WO2010018405A1

WO2010018405A1 - Chemical process and catalyst

Info

Publication number: WO2010018405A1
Application number: PCT/GB2009/051010
Authority: WO
Inventors: Michael John Watson; Martin Graham Partridge; Paul Appleton; Simon Jackson
Original assignee: Johnson Matthey Plc; Davy Process Technology Limited
Priority date: 2008-08-13
Filing date: 2009-08-12
Publication date: 2010-02-18
Also published as: GB0814784D0

Abstract

The invention comprises a process for the chemical treatment of a feed stream containing at least one organic compound comprising the step of contacting said feed stream with a catalyst comprising nickel and ruthenium in amounts to provide a mole ratio of ruthenium to nickel in the range from 0.15 x10^-3 to 0.06. We have found that such catalysts maintain activity even in the presence of acid components which normally promote deactivation of nickel catalysts.

Description

CHEMICAL PROCESS AND CATALYST

The present invention relates to chemical processes, in particular to catalytic chemical processes in which a reactant mixture containing an acidic component is in contact with a catalyst containing nickel.

WO-A-00/20375 describes the selective hydrogenation of butan-2-one and n-butyraldehyde byproducts formed in the production of ethyl acetate by the dehydrogenation of ethanol. In this process, a liquid process stream containing ethyl acetate, acetic acid, butan-2-one and n- butyraldehyde amongst other products, is passed over a 5% ruthenium on carbon catalyst to effect hydrogenation of the reactive ketone and aldehyde compounds to the corresponding alcohols. The alcohol products may then be separated from the desired ethyl acetate product by distillation. Ruthenium is relatively expensive and so the ruthenium-containing catalyst is a significant factor in the economics of this type of process. It is therefore desirable to replace the ruthenium catalyst with a less-expensive catalyst.

Chemical processes employing a nickel catalyst are widely used, for example to effect hydrogenation or dehydrogenation of oxygenates such as aldehydes, ketones and alcohols. Such feedstocks may contain small amounts of acidic compounds. When nickel catalysts are used in the hydrogenation of feed streams containing acids, they have been found to show a reduced activity and a propensity to deactivate over a short timescale. It is an object of the invention to provide a process for the treatment of feed streams containing acid components which overcomes the disadvantages of the prior art processes.

According to the invention, we provide a process for the chemical treatment of a feed stream containing at least one organic compound comprising the step of contacting said feed stream with a catalyst comprising nickel and ruthenium in amounts to provide a mole ratio of ruthenium to nickel in the range from 0.15 x10^'3 to 0.06.

We have found that the use of a nickel catalyst containing a minor proportion of ruthenium overcomes the problems found with using prior art nickel catalysts in a process where the feed stream contacting the catalyst contains an acid. Without wishing to be bound by this theory, it is believed that nickel species present in the catalysts are, in the non-ruthenium-containing catalysts, converted to a form which is leachable by acidic compounds present in the feed stream so that the amount of active nickel metal available for hydrogenation decreases as the time on-stream increases. When the catalyst contains ruthenium in intimate mixture with the nickel, then the loss of nickel appears to be prevented to a large extent. We have found that the use of catalysts of the invention in the hydrogenation of carbonyl compounds in an acid-containing feed stream has a greater efficiency than catalysts containing either nickel or ruthenium alone. The catalyst may comprise an unsupported nickel material, such as a sponge-type nickel which is widely used for hydrogenation reactions. In a preferred embodiment, however, the catalyst comprises, in addition to the nickel and ruthenium components, a catalyst support. Typical catalyst supports include carbon, and oxidic materials such as silica, alumina, silica-alumina, aluminosilicates, silicoaluminophosphat.es (SAPOs), titania, zirconia ceria and magnesia. Preferred support materials include alumina in all forms, including alpha alumina and transition aluminas such as gamma, theta and delta alumina for example. The support may be modified, treated or coated. For example an alumina support may be impregnated with a solution of a metal salt such as cerium nitrate which, upon calcination, modifies the support by forming ceria in or on a part of the alumina. The support is preferably porous, most preferably having a porosity greater than 0.2 ml/g, especially 0.3 - 1 ml/g. A high surface area support is preferred, for example a support having a surface area > 50m²/g, especially > 80 m²/g is particularly suitable.

The physical form of the catalyst may be particulate or massive. Particulate forms include powders, granules, spherical particles, tablets, lobed shaped particles or other 3-dimensional shapes. Typical particles for use in forming fixed catalyst beds have a minimum dimension in the range from 1 - 10 mm. The skilled person will appreciate that the size and shape of the particles affects the flow of gas and/or liquid through the catalyst bed and so the appropriate particle dimension may be selected dependent on the process, amount of feedstock to be treated and the acceptable pressure drop through the reactor. Powders or granules of a size less than 1 mm, especially from 50 - 500μm may be used if the reaction is to be carried out in a slurry phase or in a fluidised bed reactor. Massive forms of catalyst include structured reactors such as catalytic monolith reactors or catalyst materials supported on mesh or foamed supports.

A preferred catalyst support is a transition alumina. The transition alumina may be of the gamma- alumina group, for example a eta-alumina or chi-alumina. These materials may be formed by calcination of aluminium hydroxides at 400 - 75O⁰C and generally have a BET surface area in the range 150-400 m²/g. Alternatively, the transition alumina may be of the delta-alumina group which includes the high temperature forms such as delta- and theta- aluminas which may be formed by heating a gamma group alumina to a temperature above about 800⁰C. The delta-group aluminas generally have a BET surface area in the range 50-150 m²/g. The transition aluminas contain less than 0.5 mol of water per mole of AI₂O₃, the actual amount of water depending on the temperature to which they have been heated. The alumina should be porous, preferably having a pore volume of at least 0.2 ml/g, particularly in the range 0.3 to 1 ml/g.

Suitable catalyst supports are usually porous materials having a BET surface area greater than 50 m² per gram. The catalyst support may be a powder or may be formed into larger particles such as spheres, cylinders, lobed cylinders, clover-leaf sections, tablets, or other shape commonly used to form catalyst particles. The shape selected for use in the process is dependent on the heat-transfer properties and flow properties, such as pressure drop required for the process. One preferred catalyst support comprises a transition alumina formed into a lobed-cylinder by extrusion.

When the catalyst comprises a catalyst support, it preferably comprises from 5 - 50 % Ni and from 0.01 - 1 % of Ru, more preferably from 10 - 40 % Ni and from 0.05 - 0.25% Ru, in each case the balance being made up of catalyst support and optionally promoters, binders etc. In one preferred embodiment the catalyst consists essentially of from 10 - 40% Ni and from 0.05 - 0.25% Ru, the balance comprising particles of a porous transition alumina catalyst support.

The nickel may be present in the catalyst as a nickel compound, especially as an oxide, hydroxide, carbonate, hydroxy-carbonate, nitrate, halide or sulphate or it may be present in elemental form, i.e. as metallic nickel. In use in an oxidation process, the catalyst is likely to include an oxide of the ruthenium and / or nickel. When the catalyst is for use in a hydrogenation or dehydrogenation reaction, at least a portion of the nickel is present in the form of metallic nickel. The nickel and ruthenium compounds and/or promoter and/or an intermediate of any of them if present is typically reduced to metallic form by known methods. The reduction step may be performed in the reactor itself, by the reduction of a nickel compound with gaseous hydrogen, or the catalyst may be reduced ex-situ and transported in reduced form. The reduction may be carried out by contacting the nickel compound with stream of a hydrogen-containing gas at a suitable temperature (e.g. 150 - 500 ⁰C, more preferably from 200 - 450 ⁰C) for a suitable time (usually 1 - 8 hours) to effect reduction of the nickel compound to metallic nickel. Alternative reduction methods such as the use of liquid reducing agents, for example hydrazine, formaldehyde, sodium borohydride or an alcohol, may also be used. When the catalyst contains metallic nickel, it may be supplied in a passivated form or dispersed in a protective coating of a wax or fat. When the nickel is in the form of a sponge nickel, it is usually dispersed in a liquid in the form of a slurry.

When the catalyst comprises nickel and ruthenium on a catalyst support, it is made typically by depositing a compound of the nickel and a compound of ruthenium in or on a support material followed by drying and, if required, a step of reducing the metal compounds to the elemental form to produce very fine metal particles on the support. The nickel and ruthenium compounds may comprise a salt such as a carbonate, nitrate, chloride, sulphate, carboxylate (e.g. an acetate, citrate, malonate etc) or a complex with an organic compound such as a β-diketone or an ammine complex, including an ionic ammine complex such as an ammine chloride or ammine carbonate for example. Preferred nickel compounds include nickel nitrate, nickel chloride, nickel carbonate and nickel ammine complexes. Preferred ruthenium compounds include ruthenium nitrosyl nitrate, metal ruthenates and perruthenates and ruthenium carboxylates, e.g. ruthenium acetate. The nickel and ruthenium compounds may be deposited on the support sequentially, in any order; or they may be deposited together, for example from a solution of mixed nickel and ruthenium compounds. The metal compound(s) deposited on the support may be transformed to a different compound by an intermediate step such as calcination as is well-known in the art of catalyst manufacture, but such a step may be unnecessary.

The available methods of forming the nickel and ruthenium compounds and/or depositing them on a support are well-known in the catalyst manufacturing industry. Such methods include precipitation, e.g. of a nickel carbonate or hydroxide by mixing together a solution of a soluble nickel salt such as nickel nitrate with an alkaline precipitating agent such as sodium hydroxide or sodium carbonate to form a solid nickel carbonate product which is then filtered, washed and dried and then optionally calcined to form a nickel oxide. The precipitation may be done in the presence of a solid catalyst support, if required. The catalyst may also be made by co-precipitation methods, i.e. where the nickel and/or ruthenium compound is precipitated with a diluent or support material from a mixed solution of metal salts. If a precipitation method is used, the nickel and ruthenium compounds may be precipitated together from a mixed solution of ruthenium and nickel salts or separately, so that one of the nickel and ruthenium compounds is precipitated first and then the second compound is precipitated in the presence of the first precipitated compound.

The catalyst may alternatively be made by impregnating a solution of a nickel and/ or ruthenium salt into a porous support and then drying the impregnated support before, optionally, carrying out a calcination process to convert the impregnated salt to a different form (usually an oxide) and then, optionally, reducing the metal compound to an elemental form. Nickel or ruthenium salts include carbonate, nitrate, chloride, sulphate, carboxylate (e.g. an acetate, citrate, malonate etc) or a complex with an organic compound such as a β-diketone or an ammine or nitrosyl complex, including an ionic ammine complex such as an ammine chloride or ammine carbonate for example. In the case of ruthenium, metal ruthenates and perruthenates, e.g. sodium ruthenate, potassium perruthenate, may also be used. The solution of metal salt may be aqueous or organic. Standard impregnation methods may be used, including the incipient wetness method whereby an amount of metal salt solution calculated to fill the pores of the support, with a small excess, is sprayed onto a moving bed of catalyst support particles. The ruthenium and nickel compounds may be impregnated sequentially, optionally with a drying and/ or calcination step between each impregnation or together. More than one impregnation may be made in order to deposit more of a metal compound onto the support.

Another method which is useful to prepare the catalysts is deposition-precipitation in which a metal compound in solution is gradually decomposed in the presence of a porous catalyst support to form insoluble species in the pores of the catalyst support. An example of such a method is the impregnation of a solution of an aqueous nickel ammine carbonate complex into the pores of a support, followed by heating, usually to a temperature in the range 60 - 110 ⁰C. The heating causes the soluble ammine complex to decompose with the evolution of ammonia to yield less soluble nickel species which precipitate directly onto the support. The solid support and precipitated nickel species is then dried, optionally calcined and then reduced if required. The ruthenium compound may be applied by similar methods at the same time as the nickel or in a separate step before or after the deposition of the nickel compound. The ruthenium and nickel compounds may be formed or deposited on a catalyst support by similar methods or by different methods. For example a supported nickel catalyst may be formed by deposition-precipitation from a nickel ammine complex and then impregnated with a solution of a ruthenium salt such as ruthenium nitrosyl nitrate or sodium ruthenate. We have found that ion-exchange impregnation is a particularly convenient method of preparing the catalyst.

The chemical process is preferably a hydrogenation or a dehydrogenation reaction, more preferably a hydrogenation reaction. The feedstock may comprise fatty acids or triglycerides, alcohols, aldehydes or ketones. Selective hydrogenation may be carried out for the conversion of the feed to a desired main product such as in the hydrogenation of aldehydes, e.g. C4 and higher aldehydes such as those formed in the oxo-process. Acid contamination may be present in the aldehyde feed as an impurity or from unintended partial oxidation of the feed prior to the hydrogenation step. Natural fats and oils may also contain traces of acid arising from decomposition and oxidation of the fatty glyceride feedstock. The process of the invention may be useful for the hydrogenation of such materials, especially since the formation of nickel soaps may thereby be avoided. The hydrogenation process may alternatively be operated to convert by-product carbonyl compounds arising from an upstream process or present in a raw feedstock. A particular embodiment of the process of the invention is the hydrogenation of carbonyl compounds, especially butan-2-one and n-butyraldehyde by-products formed in the production of ethyl acetate by the dehydrogenation of ethanol as described in WO-A-00/20375. The process has been found to be particularly effective when the feed stream in contact with the catalyst contains one or more acidic compounds, especially carboxylic acids, because this type of feed appears to accelerate the deactivation of nickel catalysts. Generally the process is most advantageous when the feed stream contains a minor amount of a carboxylic acid compound, e.g. up to 1 wt% of acid based on the total weight of the feed stream. It has been found that the presence of about 500 - 1000 ppm of acid in a feed stream can reduce the activity and lifetime of a nickel catalyst by 100 and the use of the process of the invention in which the catalyst contains nickel and a minor proportion of ruthenium may alleviate this deactivation.

US-A-5196602 describes a two-stage hydrogenation of maleic anhydride to form 1 ,4-butanediol using a catalyst containing Ru, at least one of Ni and Pd, at least one of Zn and Cd and oxygen, on a low surface area support. This process using those catalysts are not included in the present invention. If the process of the present invention is used for the hydrogenation of succinic anhydride or gamma-butyrolactone as the second stage of the conversion of maleic anhydride to 1 ,4-butanediol then the catalyst does not contain Pd, Zn or Cd except in such amounts as are present in the Ru, Ni or support as unavoidable impurities. The preferred catalysts in US-A- 5196602 contain Ru and Ni in approximately equimolar quantities; the catalyst used in the present invention contain a maximum mole ratio of Ru/Ni of 0.06 and more preferably less than 0.01.

The process may be operated using a liquid phase feedstock or in the gas phase. The process may be a multi-phase reaction involving a liquid-phase feedstock and a gaseous reactant or byproduct. When a liquid feedstock is hydrogenated the hydrogen-containing gas may be present in the gas phase or alternatively partially or wholly dissolved in the liquid phase. The catalyst is present as a solid phase but may be present in the form of finely dispersed particles or as a stationary phase, either as a fixed bed of catalyst pellets or disposed on a reactor surface, particularly as a coated monolith. In a preferred embodiment the process is operated in a trickle- bed reactor, where a liquid phase reactant flows through a bed of shaped catalyst particles, in contact with a gas phase or using a dissolved gas reactant. It is preferred to operate the process at a relatively low temperature, for example less than 150 ⁰C and preferably less than 100 ⁰C, especially less than 85 ⁰C, in order to prolong the lifetime of the catalyst. The temperature at which a satisfactory reaction is achievable depends upon the nature of the chemical reaction to be carried out and must be balanced against the provision and cost of heating and cooling in the process flowsheet.

In one particularly preferred embodiment, of the invention, we provide a process for the hydrogenation of at least one carbonyl compound in a feed stream containing ethyl acetate by contacting said feed stream in the liquid phase with a hydrogen-containing gas at a temperature of between 50 and 110 ⁰C in the presence of a catalyst comprising from 10 - 40 wt% nickel, 0.05 - 0.25 wt% ruthenium and a transition alumina catalyst support such that the carbonyl compounds are hydrogenated to the respective alcohols. In this embodiment, the feed stream is preferably the product of a process for the production of ethyl acetate, preferably by the dehydrogenation of ethanol.

The invention will be further described in the following examples.

Example 1

A commercially available catalyst, HTC Ni 500, from Johnson Matthey Catalysts, in the form of tri- lobe shaped 1.2mm extrudates containing 21 % Ni as nickel oxide on a porous transition alumina support, was impregnated with an aqueous solution of ruthenium nitrosyl nitrate by an incipient wetness technique, dried and reduced in hydrogen at 430 ⁰C, followed by passivation in air. The catalyst contained 0.2% by weight of Ru.

Example 2

100 g of HTC Ni 500 catalyst in oxidic form was charged into a tumbler and rotated at 3 rpm. Na₂RuO₄ (sodium ruthenate, 4.49g at 2.34% Ru assay w/w, 5% overload) was weighed out and diluted with water to 120ml. The sodium ruthenate solution was poured onto the catalyst at room temperature and the slurry mixed for 30 minutes. The mother liquor was decanted and the catalyst decant-washed three times with water. Washing was continued until the conductivity of the supernatant was below 1 mS to ensure the removal of sodium ions was as complete as possible. The catalyst was drained and dried in an oven at 105⁰C for 16 hours then reduced and passivated. The catalyst contained 0.1 % by weight of Ru as measured by ICP-AES.

Example 3

500 g of the HTC catalyst in oxide form was charged into a tumbler and rotated at 3 rpm. Ruthenium nitrosyl nitrate (3.7 g of solution at 14.2% Ru assay w/w, 5% overload) was dissolved in water until the volume of solution reached 95% of the pore volume of Ni HTC500 oxide. This solution was added drop-wise to the tumbling catalyst over a period of 10 minutes, following which the catalyst was tumbled for a further 15 minutes. The catalyst was then dried in air at 105⁰C for 16 hours before being reduced in an atmosphere of 100% hydrogen at 45O⁰C for 3 hours followed by cooling and passivation in air. The catalyst contained 0.1 % by weight of Ru

Example 4

100 g of HTC Ni 500 in oxide form was weighed into a beaker. 100 ml of water was added to the catalyst. The mixture was stirred then transferred to a sieve. After filtration, the catalyst was charged to a tumbler and rotated at 3 rpm. Sodium ruthenate (4.3 g of solution at 2.75 % Ru assay w/w, 15 % overload) was weighed out and diluted with water to 120 ml. The mixture was added to the tumbler and tumbling continued for 30 minutes. The catalyst was then left to stand for a further 30 minutes after which time the mother liquor was filtered off. The catalyst was then washed with portions of water (2 x 150 ml) before being dried in an oven at 105⁰C. Following this the catalyst was reduced in an atmosphere of 100 % hydrogen to 45O⁰C for 3 hours followed by cooling and passivation in air. The catalyst contained 0.1 % Ru.

Example 5

50 cm³ of the catalyst made in Example 1 was packed in an oil jacketed reactor. The catalyst was activated, in order to re-reduce the passivated metals, by warming the catalyst to 23O⁰C under a stream of 10% hydrogen in nitrogen. Once activated the hydrogen was increased to 100% and the temperature reduced to the reaction temperature shown in Table 2.

A model feed was made up having the composition set out in Table 1 and fed, in the liquid phase, to the top of the reactor. A feed rate of 50 ml/hr (LSHV=l/hr) was used and a H₂ flow rate of 7.2 l/hr at 600 psig was employed. The temperature was varied as described in Table 2. The amount of 2- butanone in samples of the product taken after different times on-line was estimated using gas chromatography. The polishing efficiency is defined as amount of 2-butanone removed versus amount of 2-butanone in the feed expressed as a percentage. Table 1 : Feed composition

Examples 6 - 7

Catalysts were made using the method of Example 1 but containing 0.1 wt% and 0.05 wt% Ru respectively. The catalysts were evaluated for the hydrogenation of a similar feed stream using a similar method as described in Example 5 and the results are shown in Table 2.

Table 2

Comparative Example 8

The hydrogenation of the model feed stream was carried out as described in Example 5, but using the un-modified HTC-500 catalyst, i.e. containing no Ru. The results, in Table 3, show that this catalyst is considerably less efficient in the hydrogenation of 2-butanone than the catalysts used in Examples 3 - 5, even at higher temperatures. Comparative Example 9

The hydrogenation of the model feed stream was carried out as described in Example 5, but using a catalyst consisting of 0.2 wt% Ru on an alumina support , i.e. containing no Ni. The results, in Table 3, show that this catalyst is considerably less efficient in the hydrogenation of 2-butanone than the catalysts used in Examples 7 - 9, even at higher temperatures.

Table 3

Example 10: Conversion of hvdroxypivaldehvde to neopentylqlvcol

15 ml of catalyst, either as made in Example 3 or un-promoted HTC Ni 500 in reduced and passivated form, was charged to a spinning basket autoclave reactor. The catalyst was activated in the basket in its raised position, by heating to 23O⁰C under a stream of 100% hydrogen, whilst rotating at 700 rpm. Following this the vessel was cooled and the feed, of a composition shown in Table 4, was charged into the autoclave. The hydrogen pressure inside the vessel was then increased to 26 barg and the temperature increased to 8O⁰C. Under these conditions, the basket containing the catalyst was immersed into the feed mixture. Samples of the reaction mixture were taken at regular intervals and analysed by gas chromatography. The results are shown in Table 5. Hydroxypivaldehyde contains traces of organic acid from oxidation due to exposure to air. The results in Table 5 demonstrate that the Ru-promoted Ni catalyst shows enhanced activity compared with the un-promoted catalyst.

Table 4: Feed Composition

Table 5: Performance Data

Claims

1. A process for the chemical treatment of a feed stream containing at least one organic compound comprising the step of contacting said feed stream with a catalyst comprising nickel and ruthenium in amounts to provide a mole ratio of ruthenium to nickel in the range from 0.15 x10³ to 0.06.

2. A process according to claim 1 , wherein said treatment is a hydrogenation or dehydrogenation.

3. A process according to claim 1 or claim 2, wherein said feed stream comprises a fatty acid, a fatty triglyceride, an alcohol, an aldehyde or a ketone.

4. A process according to any one of the preceding claims, wherein the catalyst further comprises, in addition to nickel and ruthenium, a catalyst support selected from carbon, silica, alumina, silica-alumina, aluminosilicates, silicoaluminophosphat.es (SAPOs), titania, zirconia, ceria and magnesia.

5. A process according to claim 4, wherein said support comprises alumina.

6. A process according to claim 4 or claim 5, wherein said catalyst comprises from 5 - 50 % Ni and from 0.01 - 1 % of Ru, the balance being made up of said catalyst support and optionally a promoter and/or a binder.

7. A process according to claim 6, wherein said catalyst comprises from 10 - 40 % Ni and from 0.05 - 0.25% Ru.

8. A process according to any one of the preceding claims, wherein said feed stream contains one or more acidic compounds.

9. A process according to claim 8, wherein said feed stream contains up to 1 wt% of a carboxylic acid based on the total weight of the feed stream.

10. A catalyst comprising nickel and ruthenium in amounts to provide a mole ratio of ruthenium to nickel in the range from 0.15 x10³ to 0.06.