AU709482B2 - Catalyst use - Google Patents

Description

Catalyst Use The present invention relates to a catalyst use in hydroconversion processes, wherein a hydrocarbon oil comprising aromatic compounds is contacted with hydrogen in the presence of such a catalyst.

Hydrotreating catalysts are well known in the art. Conventional hydrotreating catalysts comprise at least one Group VIII metal component and/or at least one Group VIB metal component supported on a refractory oxide support. The Group VIII metal component may be either based on a non-noble metal, such as nickel (Ni) and/or cobalt or may be based on a noble metal, such as platinum (Pt) and/or palladium Useful Group VIB metal components include those based on molybdenum (Mo) and tungsten The most commonly applied refractory oxide support materials are inorganic oxides such as silica, alumina and silica-alumina and aluminosilicates, such as modified zeolite Y. Specific examples of conventional hydrotreating catalysts are NiMo/alumina, CoMo/alumina, NiW/silica-alumina, Pt/silica-alumina, PtPd/silica-alumina, Pt/modified zeolite Y and PtPd/modified zeolite Y.

Hydrotreating catalysts are normally used in processes wherein a hydrocarbon oil feed is contacted with hydrogen to reduce its content of aromatic compounds, sulfur compounds and/or nitrogen compounds.

Typically, hydrotreating processes wherein reduction of the aromatics content is the main purpose are referred to as hydrogenation processes, whilst processes predominantly focusing on reducing sulfur 25 and/or nT O« Libc/03275 WO 97/05948 PCT/EP96/03555 2 nitrogen content are referred to as hydrodesulphurisation and hydrodenitrogenation, respectively. Current environmental standards require that both aromatic content and sulphur and nitrogen content of oil products are very low and it is generally expected that specifications for aromatics, sulphur and nitrogen will become more and more severe in the future.

Accordingly, in the refining of hydrocarbon oil fractions the ability to deeply hydrogenate, deeply hydrodesulphurise and deeply hydrodenitrogenate will become increasingly important.

In US-4,469,590 a process for hydrogenating aromatic hydrocarbons is disclosed, wherein said aromatic hydrocarbons are contacted at hydrogenation conditions with a certain catalyst in the presence of hydrogen and in the absence of an inorganic sulphur compound, particularly hydrogen sulphide. The catalyst employed comprises a metal of Group VIII, preferably palladium, and (ii) a steamed support comprising a transition metal oxide selected from tungsten oxide, niobium oxide and mixtures thereof, composited with a non-zeolitic inorganic oxide, preferably alumina. The steamed support may additionally comprise a metal oxide selected from tantalum oxide, hafnium oxide, chromium oxide, titanium oxide, zirconium oxide and mixtures thereof.

In EP-A-0,653,242 a catalyst is disclosed comprising platinum and/or palladium and molybdenum and/or tungsten on a refractory oxide support. This catalyst is described to be very effective in hydrogenating aromatic compounds present in a hydrocarbon oil, even in the presence of relatively large amounts of sulphur and/or nitrogen, whilst its performance in hydrodesulphurisation and hydrodenitrogenation is also good. The catalyst is described to be particularly useful for 3 hydrotreating gas oils, whereby also mono-aromatic compounds are effectively hydrogenated which is more difficult with the traditional hydrotreating catalysts. In EP-A-0,653,242 it is furthermore described that the catalysts, due to their excellent hydrogenation activity and good desulfurisation and denitrogenation activity, could be very useful in the development of a single stage process for reducing the amount of aromatics and sulfur- and nitrogen-containing compounds. The conventional way for reducing the amounts of aromatics and sulfurand nitrogen-containing compounds, namely, is via a two-stage process within the first stage mainly hydrodesulfurisation and/or hydrodenitrogenation occurring and in the second stage mainly hydrogenation of the aromatic compounds still left. Such two-stage process is necessary, as conventional aromatics hydrogenation catalysts have a relatively low sulfur and/or nitrogen tolerance, so that 1i they exhibit poor hydrogenation activity in the presence of substantial amounts of sulfur- and/or nitrogen-containing compounds. This applies in particular for the saturation of monoaromatics.

Like the invention which is the subject of EP-A-0,653,242, the present invention aims to provide a hydrotreating/process having an excellent aromatics hydrogenation activity, even in the presence of substantial quantities of sulfur- and nitrogen containing compounds.

The present invention also aims to provide a hydrotreating/process enabling an effective reduction of the contents of aromatics, sulfurcontaining compounds and nitrogen-containing compounds in a single stage. The present invention moreover aims to provide a process which achieves an excellent hydrogenation activity towards aromatics, which is at least equal to the hydrogenation activity of the Libc/03275 4 process disclosed in EP-A-0,653,242, and having an improved hydrodesulphurisation and/or hydrodenitrogenation activity. It will be understood that such a process offers an increased potential for meeting future low-content specifications for (mono)aromatics, sulphur and nitrogen.

Accordingly, the present invention in a first aspect provides use of a catalyst which comprises, as the sole catalytically active metal components, from 0.1 to 15% by weight of platinum and/or palladium and from 2 to 40% by weight of at least one metal of the actinium series supported on an acidic carrier, said weight percentages indicating the amount of metal based on the total weight of carrier, in a hydroconversion process, wherein a hydrocarbon feedstock comprising aromatic compounds is contacted with the catalyst at elevated temperature and pressure in the presence of hydrogen.

The combination of a platinum group metal and an actinide in a catalyst has been proposed for a number of other treatments, and often one or more further components are required in the catalyst. US-A-5051392 concerns the treatment of exhaust gas, e.g. from diesel engines, utilising a three-metal containing catalyst; US-A-4886928 describes a steam dehydrogenation process utilising a three-metal, but four component, catalyst.

US-A-3788977 and equivalent FR-A-2110236, US-A-3929624 and the Derwent abstract 75-47166W all disclose reforming processes to increase the aromatic content of a hydrocarbon feedstock utilising a platinum group component, and an uranium component.

AMENDED SHEET 4a In the present invention, the actinium series refers to those elements of the Periodic Table of Elements having an atomic number ranging from 89 (Actinium, Ac) to 103 (Lawrentium, Lr). These elements are also sometimes referred to as actinides. For the purpose of the present invention the enriched forms of the actinides, i.e. the radio-active isotopes, are not likely to be used in practice. The catalytically active metals, i.e. platinum and/or palladium and the actinium series metal component, may be present in elemental form, as an oxide, as a sulphide or as a mixture of two or more of these forms.

As will be discussed in detail hereinafter, a suitable preparation method used to prepare the present catalyst includes a final step of calcination in air, which will cause the catalytically active metals to be at least partially converted into their oxides. Usually such final calcination step will cause substantially all catalytically active metals to be converted into their oxides. If the catalyst is subsequently contacted with a sulphur-containing feed, then at least a part of these oxides will be sulphided and hence converted into the corresponding sulphides ("in situ" sulphidation). Very MCSI4/TS5530PCT -v- <~47 OF~ good catalyst performance has been observed in this situation and therefore it is considered a preferred embodiment of the present invention to have the catalytically active metals at least partly present in the catalyst as sulfides. Accordingly, the catalyst may also be subjected to a separate presulfiding treatment prior to being contacted with the feed. The degree of sulfidation of the metal oxides can be controlled by relevant parameters such as temperature and partial pressures of hydrogen, hydrogen sulfide, water and/or oxygen. The metal oxides may be completely converted into the corresponding sulfides, but suitably an equilibrium state between the oxides and sulfides of the catalytically active metals will be formed, so that the catalytically active metals are present both as oxides and as sulfides.

As will be discussed in more detail below, the catalyst utilised in the present invention can suitably be used in a variety of oooo° S: 15 hydroconversion processes. The catalyst has been found to be particularly useful in the hydrotreatment of gas oils, thermally and/or catalytically cracked distillates (such as light cycle oils and cracked cycle oils) and mixtures of two or more of these. These oils usually contain a relatively large amount of aromatic compounds, sulfurcontaining compounds and nitrogen-containing compounds. The amounts of such compounds must usually be reduced in view of environmental regulations. Aromatic compounds reduction may also be desirable for reaching certain technical quality specifications, such as cetane number in the case of automotive gas oils, smoke point in the case of jet fuels and colour and stability in the case of luboil fractions.

When using the catalyst in the hydrotreatment of gas oils, thermally and/or catalytically cracked distillates and mixtures of two or more of these, the required reduction for e.g. meeting automotive gas oil specifications can be attained in a single stage. It has been found that Th 1 the catalysts are especially active in reducing the amount of mono- Libc03275 6 aromatics in the final product, even in the presence of substantial amounts of sulfur-containing compounds, such as hydrogen sulfide, and nitrogen-containing compounds.

The catalyst utilised in the present invention comprises as catalytically active metals from 0.1 to 15% by weight of platinum and/or palladium and from 2 to 40% by weight of at least one metal of the actinium series. It has been found that if lower amounts of catalytically active metals are applied, the activity of the catalyst becomes too low to be commercially attractive. If, on the other hand, the amount of catalytically active metals is higher than the upper limits indicated, the further increase in catalytic activity does not warrant the costs of the extra amount of metal. This applies in particular for platinum and palladium. Good results can be obtained with catalysts comprising from 3 to 10% by weight of platinum and/or palladium and from 5 to 30% by 15 weight of at least one metal of the actinium series.

S. As has already been indicated above the actinium series covers those elements of the Periodic Table of Elements which have an atomic number from 89 (actinium) to 103 (lawrentium). Suitably, the catalyst utilised in the present invention comprises one metal of the actinium series and preferred candidates are thorium and uranium. Of these, uranium is most preferred. With respect to the noble metal component, it is preferred to use palladium only. A very much preferred catalyst, accordingly, is a catalyst comprising palladium and uranium as the catalytically active metals.

The carrier used to support the catalytically active metals is an acidic carrier. Acidic carriers are known in the art. Examples of suitable carriers for the purpose of the present invention, then, include acidic carriers comprising an aluminosilicate or silico aluminophosphate zeolite, amorphous silica-alumina, alumina, fluorided alumina or a Libc103275 mixture of two or more of these. It will be appreciated that the type of acidic carrier to be used largely depends on the intended application of the catalyst. For most applications it is, however, preferred that the carrier comprises a zeolite. Examples of suitable zeolites are silico aluminophosphates, such as SAPO-11, SAPO-31 and SAPO-41 and aluminosilicate zeolites like ferrierite, ZSM-5, ZSM-23, SSZ-32, mordenite, beta zeolite and zeolites of the faujasite type, such as faujasite and the synthetic zeolite Y. The use of silicoaluminophosphates may, for instance, be considered in a process for producing lubricating base oils which involves a hydroconversion step. In general, however, the use of aluminosilicate zeolites is preferred. A particularly preferred aluminosilicate zeolite is zeolite Y, which is usually used in a modified, i.e. dealuminated, form.

Particularly when using the catalyst utilised in the present invention as 15 a hydrotreating catalyst for reducing the content of aromatics and sulfur- and nitrogen-containing compounds, the use of an acidic carrier comprising a modified zeolite Y is very much preferred. A particularly useful modified zeolite Y is one having a unit cell size below 24.60A, Spreferably from 24.20 to 24.45A and even more preferably from 24.20 20 to 24.35A, and a SiO 2 /AI2 3 molar ratio in the range of from 10 to 150, preferably from 15 to 110 and more preferably from 30 to 90. Such carriers are known in the art and examples are, for instance, described in EP-A-0,247,678; EP-A-0,303,332 and EP-A-0,512,652. Modified zeolite Y having an increased alkali(ne) metal -usually sodium- content, 25 such as described in EP-A-0,519,573, can also be suitably applied.

In addition to any of the aforementioned carrier materials the carrier may also comprise a binder material. The use of binders in catalyst carriers is well known in the art and suitable binders, then include inorganic oxides, such as silica, alumina, silica-alumina, boria, R zirconia and titania, and clays. Of these, the use of silica and alumina Libc/03275 is preferred for the purpose of the present invention, whereby the use of alumina is most preferred. If present, the binder content of the carrier may vary from 5 to 95% by weight based on total weight of carrier. In a preferred embodiment, the carrier comprises 10 to 60% by weight of binder. A binder content of from 10 to 40% by weight has been found particularly advantageous.

The catalyst utilised in the present invention can be used in a variety of hydroconversion processes, wherein a hydrocarbon feedstock comprising aromatic compounds is contacted with the catalyst at elevated temperature and pressure in the presence of hydrogen. Specific examples of such processes are hydrocracking, luboil manufacture (hydrocracking/hydroisomerisation) and hydrotreating.

Since the catalysts are active not only hydrogenating aromatic 15 compounds, but also in removing sulfur and/or nitrogen compounds, hydrocarbon feedstocks comprising sulfur- and/or nitrogen- containing compounds in addition to the aromatic compounds are particularly suitable.

If the catalyst is to be applied in a hydrocracking process, the 20 carrier will usually comprise either an amorphous silica-alumina or an aluminosilicate zeolite with silica and/or alumina as a binder. A carrier which is preferably used comprises zeolite Y and alumina. A hydrocracking process typically comprises contacting a hydrocarbon feedstock boiling between 100 and 500°C in the presence of hydrogen with a suitable catalyst at a temperature of between 300 and 500°C and a hydrogen partial pressure of up to 300bar. The catalyst utilised in the present invention is, due to its excellent hydrotreating performance, particularly useful as the first stage catalyst in a two Sstage hydrocracking process.

Libc/03275 In lubricating base oil manufacture processes at least one hydroconversion step may be included for removal of sulfur- and/or nitrogen- containing contaminants from the feedstock and/or hydrogenation of aromatic compounds and/or hydroisomerisation of straight chain and slightly branched hydrocarbons into further branched hydrocarbons and/or hydrocracking of waxy molecules (usually long chain paraffinic molecules or molecules containing tails of this type) into smaller molecules. For application in such lubricating base oil manufacture process, the catalyst utilised in the present invention will preferably comprise a carrier comprising amorphous silica-alumina, fluorided alumina or a zeolite with silica and/or alumina as binder. If the hydrotreating reactions are intended to occur predominantly, the use of carriers comprising modified zeolite Y is preferred. If cracking and/or hydroisomerisation of the waxy molecules is the main objective, preferred carriers comprise fluorided alumina, amorphous silicaalumina or zeolites, such as ferrierite, ZSM-5, ZSM-23, SSZ-32 and SAPO-11. A hydroconversion step in a lubricating base oil manufacture process typically comprises contacting a luboil feedstock at a temperature of between 200 and 450°C and a pressure up to 200 20 bar with a suitable catalyst in the presence of hydrogen. Examples of suitable lubricating base oil manufacturing processes are disclosed in GB-A-1,546,504 and EP-A-0, 178, 710.

The catalyst utilised in the present invention has been found to be particularly suitable for use in a hydrotreating process. Suitable hydrotreating operating conditions are a temperature in the range of from 200 to 450 0 C, preferably between 210 and 350°C, and a total pressure in the range of from 10 to 200 bar, preferably between 25 and 100 bar. Examples of suitable hydrotreatment processes have been described in European patent applications 0,553,920 and 0,611,816.

s Suitable feedstocks for such a hydrotreating process are gas oils, light Libc/03275 gas oils, gas oils, thermally and/or catalytically cracked distillates (such as light cycle oils and cracked cycle oils) and mixtures of two or more of these. All these feedstocks normally comprise at least 70% by weight of hydrocarbons boiling between 150 and 4500C. When used in such a hydrotreating catalyst, it is preferred that the carrier comprises a binder in an amount as indicated above. The preferred acidic material in the carrier in case of hydrotreating is an aluminosilicate zeolite, most preferably modified zeolite Y. It has been found that the present catalyst exhibits an excellent hydrotreating activity and is particularly effective in hydrogenating mono-aromatics, even in the presence of substantial amounts of sulfur- and nitrogen-containing compounds. In addition, the present catalyst is also very effective in the hydrogenation of di-aromatics and higher aromatics (tri+ aromatics).

The catalysts described above may be prepared by a process 15 which comprises incorporating the catalytically active metals into the refractory oxide carrier, suitably by means of impregnation or ion- 6" exchange techniques, followed by drying and calcining and optionally presulfiding. In order to obtain catalysts having a particularly good S. catalytic activity, this process can be carried out by the subsequent S 20 steps of: impregnating the carrier with a solution containing at least one compound of a metal of the actinium series and a solution containing a platinum and/or palladium compound; and drying and calcining the thus impregnated carrier at a temperature in the range of from 250 to 6500C.

A preferred method of impregnating the carrier is the so-called pore volume impregnation, which involves the treatment of a carrier with a volume of impregnating solution, whereby said volume of 1 P impregnating solution is substantially equal to the pore volume of the Libcd03275 carrier. In this way, full use is made of the impregnating solution. For the purpose of the present invention this impregnation method has been found to be particularly suitable as the resulting catalysts show a particularly good performance. The impregnation step can be carried out using one impregnation solution containing all metal components or can be carried out in two separate impregnation steps, one step for impregnation with platinum and/or palladium and one step for impregnation with the actinide, possibly with an intermediate drying and/or calcining step.

Metal compounds which can be used in the impregnating solutions for preparing the catalysts utilised in the present invention, are known in the art. Typical actinide compounds are salts thereof which are soluble in water, such as chlorides, sulfates, nitrates and acetates. In S" case of uranium, uranyl nitrate, uranium sulfate, ammonium diuranate, 15 uranyl chloride and uranium acetate may conveniently be applied in a water-based impregnating solution. Additionally, uranium salts soluble in alcohol and/or hydrocarbon solvents may be used in impregnating solutions based on such solvents. An example of a suitable uranium salt in this connection is uranyle acetylacetonate. Typical palladium nee compounds for use in impregnating solutions are tetrachloropalladium acid (H 2 PdCI 4 palladium nitrate, palladium(ll) chloride and its amine complex. The use of H 2 PdCI 4 is preferred. Typical platinum compounds for use in an impregnating solution are hexachloroplatinic acid, optionally in the presence of hydrochloric acid, platinum amine hydroxide and the appropriate platinum amine complexes.

It is common practice in catalyst preparation, to subject the catalysts in the final step to calcination in air, whereby the metals are brought in the form of their oxides. To convert the metals at least partially into their sulfides, the catalyst can be presulfided after the final Al calcination step and prior to contact with the feedstock. Suitable Libc/03275 presulfiding methods are known in the art, such as for instance from EP-A-0,181,254. Accordingly, the process for preparing the catalyst may further comprise the step of: subjecting the dried and calcined catalyst to a presulfiding treatment.

Instead of the aforementioned presulfiding methods, presulfiding can take place via in situ presulfidation, i.e. by contacting the calcined catalyst with a sulfur-containing hydrocarbon feedstock. In most cases, namely, the hydrocarbon feed to the hydroconversion process contains substantial amounts of sulfur-containing compounds and if not, it can be spiked with sulfur-containing compounds like di tertiary nonyl polysulfide for presulfiding purposes, so that the metal oxides present on the calcined catalyst are at least partially converted into the corresponding sulfides when contacted with the said hydrocarbon 15 feedstock. Suitably, such contact is conducted at conditions which are less severe than the actual hydroconversion operating conditions. For instance, in situ presulfidation can be carried out at a temperature which is gradually increased from ambient temperature to a temperature of between 150 and 2500C. The catalyst is to be maintained at this temperature for between 10 and 20 hours.

Subsequently, the temperature is to be raised gradually to the operating temperature for the actual hydroconversion process. In general, in situ presulfidation can take place, if the hydrocarbon feedstock has a sulfur content of at least 0.5% by weight, said weight percentage indicating the amount of elemental sulfur relative to the total amount of feedstock. It will be understood that in situ presulfidation of the catalyst may be advantageous for both processefficiency and economic reasons.

Libc/03275 13 The catalyst utilised in the present invention will usually slowly deactivate during use in a hydrocarbon conversion process. If the activity of the catalyst becomes too low, the catalyst can be regenerated.

S

S

Libc/03275 WO 97/05948 PCT/EP96/03555 14 Suitable methods for regeneration of catalysts are known in the art. In some cases, however, the catalyst will not be regenerated. In those cases, the catalytically active metals will usually be recovered before disposal of the catalyst. Recovery of these metals can be achieved via known methods. A typical method for recovery of the catalytically active metals from spent catalyst comprises removing the deactivated catalyst from the reactor, washing the catalyst to remove the hydrocarbons, burning off the coke and subsequently recovering the platinum and/or palladium and the actinide.

The invention is illustrated by the following examples without restricting the invention to these particular embodiments.

Example 1 An acidic carrier consisting of 80% by weight dealuminated zeolite Y (unit cell size of 24.25 A and silica/alumina molar ratio of 80) and 20% by weight of an alumina binder was used. This carrier was impregnated with an aqueous uranyl nitrate (U0 2 (N0 3 2 .6H 2 0) solution to reach 20% by weight U 3 0 8 (corresponding with 17.0% by weight of The partially prepared catalyst was then dried and calcined for 2 hours at 400 after which impregnation with an aqueous solution of H 2 PdCl 4 took place to reach a PdO content of 5% by weight (corresponding with 4.3% by weight of Pd). Finally, the completed catalyst was dried and calcined for 2 hours at 350 °C in air.

Example 2 The catalyst obtained in Example 1 was presulphided according to the method disclosed in EP-A-0,181,254.

This method involved impregnation with di-tertiary nonyl polysulphide diluted in n-heptane, followed by drying WO 97/05948 PCT/EP96/03555 15 for 2 hours at 150 OC under nitrogen at atmospheric pressure.

The presulphided catalyst was subsequently contacted with a hydrocarbon feed consisting of a blend of 25% by weight light cycle oil and 75% by weight straight-run gas oil. Feedstock characteristics are indicated in Table I means boiling point).

Operating conditions were a total pressure of bar, weight hourly space velocity (WHSV) of 1.0 kg/l/h, a gas rate of 500 Nl/kg and an operating temperature of 360 °C.

The product characteristics and conversion levels are indicated in Table I. Conversions (in are calculated by assuming that aromatics are hydrogenated through a sequential reaction pathway, i.e. it is assumed that tri+ aromatics are converted into diaromatics, diaromatics into monoaromatics and monoaromatics into naphthenics. Accordingly, the monoaromatics which are found in the product may come from three sources: from the unconverted monoaromatics already present in the feed, (ii) from converted diaromatics which were originally present in the feed and (iii) from converted diaromatics which, in return, originate from converted tri+ aromatics present in the feed.

WO 97/05948 WO 9705948PCT/EP96/03555 16 Feedstock and product characteristics TABLE I Feed Product Conversion Aromatics (mxnol/100 g) Mono 77.3 77.3 46 Di 55.3 8.9 88 Tri+ 20.4 2.4 88 Sulphur wt) 1.4 0.005 99.6 Nitrogen (ppmw) 230 6 97.4 B.P. distribution

(OC)

Initial B.P. 150 79 by weight B.P. 287 273 Final B.P. 424 420

Claims (10)

1. 2. Use according to claim 1, wherein the feedstock also comprises sulphur- and/or nitrogen-containing compounds.
2. 3. Use according to claim 1 or claim 2, wherein the process is a hydrotreating process.
3. 4. Use according to claim 3, wherein the feedstock is a gas oil, a light gas oil, a thermally and/or catalytically cracked distillate or a mixture of two or more of these. Use according to any one of claims 1 to 4, wherein the catalyst comprises from 3 to 10% by weight of platinum and/or palladium and from 5 to 30% by weight of at least one metal of the actinium series.
4. 6. Use according to any one of claims 1 to 5, wherein, in the catalyst, the metal of the actinium series is uranium.
5. 7. Use according to any one of claims 1 to 6, wherein the catalyst contains palladium. AMENDED SHEET 18
6. 8. Use according to any one of claims 1 to 7, wherein the acidic carrier of the catalyst comprises modified zeolite Y having a unit cell size below 24.60 A, and a SiO 2 /Al 2 0 3 molar ratio in the range of from to 150.
7. 9. Use according to claim 8 wherein the modified zeolite has a unit cell size from 24.20 to 24.45A. Use according to claim 8 or claim 9 wherein the modified zeolite has a molar ratio in the range of from 15 to 110.
8. 11. Use according to any one of claims 1 to 10, wherein the acidic carrier of the catalyst also comprises from 5 to 95% by weight of a binder.
9. 12. Use according to any one of claims 1 to 11, wherein the catalyst is presulfided.
10. 13. A process for hydroconversion of a hydrocarbon feedstock, substantially as hereinbefore described with reference to any one of the examples. Dated 5 March 1998 SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B. V. Patent Attorneys for the ApplicantlNominated Person 20 SPRUSON&FERGU S ON Libc/03275