added Water added
Requir
ed tem
pera
ture
°C
Figure 2-7: Trend in Required Temperature
9
Next, when activity level was stabilized before and after the addition of water, bench plant
off-gas at the same reaction temperature was introduced on-line to gas chromatograph (GC),
and the compositions of light hydrocarbons were analyzed. CO and CO2 were monitored, on the
assumption that in the reaction mechanism of the water addition process, water serves as a
hydrogen donor. The results of compositional analysis of off-gas appear in Figure 2-8. The
figure suggests that CO and CO2 are not detected and that water does not serve as a hydrogen
donor. Nevertheless, because the latest sampling took place when stability was reached after
adding water, the possibility cannot be denied that water might serve as a hydrogen donor
immediately after it has been added, causing adsorption and desorption of coke precursor, and
that thereafter, stability is reached without hydrogen supply. Moreover, from a comparison of the
composition of light hydrocarbon content in off-gas, before and after the addition of water, it
became evident that the reactant as a whole is increased by adding water but that the change
per unit molecule is small. This is ascribed to the fact that water acts as an adsorption inhibitor
against molecules of strong polarity such as coke precursor, plus the fact that the turnover
frequency (TOF) increased.
Water added
No water added
Com
positio
n p
erc
enta
ge (
vol%
)
Figure 2-8: Comparison of Offgas Compositions
2.3 Examination of Estimation Technology
To establish estimation technology suitable for long-run hydrodesulfurization (HDS) of
atmospheric residue, the relationships between metal deposits, coke deposits and catalyst
deactivation pattern must be determined. In the present fiscal year, a basic investigation was
made of the relationship between coke deposit and catalyst deactivation pattern.
In an investigation of coke deposit and catalyst deterioration pattern, the impact of metal
deposits was curtailed to the minimum, and an autoclave was used as the reactor so as to
determine the impact of coke deposit alone. An evaluation was made in which Middle Eastern
atmospheric residual oil was used, and the reaction conditions and catalysts to be evaluated
were held constant. The relationship between coke deposit volume and desulfurization activity is
presented in Figure 2-9.
10
Coke deposit per unit surface area
Rela
tive d
esulfuri
zation r
eaction
rate
consta
nt
Figure 2-9: Coke Deposit vs Desulfurization
Figure 2-9 shows that the impact of coke deposit on desulfurization activity is large, since
desulfurization activity drops sharply with an increase in coke deposit.
2.4 Analytical Investigation
In an evaluation of practical performance, as part of an investigation of processes using water,
reaction experiments were conducted in which feedstock was completely replaced with water in
order to examine impacts on catalyst, and changes in catalyst structure were confirmed. In the
reaction experiments, spent catalyst was used and reactions were carried out in a flow-type
reactor for one hour under fixed conditions of temperature and pressure. Thereafter, the catalyst
was removed from the reactor, and x-ray diffraction (XRD) analysis and electron probe
microanalysis (EPMA) were conducted. Comparisons were made between used catalyst after
reaction with water, untreated spent catalyst serving as a reference, and catalyst used for
investigation of processes involving the addition of water as described in Section 2.2.
The XRD chart of untreated spent catalyst appears in Figure 2-10.
Figure 2-10: XRD Chart of Untreated Balanced Catalyst
11
The XRD chart of catalyst after using water addition process appears in Figure 2-11.
Figure 2-11: XRD Chart of Catalyst after Using Water Addition
Process
The XRD chart of used catalyst after reaction with water appears in Figure 2-12.
Figure 2-12: XRD Chart of Spent Catalyst after Water Reaction
From the aforesaid results, the following three catalytic structures were compared.
Untreated spent catalyst: Al2O3, NiV2S4, V3S4
Catalyst after using water addition process: Al2O3, NiV2S4, V3S4
Catalyst used after reaction: Al2O3, NiV2S4, V3S4, V2O3, AlO(OH)
In used catalyst after reaction in which total water volume was used without employing
feedstock, it was conjectured that a portion of the crystal structure of alumina had been
destroyed since a peak originating in AlO (OH) could be observed. And since a peak originating
in V2O3 could also be seen, it is conceivable that vanadic acid is formed and eluted. In checking
the cumulative distribution of vanadium by means of EPMA, no conspicuous changes could be
noted.
12
In the present study, it was confirmed that a portion of the crystalline structure is destroyed
when water has been treated excessively, but that in the added volume of water actually used
(water addition process), no structural changes could be noted. Accordingly, in an evaluation of
practical performance in the water addition process, impact on catalyst was also investigated,
and it was confirmed that there are no special problems.
3. Results of Empirical Research
3.1 Catalyst Development
Desulfurization catalyst of high metal capacity was developed through the addition of 3rd
ingredient and pore control. Further, by adding an optimum amount of the new additive, which
acts to reduce the volume of coke deposit, catalyst could be developed in which deactivation is
curtailed and desulfurization action is high. Patent applications have been submitted for these
catalysts. Moreover, in order to establish industrial production technology for catalyst with 3rd
ingredient and controlled pores, industrial trial productions were implemented.
3.2 Process Examination
Three types of catalyst developed for long-run hydrodesulfurization (HDS) of atmospheric
residue were combined, and long-term evaluations were made of catalyst system combining
laboratory trial-produced products and catalyst system combining industrial trial-produced
products. For both systems, the trends in forecasts by long-run simulation were found to be
equivalent. An investigation was also conducted to elucidate the reaction mechanism in the
water addition process, and to facilitate evaluation of practical performance.
3.3 Examination of Estimation Technology
Basic data on factors in the deactivation of catalytic activity were collected for the purpose of
constructing a long-run simulation method. Respecting coke deposit in particular, which impacts
on deactivation pattern in the initial reaction period, quantitative data were collected on the
relationship between deposit volume and desulfurization action.
3.4 Analytical Investigation
In an evaluation of practical performance in the water addition process, used catalyst underwent
characterization and impacts on catalyst were investigated. It was confirmed that a portion of
the crystalline structure is damaged when water has been treated excessively, but that in the
added volume of water actually used (water addition process), there are no structural changes
and no problems in practical application.
13
4. Synopsis
4.1 R&D in JFY2001
In the present fiscal year, desulfurization catalyst whose metal capacity was sharply increased
through the addition of 3rd ingredient, plus pore control, was successfully developed and
trial-produced on an industrial scale. What is more, deactivation was curtailed by adding
optimum amounts of the new additive, which acts to reduce coke deposits, and desulfurization
catalyst of high desulfurization action was developed. Evaluations were begun on a long-run
system in which processing catalyst, developed up to the previous fiscal year, is combined with
the latest desulfurization catalyst, and it was found that the same results obtain, as anticipated,
with laboratory trial-produced products and industrial trial-produced products. Moreover, in an
investigation of the water addition process, inquiries were made for elucidating reaction
mechanism and for evaluating practical performance. Desulfurization action and deposits of
coke, a factor in the catalyst deactivation, were also investigated for the purpose of constructing
a long-run simulation method. Quantitative findings were obtained on coke deposits and on
desulfurization action.
4.2 Future Issues
1) Confirmation of performance by combined system of industrial trial-produced catalyst
(Ongoing service life testing)
2) Establishment of long-run simulation technology and forecast of practical performance by
developed catalyst
3) Verification research with industrial equipment
Copyright 2002 Petroleum Energy Center. All rights reserved.