GB2246307A - Desulphurising hydrocarbons - Google Patents

Abstract

An olefin feedstock is desulphurized using an amine-treated nickel-containing catalyst.

Description

HYDROCARBON TREATMENT This invention relates to the treatment of sulphurbearing hydrocarbon feedstocks, and more especially to the removal of sulphur from the feedstock. In particular, the invention relates to treatment of olefin feedstocks, especially those to be hydroformylated by the oxo process, including those to be dimerized before the oxo process.

Olefines, in hydroformylation feedstocks for example, frequently have sulphur-containing impurities. Thiols, thiophenes, hydrogen sulphide, and other sulphurcontaining compounds may make the feed unacceptable because of the tendency for the sulphur rapidly to poison the catalysts used, either in the hydroformylation or, more especially, if the resulting aldehyde is to be reduced over a catalyst, e.g., copper chromite, to an alcohol, or oxidized to an acid.

It would therefore be desirable to reduce the concentration of sulphur compounds in the olefin feedstock by, for example, contacting the feedstock with a desulphurization catalyst. Such catalysts are known, or have been described in the literature, but it has been found that, when used on olefin feedstocks, in addition to removing sulphur they catalyse oligomerization of the olefins, rendering them unsuitable for certain end-uses.

For example, the end product of certain olefins that are used as feedstock to the oxo process is a plasticizer, formed by esterification of an alcohol obtained by hydrogenation of the aldehyde produced by the oxo process. If the olefin feedstock contains a dimer or other oligomer of the desired olefin, it may either pass unchanged, but remain with the reactant feedstock through the hydroformylation, reduction and esterification, or it may be hydroformylated, reduced and esterified. In the first case, the residual unsaturation tends to impart unwanted colour to the plasticizer over a period of time; in the second case the presence of the resulting higher molecular weight ester may cause the properties of the ester plasticizer to be outside the customer's specification.The oligomers may, of course, be recycled with unreacted olefins from the oxo process, in which case they tend to build up in the feedstock material, necessitating an earlier disposal of recycled material.

The same problem arises if the feedstock olefin is to be dimerized before hydroformylation, for example, to make Cg alcohols, a butene feedstock is dimerized to C8 olefin then hydroformylated and hydrogenated. In such circumstances, any oligomerization of feedstock during desulphurization will cause the dimerized hydroformylation feedstock to contain C16 olefins, which are undesirable for the reasons given above.

In any event, the formation of oligomers represents a loss of the desired olefin, with a consequent increase in costs.

There accordingly remains a need for a catalytic process whereby an olefinic feedstock may be desulphurized without undesirably affecting the initial makeup of the stock.

The present invention provides a process for the desulphurization of an olefin-containing feedstock which comprises contacting a sulphur-bearing olefin-containing feedstock with an aminated nickel-containing catalyst.

The invention also provides a catalyst for use in the process, the catalyst being an aminated nickel-containing catalyst. The invention further provides the use of an aminated nickel-containing catalyst in desulphurization of olefin feedstocks.

The invention still further provides a process for the manufacture of an aldehyde by hydroformylation of an olefin-containing feedstock using a catalyst susceptible to sulphur poisoning, wherein a sulphur-bearing olefincontaining feedstock is contacted under substantially non-hydrogenating conditions with an aminated nickelcontaining catalyst, whereby the sulphur content of the feedstock is lowered, the resulting reduced-sulphur feedstock is hydroformylated, and the resulting aldehyde is, if desired, reduced to form an alcohol, or oxidized to form an acid.

The invention also provides the use of an aminated nickel-containing catalyst in desulphurization of an olefin feedstock to a hydroformylation process, especially to a hydroformylation process followed by reduction to an alcohol or oxidation to an acid.

The olefin feedstock may contain C3 to C18, advantageously C3 to C12, more advantageously C4 to C6, olefins, and preferably comprises pentene or hexene. The olefins in the feedstock may be linear or branched, and the unsaturation may be internal or terminal.

The feedstock is advantageously contacted with the aminated nickel-containing catalyst at a temperature and under a pressure such that the feedstock is liquid.

Appropriate conditions will depend to some extent on the feedstock; for hexene, for example, a pressure within the range of 20 to 4 bar and a temperature within the range of from 150 to 200"C, advantageously 165 to 1900C, are generally preferred, the precise temperature range depending also on the catalyst. Temperatures above the range indicated above are to be avoided if formation of oligomeric compounds is to be avoided; at lower temperatures the effectiveness of sulphur removal is reduced. Within the effective range, optimum temperature will depend also on the catalyst and, during operation, its sulphur loading, higher loadings corresponding to higher temperatures.

As nickel-containing catalyst, there may be mentioned more especially a supported catalyst, although unsupported catalysts are also possible, especially a catalyst supported on a refractory material, e.g., an inorganic oxide, for example silica, alumina, clay, diatomaceous earth (e.g. Kieselguhr), active carbon, zeolite, magnesia, or mixtures of any two or more such materials, especially a silica/alumina support.

A preferred support is one having a particle size of from 0.5 to 3.0 mm, surface area of at least 50m2/g, a bulk density of from 0.3 to 1.5 g/ml, an average pore volume of from 0.1 to 1.1 ml/g and an average pore diameter of about 3 to 500 nm.

The catalyst is advantageously a reduced nickel catalyst. In particular, it is preferred that the catalyst should be substantially fully reduced, and advantageously only at least 80%, preferably at least 90%, of the nickel present should be in the metallic state at the beginning of desulphurization. It is believed that during desulphurization, a sulphide of nickel, or a mixture of sulphides of nickel, -is formed.

Accordingly, at any time during the desulphurization reaction, advantageously at most 20%, and preferably at most 10%, of the nickel present is in the form of an oxide.

Advantageously, the catalyst has a nickel content of at least 35%, preferably from 45 to 65%, by weight, based on the total weight of catalyst, including support if present. It is within the scope of the invention to employ a catalyst including metals other than nickel, for example a nickel-zinc catalyst.

As examples of suitable catalysts for amination there may be mentioned Girdler G-49 RS, a nickel catalyst cz,ooorted on Kieselauhr. or Girdler G-134 RS;

Engelhard/Harshaw2Ni-5124T, or Ni-5126T; or Hoechst Ni55/5TS.

The catalyst may be aminated by direct treatment with an amine, conveniently under temperature and pressure conditions similar to those used for desulphurization. The amine may be admixed with or dissolved in an olefin at a concentration of, for example 0.1 to 10% by weight, advantageously 0.5 to 2%, and preferably about 1%, and the amine-containing olefin passed through the catalyst for, for example, from 1 to 40 hours, advantageously 10 to 30 hours, and preferably for from 20 to 28 hours. Alternatively, the catalyst may be treated with the amine, if desired in admixture with or in solution in the alcohol which results from hydroformylation and hydrogenation of the olefin under consideration, by immersing the catalyst in the amine at ambient temperature for, for example, 24 hours.

As amines there may be mentioned primary, secondary or tertiary amines, aliphatic and cycloaliphatic amines being preferred. Advantageously, the amine is a monoamine; the molecule may contain other substituents or functional groups, e.g., a hydroxy group, provided that the basicity of the molecule is not adversely affected.

Strongly basic amines, i.e., those with low PKb values, e.g., less than 4.5, but preferably less than 3.5, are preferred. Advantageously, the amine has a boiling point at or somewhat above that of the olefin being treated, under the conditions of olefin desulphurization being used.

Among suitable amines there may be mentioned, for example, methylamine, trimethylamine, ethylamine, dipropylamine, butylamine, tributylamine, ethanolamine and diethanolamine. Among amines with low PKb values and appropriate boiling ranges, and therefore preferred, there may be mentioned dimethylamine, diethylamine, triethylamine, dibutylamine, piperidine and pyrrolidine.

The rate at which the olefin may be passed over the aminated catalyst will vary with the olefin, the catalyst, the maximum proportion of sulphur tolerable in the treated feed, and the level of sulphur already in the catalyst. Advantageously, however, a space velocity in the range of 0.5 to 2.5 her~1, and preferably 1.4 to 1.6 her~1 is employed.

The reaction is advantageously carried out in substantially non-hydrogenating conditions, preferably under completely non-hydrogenating conditions, with substantially complete exclusion of hydrogen. The presence of oxygen or oxidizing atmospheres generally is also preferably avoided.

It has surprisingly been found that, as well as fresh nickel catalyst, spent as well as fresh nickel catalyst from other operations carried out on sulphurfree feedstock, e.g., hydrogenation, may be aminated and used as desulphurization catalyst. Such catalysts up to 20% contain carbon, or carbon compounds, at a level, measured as carbon, up to 20%, especially from 5 to 20%, more specifically 8 to 15%, by weight of catalyst including support if present. The present invention accordingly also provides a process for desulphurization of a hydrocarbon feed using a spent hydrogenation nickelcontaining catalyst that has been aminated. The invention still further provides the use of an aminated spent hydrogenation nickel-containing catalyst for desulphurizing a hydrocarbon feed.More especially the invention provides such a process, and a use of such a catalyst, in which the feedstock is an olefin feedstock, and preferably a feedstock to a hydroformylation (oxo) process. The desulphurized feedstock produced by the process of the invention will have a dimer content that is naturally influenced by that of the original feedstock; but the desulphurized feedstock of the invention may have a dimer level of at most 0.1% more than the original feedstock, based on the total weight of feedstock. The invention also provides a desulphurized feedstock wherein the weight ratio of major olefin:dimer is at least 400:1. Such feedstock enables alcohols to be made by the oxo process and subsequent reduction having a similar dimer content.

In the embodiments of this invention in which hydroformylation takes place, the reaction conditions of that stage of the process are Der se conventional, as are those of any subsequent reaction, e.g., hydrogenation, and will not be given in detail. It has been found, however, that by the reduction of sulphur of the feed according to the present invention catalyst life, especially in the hydrogenation stage, is much enhanced.

The following Examples illustrate the invention: Comparison Example A A tubular reactor of 13.7 mm diameter and 207 mm length was loaded with spent Girdler G-49 RS catalyst (analysis of new catalyst by weight: Uni:46; si:9%; Al:0.6%; Ca:0.3%; Fe:0.2%). After a nitrogen purge at ambient temperature, the reactor was immersed in a fluidized sandbath to maintain it at a constant temperature within a desired range.

An olefinic feedstock, primarily hexene, the carbon number distribution being given in Table 2 below, paraffin content 21.6%, chlorine content < 1 ppm, S.G.

(15/150C) 0.689, and maleic anhydride value 1.28 mg/g, was passed at the temperatures shown in Tables 1 and 2 below through the catalyst at about 29 bar (gauge), thereby maintaining the feed in the liquid phase.

As can be seen from Table 2, there were steady increases in dimer formation (C12 + C13) and reductions in the yield of hexene in the desulphurized feedstock as the run progressed.

TABLE 1 Desulphurization Results. Untreated Catalyst

RUN TOTAL REACTOR VVH SULPHUR SULPHUR SULPHUR NUMBER RUNTIME TEMPERATURE IN OUT ON CAT.

A- hrs C hr-1 ppm ppm wt% 1 24 170 1.83 180 1 0.45 2 48 170 1.63 180 5 0.84 3 71 167 1.74 180 10 1.23 4 139 175 1.69 180 11 2.33 5 187 175 1.69 180 10 3.12 6 239 180 1.75 180 9 4.00 7 305 185 1.77 180 8 5.14 TABLE 2 CARBON NUMBER DISTRIBUTION FOR HEXENE FEED AND PRODUCTS UNTREATED CATALYST

CARBON NUMBER FEED RUN A-5 RUN A-6 RUN A-7 wt % # C5 0.3 0.3 0.4 0.3 C6 87.4 85.7 85.4 84.9 C7 11.5 12.2 12.1 12.3 C8 - - - C9 - - - C10 0.1 0.1 0.1 0.1 C11 0.3 0.3 0.2 0.3 C12 0.3 1.3 1.6 1.9 C13 0.1 0.1 0.2 0.2 C14 - - - Delta C12 + C13 - 1.0 1.4 1.7 Temperature - 175 180 185 Reactor C - 175 180 185 VVH hr -1 - 1.69 1.75 1.77 Example 1 The procedure of Comparison Example A was followed except that the catalyst was aminated by passing through it triethylamine at a 1% concentration in a hexene feedstock for 24 hours at 1700C and 29 bar (gauge) to maintain the feed in the liquid phase.

The results are shown in Tables 3 and 4 below, from which it can be seen that dimer formation has been prevented, and a correspondingly improved hexene yield achieved, with a similar sulphur removal performance.

TABLE 3 Desulphurization Results, Amine Treated Catalyst

RUN | TOTAL | REACTOR | VVH | SULPHUR NUMBER RUN TIME TEMPERATURE IN OUr ON CAT.

hr-1 | ppm | .

1 24 i 170 1.70 180 ; < 1 1 0.36 | 2 2 45 1 175 1.61 180 < 1 | 0.67 3 | 69 | 180 | 1.65 | 180 | < 1 | 1.02 4 4 | 93 , 185 1.69 180 1 ss 1.38 5 | 164 | 185 | 1.63 | 180 | < 1 | 2.40 TABLE 4 CARBON NUMBER DISTRIBUTIONS FOR HEXENE FEED AND PRODUCTS::AMINE TREATED CATALYST

RUN CARBON NUMBER FEED 1-2 1-3 1-4 1-5 wt% # C5 0.3 0.5 0.5 0.6 0.4 C6 87.4 86.2 1 86.3 86.2 86.4 C7 11.5 12.3 1 12.4 12.4 12.4 | C8 | - | 0.1 | - | - | C9 - - - - - C10 0.1 0.1 0.1 0.1 0.1 C11 | 0.3 | 0.4 | 0.4 | 0.4 | 0.4 C12 0.3 0.3 0.2 0.2 0.2 C13 0.1 I 0.1 0.1 | 0.1 0.1 C14 | - | - | - | - | wt % paraffin 21.6 21.7 21.2 ' 21.5 | 21.3 Delta C12 + C13 - 0 0 0 0 Temperature Reactor C - 175 180 185 185 VVH hr-1 - 1.61 1.65 1.69 1.69 wt% sulfur 0.67 1.02 1.38 2.10 Note: During Run 1-1 hexene with 1 wt % triethylamine was passed over the catalyst at 1700C; following runs hexene only.

Example 2 This example was carried out initially in substan

tially thev same way as Comparison A, but using fresh Harshaw Ni-5126T 1/8 catalyst (analysis: Ni 59%, Si 6%; Al 5.1%; Ca 0.4%; Fe 0.1%.) and using an olefin feed as set out in Table 6 below, with a paraffin content of 9.8%, chlorine 2 ppm, sulphur 120 ppm, S.G. (20/200C) 0.693, and maleic anhydride value 0.25 mg/g. Then, after 584 hours, when sulphur loading on the catalyst had reached 7.1% by weight, 1% by weight of triethylamine was incorporated in the hexene feed for 25 hours at 1800C.

As can be seen from the results in Tables 5 and 6 below, the amination of the catalyst effectively prevented dimer formation.

TABLE 5 Desulphurization Results

RUN TOTAL REACIOR VVH SUEUR | SULPHUR : SULPHUR NUMBER RUN TIME TEMPERATURE | IN OUT ON CAT.

2- | hrs | C | hr-1 | ppm | ppm | wt% 6 274 170 1.53 120 | 1 - 3.45 8 394 170 1.55 120 6 4.90 13 584 180 1.57 120 7 7.13 14 609 180 1.54 120 12 7.41 15 632 | 180 1.61 120 10 7.68 16 656 180 1.58 120 10 7.96 17 679 180 1.58 120 11 8.22 Note: Added 1 wt% triethylamine to hexene feed during run 14.

TABLE 6 CARBON NUMBER DISTRIBUTION HEXENE FEED AND PRODUCTS CATALYST AMINE TREATED DURING RUN 2-14

RUN CARBON NUMBER FEED 2-6 2-8 2-13 2-15 2-16 2-17 wt 5 # C5 0.12 - - - - - C6 84.0 85.6 84.9 83.5 86.9 87.1 87.5 C7 15.2 13.0 13.8 14.1 12.7 12.5 12.1 I I C8 - - - - - - C9 - - - - - - C10 0.14 0.3 0.1 0.1 0.1 0.1 0.1 C11 0.18 0.1 | 0.1 1 0.1 0.1 0.1 0.1 C10 | 0.37 | 0.9 | 1.0 | 2.2 | 0.3 | 0.2 | 0.2 C13 0.07 - - 0.1 C14 - - - - - - wt% paraffin 9.85 9.87 9.76 10.01 9.67 9.42 9.53 Delta C12 + C13 wt% - : 0.5 0.6 1.9 0 0 0 Temperature - 170 170 180 180 180 180 Reactor OC VVH hr -1 - 1.53 1.55 1.57 1.61 1.58 1.58 wt% sulphur on - 3.45 4.90 7.13 7.68 7.96 8.22 the catalyst Note: During Run 2-14 for 25 hours hexene with 1 wt % triethylamine was passed over the catalyst at 1800C.

Following runs hexene only.

Comparison Example B The procedure of Comparison Example A was repeated, except that fresh Girdler G-49 RS catalyst was used, again using the primarily C6 olefin feedstock.

Table 7 Desulphurization Results, Untreated Catalyst

RUN TOTAL REACTOR VVH SULPHUR SULPHUR SULPHUR NUMBER RUN TIME TEMPERATURE IN OUT ON CAT.

A- hrs C hr-1 ppm ppm wt% 1 22 170 1.74 195 3 0.35 2 2 94 175 1 1.70 195 14 . 1.42 3 3 118 I 175 , 1.69 1 195 19 1.76 4 4 142 180 1.76 195 17 2.12 5 166 180 1.78 195 17 ' 2.48 6 190 185 1.79 195 19 2.85 i 7 261 185 1.8l 195 24 ss 3.90 The percentages of C6 hydrocarbons in the feed and the products of the various runs are given in Table 8 below. The results clearly show that the catalyst significantly reduces the yield of the C6 olefin while desulphurizing the feedstock.

Table 8 Proportion of C6 Hydrocarbons

CARBON PRODUCT OF RUN NUMBER FEED A-1 A-2 A-3 A-4 A-5 A-6 A-7 C6 87.4 70.6 70.1 70.4 69.0 66.3 66.9 Example 3 Fresh Girdler G-49 RS was aminated using the procedure described in Example 1. Its ability to desulphurize a predominantly C6 olefin feedstock (paraffin content 23%, sulphur content 135 ppm, chlorine content 4 ppm, S.G., 15/15 C, 0.6878, maleic anhydride value 0.14 mg/g) and the change in C6 content were tested. The results are shown in Tables 9 and 10 below.

Table 9 Desulphurization Results, Amine Treated Catalyst

RUN TOTAL REACTOR VVH SULPHUR SULPHUR SULPHUR NUMBER RUN TIME TEMPERATURE IN OUT ON CAT.

3- hrs C hr-1 ppm ppm wt% 1 94 175 1.03 135 1 0.75 2 139 185 1.50 135 3 1.02 3 208 185 1.82 135 6 1.44 Table 10 Percentages of C6 hydrocarbons in feed and products of Runs.

Feed Run 3-1 Run 3-2 Run 3-3 88.1 85.9 85.9 85.1 The improvement in yield of C6 product compared with that obtained in Example B is apparent from Table 10.

Claims (33)

CLAIMS:

1. A process for the desulphurization 6f an olefin-containing feedstock, which comprises contacting a sulphur-bearing olefin-containing feedstock with an aminated nickel catalyst.

2. A process as claimed in claim 1, wherein the feedstock contains an olefin with from 3 to 18 carbon atoms.

3. A process as claimed in claim 1, wherein the feedstock contains an olefin with from 3 to 12 carbon atoms.

4. A process as claimed in claim 1, wherein the feed stock contains an olefin with from 4 to 6 carbon atoms.

5. A process as claimed in any one of claims 1 to 4, wherein the olefin is a pentene.

6. A process as claimed in any one of claims 1 to 4, wherein the olefin is a hexene.

7. A process as claimed in any one of claims 1 to 6 wherein the feedstock is liquid.

8. A process as claimed in any one of claims 1 to 8, wherein the catalyst contains at least 35% by weight nickel.

9. A process as claimed in claim 8, wherein the catalyst contains from 45 to 65% nickel by weight.

10. A process as claimed in any one of claims 1 to 9, wherein the catalyst is a supported nickel catalyst.

11. A process as claimed in claim 10, wherein the support is a porous support.

12. A process as claimed in claim 10 or claim 11, wherein the support is a refractory material.

13. A process as claimed in claim 12, wherein the refractory material is silica, alumina, clay, Kieselguhr, magnesia or a zeolite.

14. A process as claimed in any one of claims 1 to 13, wherein the catalyst has been aminated with an aliphatic or cycloaliphatic amine.

15. A process as claimed in claim 14, wherein the amine is dimethylamine, diethylamine, triethylamine, dibutylamine, piperidine or pyrrolidine.

16. A process as claimed in any one of claims 1 to 15 wherein the amination of the catalyst has been carried out by direct contact of the amine with the catalyst.

17. A process as claimed in claim 16, wherein the amine is contacted with the catalyst in the presence of an olefin in the liquid state.

18. A process as claimed in claim 17, wherein the amine is contacted with the catalyst in desulphurization conditions for a period of up to 40 hours.

19. A process as claimed in claim 16, wherein the amine is contacted with the catalyst at ambient temperature.

20. A process as claimed in any one of claims 1 to 19, wherein the catalyst is a spent hydrogenation catalyst.

21. A process as claimed in claim 1, carried out substantially as described in Example 1 or in Runs 14 to 16 of Example 2.

22. An aminated nickel catalyst.

23. An aminated nickel catalyst, wherein the catalyst is as defined in any one of claims 8 to 20.

24. A desulphurized olefin feedstock, whenever prepared by a process as claimed in any one of claims 1 to 21.

25. A feedstock as claimed in claim 24, wherein the weight ratio of Cn:C2n olefins, in which n represents the carbon atom number of the olefin present in greatest proportion, is at least 400:1.

26. A process for the manufacture of an aldehyde, which comprises hydroformylation of a feedstock as claimed in claim 24 or claim 25.

27. An alcohol produced by hydroformylation and hydrogenation of a feedstock as claimed in claim 24 or clazim 25.

28. The use of an aminated nickel catalyst in the desulphurization of an olefinic feedstock.

29. The use of an aminated nickel catalyst in the desulphurization of an olefinic feedstock to a hydroformylation process.

30. The use of an aminated nickel catalyst in the desulphurization of an olefinic feedstock to a process of hydroformylation and subsequent reduction to an alcohol.

31. The use as claimed in any one of claims 28 to 30, wherein the catalyst is as defined in any one of claims 8 to 20.

32. The use as claimed in any one of claims 28 to 30 wherein the olefinic feedstock is as defined in any one of claims 2 to 7.

33. Any new feature hereinbefore described or any new combination of hereinbefore described features.