GB2599981A

GB2599981A - Catalyst for biaryl production

Info

Publication number: GB2599981A
Application number: GB2106814.3A
Authority: GB
Inventors: Marco Bellabarba Ronan; Cano-Lerida Laura; Michael Small Stuart
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 2020-05-14
Filing date: 2021-05-13
Publication date: 2022-04-20
Anticipated expiration: 2041-05-13
Also published as: WO2021229227A1; GB202106814D0; CN115279491B; GB2599981B; CN115279491A

Abstract

A method of producing a biaryl compound from an aromatic/heteroaromatic substrate using a coupling catalyst; wherein the catalyst comprises Ni on an alumina support; wherein the content of Ni is 10-30 wt% based on the total weight of catalyst; and wherein the catalyst comprises a promoter metal selected from (i) a Group 1 metal in an amount of 0.5-5.5 wt% based on the total weight of catalyst; or (ii) a Group 2 metal in an amount of 0.5-10 wt% based on the total weight of catalyst. In another aspect, the per se catalyst used in the method, wherein the catalyst is in the form of an extrudate and is free from a metal salt or metal oxide cocatalyst. In yet another aspect, a method of manufacturing said catalyst, comprising the steps of: (i) providing a solution comprising a nickel salt and a solution comprising a promoter metal salt; (ii) carrying out incipient wetness impregnation of an extruded alumina support with the solution(s) from step (i); (iii) drying the product of step (ii); (iv) calcining the product of step (iii); and (v) reducing the product of step (iv). The catalysts are particularly suitable for the conversion of pyridine to 2,2’-bipyridine.

Description

Catalyst for biaryl production

Field of the Invention

The present invention relates to catalysts for carrying out the coupling of an aromatic or heteroaromatic substrate to form a corresponding biaryl compound, especially the coupling of pyridine to form 2,2'-bipyridine.

Background

Diquat (the organic di-cation 1,1'-ethylene-2,2'-bipyridylium) is a non-selective herbicide with a global market of approximately 100 million USD per annum. Diquat is commonly used as the dichloride or dibromide salt, which are manufactured industrially by the reaction between 2,2'-bipyridine (2,2'-bipy, or "bipy") and 1,2-dibromoethane or 1,2-dichloroethane.

2,2'-bipy itself is manufactured by the catalytic coupling of pyridine.

It is known to produce biaryl compounds through coupling of the corresponding aromatic or heteroaromatic compound using Ni catalysts such as Raney Nickel. However, Raney Nickel is known to suffer from handling issues, and when applied to the production of bipy, is known to rapidly lose activity as the reaction proceeds. Efforts have been made to provide Raney Nickel catalysts which have longer activity, such as CN105130883A (Anhui Costar Bio Chemical Co Ltd) which describes a method of producing 2,2'-bipy using a catalyst of Raney nickel in conjunction with a metal salt, such as sodium ethoxide, sodium amide and aluminium isopropoxide. It is also known from GB1202711 (ICI Ltd) to regenerate Raney Nickel catalysts by washing used catalyst with an alcoholic solution of an alkali metal hydroxide. However, the handling issues associated with Raney Nickel still remain.

It is also known to produce biaryl compounds using supported Ni catalysts, which generally do not suffer from the same handling issues as Raney Nickel. For instance, US Patent No. 5221747 (Reilly Industries, Inc) describes a process involving reacting a pyridine base with a supported Ni catalyst at a temperature of 175-240 °C and at a pressure sufficient to maintain at least some of the base in a liquid state during the reaction. US Patent No. 5416217 (Reilly Industries, Inc) describes a process involving reacting a pyridine base with a supported Ni catalyst in the presence of a borohydride salt and ammonium hydroxide.

EP0539505B1 (Zeneca Ltd) also describes a process involving reacting pyridine or 2-or 4-methyl pyridine in the presence of a supported nickel catalyst in the presence of a borohydride salt and ammonium hydroxide.

More recently, CN107935919A (Nanjing Red Sun Biochemistry Co Ltd) describes coupling catalysts comprising Ni and at least one other metal on a composite support of A1203-5i02MgO. Exemplified catalysts comprise Ni and two or all of Ce, Mn and La on a support of A1203-Si02-MgO. Tuning of the Si02 and MgO components is required to control the acidity of the support which can otherwise lead to by-product formation if the acidity of the support is too high. Furthermore, the catalyst uses relatively expensive metals Ce, Mn and La.

There is a need for alternative catalysts which are selective for the coupling of pyridine to bipy, which have good activity and long lifetimes, ideally being straightforward to manufacture. The present invention addresses these issues.

Summary of Invention

The present inventors have surprisingly established that a Group 1 or Group 2 metal promoted catalyst of Ni on a support of alumina shows good activity in the conversion of pyridine to bipy, maintains its activity for a longer period, and is more selective for the production of the desired bipy product. The use of alumina rather than a composite support (as for instance in CN107935919A) simplifies the manufacturing process. Furthermore, the instant catalysts only require the presence of the relatively inexpensive Ni and Group 1 or Group 2 metal(s).

In a first aspect the invention provides a method of producing a biaryl compound from a heteroaromatic substrate using a catalyst comprising Ni on an alumina support; wherein the content of Ni is 10-30 wt% based on the total weight of catalyst; and wherein the catalyst comprises a promoter metal selected from (i) a Group 1 metal in an 25 amount of 0.5-5.5 wt% based on the total weight of catalyst; or (ii) a Group 2 metal in an amount of 0.5-10 wt% based on the total weight of catalyst.

In a second aspect the invention provides a catalyst comprising Ni on an alumina support; wherein the content of Ni is 10-30 wt% based on the total weight of catalyst; wherein the catalyst comprises a promoter metal selected from (i) a Group 1 metal in an amount of 0.5-5.5 wt% based on the total weight of catalyst; or (ii) a Group 2 metal in an amount of 0.5-10 wt% based on the total weight of catalyst; and wherein the catalyst is in the form of an extrudate and is free from a metal salt or metal oxide cocatalyst.

The present inventors discovered, in hindsight after making the present invention, that Group 1 and Group 2 promoted Ni on alumina catalysts were known but for an entirely different application. EP 0 566 197 Al (Engelhard de Meern B.V.) describes a process for preparing primary amines by hydrogenation of a mono and/or dinitrile with hydrogen in the presence of a nickel and/or cobalt catalyst on a support. Exemplified catalysts have either 5 or 20 wt% nickel on an alumina or silica-alumina support, and include between 3-10 wt% Group 1 and/or Group 2 metals.

The catalysts exemplified in EP 0 566 197 Al differ from those according to the second aspect of the invention because they are prepared by pre-, co-or post-impregnation of the Ni and Group 1 or Group 2 metal salts onto a powdered support material and are therefore not extruded catalysts. The only suggestion within EP 0 566 197 Al to use shaped catalyst bodies is in the context of combining the supported catalyst with a cocatalyst into combined particles. The cocatalyst is generally a metal salt or metal oxide. However, the catalysts according to the second aspect of the present invention do not include a metal salt or metal oxide as cocatalyst.

The invention also relates to the use of a catalyst as defined in the first aspect or according to the second aspect, as a coupling catalyst in the coupling of an aromatic or heteroaromatic 25 substrate to produce a biaryl compound.

In a third aspect the invention provides a method of manufacturing a catalyst according to the second aspect, comprising the steps of: (i) providing a solution comprising a nickel salt and a solution comprising a promoter metal salt; (ii) carrying out incipient wetness impregnation of an extruded alumina support with the solution(s) from step (i); (iii) drying the product of step (H); (iv) calcining the product of step (iii); and (v) reducing the product of step (iv)

Description of the Drawincis

Figure 1 is a plot of bipy productivity as a function of K content of the catalyst.

Figure 2 is a plot of (2-picoline + piperidine) bipy selectivity as a function of K content of the catalyst.

Figure 3a is a plot of K content of the catalyst against product selectivity for the main 4 products of the reaction.

Figure 3b is an expanded view of Figure 3a focussing on the product selectivity of the main 3 by-products of the reaction.

Figure 4 is a plot of pyridine conversion as a function of time online for various catalysts 15 with different promoter metals.

Figure 5 is a plot of (2-picoline + piperidine) : bipy selectivity for various catalysts with different promoter metals.

Detailed Description Terminology

The term "catalyst" is used herein to refer to a material in which the support, as defined herein, has been impregnated with Ni and one or more promoter metals. As used herein a "promoter metal" is a Group 1 or Group 2 metal. Unless context permits otherwise, the term "catalyst" can refer to the material formed following incipient wetness impregnation, the material formed following calcination of that material ("calcined material" or "oxidic material"), and the material formed following reduction of the calcined material ("reduced material"). The reduced material may also be passivated before use ("passivated material").

The term "promoter metal" as used herein means a Group 1 or Group 2 metal. The term "promoted" as used herein means that the presence of the promoter metal improves one or more of: the lifetime of the catalyst, the activity of the catalyst for bipy formation, or the selectivity of the catalyst for bipy formation, as compared to an equivalent catalyst in which the promoter metal(s) are absent.

The term "biaryl" refers to a molecule having a unit in which two aryl or heteroaryl groups are joined together by a single carbon to carbon bond.

The term "aryl group" is used to refer to a unit comprising an aromatic ring in which all of the ring atoms are carbon. The ring may be substituted or unsubstituted. An aromatic substrate is a starting material which comprises an aryl group.

The term "heteroaryl group" is used to refer to a unit comprising an aromatic ring in which at least one of the ring atoms is a heteroatom. The ring may be substituted or unsubstituted. 15 A heteroaromatic substrate is a starting material which comprises a heteroaryl group.

Any sub-headings are included for convenience only, and are not to be construed as limiting the disclosure in any way.

Catalysts used in the aryl coupling reaction The first aspect of the invention is a method of producing a biaryl compound from a 20 heteroaromatic substrate using a nickel catalyst on an alumina support which is promoted with a Group 1 or Group 2 metal The catalysts described in the present specification have a Ni content of 10-30 wt% based on the total weight of the catalyst. The content of Ni is preferably 12-28 wt%, such as 15-25 wt%. A Ni content of 25 wt% ± 2 wt% is especially preferred. Typically, the Ni in the catalyst will be present as a mixture of metallic Ni and nickel oxide. The Ni content referred to herein is the total amount of Ni based on the amount of the catalyst, whether in the metallic state (Ni(0)) or in another state, such as Ni(II) e.g. in the form of nickel oxide). The Ni content of the catalyst can be measured by inductively coupled plasma analysis (ICP analysis) as is well known in the art.

In preferred embodiments the catalyst has a Ni surface area of 100-150 m2/ g Ni, preferably 5 of 110-140 m2/ g Ni, preferably of 120-140 m2 / g Ni. In preferred embodiments the catalyst has a Ni surface area of 15-40 rri2 / g catalyst, preferably of 20-40 rri2 / g catalyst, preferably of 20-35 m2/ g catalyst. Ni surface is measured by H2 chemisorption, by reducing the oxidic catalyst in flowing hydrogen at a temperature of 430°C for 1 h followed by a 6 h evacuation, then Ni surface area analysis at 50°C using a Micromeritics Chemisorb HTP unit, ASAP 10 2480.

The catalysts described in the present specification comprise a promoter metal selected from a Group 1 metal or a Group 2 metal. The present inventors have surprisingly established that the inclusion of a Group 1 or Group 2 metal increases the lifetime of catalyst, improves catalyst activity and improves the selectivity of the catalyst towards the 1 5 biaryl product.

A Group 1 metal is a metal selected from the group consisting of Li, Na, K, Rb and Cs. Where a Group 1 metal is used as the promoter metal then the catalyst includes a Group 1 metal in an amount of 0.5-5.5 wt% based on the total weight of catalyst. The Group 1 metal content is preferably 1.0-5.5 wt%, more preferably 1-5 wt%, more preferably 1.5-3.5 wt%.

Where a mixture of Group 1 metals are used, these ranges refer to the combined amounts of Group 1 metals.

The Group 1 metal is preferably one or more of Li, Na or K, more preferably Na or K, most preferably K. Where a mixture of Group 1 metals are used, it is preferred that at least one of Li, Na or K is present, more preferably at least one of Na or K is present, most preferably K is present. It is preferred that a single Group 1 metal is used, most preferably the only Group 1 metal present is K. The Group 1 metal content can be measured by inductively coupled plasma analysis (ICP analysis) as is well known in the art.

It is particularly preferred that the promoter metal is K. When the promoter metal is K, a particularly preferred content of K is 1-4 wt%, preferably 1.5-3.5 wt%, preferably 2-3 wt%. These values of K content provide a catalyst which has a good balance of productivity and selectivity, particularly when used for the conversion of pyridine to bipy.

A Group 2 metal is a metal selected from the group consisting of Be, Mg, Ca, Sr, Ba and Ra. Where a Group 2 metal is used as the promoter metal then the catalyst includes a Group 2 metal in an amount of 0.5-10 wt% based on the total weight of catalyst.

Where the catalyst includes a mixture of Group 2 metals as promoter metals then the total content of Group 2 metals is 0.5-10 wt%, preferably 0.5-8 wt%, more preferably 0.5-5 wt%. 10 It is preferred that a single Group 2 metal is used Where a Group 2 metal is used as the promoter metal then the catalyst preferably comprises one or more of Mg, Ca and Sr, more preferably Mg or Ca. Where a mixture of Group 2 metals are used, it is preferred that at least one of Mg or Ca is present. It is preferred that a single Group 2 metal is used. The Group 2 metal content can be measured by inductively coupled plasma analysis (ICP analysis) as is well known in the art.

It is also within the scope of the present invention that the catalysts include a mixture of Group 1 and Group 2 as promoter metals, in which case the total content of promoter metals is 0.5-10 wt%. However is it preferred that a single type of promoter metal is used (Group 1 or Group 2 metals), more preferably only a single promoter metal is used.

The catalysts described in the present specification comprise an alumina support. In all embodiments it is preferred that the alumina support is substantially free of other materials, e.g. metal oxides other than alumina. Preferably the support is at least 90 wt% alumina, preferably at least 95 wt% alumina, such as at least 98 wt% alumina.

Alumina exists in a variety of different forms (phases) which are well known in the literature, any of which may be used as the support in the present invention. The support may comprise alumina in a single phase, or may comprise a mixture of different phases. Where the support comprises different alumina phases the support may comprise separate crystallites of each alumina phase, or may comprise crystallites having two or more phases within each crystallite. In a preferred embodiment the alumina comprises one or more of y, 5-or 8-alumina. In an embodiment the alumina comprises y-alumina. In an embodiment the alumina comprises a mixture of 5-alumina and 0-alumina.

In a preferred embodiment the catalyst consists essentially of, or consists of, the Ni 5 component (which is typically a mixture of metallic Ni(0) and nickel oxide), the promoter metal component and the support. Herein, "consists essentially of" means that the catalyst includes less than 2 wt% of components other than the Ni-component, promoter metal component and the support, preferably less than 1 wt% of other components, preferably less than 0.5 wt% of other components, preferably less than 0.1 wt% of other components. 10 Preferably the catalyst consists of the Ni, the promoter metal component and the support.

In a preferred embodiment the catalyst comprises 15-25 wt% Ni based on the total weight of catalyst, 1-5 wt% K based on the total weight of catalyst and the support is at least 95 wt% alumina. In this embodiment the support is preferably a mixture of 6-alumina and 9-alumina. It is further preferred in this embodiment that the catalyst consists essentially of, or consists of, the Ni, K and alumina support.

In a preferred embodiment the catalyst comprises 15-25 wt% Ni based on the total weight of catalyst and 1.5-3.5 wt% K based on the total weight of catalyst and the support is at least 95 wt% alumina. In this embodiment the support is preferably a mixture of 6-alumina and 9-alumina. It is further preferred in this embodiment that the catalyst consists essentially of, or consists of, the Ni, K and alumina support.

In preferred embodiments the catalyst is in the form of granules, pellets or extrudates, preferably pellets or extrudates. It is preferred that the catalyst is in the form of an extrudate, 25 because extrudates offer higher geometric surface area than pellets or granules. It is especially preferred that the catalyst is in the form of a trilobe extrudate.

Features described above in relation to the catalysts used in the biaryl coupling reaction (first aspect) also apply to the catalysts of the second aspect of the invention.

The catalysts according to the second aspect of the invention are in the form of extrudates. The catalysts of the second aspect are also free from a metal salt or metal oxide cocatalyst; that is, the extrudates do not include separate particles of a metal salt or metal oxide cocatalyst.

Catalyst manufacture Catalysts according to the invention can be prepared by incipient wetness impregnation. This procedure will be known to those skilled in the art and as is described for instance in W02011/080515. In this technique a support material is combined with an aqueous solution of metal salt(s), using a volume of aqueous solution which is sufficient to fill the pores of the support. The impregnated support is then dried. This process leads to the metal salt(s) becoming supported on the support material. The steps of impregnation and drying may be repeated several times.

In a step (i) a solution comprising a nickel salt and a promoter metal salt is provided.

The nickel salt and the promoter metal salt may be present as separate solutions or may be present in a single solution. Preferably, the nickel and promoter metal salts are present together in the same solution.

In a step (ii) an extruded alumina support is impregnated with a solution of metal salt(s).

Incipient wetness impregnation is preferably carried out by impregnation using a single solution comprising both a nickel salt and a promoter metal salt (co-impregnation).. In general, the amount of solution is chosen to be approximately equal to the pore volume of the support material. Co-impregnation is particularly suitable in the case where the promoter metal is a Group 1 metal, especially where an aqueous ammoniacal solution comprising nickel carbonate and potassium carbonate is used for co-impregnation, since these salts readily dissolve in aqueous ammoniacal solution.

In an alternative embodiment the support material may be impregnated sequentially with separate solutions of a nickel salt and a promoter metal salt, in any order. This embodiment is particularly suitable where aqueous ammoniacal solutions comprising both a nickel salt and a promoter metal salt are difficult to form, e.g. because of poor solubility of the promoter metal salt is aqueous ammoniacal solution. The impregnation may be a post-impregnation (impregnation of the Ni salt before the promoter metal salt) or a pre-impregnation (impregnation of the Ni salt after the promoter metal salt), preferably a post-impregnation. Post-impregnation is particularly appropriate where the promoter metal is a Group 2 metal. A drying step will typically be performed between each impregnation.

The solution of metal salt (or metal salts) used during the impregnation step is typically aqueous and preferably has a pH above 7, preferably from 8-12 such as from 9-12. The 1.0 desired pH can be achieved by the addition of a metal-free base to the impregnation solution, such as ammonium hydroxide.

A wide variety of Ni salts can be used. The counterion (anion) is preferably one which can be converted to oxide in a subsequent calcination step. Preferred Ni salts are carbonate, nitrate, acetate and halide (e.g. chloride). A preferred Ni salt is nickel carbonate.

The concentration of Ni in the impregnation solution is not especially limited. However, it will be appreciated that if using a dilute solution of Ni the impregnation step may have to be repeated more times compared with using a more concentrated solution of Ni. A suitable Ni concentration is 5-20 wt%, this value being the wt% of Ni in the solution rather than the wt% of Ni salt. A particularly preferred concentration of Ni is 5-15 wt%.

The promoter metal salt is water soluble. The counterion (anion) is preferably one which can be converted to oxide in a subsequent calcination step. Preferred promoter salts are carbonates, nitrates, acetate, hydroxide and halide (e.g. chloride). It is preferred that the promoter metal salt is a carbonate, preferably Na2CO3 or K2CO3, especially K2CO3.

The concentration of promoter metal salt in the solution is not especially limited. However, 25 it will be appreciated that if using a dilute solution of promoter metal the impregnation steps may have to be repeated more times to achieve the desired content of metals in the catalyst compared with using a more concentrated solution of promoter metal. For K, a suitable concentration is 0.5-5 wt%, this value being the wt% of K rather than the wt% of K salt. A particularly preferred concentration for K is 1-3 wt%.

It will be understood that the number of impregnation steps depends both on the concentration of metals in the aqueous solution and on the desired metal content in the catalyst. The process includes at least 1 impregnation step. Preferably the process includes 2, 3, 4 or 5 impregnation steps. Most preferably the process includes 2 or 3 impregnation steps.

In a step (iii) the product of incipient wetness impregnation is dried. Preferably the catalyst will be allowed to dry after each successive impregnation step. Drying is typically performed at an elevated temperature for several hours, preferably at a temperature of 50-150 °C for 1-6 hours, such as 100-150 °C for 2-4 hours. Those skilled in the art will be readily able to determine suitable conditions.

In a preferred embodiment steps (ii) and (iii) are repeated at least once, preferably twice.

Once the desired number of impregnation steps have been carried out, the material is calcined (step (iv)). This typically involves heating the catalyst to a temperature of 200-600 °C for a period of 2-6 hours in an atmosphere containing oxygen, preferably at a temperature of 300-500 °C for a period of 2-6 hours. In a preferred embodiment calcination is performed in air.

Following calcination the catalyst is reduced (step (v)). The purpose of this step is to convert at least a portion of the nickel oxide formed in the drying and calcination steps back into active nickel metal. Typically, the reduction step is carried out by treating the calcined material under an atmosphere of H2 at an elevated temperature. The atmosphere may be 100% H2 or a mixture of H2 with an inert diluent. A suitable range of temperatures is 200- 2 5 700 °C, preferably 35050000 for a period of 1-5 hours, preferably 1-3 hours.

In an optional further step the catalyst produced following reduction may be passivated. Typically this involves gradually exposing the catalyst to an atmosphere containing oxygen so as to partially oxidize the active nickel. Passivation is well known in the art.

Braryl formation A typical method for producing biaryls involves treating a substrate having an aryl or heteroaryl group with the catalyst at an elevated temperature. It is preferred that the substrate includes a 6-membered aromatic or heteroaromatic ring, which may be substituted or unsubsfituted, and which may be part of a fused system (e.g. naphthalene, quinoline, etc.).

In a preferred embodiment the substrate is a heteroaromatic substrate, preferably comprising a 6-membered heteroaromatic ring in which one of the ring atoms is a heteroatom. Preferably the heteroatom is N. In a preferred embodiment the substrate is a substituted or unsubstituted pyridine. In an embodiment the substrate is pyridine and the biaryl product is 2,2'-bipyridine.

The coupling reaction will typically give rise to a mixture of biaryl products, predominantly mono-and di-substituted products. For example, catalysts of the invention when applied to pyridine may give a mixture of 2,2'-bipyridine and 2,2',6',2"-terpyridine, predominantly 2,2'-bipyridine.

The invention includes the following embodiments: 1. A method of producing a biaryl compound from an aromatic or heteroaromatic substrate using a coupling catalyst, wherein the catalyst comprises Ni on an alumina support; wherein the content of Ni is 10-30 wt% based on the total weight of catalyst; and wherein the catalyst comprises a promoter metal selected from (i) a Group 1 metal in an amount of 0.5-5.5 wt% based on the total weight of catalyst; or (ii) a Group 2 metal in an amount of 0.5-10 wt% based on the total weight of catalyst.

2. A method according to embodiment 1, wherein the promoter metal is a Group 1 metal selected from Li, Na and K. A method according to embodiment 2, wherein the promoter metal is K. 4. A method according to embodiment 2 or embodiment 3, wherein the content of promoter metal(s) is 1-5 wt% based on the total weight of catalyst.

5. A method according to any of embodiments 2 to 4, wherein the content of promoter metal(s) is 1.5-3.5 wt% based on the total weight of catalyst.

6. A method according to embodiment 1, wherein the promoter metal is Group 2 metal selected from Mg and Ca.

7. A method according to embodiment 6, wherein the content of promoter metal is 1-wt% based on the total weight of catalyst.

8. A method according to any of embodiments 1 to 7, wherein the content of Ni is 15- 1 5 25 wt% based on the total weight of catalyst.

9. A method according to any of embodiments 1 to 8, wherein the support is at least wt% alumina.

10. A method according to any of embodiments 1 to 9, wherein the support comprises one or more of y-alumina, 6-alumina and 0-alumina.

11. A method according to any of embodiments 1 to 10, wherein the support comprises 6-alumina and 8-alumina.

12. A method according to any of embodiments 1 to 11, wherein the catalyst is in the form of a trilobe extrudate.

13. A method according to any of embodiments 1 to 12, wherein the catalyst has a Ni surface area of 110-140 m2 / g Ni as measured by H2 chemisorpfion.

14. A method according to any of embodiments 1 to 13, wherein the catalyst has a Ni surface area of 20-40 m2/ g catalyst as measured by H2 chemisorption.

15. A method according to any of embodiments 1 to 14, wherein the catalyst is in the 5 form of granules, pellets or extrudates.

16. A method according to any of embodiments 1 to 15, wherein the catalyst satisfies the following: the content of Ni is 15-25 wt% based on the total weight of catalyst; the promoter metal is K and is present in an amount of 1.5-3.5 wt% based on the total weight of catalyst; and the support is at least 95 wt% alumina.

17. A method according to any of embodiments 1 to 16, wherein the substrate is a 15 substituted or unsubstituted pyridine.

18. A method according to any of embodiments 1 to 17, wherein the substrate is pyridine and the biaryl product is 2,2'-bipyridine.

19. A catalyst comprising Ni on an alumina support; wherein the content of Ni is 10-30 wt% based on the total weight of catalyst; wherein the catalyst comprises a promoter metal selected from (i) a Group 1 metal in an amount of 0.5-5.5 wt% based on the total weight of catalyst; or (ii) a Group 2 metal in an amount of 0.5-10 wt% based on the total weight of catalyst; and wherein the catalyst is in the form of an extrudate and is free from a metal salt or metal oxide cocatalyst.

20. A catalyst according to embodiment 19, wherein the promoter metal is a Group 1 metal selected from Li, Na and K. 30 21. A catalyst according to embodiment 20, wherein the promoter metal is K. 22. A catalyst according to embodiment 20 or embodiment 21, wherein the content of promoter metal(s) is 1-5 wt% based on the total weight of catalyst.

23. A catalyst according to any of embodiments 20 to 22, wherein the content of 5 promoter metal(s) is 1.5-3.5 wt% based on the total weight of catalyst.

24. A catalyst according to embodiment 19, wherein the promoter metal is Group 2 metal selected from Mg and Ca.

25. A catalyst according to embodiment 24, wherein the content of promoter metal is 1-5 wt% based on the total weight of catalyst.

26. A catalyst according to any of embodiments 19 to 25, wherein the content of Ni is 15-25 wt% based on the total weight of catalyst.

27. A catalyst according to any of embodiments 19 to 26, wherein the support is at least 95 wt% alumina.

28. A catalyst according to any of embodiments 19 to 27, wherein the support 20 comprises one or more of y-alumina, 6-alumina and 0-alumina.

29. A catalyst according to any of embodiments 19 to 28, wherein the support comprises 6-alumina and 0-alumina.

30. A catalyst according to any of embodiments 19 to 29, wherein the catalyst is in the form of a trilobe extrudate.

31. A catalyst according to any of embodiments 19 to 30, wherein the catalyst has a Ni surface area of 110-140 m2/ g Ni as measured by H2 chemisorption.

32. A catalyst according to any of embodiments 19 to 31, wherein the catalyst has a Ni surface area of 20-40 m2/ g catalyst as measured by H2 chemisorption.

33. A catalyst according to embodiment 19, wherein the catalyst satisfies the following: the content of Ni is 15-25 wt% based on the total weight of catalyst; the promoter metal is K and is present in an amount of 1.5-3.5 wt% based on the total weight of catalyst; and the support is at least 95 wt% alumina.

34. A catalyst according to embodiment 33, wherein the catalyst is in the form of a trilobe extrudate.

35. A method of manufacturing a catalyst according to any of embodiments 19 to 34, comprising the steps of: CO providing a solution comprising a nickel salt and a solution comprising a promoter metal salt; (ii) carrying out incipient wetness impregnation of an extruded alumina support with the solution(s) from step (i); (iii) drying the product of step (H); (iv) calcining the product of step (iii); and (v) reducing the product of step (iv).

36. A method according to embodiment 35, wherein the nickel salt and the promoter metal salt are present in a single solution in step (i).

37. A method according to embodiment 35, wherein the nickel salt and the promoter metal salt are present as separate solutions in step (i).

38. A method according to embodiment 37, wherein step 00 involves sequential treatment of the support with the solution of promoter metal salt and solution of nickel salt, in any order.

Examples

The invention will now be illustrated by the following non-limiting examples.

Procedures ICP analysis The sample was fused for one hour at 1050 °C with a Lithium tetraborate/lithium bromide flux in a platinum crucible using a Garbolite AAF 1100 furnace. After cooling the resulting bead was left overnight at 90 °C in 10% nitric acid (using a ST 15 power IKAMAG heated stirrer) until fully dissolved. The resulting liquid was analysed on an ICAP 7600 ICPOES.

H2 chemisorption Ni surface area was measured via H2 chemisorption using a Micromerifics Chemisorb HTP unit, ASAP 2480. The samples were reduced in flowing hydrogen at the temperature specified (430°C or 230 °C if they were pre-reduced and passivated) for 1 h followed by a 6 h evacuation, prior to nickel surface area analysis at 50°C. Uncertainty on metal area is +/-1%. The limit of detection was 0.10 m2/g.

1 5 Catalyst preparation Aqueous ammonium hydroxide was placed in a glass beaker with a magnetic stirrer. Ammonium carbonate and nickel carbonate were added gradually and alternating each other (to avoid the solution becoming too hot) to this beaker with mild agitation. The amount of ammonium carbonate was sufficient to achieve a pH of approximately 11.0. The stirring was maintained overnight. The morning after the solution was homogeneous with no solids, and of the characteristic intense blue colour. Potassium carbonate was added to this solution.

The solution described above was added dropwise to an alumina support (1.2 mm trilobes containing a mixture of 6-and 8-alumina phases) in a Pascal mixer with gentle rotation. The 25 samples were dried at 120°C for 3 h in an oven between impregnations. Once dried, the samples were calcined at 350 °C for 4 h. The resulting materials were oxidic and had the properties in Table 1.

Examples 1R and 2R were prepared from a commercially available Ni on alumina catalyst (HTCT" Ni500 RP, 1.2 mm trilobes, batch 0600319 from Johnson Matthey).

Example 9R was prepared from a commercially available catalyst of Ni on a support of calcium aluminate / kaolin (KatalcoTM 11-4R, batch 121820 from Johnson Matthey).

Examples 10-13 were prepared by a post-impregnation procedure using HTCT" Ni 500 (oxidic form, 1.2 mm trilobes, batch 0502041 from Johnson Matthey). A solution of the appropriate promoter metal salt was prepared by dissolving the promoter metal in demineralised water. The HTCT" Ni 500 trilobes were impregnated with the solution of promoter metal salt by incipient wetness impregnation in a Pascal mixer with gentle rotation. The volume of solution used was approximately equal to the pore volume of the trilobes. The samples were dried at 105 °C for 3 hours then calcined at 430 °C (example 10) and 400°C (examples 11-13) for 4 hours.

Example 10 used lithium hydroxide monohydrate (Acros Organics). Example 11 used sodium nitrate (Acros Organics).

Example 12 used magnesium nitrate hexahydrate (Acros Organics). Example 13 used calcium nitrate tetrahydrate (Acros Organics).

Oxidic Ni content Promoter content Reduced Reducing Sample (wt% from (wt% from ICP) sample conditions ICP) (Promoter metal) Example 1* 21.00 0.00 Example 1R a (Comparative) (Comparative) Example 2* 21.00 0.00 Example 2R b (Comparative) (Comparative) Example 3 20.16 1.63 (K) Example 3R b Example 4 19.42 2.17 (K) Example 4R b Example 5 20.88 2.55 (K) Example 5R a Example 6 20.02 3.04 (K) Example 6R a Example 7 18.78 4.41 (K) Example 7R b Example 8 17.42 6.01 (K) Example 8R b (Comparative) (Comparative) Example 9 25.00 0.00 Example 9R b (Comparative) (Comparative) Example 10 19.8 0.94 (Li) Example 1OR b Example 11 19.11 1.63 (Na) Example 11R b Example 12 19.04 1.77 (Mg) Example 12R b Example 13 18.91 2.56 (Ca) Example 13R b

Table 1.

a 100% H2 with a ramp rate of 30 °C/h to 230 °C and held for 2 hours.

b 100% H2 with a ramp rate of 30 °C/h to 430 °C and held for 2 hours. Reduction 12 mL of catalyst was charged to a slurry autoclave reduction unit and reduced under a 1 Umin flow of H2 using the following temperature program: (i) ramp to 230 °C (condition a) or 430 °C (condition b) at a rate of 30 °C/hr; (ii) dwell for 2 h at 230 °C or 430 °C; (iii) cool to room temperature. The resulting catalysts had the properties shown in Table 2.

Ni surface area (m2 / g Ni) Ni surface area (m2 / g cat)

Example 1R 138 29.0

(Comparative)

Example 2R 138 29.0

(Comparative)

Example 3R 157 31.6

Example 4R - -

Example 5R 139 29.0

Example 6R 145 29.0

Example 7R - -

Example 8R 135 23.6

Example 9R 55.6 13.9

(Comparative)

Example 1OR - -

Example 11R 96.28 18.4 Example 12R 77.73 14.8 Example 13R 121.63 23.0

Table 2.

Pyridine Coupling Catalyst testing was carried out using a Falling Basket Rig (manufactured by Autoclave Engineers). Once cool, the reduced catalyst in a glass reduction vessel was transferred to a nitrogen glove box. The catalyst was charged in the basket of the Falling Basket Rig and submerged in a container of pyridine. The container was sealed, removed from the glovebox and transferred to the upper portion of the Falling Basket Rig.

The autoclave body of the rig was filled with 500 ml of pyridine, purged with nitrogen then pressure tested. Pressure testing was completed under nitrogen up to 10 barg. The autoclave was subsequently depressurized to 1 barg, then heated to 200 °C at a ramp rate of 180 °C/h. Once the autoclave reached 200 °C the nitrogen pressure was increased to 5 8.5 barg and a sample of the feedstock taken for analysis. The catalyst was then submerged into the charged pyridine by dropping the basket and the stirring rate was set to -750 rpm. Samples were taken periodically over 4 hours and analysed by gas chromatography for the concentration of pyridine, 2,2'-bipyridine, 2-picoline, piperidine, and 2,2':6',2'-terpyridine. Once complete the autoclave was emptied of product through the sample line and a portion 10 of this filtered and analysed by ICP for evidence of metal leaching. The rig was subsequently cooled to room temperature. The results are shown in Table 3.

Catalyst Productivity Average selectivity (gbipthigeat) piperidine 2-picoline 2,2'-bipy 2,2':6,6'- Others terbypyri di ne 1R 0.215 4.11 16.43 72.86 4.05 2.55 (Comparative) 2R 0.224 3.84 17.7 65.49 6.09 6.88 (Comparative) 3R 0.929 7.96 5.34 77.93 5.42 3.34 4R 1.150 8.91 3.13 77.92 6.44 3.60 5R 1.267 8.12 2.46 81.29 5.14 2.98 6R 1.012 9.07 2.16 84.97 1.20 2.78 7R 0.350 4.41 4.94 82.91 5.08 2.67 8R 0.038 5.73 9.28 81.11 3.71 0.17 (Comparative) 9R 0.015 1.43 22.20 72.05 4.32 0.00 (Comparative) 1OR 0.558 10.13 6.68 77.32 4.38 1.49 11R 0.436 6.86 6.43 78.78 4.73 3.20 12R 1.04 7.94 5.31 77.64 5.40 3.72 13R 0.64 9.03 6.22 78.56 3.81 2.39

Table 3

Catalysts 3R to 7R having K contents between 1.6 and 4.4 wt% showed much higher productivities for bipy formation than either of the comparative catalysts Ni HTCT" 500 (Comparatives 1R and 2R) or KatalcoTM 11-4R (Comparative 9R). At high loadings, K reduced the catalyst productivity. Catalysts 10R to 13R, promoted respectively with Li, Na, Mg and Ca, also had a higher productivity than either of the Comparative catalysts.

Figure 1 shows that at an approximately constant Ni content, promoting the catalyst with K caused a gradual increase in catalyst productivity for bipy formation, with the highest productivity achieved by catalyst 5R with a K content of 2.55 wt% On its oxidic form). As K content was increased further the productivity of the catalyst reduced.

Figure 2 shows the selectivity ratio (2-picoline + piperidine) : (bipy) for catalysts 3R-8R.

Promoting the catalyst with K up to a loading of approximately 2.5 wt% caused an increase in catalyst selectivity for bipy formation. As K content was increased further the selectivity of the catalyst for bipy formation increased only moderately.

Figures 4 and 5 show the pyridine conversion (Figure 4) and selectivity ratio (2-picoline + piperidine) : (bipy) (Figure 5) for catalysts 6R (K promoted), 1OR (Li promoted), 11R (Na promoted), 12R (Mg promoted) and 13R (Ca promoted). Each of these catalysts had a pyridine conversion above that of reference catalyst 2R and showed a greater selectivity for pyridine.

Claims

Claims 1. A method of producing a biaryl compound from an aromatic or heteroaromatic 5 substrate using a coupling catalyst; wherein the catalyst comprises Ni on an alumina support; wherein the content of Ni is 10-30 wt% based on the total weight of catalyst; and wherein the catalyst comprises a promoter metal selected from (i) a Group 1 metal in an amount of 0.5-5.5 wt% based on the total weight of catalyst; or (ii) a Group 2 metal in an 10 amount of 0.5-10 wt% based on the total weight of catalyst.
2. A method as claimed in claim 1, wherein the promoter metal is a Group 1 metal selected from Li, Na and K.
3. A method as claimed in claim 2, wherein the promoter metal is K.
4. A method as claimed in claim 2 or claim 3, wherein the content of promoter metal(s) is 1-5 wt.% based on the total weight of catalyst.
5. A method as claimed in any of claims 2 to 4, wherein the content of promoter metal(s) is 1.5-3.5 wt% based on the total weight of catalyst.
6. A method as claimed in claim 1, wherein the promoter metal is Group 2 metal selected from Mg and Ca.
7. A method as claimed in claim 6, wherein the content of promoter metal is 1-5 wt% based on the total weight of catalyst.
8. A method as claimed in any of claims 1 to 7, wherein the content of Ni is 15-25 wt% based on the total weight of catalyst.
9. A method as claimed in any of claims 1 to 8, wherein the support is at least 95 wt% alumina.
10. A method as claimed in any of claims 1 to 9, wherein the support comprises one or more of y-alumina, 6-alumina and 0-alumina.
11. A method as claimed in any of claims 1 to 10, wherein the support comprises 6-alumina and 0-alumina.
12. A method as claimed in any of claims 1 to 11, wherein the catalyst is in the form of a trilobe extrudate.
13. A method as claimed in any of claims 1 to 12, wherein the catalyst has a Ni surface area of 110-140 m2 / g Ni as measured by H2 chemisorpfion.
14. A method as claimed in any of claims 1 to 13, wherein the catalyst has a Ni surface 15 area of 20-40 m2/ g catalyst as measured by H2 chemisorption.
15. A method as claimed in any of claims 1 to 14, wherein the catalyst is in the form of granules, pellets or extrudates.
16. A method as claimed in any of claims 1 to 15, wherein the catalyst satisfies the following: the content of Ni is 15-25 wt% based on the total weight of catalyst; the promoter metal is K and is present in an amount of 1.5-3.5 wt% based on the total weight of catalyst; and the support is at least 95 wt% alumina.
17. A method as claimed in of claims 1 to 16, wherein the substrate is a substituted or
18. A method as claimed in any of claims 1 to 17, wherein the substrate is pyridine and the biaryl product is 2,2'-bipyridine.
19. A catalyst as defined in any of claims 1 to 16, wherein the catalyst is in the form of an extrudate and is free from a metal salt or metal oxide cocatalyst.
20. A catalyst as claimed in claim 19, wherein the catalyst is in the form of a trilobe extrudate.
21. A method of manufacturing a catalyst as claimed in claim 19 or claim 20, comprising the steps of: (0 providing a solution comprising a nickel salt and a solution comprising a promoter metal salt; (ii) carrying out incipient wetness impregnation of an extruded alumina support with the solution(s) from step (i); (iii) drying the product of step (H); (iv) calcining the product of step (iii); and (v) reducing the product of step (iv).
22. A method as claimed in claim 21, wherein the nickel salt and the promoter metal salt are present in a single solution in step (i).
23. A method as claimed in claim 21, wherein the nickel salt and the promoter metal salt are present as separate solutions in step (i).
24. A method as claimed in claim 23, wherein step 00 involves sequential treatment of the support with the solution of promoter metal salt and solution of nickel salt, in any order.