NZ275799A - Silicon compound-impregnated hydrotreating catalyst and use in hydrogenation of oils - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £75799 New Zealand No. 275799 International No. PCT/EP94/03543 Priority Dete{s): Complete Specification Fited: Claw, m ■tww Ltir.!.Hr.

Publication P.O. Journal-No: NO DRAWINGS NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention: Hydrotreating catalyst and process Name, address and nationality of applicant(s) as in international application form: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V., of Carel van Bylandtlaan 30, 2596 HR The Hague, the Netherlands ( & CCyv* 1 275799 HYDROTREATING CATALYST AND PROCESS The present invention relates to a hydrotreating catalyst, to a method for improving the hydrodesulphurization and hydro-denitrification activity of a hydrofining catalyst, and to a hydrotreating process.

The sulphur-containing compounds and nitrogen-containing compounds found in petroleum fractions can cause a variety of adverse effects. For example, sulphur-containing compounds in fuels are known to adversely effect air quality. As a result, sulphur-containing compounds must be reduced in petroleum fractions to a 10 level within the air quality guidelines as set out by the various governmental instances. Nitrogen compounds can adversely affect the storage stability and octane value of naphthas and may poison also downstream catalysts. In addition, by removing nitrogen compounds, air quality is improved to some extent, since it lowers the 15 potential for NOx formation during subsequent fuel combustion.

Crude and other heavy petroleum fractions are typically subjected to hydrodesulphurization and hydrodenitrification in a hydrotreater to significantly reduce the sulphur and nitrogen compounds prior to being subjected to further processing. There has 20 now been found a catalyst having improved hydrodesulphurization activity as well as hydrodenitrification activity. The more active catalyst can be operated at a lower temperature to obtain the same degree of sulphur and nitrogen conversion as a less active catalyst. A lower operating temperature will also prolong catalyst life and 25 decrease operating expenses.

In the prior art several examples of modifications to catalysts are disclosed using silicon compounds as modifying agents. U.S. patent no. 4,038,337, for instance, discloses the treatment of alumina with silicon compounds to provide catalysts which are more 30 active and selective for olefin isomerization. U.S. patents Nos. 4,013,589 and 4,013,590 and Reissue number 30,668 all disclose 2.1 methods for improving the thermal and mechanical properties of alumina by treating it with silicon compounds. U.S. patent No. 3,089,845 discloses that the properties of naphtha catalysts are improved by treatment with a silicon compound such as tetraethyl orthosilicate. U.K. patent number 2,121,430 discloses also the treatment of isomerization catalysts by the treatment with silicon compounds such as ethyl orthosilicate.

European patent application No. 0,494,528 discloses a catalyst composition, useful in hydrotreating hydrocarbon oils, which catalyst composition is comprised of at least one salt and/or complex of at least one Group VIII metal with at least one Group VI metal heteropolyacid on an inorganic oxide support material and which catalyst composition is substantially free of free water. The inorganic oxide support may be treated with a silicon compound prior to incorporation of the catalytically active metals in the aforesaid form of a salt and/or complex. No calcination of the catalyst after incorporation of the metals takes place, as this would destroy the salt and/or complex.

The instant invention relates to a hydrotreating catalyst which comprises a Group VIB metal component and/or a Group VIII metal component on an alumina support, which catalyst has been impregnated with a liquid form of a silicon compound having the general formula U I (OSi ) aW I V wherein U, V, W, X, Y, and Z can individually be -R, -OR, -CI, -Br, -SiH3, -COOR, -SiHnClm, R being either hydrogen, or an alkyl, cycloalkyl, aromatic, alkyl aromatic, alkylcycloalkyl radical having from 1 to 30 carbon atoms, "nM and "m" being whole numbers in the range of. front-I .to: 3. and..-"*.", being.; whole.- numb rex • in:, the ranqe.jof. from 0 to 80 in an amount sufficient'to-deposit: -from-215 ;to..-8r.0;'.pcrccntt . by weight of the total.catalyst of SI, and.subsequently calcined at a temperature ranging from 300. °C. to 60Q °C in an oxidizing X I Y Si I Z SHEE~ AMtriULQ SHEET 2."7S"79? - 2a - atmosphere. The instant catalysts have an enhanced hydrodesulphurization and hydrodenitrification activity.

The present invention also relates to a process for improving the hydrodesulphurization and hydrodenitrification activity of a hydrotreating catalyst which comprises a Group VIB and/or Group VIII metal component supported on an alumina support, which process comprises impregnating this catalyst with a liquid form of the above defined silicon compound and subsequently calcining the impregnated catalyst at a temperature ranging from 300 ®C to 600 *C in an oxidizing atmosphere.

The catalysts that are to be treated with the silicon- AMF.NiiCD containing organo-corapounds according to the method of the instant invention comprise Group VIB and/or Group VIII metals supported on an alumina support. Preferably, they comprise a Group VIB hydrogenating metal component selected from nickel, cobalt and 5 mixtures thereof and a Group VIII non-noble metal component selected from molybdenum, tungsten and mixtures supported on alumina. More preferably the catalysts comprise nickel and molybdenum supported on alumina or cobalt and molybdenum supported on alumina. The catalysts may optionally be promoted with phosphorous. The Group VIB 10 and/or Group VIII metals present in the catalyst may be present in elemental form, as oxides, as sulphides or as a combination of two or more of these forms.

The metal-containing catalysts that are to be treated with silicon are catalysts that are known in the hydrocarbon 15 hydroprocessing art. These catalysts are made in a conventional fashion as described in the prior art. For example, porous alumina pellets can be impregnated with solution(s) containing the Group VIB and/or Group VIII metal compounds and optionally phosphorous compounds, the pellets subsequently dried and calcined at elevated 20 temperatures. Alternately, one or more of the components can be incorporated into an alumina powder by mulling, the mulled powder formed into pellets and calcined at elevated temperature. Combinations of inpregnation and mulling can be utilized. Other suitable methods can be found in the prior art. Examples of 25 catalyst preparative techniques can be found in U.S. patents Nos. 2,510,189; 4,530,911; 4,520,128. The catalysts are typically formed into various sizes and shapes. They may be suitably shaped into particles, chunks, pieces, pellets, rings, spheres, wagon wheels, and polylobes, such as bilobes, trilobes and tetralobes. 30 The metals-containing catalysts are impregnated with a liquid form of a silicon compound having the general formula X U I I Y—Si—(OSJ )aW I I Z V WO 95/11753 PCT/EP94/03543 > _ 4 - wherein U, V, W, X, Y, and Z can individually be -R, -OR, -CI, -Br, -SiH3, -COOR, -SiHnClm, R being either hydrogen, or an alkyl, cycloalkyl, aromatic, alkyl aromatic, alkylcycloalkyl radical having from 1 to 30 carbon atoms, "n" and "m" being whole numbers in the S range of from 1 to 3 and na" being a whole number in the range of from 0 to 80, preferably in the range of from 5 to 60, in an amount sufficient to deposit from 2.5 percent to 8.0 percent, preferably from 3.0 percent to 6.0 percent by weight of the total catalyst of Si, and subsequently calcining said impregnated catalyst at a 10 temperature ranging from 300 °C to 600 °C in an oxidizing atmosphere.

In a particularly preferred embodiment, the cobalt/molybdenum catalysts are impregnated with a liquid form of the aforementioned silicon compound wherein U, V, W, X, Y, and Z can individually be -R or -OR, R being either hydrogen, or an alkyl, cycloalkyl, IS alkylcycloalkyl radical having from 1 to 30 carbon atoms.

The silicon-containing compounds are used in the liquid form to impregnate the catalysts. The silicon compounds may be used neat when they are in liquid form and their viscosity is such that they can readily be impregnated. Viscosities of less than 100 20 centiStokes (cSt), measured at 40 °C are suitable, and viscosities of less than 75 cSt are preferred. The viscosity of the silicon compound is directly related to the value of "a" in the above formula. Listed below are the viscosities for silicon compounds of the above formula in which U, V, W, X, Y, and Z are individually 25 methyl and the corresponding value for "a" is as noted: a Viscosity (cSt) 0 0.65 1 1.0 2 1.5 3 2.0 3.0 9 .0 11 7.0 .0 .0 49 50.0 79 100.0 In order to facilitate impregnation, the silicon compounds may be dissolved in suitable organic solvents, such as lower alkanes, alcohols, ketones, aromatics and the like. Also, aqueous emulsions of the organo silicon compounds can be used. The silicone oils are 5 particularly useful, either neat or diluted with an appropriate organic solvent or in aqueous emulsion form. These silicone oils are readily available commercially from various manufacturers, such Dow Corning, Aldrich Chemical Co. (e.g., Aldrich 14,615-3; Aldrich 17,563-3), Petrarch Systems (e.g., Silicone Antifoam aqueous 10 emulsion with 11.8% Si Petrarch PS039.5) and Union Carbide (e.g., L45 (350)}. Preferre erminal groups for the silicone oils are trimethylsilyl groups. Silicone oils with terminal hydroxy groups impregnate with difficulty, probably because of an interaction of the hydroxy group with the alumina support.

In general terms the alumina r sported metals-containing catalysts are impregnated with a I...aid organo silicon compound and subsequently calcined in an oxidizing atmosphere in order to decompose the organo silicon compound to a silicon oxide. The oxidizing atmosphere is one that contains oxygen, and preferably is WO 95/11753 PCT/EP94/03543 ► air. The air may be mixed with nitrogen during the initial stages of the calcination in order to prevent overheating of the catalyst as the silicone material oxidized. To obtain the benefits of the invention it is important that the silicon impregnation be carried 5 out after the metals have been incorporated onto the carrier, rather than before. Thus, the silicon impregnation is applied to a finished catalyst comprising Group VIB and/or Group VIII metals supported on an alumina support.

As indicated, the preferred catalysts to be treated with the 10 silicon compound described above comprise either cobalt and molybdenum or nickel and molybdenum supported on a porous alumina support, preferably comprising gamma alumina. It contains from 1 to 5, preferably from 2 to 4 percent by weight of cobalt or nickel (measured as the metal) and from 8 to 20, preferably from 12 to 16 15 percent by weight of molybdenum (measured as the metal) and, if present at all, - from 1 to 5, preferably from 2 to 4, percent by weight of phosphorous (calculated as the element), all per total weight of the catalyst. The catalyst suitably has a surface area, as measured by the B.E.T. method (Brunauer et al, J. Am. Chem. Soc,, 20 60, 309-16 (1938)) of greater than 120 m^/g and a water pore volume between 0.2 to 0.8, preferably between 0.4 to 0.7 ml/g.

The catalysts of the instant invention are normally presulphided prior to use. Typically, the catalysts are presulphided by heating in H2S/H2 atmosphere at elevated 25 temperatures. For example, a suitable presulphiding regimen comprises heating the catalysts in a hydrogen sulphide/hydrogen atmosphere (5%v H2S/95%v H2) for about two hours at about 204 °C (400 °E) increasing the tenqperature to 316 °C (600 °F) and holding for 1 hov^r a^d finally increasing the temperature to 371 °C (700 °F) 30 and holding for 2 hours. Other methods are also suitable for presulphiding and generally comprise heating the catalysts to elevated temperatures (e.g., 200 °C-500 °C) in the presence of hydrogen and a sulphur-containing material.

The instant invention also relates to a process for reducing 35 the sulphur and nitrogen content of a hydrocarbon feedstock, i.e. a process for hydrogenating sulphur-containing and nitrogen-containing hydrocarbons present in a hydrocarbon feedstock, by contacting the feedstock with hydrogen in the presence of a catalyst as described hereinbefore at hydrotreating conditions, i.e., at conditions of temperature and pressure and amounts of added hydrogen such that significant quantities of sulphur-containing hydrocarbons and nitrogen-containing hydrocarbons are reacted with hydrogen to produce gaseous sulphur compounds and gaseous nitrogen compounds which are removed from the feedstock.

The feedstock to be utilized is any crude or petroleum fraction containing in excess of 100 parts per million by weight (ppm) of sulphur in the form of sulphur-containing hydrocarbons and in excess of 20 parts per million by weight (ppm) of nitrogen in the form of nitrogen-containing hydrocarbons. Examples of suitable petroleum fractions include catalytically cracked light gas and heavy cracked oils, straight run heavy gas oils, light flash distillates, light cycle oils, vacuum gas oils, coker gas oil, synthetic gas oil and mixtures thereof. Hydrotreating conditions usually comprise temperatures ranging from 250 °C to 450 eC. The total pressure will typically range from 15 bar (200 psig) to 173 bar (2500 psig). The hydrogen partial pressure will typically range from 8 bar (100 psig) to 153 bar (2200 psig). The hydrogen feed rate will typically range from 36 to 1780 rs?/v? (from 200 to 10,000 standard cubic feet per barrel ("SCF/BBL")). The feedstock rate will typically have a liquid hourly space velocity ("LHSV**) ranging from 0.1 to 15 (1/1.hr).

The invention will be described by the following examples which are provided for illustrative purposes and are not to be construed as limiting the invention.

Example 1 A commercially available hydrotreating catalyst comprising cobalt and molybdenum on a garana alumina support was used as a base catalyst. The base catalyst was dried at 480 °C '896 °F) for 0.5 hours and 195 grains were weighed into a plastic container and 21.0 grains of silicone fluid obtained from Aldrich (14,615-3) was used to impregnate the catalyst. After impregnation, the catalyst was then heated from 25 °C (77 °F) to 482 °C (900 °F) over a period of 30 minutes and then the catalyst was held at 482 °C (900 °F) for 1.5. hours. The catalyst was then cooled to room tenperature in a desiccator. The catalyst contained about 3.7%wt of silicon, measured as the metal. This catalyst is denoted SPC-1 (Silicon-Promoted Catalyst #1) in the following examples.

Example 2 A commercially available hydrotreating catalyst comprising cobalt and molybdenum supported on a gamma alumina support was used as a base catalyst. The base catalyst was dried at 399 °C (750 °F) for 2.0 hours and 100 grams were weighed into a plastic container and 10.94 grams of silicone fluid obtained from Dow Coming (Dow Corning 200 (5cSt)) was used to impregnate the catalyst. After impregnation, the catalyst was then heated from 25 °c (77 °F) to 482 °C (900 °F) over a period of 30 minutes and then the catalyst was held at 482 °C (900 °F) for 1.5 hours. The catalyst was then cooled to room temperature in a desiccator. The catalyst contained about 3.6%wt of silicon, measured as the metal. This catalyst is denoted SPC-2 (Silicon-Promoted Catalyst #2) in the following examples. Example 3 A commercially available hydrotreating catalyst comprising cobalt and molybdenum supported on a gamma alumina support was used as a base catalyst* The base catalyst was dried at 399 °C (750 °F) for 1 hour and 100 grams were weighed into a plastic container and 4.98 grams of silicone fluid obtained from Dow Corning (Dow Corning 200 (5cSt)) was used to impregnate the catalyst. After ~2r? impregnation, the catalyst was then heated from 25 °C (77 °F) to 482 °C (900 °F) over a period of 30 minutes and then the catalyst was held at 482 °C (900 °F) for 2 hours. The catalyst was then cooled to room temperature in a desiccator. The catalyst contained about 1.8%wt of silicon, measured as the metal. This catalyst is denoted SPC-3.

Example 4/Comparatlve Example 1 Three silicon-promoted catalysts (SPC-1, SPC-2 and SPC-3) were tested for their hydrodesulphurization activity and hydrodenitrification activity on a diesel feedstock. Two of the catalysts, SPC-1 and SPC-2, illustrate specific embodiments of the present invention while SPC-3 illustrates a silicon-promoted catalyst which contains a less than optimum amount of silicon. For comparison, a base catalyst (no silicon added, catalyst denoted as CC-1 (comparative catalyst 1) was also tested. The properties of all catalysts are shown in Table 1 below.

TABLE 1; CATALYST PROPERTIES CATALYST Metals, %wt SPC-1 SPC-2 SPC-3 CC-1 Co 2.9 2.9 3.0 3.1 Mo 11.4 11.4 11.9 12.4 Si 3.7 3.C> 1.8 - CBD, glee 0.809 0.808 0.775 0.745 The catalyst testing was performed in pilot scaled microreactors using whole pellets. The catalysts were loaded and diluted with silicon carbide obtained through a sieve having 24-31 openings per cm (60-80 mesh SiC) to minimize feed channeling and to allow for unifocal isothermal operation of the reactor.

In this technique^each 'at: Sri 20.- mlr (fdar. ouncetr bottles-' are*' - , loaded with 18.2 grains of-silicon* carbide obtained throughr aLaieve- ' having 24-31 openings per. cm (60-80 mesh- silicon•carbide).and 20% of the. catalystrchargesof'. 50 ml is. added .to each bottle and loaded into 2"7<T-7<?<7> the reactor. To determine the loading weight, the catalyst bulk density (CBD) was multiplied by 100.

The catalysts were sulfided with 5% hydrogen sulfide in hydrogen at a gas flow rate of 0.11 m^/hr (4.0 SCF/hr). Gas flow was established at room temperature and then the reactor temperature was increased to 204 °C for 2 hours, increased to 316 °C and held for 1 hour, and finally increased to 371°C and held for 2 hours. The following test conditions were used (LHSV «= Liquid hourly space velocity): LHSV Pressure H2 Circulation Temperature 1.0 hr"1 41 bar (600 psig) 178 m3/m3 (1000 SCF/bbl) 363 °C (685 °F) For measuring hydrodesulphurization (HDS) activity and hydrodenitrification (HDN) activity, the catalysts were broken in at 363 °C (685 °F) for about 100 hours. Activities of the catalysts are shown in Table 2.

Properties of the feedstock utilized to illustrate the instant invention are also detailed in Table 2.

AMENDED SHEET - 11 -TABLE 2 O.xALYST# SPC-1 3. 7%Si SPC-2 3.6%Si SPC-3 1.8%Si CC-1 % Si TARGET Temperature, "C (*F) 362 (685) 362 (683) 361 (682.5) 363 (685.5) 363 (685) LHSV, hr-1 1 0.97 0.86 0.93 1.01 PRODUCT PROPERTIES DENSITY FEEDSTOCK 0.9032 0.8809 0.8808 0.8826 COMPOSITION HYDROGEN (%wt) 11.56 12.1855 12.17 12.1565 12.241 CARBON (%wt) 8*7.003 87.795 87.804 87.8985 87.615 OXYGEN (%wt) 0.17 0.04 0.02 0.04 0.04 SULPHUR (%wt) 1.216 0.03 0.0267 0.0393 0.041 NITROGEN (ppm) 916 268 194 248 406 Basic nitrogen (ppm) 319 18 24 101 HYDROGEN CONSUMPTION, m3/ra3 (SCF/bbl) 65.7 (369) 64.4 (362) 61.2 (344) 73.9 (415) TEMPERATURE REQUIRED FOR 400PPM S, °C (°F) 355 (671) 354 (670) 365 (689) 363 (686) OLEFINS Bromine number (gmf Br/lOOgm) .9 0.7 0.93 0.54 1.05 FIA Analysis 0 0 0 0 0 AROMATICS FIA Analysis 59.7 47 50.3 46.4 50.2 COLOUR 2 2.5 3 4 CLOUD POINT 19 19 17 REFRACTIVE INDEX 1.5058 1.4915 1.4916 N/A 1.4907 CETANE • -NUMBER * 34;9.>"- '. .a-:-"- • N/A- N/A-> • •38.2 1 PRODUCT RECOVERY (%) 98.07 99.6 98.1\ 99-. 32' AMtNOtO SHEET Example 5 As a base catalyst was used a commercially available hydrotreating catalyst comprising nickel, molybdenum and phosphorous supported on a gamma alumina support. The base catalyst was dried 5 at 400°C for 1 hour and 201 grains were weighed into a 400 milliliter round bottom flask and 26.5 grams of silicone fluid obtained from Dow Coming (Dow Corning 200 (50cSt)) was used to impregnate the catalyst. After impregnation, the catalyst was then heated from 121 °C (250°F) to 538°C (1000°F) over a period of 30 minutes and then 10 the catalyst was held at 538°C (1000°F) for 2 hours. The catalyst was then cooled to room temperature in a desiccator. The catalyst contained about 3%wt of silicon, measured as the metal. This catalyst is denoted SPC-4.

SPC-4 was subsequently tested on an Arabian Heavy Flashed IS Distillate feedstock. For comparison, the base catalyst (no silicon) was also tested (CC-2). The properties of the catalysts are shown in Table 3 below.

TABLE 3; CATALYST PROPERTIES Catalyst SPC-4 CC-2 Metals, %wt Ni 2.4 3.0 Mo 13.4 13.0 P 2.6 3.2 Si 3.0 — CBD, g/cc 0.920 0.824 S.Area, m?/g 155 166 Properties of the feedstock utilized to illustrate the instant invention are detailed in Table 4 below.

PCT/EP94A03543 TABLE 4: PROPERTIES OF ARABIAN HFD FEEDSTOCK Physical Properties Density, 60°F, 70°C Viscosity (Cs), 60°C, 100°C Molecular Wt. 0.9346, 0.8968 46.5, 11.7 442 Elemental Content Hydrogen Carbon Oxygen Nitrogen Sulphur 11.9380wt.% 85.2970wt.% 0.1180wt.% 0.1080wt.% 2.7300wt.% Asphaltenes (wt.%) C5 c7 0.07 0.07 Carbon Residue (wt.%) Ramsbottom microcarbon 0.50 1.06 UV Aromatics Content (wt.%) Mono Di Tri Tetra Total MWR 4.7 3.2 4.3 4.4 16.6

Claims (17)

WO 95/11753 PCT/EP94/03543 - 14 - TABLE 4 (COKT'D); PROPERTIES OF ARABIAN HFD FEEDSTOCK Boilinq Point Distribution TBP —GLC IBP 674 • F (357 *C) lOwt.% 764 (407) 30wt.% 837 (447) 50wt.% 892 (478) 70wt.% 945 (507) 86wt.% 1000 (538) The catalyst testing was performed in pilot scaled niicro-eactors using whole pellets. The catalysts were loaded and sulphided in the same way as described in Example 4. The following test conditions were used (WHSV = weight hourly 5 spce velocity): WHSV : 1.0 kg feed/l-catalyst-hr Pressure : 1725 psig (120 bar) H2 Circulation : 5000 SCF/bbl (1000 Nl/kg feed) For measuring hydrodenitrification (HDN) activity, the 10 catalysts were broken in at 357oC for about 200 hours and then the temperature was increased to the temperature at which 7.5 ppm of nitrogen were found in the product. Catalysts with higher hydrodenitrification activities require lower temperatures. It was found that for SPC-4 the temperature, at which 7.5 ppm of nitrogen were found in the product, was 383 #C (721 °F), whereas for CC-2 this temperature was found to be 389 *C (733 °F). From this it can be concluded that SPC-4 has a higher HDN activity than CC-2. 27T799 - 15 - TH 0251 PCT CLAIMS

1. Hydrotreating catalyst comprising a Group VIB metal component and/or a Group VIII metal component supported on an alumina support, which catalyst has been impregnated with a liquid form of a silicon compound having the general formula X U II Y Si (OS3 )aW I I Z V wherein U, V, W, X, Y, and Z can individually be -R, -OR, -Cl, -Br, -SiH3, -COOR, -SiHnClm, R being either hydrogen, or an alkyl, cycloalkyl, aromatic, alkyl aromatic, alkylcycloalkyl radical having from 1 to 30 carbon atoms, HnM and "m" being whole numbers in the range of from 1 to 3 and "a" being a whole numbers in the range of from 0 to 80, in an amount sufficient to deposit from 2.5 to 8.0 percent by weight of the total catalyst of Si, and subsequently has been calcined at a temperature ranging from 300 °C to 600 °C in an oxidizing atmosphere.

2. Catalyst according to claim 1, comprising a molybdenum component as the Group VIB metal component and/or a nickel or cobalt component as the Group VIII metal component.

3. Catalyst according to claim 2, comprising either molybdenum and nickel components or molybdenum and cobalt components.

4. Catalyst according to any one of the preceding claims, wherein U, V, W, X, Y and Z are individually hydrogen, methyl or ethyl.

5. Catalyst .according to any one of the preceding claims, wherein "a" ranges*from 5 to 60.

6. Catalyst according to any one of the preceding claims, wherein .■ the silicon.-'compound, is in. the-form..of .a .liquid.having a. viscosity . at 40 *C of less thanr.100'eSt."i '

7. Catalyst according to any one of the preceding: claims,- wherein the amount of. Si. deposited, on the catalyst ranges from 3.0 percent to 6.0 percent-by weight of1 tiie-catalyst. AMEKCIV.O 2?<r ?c?9 - 16 -

8. Process for hydrogenating sulphur-containing and nitrogen-containing hydrocarbons in a hydrocarbon feedstock, which process comprises contacting at hydrofining conditions said feedstock with hydrogen in the presence of a catalyst according to any one of claims 1 to 7.

9. A method for improving the hydrodesulphurization activity and the hydrodenitrification activity of a hydrotreating catalyst which comprises a Group VIB metal component and/or a Group VIII metal component supported on an alumina support, said method comprising impregnating said hydrotreating catalyst with a liquid form of a silicon compound having the general formula X U I I Y—Si (OSi )aW 1 I 2 V wherein U, V, W, X, Y, and Z can individually be -R, -OR, -Cl, -Br, -SiHj, -COOR, -SiHnClm, R being either hydrogen, or an alkyl, cycloalkyl, aromatic, alkyl aromatic, alkylcycloalkyl radical having from 1 to 30 carbon atoms, "n" and "m" being whole numbers in the range of from 1 to 3 and "a" being a whole number in the range of from 0 to 80, preferably 5 to 60, in an amount sufficient to deposit from 2.5 to 8.0, preferably 3.0 to 6.0 percent by weight of the total catalyst of Si, and subsequently calcining said impregnated catalyst at a temperature ranging from 300 °C to 600 °C in an oxidizing atmosphere.

10. The method of claim 9, wherein U, V, W, X, Y and Z are individually hydrogen, methyl or ethyl.

11. The method of claim 9 or 10, wherein the silicon compound is in the;'form of a liquid having a viscosity at 40 'C of less than lOOcSt. . 12«... The. method of .any one of claims 9 to 11, wherein the hydrotreating-catalyst: -caapx±a.*a? • eifche r.r cob » Lfc •and.wTlYbdwuneari.,;^ nickel and molybdenums: ■ ■ . •

MCS3/TH251ECT: - 17 - 27 5 7 9 9

13. A method according to any one of claims 9 to 12, substantially as herein described.

14. A hydrotreating catalyst whenever impregnated according to the method of any one of claims 9 to 13.

15. A process according to claim 8, substantially as herein described.

16. A hydrogenated sulphur-containing or nitrogen-containing hydrocarbon whenever produced by a process according to claim 8 or 15.

17. A hydrotreating catalyst according to any one of claims 1 to 7, substantially as herein described. Dm the AiithnrlsAd a (rants