The present invention concerns a catalyst containing copper and the use of such a catalyst in catalytic processes.

Fatty alcohols are useful feedstocks, in particular for the production of surfactants and detergents. They may be produced in a variety of ways. One process yielding fatty alcohols is the hydrogenolysis of methyl esters of fatty acids (FAMEs) which are usually derived from triglycerides found in animal fats and vegetable oils. The hydrogenolysis or hydrogenation of FAME feedstocks using catalysts containing copper and chromium has been described in the prior art, for example in US2091800. WO91/04789 describes an acid-resistant copper chromite catalyst material containing promoter metal compounds as well as colloidal silicic acid, and a process for their production and use for direct fixed-bed hydration of fatty acids to produce fatty alcohols of appropriate chain-length. It is, however, desirable to avoid the use of chromium compounds in this process so that contact with toxic chromium compounds is avoided in the manufacture and use of the catalyst and also to ensure that the products are free of chromium.

US5364986 describes the production of C6-22 fatty alcohols by a process which comprises contacting a triglyceride with hydrogen in the presence of a copper-zinc catalyst and in a reaction zone. We have found, however, that catalysts of the type described in US5364986 are not resistant to the process conditions found in some commercial hydrogenolysis processes and may become weak during use, leading to a change in the structure of the catalyst bed. US5475159 describes a process for the direct hydrogenation of methyl esters in the presence of a catalyst comprising a copper compound, a zinc compound and at least one compound selected from the group consisting of aluminium, zirconium, magnesium, a rare earth and mixtures thereof. It is an object of the invention to provide a catalyst and process which avoids some of the problems found in the prior art catalysts and processes.

According to the invention we provide a catalyst comprising copper or a compound thereof, zinc or a compound thereof and a material containing silica and alumina.

A process according to the invention for the hydrogenation or dehydrogenation of an organic feedstock comprises the steps of providing a feed stream comprising a hydrogenatable or dehydrogenatable organic feedstock, providing a catalyst comprising copper or a compound thereof, zinc or a compound thereof and a material containing silica and alumina and contacting said feed stream with said catalyst.

The process may be a hydrogenation process. By hydrogenation, we include hydrogenation of a carbonyl group, hydrogenolysis of an ester, hydrogenolysis of a carboxylic acid, hydrogenolysis of an alcohol, especially a polyol such as glycerol, and hydrogenation of carbon monoxide to form hydrocarbon products. A process, according to the invention, for producing an alcohol comprises contacting a feedstock comprising an organic aldehyde, ketone, an ester of a carboxylic acid or a carboxylic acid with hydrogen in the presence of a catalyst comprising copper or a compound thereof, zinc or a compound thereof and a material containing silica and alumina.

Hydrogenation processes according to the invention may comprise a process for the hydrogenation of organic aldehydes to alcohols, for example C3 - C32 alcohols, for example in the production of oxo- alcohols or glycols. Alcohols formed in such processes may include short chain alcohols, e.g. containing from 3 - 10 C atoms, and longer chain alcohols, such as fatty alcohols, e.g. containing 12 - 22 C atoms. Hydrogenation processes according to the invention may comprise the hydrogenation of esters, mono-, di- or tri-carboxylic acid compounds for the production of alcohols, diols or polyols, such as the production of 1 ,6-hexane diol from adipic acid for example. Hydrogenolysis of an ester of a carboxylic acid or of a carboxylic acid comprises contacting an ester of a carboxylic acid and/or a carboxylic acid with hydrogen in the presence of a catalyst.

A dehydrogenation process of the invention may comprise the step of contacting an alcohol with a catalyst to form an aldehyde, ketone or an ester.

According to a particular embodiment of the invention, a hydrogenolysis process, according to the invention, for producing an alcohol comprises contacting an ester of a carboxylic acid with hydrogen in the presence of a catalyst comprising copper or a compound thereof, zinc or a compound thereof and a material containing silica and alumina. The ester of a carboxylic acid may be an ester of a fatty acid, i.e. a carboxylic acid containing from 12 to 32 C atoms. The ester may be an ester of a carboxylic acid containing from 6 to 32 carbon atoms. In other words, the carboxylic acid residue of the ester may contain from 6 to 32 carbon atoms. The carboxylic acid residue of the ester may contain from 6 to 22 carbon atoms, for example 10 - 18 C atoms. The ester may contain the residue of an alcohol containing from 1 to 32 carbon atoms. For example, the ester may be an ester of a lower alkyl alcohol, such as a methyl, ethyl or propyl ester or it may be an ester of a higher alcohol or fatty alcohol, containing from 12 to 32 C atoms. The ester may comprise a wax ester, i.e. an ester of a fatty alcohol and a fatty acid. The ester may contain the residue of an alcohol containing from 1 to 22 carbon atoms, for example 1 - 18 C atoms. The ester may be present in a feedstock comprising a mixture of more than one ester. The feedstock may further comprise other compounds such as carboxylic acids and water, for example.

The process may be a hydrogenation process or a hydrogenolysis process. The alcohol produced in the process for the hydrogenolysis of an ester may be a fatty alcohol. The alcohol may comprise an alcohol containing from 6 to 32 carbon atoms. The alcohol may comprise an alcohol containing from 8 to 32 carbon atoms. The alcohol produced from the ester may contain the same number of carbon atoms as the carboxylic acid residue of the ester. For example, dodecanol (ΟΗ ₃ (ΟΗ ₂ )ιιΟΗ) may be produced by a hydrogenolysis process of the invention when the ester is methyl laurate (CH ₃ (CH2)ioC(0)0-CI-l3) . The process may be a liquid-phase process. The process may alternatively take place in the gas phase. The process may take place in a batch reactor, such as a stirred tank or an autoclave. Alternatively the process may be a continuous process, wherein a liquid phase feedstock containing the organic feedstock, such as an ester of a carboxylic acid, is caused to flow through a bed of catalyst particles. The liquid hourly space velocity (LHSV) may be from 0.1 to 10 hr ¹ , for example from 0.1 to 3 hr ¹ . Hydrogen may be fed to the reactor as a gas, optionally mixed with at least one other gas such as nitrogen. Hydrogen may be dissolved in the liquid-phase feed prior to, or during, the process of feeding the liquid-phase feedstock to the reactor. The hydrogen pressure may be in the range from 1 - 300 bar gauge. In a typical reaction, the hydrogen pressure may be in the range from 200 - 300 barg. Alternatively a lower hydrogen pressure may be used, in the range 1 - 200 barg. The reaction conditions to be used depend upon the nature of the reaction and the starting materials used. The reaction may take place at a temperature of at least 120°C. When the process of the invention is a process for the hydrogenolysis of a fatty ester, for example, a suitable temperature may be within the range from 150 - 250°C.

The catalyst comprises copper or a compound thereof. In the active form of the catalyst, the copper is present as copper metal. As the skilled person will be aware, it is common to provide catalysts in which the active metal is present as a compound which is catalytically inactive or less active than the metal. Catalysts in that form may be activated by treatment to convert the less active compound to the active metal by reduction. The treatment conventionally involves contact with a hydrogen-containing gas at elevated temperature and may therefore be carried out in the reactor to be used for hydrogenation. After activation the catalyst contains active metallic copper although there is usually also some unreduced copper present since the reduction process is rarely 100% efficient. Catalysts may be supplied in a reduced form; however such catalysts must be protected from contact with an oxygen-containing gas because they are pyrophoric. The protection methods include encapsulation, e.g. in a fat or wax material, and passivation. When the catalyst is passivated, a proportion of the active copper metal is reacted to form passivating compounds such as an oxide or carbonate under controlled conditions. The passivated catalyst can then be handled and the passivating compounds can be reduced on contact with hydrogen. The catalyst of the invention and used in the process of the invention therefore comprises copper metal and/or a compound of copper which is reducible to copper metal. The compound of copper is preferably copper oxide.

The catalyst may comprise from 10 - 70% of copper, by weight, calculated as copper metal. The catalyst may comprise 20 - 60% by weight of copper (calculated as copper metal). In particular, the catalyst may contain 25 - 45% by weight of copper (calculated as copper metal).

The catalyst further comprises a compound of zinc. The catalyst preferably contains 10 - 70% by weight of zinc (calculated as zinc metal). The catalyst may comprise 20 - 60% by weight of zinc (calculated as zinc metal). In particular, the catalyst may contain 25 - 45% by weight of zinc (calculated as zinc metal). The zinc is preferably present in the catalyst as zinc oxide. The catalyst may contain up to about 85% of zinc oxide, by weight.

The catalyst contains a material containing silica and alumina. The material containing silica and alumina may be a structural promoter. By "structural promoter" we mean a material which affects, especially improves, the mechanical properties of the catalyst. The improvement in mechanical properties may have the effect of improving the activity of the catalyst in the reaction, through promotion of resistance of the catalyst to the feedstock, leading to retention of mechanical properties. The material containing silica and alumina maybe a catalyst support. A catalyst support is effective in improving the distribution and form of the catalytically active metals in the finished catalyst. The material containing silica and alumina may affect the catalytic properties of the catalyst.

The catalyst may contain from 1 to 40%, preferably 5 - 20%, by weight of the material containing silica and alumina. The material containing silica and alumina may contain from 1 % to 70% of silica by weight and from 10% to 99% of alumina by weight. In some embodiments the material containing silica and alumina may contain from 1 % to 40% of silica by weight and from 60% to 99% of alumina by weight. The material containing silica and alumina may contain other elements or compounds, such as magnesium, for example, which occurs in some clay minerals, The alumina in the material containing silica and alumina may be in the form of a hydrated alumina, e.g. boehmite, or a transition alumina, i.e. a partially hydrated alumina such as gamma, theta or delta alumina. In one embodiment, a precursor to the catalyst of the invention contains a hydrated form of alumina and the catalyst formed from the precursor contains a less-hydrated form of alumina. The catalyst formed from a precursor containing hydrated alumina may contain a transition alumina. The transition alumina may comprise gamma, theta or delta alumina.

Transition aluminas are formed when a hydrated or partially hydrated alumina is heated (i.e. calcined) at a temperature in excess of about 300 °C for a time sufficient to form a transition form of alumina.

Calcination is normally continued for at least one hour and may take several hours. Examples of materials containing silica and alumina which are suitable for use in the catalysts of the present invention or their precursors include silica-doped alumina materials and clays, e.g. kaolin, montmorillonite, attapulgite. The material containing silica and alumina may contain, comprise or consist of

aluminosilicates species. For the purpose of this patent application, we define aluminosilicates as aluminium silicates in which some of the Si ⁴⁺ ions in silicates are replaced by Al ³⁺ ions and in which the charge is balanced by other positive ions. Zeolites are microporous crystalline aluminosilicates having an ordered pore structure. The material containing silica and alumina does not consist of a zeolite. When the material containing silica and alumina contains, comprises or consists of aluminosilicates species, they are non-zeolitic aluminosilicates species. It is not intended that the catalyst of the invention contains a zeolite. Therefore in preferred embodiments of the catalyst of the invention, the catalyst does not comprise or contain a zeolite. The catalyst used in the process of the invention may be formed from a catalyst precursor comprising a copper compound, a zinc compound and a material containing silica and alumina.

The formation of a catalyst for use in the invention from a catalyst precursor may include the processes of calcination, reduction, and/or shaping. Shaping processes may include tabletting, extrusion and/or granulation. The catalyst may contain ingredients such as lubricants, pore-formers, pelleting aids etc. For example the catalyst may contain up to about 5% by weight of graphite as a pelleting aid.

The catalyst used in the invention may be made by conventional methods used in catalyst manufacturing. A catalyst precursor may, for example, be made by forming a solution of a soluble compound of copper and a soluble compound of zinc and then causing the precipitation of insoluble compounds of copper and zinc by adding a precipitating agent. The material containing silica and alumina may be present in the solution before the precipitation of the copper and zinc compounds. Alternatively the material containing silica and alumina may be mixed with the precipitated copper and zinc compounds. As a further alternative, a copper or a compound thereof, a zinc compound and the material containing silica and alumina may be mixed together to form the catalyst or a precursor thereof.

A precursor to the catalyst comprising the material containing silica and alumina, a copper compound and a compound of zinc may be calcined for at least 30 minutes at a temperature of at least 400 °C. The calcination temperature may be at least 500 °C.

The catalyst may take the form of particles having a minimum dimension of 0.5 mm. For example, catalyst particles suitable for use in a fixed catalyst bed may take the form of regular shapes such as spheres, cylinders, tablets, rings, wheels, saddles, lobed cylinders or irregular shapes such as granules. Such catalyst shapes may be prepared by various methods which are known to the skilled person. The catalyst precursor may be shaped into the desired shape, e.g. spheres, tablets, cylinders, lobed cylinders, rings or granules, before or after a calcination step, if a calcination step is carried out.

The catalyst precursor may be reduced so that at least some metallic copper is formed from the copper compound. Reduction may be carried out by contacting the catalyst precursor with a hydrogen- containing gas at a temperature of at least 100 °C. Reduction may take place in a chemical reactor for carrying out the process of the invention. Reduction of the catalyst precursor may be carried out by the manufacturer of the catalyst after the calcination step, if used. Reduced catalysts may be passivated or encapsulated. Storage and transport of reduced catalysts may take place under an oxygen-free atmosphere.

The catalyst and process of the invention will be further described in the following examples. Example 1 : Preparation of a Catalyst according to the Invention A mixed aqueous solution (1 1 .5 litre) of copper nitrate and zinc nitrate and nitric acid, containing 37.5 g l of copper and 40g/l of zinc, was heated to 90 °C. An aqueous solution of sodium carbonate (20 litres, 106 g/l) was heated to 90 °C. 125 g of a silica-alumina material containing 10% silica was slurried in 11 litres of water and heated in a vessel. The mixed Cu/Zn solution and Na ₂ C0 ₃ solutions were then added to the slurry at 90°C over 30 minutes, with agitation. The solids were filtered, washed with deionised water and re-slurried in deionised water. The wet filter cake was formed into noodles and dried for 12 hours at 90 °C. The dried solids were calcined at 590 °C for 2 hours, blended with pelleting aids and pelleted to form cylinders (3.2mm x 3.2mm) of catalyst according to the invention. The dried and calcined material has a composition 45% CuO, 45% ZnO, and 10% silica-alumina, i.e. excluding water, pelleting aids etc.

Comparative Example 2: Preparation of a Comparative Catalyst

A catalyst was made by the method described in Example 1 but using a commercial amorphous silica support instead of the silica-alumina.

Comparative Example 3: Preparation of a Comparative Catalyst

A catalyst was made by the method described in Example 1 but using an alumina material pre- precipitated from a solution of aluminium nitrate instead of the silica-alumina.

Example 4: Preparation of a Catalyst according to the Invention

A catalyst was made by the method described in Example 1 but using a silica-alumina material containing 20% silica.

Example 5: Preparation of a Catalyst according to the Invention

A catalyst was made by the general method described in Example 1 in which the proportion of Cu and Zn was changed to 37.5 g/L of Cu and 17 g/L of Zn, resulting in a catalyst containing 63% CuO, 27% ZnO, and 10% of the silica-alumina, excluding water, pelleting aids etc.

Comparative Example 6 was a commercially available copper chromite catalyst in the form of cylinders having a particle size of 3mm diameter x 3mm length.

Example 7: Preparation of a Catalyst according to the Invention

A catalyst was made by the method described in Example 1 but the dried solids formed by drying the wet filter cake were calcined at 700 °C for 2 hours instead of at 590 °C.

Example 8: Preparation of a Catalyst according to the Invention

A catalyst was made by the method described in Example 1 except that the precipitation step of adding the mixed Cu/Zn solution and Na ₂ C0 ₃ solutions to the heated slurry was carried out at 70 °C instead of 90 °C.

Example 9: Preparation of a Catalyst according to the Invention A catalyst was made by the method described in Example 1 except that following the addition of the mixed Cu/Zn solution and Na ₂ C0 ₃ solutions to the heated slurry over 30 minutes, the mixture was held at 90 °C for 60 minutes prior to filtration.

Example 10: Preparation of a Catalyst according to the Invention

A catalyst was made by the method described in Example 1 but the dried solids formed by drying the wet filter cake were calcined at 500 °C for 2 hours instead of at 590 °C.

Example 1 1 : Process according to the invention

The catalysts were tested in a stirred batch autoclave at 100 bar hydrogen and 220 °C. 12 ml of catalyst was used each time along with 500 ml of methyl laurate as feedstock. The catalysts were reduced in the reactor, prior to the addition of the methyl laurate feed, for 10 hours at 240 °C in a flow of 5% hydrogen in nitrogen. A sample of the feedstock was taken and samples were also taken periodically throughout the duration of the reaction. After 24 hours online the reactor was cooled, depressurised and the catalyst and feedstock were discharged. The samples of the liquid reaction mixture were analysed by gas chromatography. Table 1 shows, for each reaction mixture, the % conversion (calculated from 100 - wt % of methyl ester in product mixture) and wt% of alcohol in the reaction mixture after at least 20 hours online.

Example 12: Crush strength tests

Catalyst pellets were tested for horizontal crush strength using a commercial compression testing machine (Model CT6 available from Engineering Systems (Nottm) Ltd) to measure the force that must be applied in order to break the catalyst pellet. The pellets were tested using a 50 kg load cell with flat plattens and a speed of 22 mm/minute. 20 pellets were analysed for each sample and the mean horizontal crush strength was calculated.

Samples of fresh catalyst were tested, and these results are indicated in Table 1 as "initial crush strength". Samples of these catalysts were then charged to a batch autoclave and reduced in the reactor at 240 °C in a flow of 5% hydrogen in nitrogen. 500 ml of methyl laurate was charged and contacted with the catalysts at 100 bar hydrogen and 220°C for 24 hours, The reactor was then cooled, the catalyst was discharged and the crush strength measured. For each test, the percentage difference between the mean crush strength of the fresh catalyst and that of the spent catalyst was calculated to give the % strength lost during the reaction. The results are shown in Table 1 .

The results show that, although the conversion and alcohol yield is high using the catalyst of Example 3, i.e. containing an alumina material instead of silica and alumina, the catalyst pellets were found to have lost 52% of their strength during the course of the reaction. This level of strength loss from catalyst pellets in a catalyst bed is unacceptable in practice, because the load on the catalyst pellets is likely to cause them to collapse, leading to a very significant loss of void space in the bed through which the reactants can pass. Whilst the silica-containing catalysts of Example 2 are strong, the conversion and alcohol yield are very low. The catalysts of the invention provide a high conversion and yield and an acceptable retention of strength during the reaction.

Table 1

Example 13: Catalyst according to the invention

A catalyst was made by the method described in Example 1 but using an attapulgite clay (65% silica) as the silica-alumina material.

Example 14: Use of catalysts in fixed bed hydrogenolysis

The catalysts of Example 1 and Example 13 were tested (separately) in a fixed bed reaction as follows. A catalyst bed was formed from 80 ml of the catalyst pellets in an oil-heated, jacketed tubular reactor (22mm i.d, 850mm length), supplied with hydrogen and nitrogen gas feed and means to feed liquid methyl ester feedstock (C12 - C18 methyl ester feedstock derived from palm kernel oil) to the top of the catalyst bed. The temperatures reported in this example refer to the temperature of the circulating heating oil. The catalyst was reduced in the reactor in a flowing stream of 5% hydrogen in nitrogen for 18 hours as the temperature was raised to 240 °C. The temperature was then adjusted to the desired reaction temperature and allowed to equilibrate under nitrogen. The reaction was begun by starting the feed of ester and hydrogen and the reaction conditions were set as shown in Table 2. The results in Table 2 are from samples taken after the reaction had been allowed to equilibrate for 8 hours at each set of reaction conditions. A fresh catalyst sample was used for each run at each pressure. Samples of the feedstock and of the reactor outlet were analysed by gas chromatography. Table 2

Example 15: Use of catalysts in fixed bed hydrogenolysis

The catalysts of Example 1 and Comparative Example 6 were tested (separately) in a fixed bed reaction as follows. A catalyst bed was formed from 100 ml of the catalyst pellets in an electrically heated tubular reactor (28mm i.d, 900mm length), supplied with hydrogen and nitrogen gas feed and means to feed liquid methyl ester feedstock (C12 - C18 methyl ester feedstock derived from palm kernel oil) to the top of the catalyst bed. The temperature of the catalyst bed was monitored using thermocouples positioned inside a thermowell within the catalyst bed. The catalyst was reduced in the reactor in a flowing stream of 2% hydrogen in nitrogen for 18 hours as the temperature was raised to 240 °C. The temperature was then adjusted to the desired reaction temperature and allowed to equilibrate under nitrogen. The reaction was begun by starting the feed of ester and hydrogen and the reaction conditions were set as shown in Table 3. The results in Table 2 are from samples taken after the reaction had been allowed to equilibrate for 16 hours at each set of reaction conditions. Samples of the feedstock and of the reactor outlet were analysed by gas chromatography. Table 3

Example 16: Use of catalysts in fixed bed hydrogenation of aldehyde

The catalysts of Example 1 , 4 and 5 were tested (separately) in a fixed bed reaction as follows. A catalyst bed was formed from 250 ml of the catalyst pellets in a tubular reactor supplied with hydrogen and nitrogen gas feed and means to feed a liquid feedstock comprising a 20wt% solution of butanal in butanol to the top of the catalyst bed, with a recycle of the reaction product. The catalyst was reduced in the reactor in a flowing stream of 1 % hydrogen in nitrogen for 35 hours at 210 °C. The temperature was then adjusted to the desired reaction temperature and the butanal feed solution and hydrogen were fed to the catalyst bed, with partial recycle of the product stream. The same reaction conditions were used for each catalyst. Samples were taken periodically. Samples of the feedstock and of the reactor outlet were analysed by gas chromatography. The results in Table 4 are from samples taken during stable operation of the process.

Table 4

Example 17: Use of catalysts in batch hydrogenation of aldehyde

The catalysts from Example 1 and 6 were tested in a stirred batch autoclave at 20 bar hydrogen and 140 °C. 12 ml of catalyst was used each time along with 500 ml of a 20% (by volume) solution of butanal in butanol (i.e. 100 ml of butanal mixed with 400 ml of butanol). The catalysts were reduced in the reactor, prior to the addition of the feed, for 10 hours at 240 °C in a flow of 5% hydrogen in nitrogen. A sample of the feedstock was taken and samples were also taken periodically throughout the duration of the reaction and analysed by gas chromatography. The reaction was run until conversion reached 99.98%. The results in Table 5 show the composition of the sample taken at that final conversion.

Table 5

Catalyst Time to 99.98% conversion butanol di-n-butyl ether n-butyl butyrate

(minutes) (wt%) (wt%) (wt%)

1 259 92.78 0.01 0.48

6 186 94.71 0.01 0.04