CA1071561A - Process for the conversion of hydrocarbons - Google Patents

Abstract

A B S T R A C T

Life of a combination of two or more catalysts in a hydro-desulphurization process of a residual oil without catalyst re-plenishment and in the presence of steam, is longer than that of each of the catalysts is applied separately, provided that each of the catalysts has a porosity and particle size within specified ranges depending on the porosity and particle size of the other catalysts in the combination and on the applied hydrogen partial pressure and that the catalysts are applied in a given volume ratio.

Description

The invention relates to a process for the catalytic hydro-desul-phurization of vanadium- and nickel-containing residual-hydrocarbon oils without catalyst replenishment, which process is carried out in the presence of a quantity of water corresponding with a water vapour partial pressure during the process of 0.5-30 bar. A process of this type is described in our co-pending Canadian patent application 210,553 now Canadian Patent 1,038,789.
According to this patent application, catalysts are used for this purpose showing a life and average activity which exceed established minimum values if they are used for residue desulphurization in a standard catalyst test.
They have a total pore volume of more than 0.30 ml/g of which less than 10%
is present in pores having a diameter of more than 100 nm and they have a specific average pore diameter (p) and a specific average particle diameter ~d) such that the quotient p/(d)0 9 satisfies the requirement:
4 x 10 x ~PH ) ~ p/(d) < 5+24 x 10 x (PH ) , where PH represents the hydrogen partial pressure used (p in nm, d in mm, PH in bar). As is demonstrated in the above-mentioned Canadian patent, catalysts having a quo-tient p/(d)0 9 of less than 4 x 10 4 x (PH )2 or larger than 5+24 x 10 4 x (PH ) show a life in the standard catalyst test which is too short and/or an average activity which is too low to satisfy the minimum requirements in res-pect of life and average activity stated in the Canadian patent application.
Since the life of a catalyst for the hydrodesulphurization of van-adium- and nickel-containing residual hydrocarbon oils in the presence of water without catalyst replenishment, is shorter according as the catalyst displays a higher average desulphurization activity, the said Canadian patent is in fact based on a compromise between these two catalyst properties.
Continued research by applicant into this subject has shown that ; considerably better results can be obtained if the residual hydrocarbon oil is successively contacted with two or more different catalys~s as compared with a process in which only one catalyst is used. The use of a suitable combination of two or more different catalysts produces an improvement in activity and/or life of the combination in respect of each of the catalysts Individually, i.e.

under the same conditions a more thorough desulphurization is effected or by maintaining a certain desulphurization level (as is customary in practice) the catalyst life is prolongea. However, these better results are only achieved if the catalysts used satisfy a number of requirements in respect of t.~eir porosity, particle size and volumetric ratio.
For the sake of simplicity a combination of two or more catalysts will in this patent application be considered as consisting of a catalyst I and a catalyst II, the desi,~1ation "catalyst II" re~erring to the second catalyst when using a combination of two catalysts 9 or to the last catalyst when using a combination of more than two cata-lysts and the de~ignation "catalyst I" referring to the first catalyst when using a combination of two catalysts, or to the combination of all catalysts with the exception of the last one when using a combi-nation of more than two c~talysts ("first", "second" and "last" as seen in the direction of the liquid flow over the catalyst combination).
When a combination of two catalysts is used, the requirements in respect of porosity, particle si~e and volumetric ratio of the ~atP~ysts are BS follows:
(a) in respect of the total pore volume and the percentage thereof present in pores having a di~meter in excess of 100 nm the same requirements apply to catalyst I and~ catalAyst ~I as to the catalysts according to the U.~ s~ ~ ~ mentioned above, i.e. they should have a total poxe volume of more than 0 30 ml/g of which less than 10% is present in pores having a diameter in excess of 100 nm;
(b) catalyst II should have a p and d such that the quotient ~p/(d) 9 ~cat II satisfies the requirement:
( H2) - [ P/( ) ~cat.II - 3 x x (PH2) (c) catalyst I should have a p and d such that the quotient p/(d) 9 ~cat I satisfies the requirement:
P ~7cat.II ~ ~ p/(d) ~cat I c 5+30 x 10~4 x (p )2 (d) the percentage of the total catalyst volume taken up by catalyst II (% vol. of cata1yst II) should lie between 10 and 90% and should satisfy the following requirement:

40 x( FS P x 100)2 x (P~l ) 2 s %vol.cat.II _ 300x ~ 100) x(PH ) where SF represents the sulphur content of the feed and Sp the desired sulphur content of the desulphurized product, expressed in percentage by weight.
When a combination of more than two catalysts is used, the require-ments in respect of porosity, particle size and volumetric ratio of the catalysts are essentially in agreement with those mentioned above under (a) -(d) for a combination of two catalysts, with the proviso that: (e) the requirements mentioned under (a) in respect of the total pore volume and the percentage thereof in pores having a diameter in excess of 100 nm now apply to each of the individual catalysts of which the combination of catalyst-I and catalyst II is composed, (f) the requirement mentioned under (c) in respect of ~p/(d~ ~ cat I now applies to the average p/(d)0 9 of catalyst I, determined as the weight average of the values p/(d)n 9 of each of the individual catalysts of which catalyst I is composed, and (g) each of the individual catalysts of which catalyst I is composed has a p and d such that the quotient p/(d)0 9 of each of these catalysts exceeds ~p/~d) ~ cat II

The present patent application therefore relates to a process for the catalytic hydrodesulphurization of vanadium-and nickel-containing residual hydrocarbon oils without catalyst replenishment, which process is carried out in the presence of a quantity of water corresponding with a water vapour partial pressure during the process of 0.5-30 bar, the hydro-carbon oil being consecutively contacted with a catalyst I and a catalyst II
which satisfy the following requirements ~a) each of the individual catalysts of which the combination of catalyst I and catalyst II is composed has a total pore volume in excess of 0,30 ml/g of which less than 10% is present in pores having a diameter in excess of 100 nm; (b) catalyst II has a specific average pore diameter (p) and a specific average particle diameter (d) such that the quotient p/(d) '9 of catalyst II satisfies the requirement:

~ =J ~ - 4 -s~

X(PH ) C ~ /~d) ~ cat II ~ 4~13xlO x(PH ) ;
(c) if the combination of catalyst I and catalyst II is composed of two catalysts, ca~alyst I has a p and d such that the quotient p/(d)0-9 of catalyst I satisfies the requirement:

~ P ) ~ cat-II ~ CP~d~ ~ cat I ~ 5+30xlO 4x(PH )2 while if the combination of catalys~ I and catalyst II is composed of more than two catalysts, the above requirement in respect of ~p/(d) ~ cat I
applies to the average P/td)Q~9 of catalyst I which is deter~ined as the weight average of the values of p/(d)0 9 of each of the individual catalysts of which catalyst I is composed; (d) the percentage of the total catalyst volume which is taken up by catalyst II (~vol. of catalyst II) is between 10 and 90% and satisfies the requirement:

40x ~ xlO0) x(P~I ) c %vol.cat.II<300x~ ~ 100) x~PH ) wherein SF represents the sulphur content of ~he feed and Sp the required sulphur content of the desulphurized product, and ~e) if the combination of catalyst I and cata;lyst II is composed of more than two catalysts, each of the individual catalysts of which catalyst I is composed has a p and d such that the quotient p/(d)0 9 of each of these catalysts is greater than ~p/~d~ ~cat II ~P in nm, d in mm, PH in bar, Sp and SF in percentage by weight).
When the requirements which are now made of the quotient p/~d)0-9 of catalyst I and catalyst II are compared with those which were made in the past of this quotient of the catalysts applicable according to the Canadian patent mentioned above, it is found that a number of the catalysts which were rejected in the past are now eligible for application in the catalyst com-bination according to the invention. Catalysts outside the scope of the Canadian patent mentioned above which are now eligible for applications are:

- 4a ~

(a) As catalyst II, a catalyst having a p and d such that the quotient [p/(d) ]cat II satisfies the requirement:

x (PH2) < [p/~d) ]cat II<4 x 10 x (PH )2 (b) When using one catalyst as catalyst I, a catalyst I having a p and d such that the quotient [p(d)0 9] at I satisfies the requirement:
x ( H2) ~ [p/(d) ]cat I ~4 x 10 4 x (p )2 (c) ~hen using one catalyst as catalyst I, a catalyst I having a p and d such that the quotient [p/(d)0 9] t I satisfies the requirement:

( H2) ~[P (d) ]cat I < 5 + 30 x 10 4 x (PH )2 In addition to an extension in respect of the Canadian patent mentioned above as regards the applicable catalysts, the present invention also entails limitations. Catalysts usable according to the Canadian?~men-tioned above which are not eligible for application in the present case are inter alia:
(a) as catalyst II, a catalyst having a p and d such that the quotient [p/(d) ]cat II satisfies the requirement:

( H2) > [P/(d) ]cat II> 4 + 13 x 10 4 x (PH )2-(b) ~hen using one catalyst as catalyst I, a catalyst I having a p and d such that the quotient [p/(d)0 9]cat I satisfies the requirement:

(pH2) < [p/(d) ]cat I<1 2 x [p(d)0 9] t II-This situationoccursif as catalyst II a catalyst is used having a p and d such that the quotient [p/(d)0 9] at II satisfies the requirement:

[p/(d) ]cat II >3 3 x 10 x (PH ) -For the way in which p and d are determined, reference is made to the Canadian Patent 985,651, wherein the determination of these parameters has bcen described in detail.

P'~ ~L~

According to the present invention the hydrodesulphurization is carried out in the presence of a quantity of water corresponding with a water vapour partial pressure during the process o~ 0.5-30 bar.
The quantity of wa'cer used preferably corre~ponds with a water vapour partial pressure during the process of 1-15 bar and in particular of 1-5 bar. The required quantity of water may be added to the gas and/or liquid stream which is passed over the catalysts. The wa-ter may be added as such or in the form of steam. Water as such may, for example, be added to the residual hydrocarbon oil to be desulphurized, or steam may be &dded to the hydrogen stream which is supplied to the process, If desired, instead of water a compound may be added from which water is formed under the prevailing reaction conditions, such as a lower alcohol.
The catalysts which are used in the process according to the invention as catalyst II preferably have a total pore volume in excess of 0.45 ml/g and a surface in excess of 100 m2/g and in particular a surface in excess of 150 m2/g. In addition, they preferably have a p and d such that the quotient r p/(d) 9 ~cat II
satisfies the requirement:
~ p/(d) 9 ~cat II ~ 1.2 x 10 x (PH )2 -In the hydrodesulphurization according to the invention there is particular preference for using a catalyst II which has a p and d such that the quotient ~ p/(d) 9 ~cat II satisfies the requirement:

(PH2) ~ ~ p/(d) ~cat II ~ 4 ~ 13 x 10 4 x (PH )2, which catalyst also has a total pore volume in excess of 0.~5 ml/g o~ which at least 0.4 mlJg is present in pores having a diameter of at least 0.7 x p and at most 1.7 x p and a sharp pore diameter distribution characterized in that (a) less than 20% of the total pore volu~e is present in pores having a diameter smaller than 0.7 x p and (b) less than 20% o~ the total pore volume is present in pores having a diameter greater than 1.7 x p.
As has already been noted above, one sinele catalyst or a combination of two or more catalysts can be used as catalyst I in the process according to the invention. The process is preferably carried out using one single catalyst as catalyst I. If use is made of a combination of two or more catalysts as catalyst I, the catalysts of which catalyst I is composed may occur in the desulphur-ization reactor both mixed with each otber and separated ~rom each other (for example in separate beds or layers). When a combination of two or more catalysts is used as catalyst I, preference is given to a process in which the catalysts of which catalyst I is composed occur in the reactor separated from each other, in particular in such a sequence that the quotient p/(d! 9 of each of the catalysts of which catalyst I is composed is smaller than that of the pre-ceding catalystl i.e. that the ~uotient p/(d)-9 decreases in the direction of the liquid flow over the catalyst combination. When one single catalyst is used as catalyst I and also when a combination of two or more catalysts is used as catalyst I, catalysts having a tot~1 pore volume in excess o~ 0.40 ml/g are preferred. It is also preferred that a catalyst I is used with a p and d such that the quotient [ p/(d) 9 ]cat I satisfies the requirement: -P ~cat,I _ 1-4 x r Pl(d) ~cat II with the proviso that when a combination of two or more catalysts is used as catalyst I, this preference in respect of [ p/(d) ~cat I applies to the average p/(d)-9 of catalyst I, which is determined as the weight averaæe of the values p/(d)0-9 of each of the individual catalysts Or which catalyst I is composed.
Catalysts which are used according to the invention preferably contain 0.5 - 20 parts by weight and in particular 0.5 - 10 parts by weight of nickel andlor cobalt and 2.5 ~ 60 parts by weight and in particular 2.5 - 30 parts by weight of molybdenum and/or tungsten per 100 parts by weieht of carrier. The atomic ratio between nickel and/or cobalt on the one hand, and molybdenum andlor tungsten on the other, may vary within wide limits, but is prePer-ably between 0.1 and 5. Examples of very suitable metal combi-nations for the present c~talysts are nickel/tungsten, nickel/
molybdenum, cobalt/molybdenum and nickel/cobalt/molybdenum. The metals may be present on the carrier in metallic form or in the form of their oxides or sulphides. It is preferred to use catalysts according to the invention in which the metals are present on the carrier in the form of their sulphides. In addition to the catalytically active metals mentioned above, the catalysts may also contain other catalytically active metals and promoters such as phosphorus, boron and halogens, such as fluorine and chlorine. Very suitable carriers for the present catalysts are oxides of elements of the Groups II, III and IV of the periodic system, such as silica, alumina, magnesia and zirconia, or mixtures of the said oxides, such as silica-alumina, silica-magnesia, alumina-magnesia and silica-zirconia.
Aluminas and silica-aluminas are preferred as carriers for the present catalysts. ~ ~
The metal loads of most commercial catalysts which contain the ~ -cobal~/molybdenum metal combination supported on alumina or silica-alumina as carrier and which are recommended for the treatment of hydrocarbons with hydrogen as a rule amount to approximately 15 parts by weight of metal per 100 parts by weight of carrier. In the experimental work upon which the Canadian patent mentioned above is based, which patent refers to the relationship between porosity and particle si~e of catalysts and the hydrogen partial pres-sures used on the one hand, and the suitability of these catalysts for hydro~
desulphurization of vanadium- and nickel-contalning residual hydrocarbon oils in the presence of water without catalyst replenishment on the other, it was assumed that also for this Canadian patent the above metal load pro-duces the most attractive results. As can be seen from the examples of this Canadian patent~ the metal load of the cobalt-molybdenum catalysts is only varied between 13.3 and 16.1 parts by weight per 10~ parts by weight of carrier. Continued research has now shown that the metal load of these cat-alysts can be greatly reduced without impairing their suitability for the desulphurization of residual hydrocarbon oils. Thus, for example, it was found that a catalyst which contained 2.0 parts by weight of cobalt and 5.5 parts by weight of molybdenum per 100 parts by weight of alumina possessed the same excellent suitability for the desulphuri~ation of -residual hydrocarbon oils in the presence of water as a catalyst which contained 4.3 parts by weight of cobalt and 10.9 parts by weight of molybdenum per 100 parts by weight of alumina, p, d and PH remaining the same. The discovery of the fact that a lower metal load can be used than had been assumed until recently is of course very important with a view to the cost of catalyst preparation.
A lower metal load saves metals and may result in a simplifi-cation in the catalyst preparation. If use is made in the process lO according to the invention of a catalyst which contains cobalt and molybdenum supported on alumina or silica-alumina as a carrier, it is preferred, in view of the above, to select a catalyst which contains 5-10 parts by weight of metal per 100 parts by weight ~r~ of carrier. This preference for a low metal load of course alsot 15 ~ applies if in the process according to the 'J~ t -r ~ -~
mentioned above a catalyst is used which contains cobalt and molybdenum supported on alumina or silica-alumina.
The catalysts which are applicable according to the invention may be prepared by supporting the relevant metals on a carrier having such a specific average pore diameter that after the metals have been supported thereon, a catalyst is obtained which satisfies the requirements of the invention, either as such or after the specific average particle diameter has been increased or re-duced. The preparation of the present catalysts is preferably carried out by single-stage or multistage co-impregnation of a carrier with an aqueous solution compris;ng one or more nickel and/or cobalt compounds and one or more molybdenum and/or tungsten compounds, followed by drying and calcination of the composition.
When drying the compositions, which drying is usually carried out at temperatures between 100 and 15ooc~physically bound water is removed from the compositions; during calcination of the compositions, which calcination usually takes place by heating the compositions to a final temperature between 450 and 550C and maintaining the com-positions for some time at this final temperature, decomposition of the metal salts occurs with formation of the corresponding metal ; oxides. The nickel and cobalt compounds used in the preparation of the present catalysts are often the nitrates. As molybdenum and tungsten compounds ammonium molybdate and ammonium tungstate are often used.
It has been found that considerable thermal effects may occur in the calcination of the present compositions, which effects may have a detri-m~ntal influence on the activity of the ultimate catalysts. For the prepara-tion of catalysts with high activity it is therefore important to keep these thermal effects in the calcination as small as possible. One of the causes of strong thermal effects in the calcination is the simultaneous decomposition of nitrates and ammonium compounds. The thermal effects associated with this decomposition can be avoided by using nickel or cobalt formates instead of nitrates in the preparation of the catalysts. Another possibility to keep the thermal effectsoccurring in the calcination as small as possible is to carry out the calcination very cautiously, for example by using a low rate of heating-up, step-by-step heating, etc. Local overheating of the composi-tion during calcination with all its detrimental effects on the activity of the ultimate catalyst can largely be avoided by ensuring effective heat re-moval during calcination, for example by passing a high-velocity gas stream over the material to be calcined and by calcining the material in a relative-ly t~in layer.

For information on methods which can be used to influence the po~osity of the carrier material of the catalyst and for further particulars of preferred methods of preparation for the present catalysts, reference is made to the Canadian Patent 985,651, wherein these subjects are discussed in detail.
The catalytic hydrodesulphurization of residual hydrocarbon oils without catalyst replenishment is preferably carried out by passing the hydro-carbon oil at elevated temperature and pressure and in the presence of hydrogen in an upward, downward or radial direction through two or more ver-tically arranged fixed catalyst beds. The hydrocarbon oil to be desulphurized may be completely or partly saturated with hydrogen and a hydrogen-containing gaseous phase may be present in the reactor in addition to the hydrocarbon phase and the catalyst phase.

p~

The hydrodesulphurization according to the invention may be carried out in one single reactor or in two or more reactors. If the process accord-ing to the invention is carried out in one reactor, it should at least contain two catalyst beds J the first catalyst bed of which (viewed in the direction of the liquid flow) and possibly one or more immediately subsequent beds contain a catalyst or combination of catalysts designated hereinbefore as catalyst I
and the final catalyst bed ~viewed in the direction of the liquid flow) and possibly one or more immediately preceding beds contain a catalyst designated hereinbefore as catalyst II. If the process according ~o the invention is carried out in ~wo or more reactors, the first reactor and possibly one or more immediately subsequent reactors should contain catalyst I and the final reactor and possibly one or more 1mmediately preceding reactors should contain catalyst II. The catalysts which are applied in the individual catalyst beds and/or individual reactors may differ from each other as regards their chemi-cal composition.
An attractive manner to supply steam in the process according to the invention consists in that water is added between two or more of the catalyst beds or reactors. In this manner the addition of water assists in reducing the temperature of the partl~ desulphurized product, which has risen as a result of the exothermic desulphurization reaction.
The speci~ic average particle diameter of the catalysts which are used according to the invention is as a rule 0.5-2.5 mm and preferably 0.6-2.0 mm. If the value d which is required according to the invention to achieve a good catalyst performance at a given p and PH is too small for practical application, the desulphurization may be carried out in the presence of porous agglomerates prepared from the small catalys~ particles in a manner as de-scribed in Canadian Patent 985,651.
The reaction conditions used in the hydrodesulphurization according to the invention may vary between wide limits. The hydro-desulphurization is preferably carried out at a temperature between 300C and 475C, a hydrogen partial pressure of 30-200 bar, a space velocity of 0.1-10 parts by weight of fresh feed per part by volume 7~

of cat~lyst per ho~ and a hydrogen/feed ratio of 150~2000 Nl of H2/kg of feed. Special preference is given to a temperature of 350C-445C, a hydrogen partial pressure o~ 40-160 bar, a space ve ocity of 0.3-3 parts by weight of fresh feed per part by volume of catalyst per hour and a hydrogen/~eed ratio of 250-1000 ~l of H2/kg of feed.
The hydrodesulphurization accoraing to the in~ention may very suitably be preceded by a demetallization treatment. As a result of the demetallization ~e deactivation of the desulphur-ization catalyst combination is suppressed and its life is con-sequently prolonged. The demetallization of residual hydrocarbon oils is preferably carried out in the presence of hydrogen and a catalyst. Demetallization may ver~ suitably be effected by passing the hydrocarbon oil at elevated temperature and pressure and in the presence of hydrogen in an upward, downward or radial direction through one or more vertically arraneed reactors which contain a fixed or moving catalyst bed. In a very attractive embodiment o~
the demetallization, the hydrocarbon oil is passed through a vertically arranged catalyst bed into which, cluring operation,

2 ~resh catalyst is inter~ittently introduced at the top of the bed and spent catalyst is withdrawn from the lower part thereof (demetallization according to the bunker flow principle). In another very attractive embodiment of the demetallization treatment several reactors containing a ~ixed catalyst bed are present5 which reactors are alternately used for the demetallization treatment. While demetallization is carried out in one or more of these reactors, the catalyst is replenished in the remaining re~ctors (demetallization according to the fixed bed swing principle). If desired, demetallization can also be carried out by suspending the catalyst in the hydrocarbon oil to be de-metallized (demetallization according to the slurry phase principle).
If the desulphurization a~cording to the in~ention is preceded by a demetallization treatment, steam may very suitably be introduced by adding water to the demetallized product after the latter has left the demetallization reactor and before it enters the first de-sulphurization reactor. In this manner the addition of water assists in reducing the temperature of the demetallized product, which has risen as a result of the exothermic demetallization reaction.
Suitable catalysts for demetallizing residual hydrocarbon oils are catalysts which contain one or more metals ha-ving hydrogen-ating activity supported on a carrier.
If the desulphurization according to the invention is preceded by a demetallization treatment, the demetallization is preferably ~arried out according to the bunker flow principle or according to the fixed bed swing principle and the desulphurization is effected over two or more conventional fixed catalyst beds.
As has been noted above, the demetallization of a vanadium-and nickel-containing residual hydrocarbon oil results in a prolonged life of the catalyst combination which is used for the hydrodesulphur-iz~tion of the demetallized oil. For the catalytic hydrodemetallization f a vanadium- and nickel-containing residual hydrocarbon oil fol-lowed by desulphurization of the demetallized oil according to the present invention, applicant has derived the following equation:
M2 C (1.o5~o~2o)xM1x(L1/L2) 5 , wherein M1 and M2 represent the metal contents of the non-demetallized and the demetallized oil respectively and L1 and L2 represent the lives of the desulphurization catalyst combination when used for the non-demetallized and the demetallized oil respectively. In drawing up this equation the following limitations have been taken into account:
(l) the metal content of the hydrocarbon oil before de-metallization (M1) may vary between 25 and 1500 ppmw (parts by weight per million), (2) the life of the desulphurization catalyst combination used for the demetallized oil (L2) may vary between 2000 and 16,000 hours;

(3) the quotient of the metal contents o~ the hYdrocarbon oil after and before demetallization (M2 and M1) may vary between 0.75 and 0.10, and

(4) the product of the metal content of the hydrocarbon oil before demetallization (M1) and the life of the desulphur-ization catalyst combination used for the demetallized oil (L2) may vary between 2 x 105 and 3 x 1 o6 .
The above-mentioned relationship between L1, L2, M1 and M2 offers the possibility, during the hydrodesulphurization of a residual hydrocarbon oil according to the present invention, using prior catalytic hydrodemetallization of the feed, to establish to what value the metal content of the feed has to be reduced in order to prolong ~e life of the desulphurization catalyst combination by a certain number of hours.
As observed hereinbefore, the deactivation of the desulphur-ization catalyst combination can be suppressed and consequently its life prolonged, by preceding the desulphurization by a catalytic demetallization. This observation implies that, if a feed that has previously been catalytically demetallized is processed over a certain quantity by volume of the catalyst combination9 the liEe of the catalyst combination will be longer than when the non-demetallized feed is processsed over the same quantity by volume of the catalyst combination. Therefore, upon application of a catalytic demetallization as referred to hereinbefore, the feed will be contacted with a larger quantity by volume of catalyst than when no demetallization is applied, since in the former case, besides a specific quantity by volume of the desulphurization catalyst combination, which is the same in both cases, a certain quantity by volume of demetallization catalyst is used in addition.
Upon continuation of the studies concerning the catalytic hydroaemetallization of vanadium and nickel-containing residual hydrocarbon oils followed by catalytic hydrodesulphurization of the demetallized oil using a com~ination of two desulphurization catalysts according to the present patent application, it was found that the life of the desulphurization catalyst combination in maintaining a certain desulphurization level can be con-siderably prolonged, while keeping the total quantity by volume of catalyst constant, when part of the desulphurization 7~

catalyst combination is replaced by a demetallization catalyst and when, in addition, the following requirements are met.
1) The desulphurization catalyst combination comprises only two single desulphurization catalysts, of which the first is indicated as catalyst I and the second as catalyst II, 2) the residual hydrocarbon oil that is used as the feed has a total vanadium and nickel content above 120 ppmw;
3) the demetallization catalyst, indicated as catalyst 0, meets the following requirements:
a) the catalyst comprises one or more metals having hydrogenation activity on a carrier;
b) p/d>3.5-0.02 v, in which v is the percentage of the total pore volume that consists of pores with a diameter larger than 100 nm;
c) the total pore volume is larger than 0.40 ml/g;
d) the specific surface area is larger than 100 m2/g, but in cases where the catalyst has such a p and d that the quotient p/d is lsrger than 3.5-0.02 v, but at most 10-0.15 v, the catalyst has to meet the following 2 additional requirements:
e) the nitrogen pore volume is larger than o.60 ml/g;
f) the specific surface area is larger than 150 m /g, and g) p i5 larger th~n 5 nm, 4~ catalyst 0 hss a larger totsl pore volume than catalyst I,

5) catalyst 0 and catalyst I have such a p, d and v that the following relation is met:

C P ( ) ~cat.0 1-2X(L~P/(d) ~cat I-0.8(vo~v~

6) the percentage of the joint catalyst volume of catalysts 0, I and II that is occupied by catalyst 0 amounts to at least 1 O%v.

Tr~e cataly~tic h~drodemetallization of residual hydrocarbon oils us-ing a catalyst ~hich meets the requirements given hereinbefore under a) to g) is described in Canadian Patent Applications Nos. 172,040; 221>547; 212,563;
230,072 and 232,027.
The present patent application therefore also relates to an improved process for the catalytic hydrodesulphurization without catalyst replenishment of vanadium and nickel-containing residual hydrocarbon oils, which process is carried out in the presence of a quantity of water corresponding with a water vapour partial pressure during the process of 0.5-30 bar ~further called "im-proved embodiment of the invention"), in which process the hydrocarbon oil is successively contacted with a single catalyst I and a single catalyst II, which catalysts meet the following requirements:
~a) Both catalysts have a to~al pore volume larger than 0.30 ml/g of which the percentage ~v) that consists of pores with a diam-eter larger than 100 nm is less than 10;
; C5) catalyst II has such a specific average pore diameter ~p) and a specific average particle diameter (d) that the quotient p/~d)0'9 meets the requirement 10 X(PH ) ~ [p/(d) ~cat II ~ 4-~13xIo 4x(PH )2;

2U ~c) the percentage of the joint catalyst volume of catalysts I and II that is occupied by catalyst II ~%v cat. II~ lies between 10 and 90% and meets the requirement:

40x~ 5 xlO0) x(PH ) < ~Ov cat.II < 300x( Px100)2x~PH ) 2, in which SF is the sulphur content of the feed and Sp is the desired sulphur content of the desulphurized product ; (p in nm, d in mm, PH in bar, Sp and SF in %w).
The improvement consists in the fact that the desulphurization is preceded b~ a catalytic hydrodemetallization using a demetallization catalyst 0, the requirements given hereinbefore under 2) to 6) being met.

As demetallization catalysts preference is given to the catalysts described in above-mentioned Canadian Patent Application Nos. 172,040;
221,547; 212,563; 230,072; and 232,027.
Examples o~ ~eeds to which the process according to the invention can be applied are crude oils and residues obtained by distillation of crude oils at atmospheric or reduced pressure. Residues obtained during the dis-tillation of products originating ~rom thermal or catalytic cracking of heavy hydrocarbon oils ma~ also be treated in accordance with the invention.
The invention will now be elucidated with reference to the follow-ing Examples.
EXAMPLE I
; Seven combinations of two different catalysts as well as each of these catalyst separately (catalysts A-M) were used for the hydrodesulphuriza-tion of five vanadium- and nickel-containing residual hydrocarbon oils ~oils A-E) without catalyst replenishment. Desulphurization of the oils was effect-ed ~y passing these oils at elevated temperature and pressure and in the pre-sence o~ hydrogen and steam in a downward direction through two cylindrical fixed catalyst beds.
The experiments were carried out in series of three. Per series oE
2a three experiments the same oil was desulphurized under the sc~me conditions and with the same volume of catalyst to the same sulphur content in the product ~Sp). In one of the three experiments the first catalyst bed contained the catalyst referred to below as catalyst I and the second bed the catalyst refer-red to below as catalyst II. In the two remaining experiments both catalyst beds contained either exclusively catalyst I or exclusively catalyst II.
The desulphurization experiments were carried out at an initial temperature of 360 + 5C, a space velocity of 0.7 kg.l l.h 1, a gas velocity of 600 Nl of H2/kg 1, a hydrogen partial pressure varying from 75 to lS0 bar and a water vapour partial pressure varying from 2 to 10 bar. To prepare a praduct having a constant sulphur content, the temperature had to be gradu-ally increased during the experiments. The desulphurization experiments were terminated at the moment when a temperature in excess of 420C

had to be used in order to prepare a product with the d0sired sulphur content.
The composition and properties of the catalysts 9 which were used in the form of their sulphides, are stated in Table A.
For info~mation on the preparation of the nine catalysts used in the present experiments reference is made to the examples of our ~etherlands patent application 7214397, wherein the preparation of these catalysts has been described in detail.
The preparation of the catalysts B~ and D~ was effected in the same manner as described for the catPlysts B and D, with the proviso that a lower metal load was used in the preparation of the catalys~ B~ and D~. The five residual oils involved in the investigation are described in greater detail below. The results of the desulphurization experiments are stated in Table B.
OIL A
Oil having a total van~dium and nickel content of 75 ppmw and a sulphur content of 4.0% by weight, obtained as residue in the distillation at atmospheric pressure of` a Middle East crude oil.
OIL B
Oil having a total vanadium and ni~kel content of 6l~ ppmw and a sulphur content of 4.0% by weight, obtained as residue in the distillation at at~ospheric pressure of a Middle East crude oil.
OIL C
Oil having a total vanadium and nic~el content of 77 ppmw and a sulphur content of 2.0% by weight, obtained as residue in the distillation at atmospheric pressure of a product prepared by the thermal cracking of an atmospheric distillation residue of a Middle East crude oil.
OIL D
Oil having a total vanadium and nickel content of 225 ppmw and a sulphur content of 2.0% by weight, obtained as residue in the distillation at atmospheric pressure of a Caribbean crude.
OIL E
Oil having a total vanadium and nickel content of 130 ppmw and a sulphur content of 1.9~ by weight, obtained by demetalli~ation of oil D. The demetallization of oil D was carried out by passing it at elevated temperature and pressure and in the presence of hydrogen in a downward direction through a ~rtically arranged fixed bed of a demetallization catalyst. The demetallization 5 catalyst contained 0.5 par~ by weight of nickel and 2.0 parts by weight of vanadium per 100 p~rts by weight of silica carrier.

.; , _ 20 --. ~ . . .

- . _. _. , . . - O O ~

0 ~ D CO
~O ~O 0 ~ ~ C~

C~d ~ ~1 ~ h ~ ~ ~ ~ C ~ ~S
,~ O ~ O~ rl r p.,( P
.
~, h 8 ~ ~ ~ ~o 0 ~ ~ ~ ~ u~ ~
,~ O o ~ O ~ v-- U~ V . . r~ D 0 ' ~ ~ p~ p ~ \
~, ~
~ ~ o o~ ~ 0 ~ .
O Q~ h ,1 h ~ ~ ~o ~ ~i 0 C~i ~U co u~
,s:: Q o ~ O~ ,1 o ,_ ~_ .
. ~ p~ lx .' E~bO C~l ~ O ~ ~ O W t-c~ I ~h h ~ O u~ ~o ~ O Lr~ . .
a~ ~ ~ ~:
; h r-l h ~ ~ ~ ~ J~
~,~ pO S~ æ~~!~'vl~ . . .
~ I ^ bD ~ t-- C0 c0 O ~ N (~
h ~-1 a) ~ Lr~ o 0 ~ Po a ~ 0 0 0 0 0 0 0 0 ,, ~
. __ O O O O O O O O
. .
, ~ ~-- -- . -- .. .... , _ , 5~ ~ ~ U~ ~
h :~ ~ ~ o O

n ~j~l C) ~ C~ O t~ ~ ~0 .. : .
~0 _ . .~
rl _ ~ 1_1,,1,.~1 1~. ' ~ _ _ TABLE B

_, _ , _ Exp. Oil SEl~ Sp, H ' H O' Cat.I, Cat.II, %v, Li~e of No. No. %w %w bar ba2r No. No. Cat.II cat combination, hours _ _ _ _ .
I A 4.0 o.5 150 5 B D 30 3000 I ' A 4 . 0 o. 5 150 5 B~ _ O 1400 I" A 4.0 o.5 150 5 _ D100 2000 II B 4.0 1.0 125 10 M D 30 5800 II' B 4.0 1.0 125 10 M _ O 4200 II" B 4.0 1.0 125 10 _ D100 3800 III B 4.0 o.5 125 3 M D 50 3600 III' B 4.0 o.5 125 3 M _ O 300 III" B 4 . 0 o. 5 125 3 _ D100 2000 IV A 4 . 0 o . 5100 7 B D 35 4500 IV ' A 4 . 0 o . 5100 7 B _ O 2200 Ir' A 4.0 o.5 100 7 _ D100 2800 V A 4.0 1.0 75 2 C D 50 4200 V' A 4.0 1.0 75 2 C _ O 200 V" A 4 . 0 1 . 075 2 _ D100 2400 VI D 2.0 o~5 150 10 M D 30 t300 VI' D 2.0 o~5 150 10 M _ 3 700 VI" D 2.0 o.5 150 10 _ D100 800 VII E 1.9 0.5 150 10 M D 40 4200 VII' E 1.9 o.5 150 10 M _ O 1500 VII" E 1.9 o.5 150 10 _ D100 2700 VIII A 4.0 1.0 75 10 C H 70 3800 VIII' A 4.0 1.0 75 10 C _ O 400 VIII" A 4.0 1.0 75 10 _ , H 100 3000 IX A 4.0 1.0 100 5 A D 35 5500 IX' . A 4.0 1.0 100 5 A _ O 3300 IX" A 4.0 1.0 100 5 _ D100 4300 X A 4.0 o.5 100 10 A D60 3900 X' A 4.0 o~5 100 10 A _ O 700 X" A 4.0 ~.5 100 10 _ D100 2800 XI D 2.0 o~5 100 5 A D35 2000 XI' D 2.0 o~5 100 5 A _ O 1300 XI" D 2.0 o~5 100 5 _ D100 1550 XII C 2.0 o~5 100 5 A D50 2000 XII' C 2.0 o.5 100 5 A _ O - 400 XII" C 2.0 o.5 100 5 _ D 100 1200 A A 4.0 o.5 150 5 A H40 1500 A' A 4 5 150 5 A _ O 1000 A" A 4 . 0 0 . 5150 5 _ H 100 2200 _ ~ . _ _ _ . . ... _ I

Of the experiments stated in Table B, only experiments I~XII
are desulphurization experiments according to the invention. The remaining experiments have been incorporated in the Table ~or the purpose of comparison.
In the experiments I-XII, catalyst combinations were used of which each catalyst satisfied the requirements made in respect of porosity and particle size; in these experiments the requirements made in respect of "~vol. of catalyst II" were also satisfied.
Wben the life of each~f the catalyst combinations used in the experiments I-XII as stated in the final column of Table B is compared with the life of the individual catalysts used in the relevant experiments I'-XII' and I"~XII", the improvement in catalyst life which is achieved by using the catalyst combinations of the invention is ~early demonstrated.
The experiments A, A' and A" have also been incorporated in Table B for the purpose of comparison. Althoueh a combination of t~o catalysts was used in the experiment A, it did not satisfy the - reguirements set. In the experiment A a catalyst was used as catalyst I of which the quotient p/(d) 9 was too small. When the life of the catalyst combination used in the experiment A as stated in the final column of Table B is compared with the life of the individual catalysts used in the relevant experiments A' and A", it is found that although application of this catalyst combination produces an improvement in catalyst life in respect of individual applic~tion of one of the two catalysts of the combination, it produces a loss in catalyst life in respect of separate application of the other catalyst of the combination.
EXAMPLE II
.
This example demonstrates the "improved embodiment of the invention" discussed hereinbefore.
Ca~alyst combinations consisting of a demetallization catalyst (catalysts 1, 11 and 40), a ~irst desulphurization catalyst (catalyst A) and a second desulphurization catalyst (catalyst D) were employed for hydrodemetallization followed by hydrodesulphurization without catalyst replenishment of two vanadium and nickel-containing reElidual hydrocarbon oils

7~

(oils D and F). Moreover, catalyst combinations consisting of the two desulphurization catalysts A and D and also each of these two catalysts separately were employed for the hydrodesulphurization without catPlyst replenishment of the two oils. Demetallization/
desulphurization or only desulphurization of the oils was carried out by~passing the oils together with hydrogen and steam downwards through three cylindrical vertically disposed fixed catalyst beds at elevated temperature and pressure.
The experiments were carried out four by four. In each set of four experiments the same oil was desulphurized under the same con-ditions and with the same volume of catalyst, down to the same sulphur content in the product. (In all the experiments Sp was 0.5%w). In one of the four experiments the first catalyst bed contained the demetallization catalyst indicated hereinafter as cQtalyst 0, the second catalyst bed the desulphurization catalyst indicated hereinafter as catalyst I and the third catalyst bed the desulphurization catalyst indicated hereinafter as catalyst II.
In the three remaining experiments the three catalyst beds con-tained either a combination of catalyst I and catalyst II suc~
cessively or catalyst I exclusively or catalyst II exclusively.
The desulphurization experiments were carried out at an initial temperature of 360 ~ 5C, a space velocity of 0.7 kg.l 1.h 1, a gas rate Or 600 Nl H2.kg 1, a hydrogen partial pressure of 100 or 150 bar and a water vapour partial pressure varying from 5 to 15 bar. For the preparation of a product hsving constant sulphur content the temperature had to be Eradually increased during the experiments.
The desulphurization experiments were ended when a temperature of 420C had to be applied to prepare a product having the desired sulphur content.
The demetallization was carried out at a constant temperature of 420 C and a hydrogen partial pressure and gas rate corresponding with those applied in the desulphurization. In ~ase of demetallization followed by desulphurization the space velocity throughout the catalyst system amounted to 0.7 kg.l 1.h 1.
The catalysts were applied in the form of their sulphides~ The desulphurization catalysts A and D have already been described in Example I. The composition and properties of the demetallization catalysts 1, 11 and 40 are given in Table C. For information concerning the preparation of catalysts 1 and 11 reference is made to the working examples of Netherlands patent application No.
7309387 in which the preparation o~ these catalysts is described ~, in detail. Catalyst 40 is a demetallization catalyst within the scope of Netherlands patent application ~o. 7309387, which catalyst was prepared by co-impregnation of an alumina carrier with ~n aqueous solution containing vanadyl oxalate and nickel nitrate, followed by drying and calcination of the composition.
Of the two residual oils u ed in the experiments oil D has already been described in Example I. Oil F is further described hereinafter. The results of the experiments are given in Table D.
OIL F
An oil having a total vanadium and nickel content of 410 ppmw and a sulphur content of 2.0%w, which oil had been obtained as a residue in the atmospheric distillation of a Caribbean crude oil.
TABLE C

Cat. Metal load, Carrier Pore Total ~itrogel v, % P, nm d, ~:
No. pbw per 100 vol., pore pore pbw o~ mllg volume, volume, c~rrier ml/g ml¦g __. . _ 1 _ 2.0 A1203 225 0.57 o.56 <0.5 IQ.2 0.7 11 o.5 2.0 SiO2 243 o.81 0.74 9 9.0 2.2 0.5 2.0 A1203 220 o.60 0.57 1.5 14.9 1.5 TABLE D

Exp. Oil P~ . H O' C~t.O %v %v Cat.I %v Cat.II Cat. life of No. ~o. 2 2 No. Cat.O (Cat. (Cat.cat. or cat.
bar bar ~o. A) No. D) combination, _ _ . _ XIII D ~ 50 10 1 ~0 ~5 15 ~goo XIII' D 150 10 _ _ 75 25 1300 XIII" D 150 lO _ _ 100 _ 600 XIII"' D 150 10 _ _ _ 100 ôO0 XIV D tO0 5 1 40 42 18 4000 XIV' D 100 5 _ _ 70 30 2800 XIV" D 100 5 _ _ 100 _ 1300 XIV"' D 100 5 _ _ _ 100 1550 XV F 150 5 11 5o37.5 12.5 t200 XV' E 150 5 _ _ 75 25 800 XV" F 150 5 _ _ 100 _ 300 XV"' F t50 5 _ _ _ 100 35 XVI' D t50 15 _ _ 75 25 1300 XVI" D 150 15 _ _ 100 _ 600 XVI"' D 150 15 - - - loo 80o . . _ __ __ _ _ _ Of the experiments given in Table D only experiments XIII-XV are demetallization1desulphurization experiments sccording to the "improved embodiment of the invention". The other experiments have been included in the Table for comparison.
In experiments XIII-XV catalyst combinQ~ions were applied in which each of the catalysts satisfied the requirements concerning - porosity and particle size; the other requirements according to the "improved embodiment of the invention" were also satisfied in these experiments. Comparison of the lives of each of the catalyst com-binations O/IlII given in the last column o~ Table D and applied in experiments XIII-XV with the lives of the catalyst combinations IIII applied in the associated experiments XIII'-XV' clearly shows the gain in catalyst life which is achieved upon application of catalyst combinstions according to the "improved embodiment o~
the m vention".

.

t~

It is true that a suitable catalyst combination I/II was a:pplied in experiment XVI (and that this experiment therefore fslls within the scope of the present patent application), but the quotient p/(d)9 of the cataly~t O applied was too low - 5 to meet the requirements of the "improved embodiment of the invention".
Experiments XIII'-XVI' are also experiments within the scope Or the present patent application.
It i8 pointed out that experiments XIII', XIII" and XIII"' given in Table D are identical with experiments XVI', XVI" and XVI"' , respectively, also in this Table and that experiments XIV" and XIV"' in Table D are identical with experiments XI' and XI" in Table B.

Claims (29)

C L A I M S

1. A process for the catalytic hydrodesulphurization of vanadium-and nickel-containing residual hydrocarbon oils without catalyst replenishment, which process is carried out in the presence of a quantity of water corresponding with a water vapor partial pressure during the process of 0.5-30 bar and in which process the hydrocarbon oil is consecutively contacted with a catalyst I
and a catalyst II which satisfy the following requirements:
(a) each of the individual catalysts of which the combination of catalyst I and catalyst II is composed has a total pore volume in excess of 0.30 ml/g of which less than 10% is present in pores having a diameter in excess of 100 Nm;
(b) catalyst II has a specific average pore diameter (p) and a specific average particle diameter (d) such that the quotient p/(d)0.9 of catalyst II satisfies the requirement:
104x(PH2)2 ? [ p/(d)0.9]cat.II?4 +13x10-4x(pH2)2;
(c) if the combination of catalyst I and ca-talyst II is composed of two catalysts, catalyst I haa a p and d such that the quotient p/(d)° 9 of catalyst I satisfies the requirement:
1.2[p/(d)]cat.II?[p(d)]catI?5+30x10-4x(pH2)2, while if the combination of catalyst I and catalyst II is composed of more than two catalysts, the above requirement in respect of [p/(d)0.9]cat.I applies to the average p/(d)0.9 of catalyst I which is determined as the weight average of the values of p/(d)0.9 of each of the individual catalysts of which catalyst I is composed;
(d) the percentage of the total catalyst volume which is taken up by catalyst II (%vol. of catalyst II) is between 10 and 90%
and satisfies the requirement:
wherein SF represents the sulphur content of the feed and Sp the required sulphur content of the desulphurized product, and (e) if the combination of catalyst I and catalyst II is composed of more than two catalysts, each of the individual catalysts of which catalyst I is composed has a p and d such that the quotient p/(d)0.9 of each of these catalysts is greater than [p/(d)cat.II (P in nm, d in mm, PH2 in bar, Sp and SF in percentage by weight).

2. A process as claimed in claim 1, in which the quantity of water used corresponds with a water vapour partial pressure during the process of 1-15 bar

3. A process as claimed in claim 2, in which catalyst II has a total pore volume in excess of 0.45 ml/g.

4. A process as claimed in claim 3, in which catalyst II has a surface in excess of 100 m2/g.

A process as claimed in claim 4, in which catalyst II has a p and d such that the quotient [p/(d)0.9]cat.II satisfies the requirement:
[p/(d)]cat.II?1.2x10-4x(PH2)2.

6 A process as claimed in claim 5, in. which catalyst II has a total pore volume in excess of 0 45 ml/g of which at least 0.4 ml/g is present in pores having a diameter of at least 0.7xp and at most 1.7xp and a sharp pore diameter distribution, in which (a) less than 20% of the pore volume is present in pores having a diameter smaller than 0.7xp;
(b) less than 20% of the pore volume is present in pores having a diameter greater than 1.7xp.

7. A process as claimed in claim 6, which is carried out using one single catalyst as catalyst I.

8. A process as claimed in claim 7, in which the catalyst used as catalyst I has a total pore volume in excess of 0 40 ml/g.

9. A process as claimed in claim 7 or 8 in which the catalyst used as catalyst I has a p and d such that the quotient [p/(d)0.9cat. I satisfies the requirement:
[p/(d)]cat.I?1.4x[p/(d)]cat.II

10. A process as claimed in claim 6, which is carried out using a com-bination of two or more catalysts as catalyst I, which catalysts occur in the reactor separated from each other and preferably in such a sequence that the quotient p/(d)0.9 of each of the catalysts of which catalyst I is composed is smaller than that of the preceding catalyst.

11. A process as claimed in claim 6 which is carried out using a com-bination of two or more catalysts as catalyst I, which catalysts have a total pore volume in excess of 0.40 ml/g.

12. A process as claimed in claim 11, which is carried out using a com-bination of two or more catalysts as catalyst I, which catalysts have a p and d such that the average p/(d)0.9 of catalyst I, which is determined as the weight average of the values of p/(d)0.9 of the individual catalysts of which catalyst I is composed, is at least 1.4 x [p/(d)0.9cat.II.

13. A process as claimed in claim 12 wherein the catalysts contain between 0.5-10 parts by weight of nickel, cobalt, or both and 2,5 to 30 part by weight of molybdenum, tungsten or both per 100 parts by weight of carrier.

14. A process as claimed in claim 12, in which catalysts are used wherein the atomic ratio between nickel and/or cobalt on the one hand and molybdenum and/or tungsten on the other, is between 0.1 and 5.

15. A process as claimed in claim 14 in which the catalysts are used in sulphidic form.

16. A process as claimed in claim 15 in which the catalysts contain alumina or silica-alumina as carrier.

17. A process as claimed in claim 12 13 or 16, in which catalysts are used which contain the cobalt-molybdenum metal combination supported on alumina or silica-alumina as carrier and which contain 5-10 parts by weight of metal per 100 parts by weight of carrier.

18. A process as claimed in any one of claims 12 13 or 16, in which catalysts are used which have been prepared by co-impregnating a carrier in one or more steps with an aqueous solution containing one or more nickel and/
or tungsten compounds, followed by drying and calcining of the composition.

19. A process as claimed in any one of claims 12 13 or 16, in which the catalysts have a specific average particle diameter of 0.5-2.5 mm and preferably of 0.6-2.0mm.

20. A process as claimed in claim 12 which is carried out by passing the hydrocarbon oil to be desulphurized at elevated temperature and pressure and in the presence of hydrogen in an upward, downward or radical direction through two or more vertically arranged fixed catalyst beds, the hydrocarbon oil first coming into contact with one or more catalyst beds which contain catalyst I and subsequently with one or more catalyst beds which contain catalyst II.

21. A process as claimed in claim 20, which is carried out at a temp-erature between 300°C and 475°C, a hydrogen partial pressure of 30-200 bar, a space velocity of 0.1-10 parts by weight of fresh feed per part by volume of catalyst per hour and a hydrogen/feed ratio of 150-2000 N1 of H2/kg of feed.

22. A process as claimed in claim 20, which is carried out a temperature between 350 and 445°C, a hydrogen partial pressure between 40-160 bar, a space velocity of 0.3-3 parts by weight of fresh feed per part by volume of catalyst per hour and a hydrogen/feed ratio of 250-1000 Nl of H2/kg of feed.

23. A process as claimed in claim 20, in which the desulphurization is preceded by a demetallization treatment.

24. A process as claimed in claim 23, in which the desulphurization is preceded by a catalytic hydrodemetallization treatment.

25. A process as claimed in claim 24, in which, in order to prolong the life of the desulphurization catalyst combination, the desulphurization is preceded by a catalytic hydrodemetallization in which the metal content of the oil is reduced from M1 to M2, the degree of demetallization being selected in dependence on the desired extension of the life of the desulphurization catalyst combination in accordance with the equation:
M2=(1.50?0.20)x M1 x (L1/L2)0.5, wherein L1 and L2 represent the lives of the desulphurization catalyst combination when it is used for the non-demetallized oil with a metal content M1 and for the demetallized oil with a metal content M2 respectively, the fol-lowing requirements being also satisfied:
(1) 25?M1?1500 (2) 2000?L2?16000 (3) 0.10?M2/M1?0.75, and (4) 2 x 105?Ml x L2 ? 3 X 106, (L1 and L2 in hours, M1 and M2 in ppmw).

26. A process as claimed in claim 25, in which the dematallization is carried out by passing the hydrocarbon oil at elevated temperature and pres-sure and in the presence of hydrogen in an upward, downward or radial direction through one or more vertically arranged reactors containing a fixed or moving catalyst bed.

27. A process as claimed in any one of claims 25, or 26 in which the demetallization catalyst contains one or more metals with hydrogenating activity, supported on a carrier.

28. A process as claimed in any one of claims 25 or 26 in which the demetallization of the residual hydrocarbon oil is carried out according to the bunker flow principle or according to the fixed-bed swing principle and that the desulphurization is carried out over two or more conventional fixed catalyst beds.

29. An improved process for the catalytic hydrodesulphurization without catalyst replenishment of vanadium- and nickel-containing residual hydro-carbon oils according to any one of claims 25 or 26 in which process the hydrocarbon oil is successively contacted with a single catalyst I and a single catalyst II, which catalysts meet the following requirements:
(a) both catalysts have a total pore volume larger than 0.30 ml/g of which the percentage (v) that consists of pores with a diameter larger than 100 nm is less than 10;