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[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.

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(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.

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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.

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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

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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.

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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.

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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.

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(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

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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.

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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

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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.

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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.

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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.