GB2269116A

GB2269116A - A process for the production of aromatic alcohol by selective hydrogenation of aromatic ketone

Info

Publication number: GB2269116A
Application number: GB9315459A
Authority: GB
Inventors: Francis Humblot; Jean-Pierre Candy; Catherine Santini; Blaise Didillon; Peltier Fabienne Le; Jean-Paul Boitiaux
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 1992-07-28
Filing date: 1993-07-27
Publication date: 1994-02-02
Anticipated expiration: 2013-07-27
Also published as: NL194965C; FR2694286A1; DE4324222A1; NL9301294A; GB2269116C; GB2269116B; GB9315459D0; DE4324222B4; NL194965B; FR2694286B1

Abstract

The invention relates to a process for the production of aromatic alcohol from aromatic ketone by selective hydrogenation in the presence of a catalyst comprising: a) at least one group VIII metal selected from the iridium, nickel, palladium, platinum, rhodium and ruthenium, b) and at least one additional metallic group IVa element selected from tin, germanium and lead. The invention is particularly suited to the production of methyl phenyl carbinol from acetophenone.

Description

22691116 A PROCESS FOR THE PRODUCTION OF AROMATIC ALCOHOL BY SELECTIVE

HYDROGENATION OF AROMATIC KETONE The present invention is concerned with the preparation of aromatic alcohols by selective hydrogenation of corresponding ketones and more particularly, but not exclusively, methyl phenyl carbinol by the reduction of acetophenone. It requires the use of a catalyst based on a group VIII metal and another metal belonging to the tin family (germanium, tin, lead).

Acetophenone is a compound containing not only a ketone function but also an aromatic cycle. Its formula is as follows:

CH3-CO-C5H5. Hydrogenation of the ketone function results in a secondary alcohol, methyl phenyl carbinol of the formula CH3-CHOH-C6H5.

Methyl phenyl carbinol is a raw material in basic chemistry. However, it can only be used if it is produced by way of an inexpensive process which enables it to be obtained in a very pure state.

Catalytic hydrogenation of the acetophenone can result not only in methyl phenyl carbinol, but also in reduction products from the aromatic cycle (methyl cyclohexyl ketone and methyl cyclohexyl carbinol), and in products from hydrogenolysis, dehydroxylation, decarbonylation, dimerisation reactions and the like.

The reduction of acetophenone has already been dealt with in several publications.

Metallic coordination complexes (comprising one group VIII metal and at least one phosphine or an optically active arsine as the ligand) are most frequently recommended (US Patent 3 883 580) for carrying out asymmetric reductions, but these catalysts are usually expensive and difficult to separate from the reaction medium which makes it hard to use them for the type of applications envisaged.

Catalysts are also known of the general formulae AB, (with A = Ca, Th, Y, rare earth and B = Ni, Co, Cu) which can be recovered reversibly and freed from hydrogen, but they only enable yields of methyl phenyl carbinol to be obtained of close to 87%.

The use of group VIII metals has been little studied. In this group, copper is certainly the most studied metal. It can be used in the presence of zinc oxide (US 3927120) or chromium (US 3927121). The catalysts used enable high selectivities to be obtained, but the number of acetophenone molecules transformed per metallic atom is still low.

We have now found that it is possible to carry out selective hydrogenation of aromatic ketone (containing the C6H5-CO- group) into the corresponding aromatic alcohol to obtain a reduced quantity of cyclohexyl ketone and cyclohexyl carbinol and without other secondary products. The operation may be carried out in a continuous or discontinuous reagent in the presence of hydrogen preferably at a total pressure of between 1 and 10 MPa and even more preferably between 2 and 8 MPa and preferably at a temperature of between 0 and 1000C and even more preferably between 20 and 700C in the presence of a metal catalyst containing (a) at least one group VIII metal selected from iridium, osmium, nickel, palladium, platinum, rhodium (rhodium being the preferred metal) and whose percentage by weight is selected between 1.1 and 5% and preferably between 0.5 and 1.5% in the case of supported metals and from 80 to 99% in the case of Raney nickel, (b) at least one additional metal selected from the group IVa constituted by tin, germanium and lead, whose percentage by weight is selected between 0.01% and 15% and usually from 0. 01% to 5% when a support is used and usually between 0.5% and 15% with Raney Ni. The molar ratio between the group VIII element and the group IV element (when the elements are supported) is preferably between 0.3 and 3 and even more preferably between 0.8 and 2.5. The support, when used, can be selected from refractory oxides, in particular from the group constituted by silica, 3 alumina, silica aluminas and carbon-based supports, and, in particular, carbon and graphite.

Various preferred features and embodiments of the present invention will now be described by way of non-limiting example.

The catalyst can be prepared using various procedures for impregnating the support. The impregnation operation consists, for example, in contacting the support with an aqueous or organic solution of a compound of the metal, or metals, selected. It is possible to introduce the group VIII metal(s) and the additional metal(s) simultaneously or successively. After having left the support and the solution in contact for several hours, the impregnated support is filtered, washed in water or with a hydrocarbon, dried and calcined in air preferably between 1100C and 6000C and even more preferably between 1000C and 5000C.

The additional element selected from the group formed by tin can be introduced in an aqueous or organic solution as a function of the precursor used.

The catalyst is preferably obtained by impregnating the support using an aqueous or organic solution of at least one group VIII metal compound. The impregnated support is then filtered, dried, and possibly washed in water or with an organic solvent and calcined in air, usually between 1100C and 6000C and preferably between 1100C and 5000C and then reduced in hydrogen at a temperature of usually between 2000C and 600OG, and preferably between about 3000C and 500OC; the product obtained is then impregnated with an aqueous or organic solution of a germanium, tin and/or lead compound. Advantageously, a solution is used of at least one germanium alkyl or aryl, tin alkyl or aryl, lead alkyl or aryl in accordance with the technique described in the Applicant's US Patent 4. 548.918.

4 - Organic solvents which can be used within the scope of the invention can be cited, by way of example, as hydrocarbons, halogenated hydrocarbons, ketones, ethers and aromatic derivatives. When the compound of tin, germanium or lead is liquid or gaseous under the impregnation conditions, the solvent is not indispensable.

After maintaining the impregnated support in contact with the group VIII metal(s) and the solution containing at least one group IVa compound (taken from germanium, tin and lead) for a specified period of time between 0.2 and 10 hours at a temperature which is usually between 200C and 1500C, the product is possibly washed with a solvent used to impregnate the group IVa compound, possibly dried and possibly calcined in air at a temperature of between 900C and 6000C and reduced between 50 and 6000C or possibly used directly after impregnation of the group IVa compound(s).

Another method consists of mixing the damp support powder with the catalyst precursors and then shaping and drying.

Examples of metallic precursors which can be used in the preparation of the catalyst are as follows: in the case of group VIII metals it is possible to use compounds such as chlorides, nitrates, haloamino compounds, amino compounds, organic acid salts.

It is also possible to use organometallic compounds of a group VIII metal in solution in an organic solvent, such as a hydrocarbon. As examples of hydrocarbons reference can be made to saturated paraffinic hydrocarbons whose chain contains 6 to 12 carbon atoms per molecule, or aromatic hydrocarbons containing an equivalent number of carbons. As examples of organometallic compounds of group VIII metals reference can be made to carbonyl, halocarbonyl compounds and acetyl acetonates, but this list is not limitative.

The element selected from tin, germanium and lead can be introduced in the form of polyketone or hydrocarbyl complexes such as alkyls, aryls, alkylaryls. The group IVa metal(s) is/are advantageously introduced using a solution in an organic solvent of the organometallic complex of said metal. As the organometallic complex of the group IVa metal reference can be made, in particular, to tetrabutyl tin, tetramethyl tin, tetraethyl tin, tetrapropyl tin, tetraethyl germanium, tetramethyl germanium, tetraethyl lead, diphenyl tin, tributyl tin hydride, tributyl tin chloride, but this list is not exhaustive.

The impregnation solvent is selected from the hydrocarbons paraffin, naphthene, aromatic hydrocarbons containing 6 to 12 carbon atoms per molecule and halogenated organic compounds containing 1 to 12 carbon atoms per molecule. n-heptane, methyl cyclohexane, toluene, chloroform can be cited. It is also possible to use well defined mixtures of the above solvents or other solvents.

The element selected from tin, germanium or lead can also be introduced by the intermediary compounds such as tin chlorides, bromides, nitrates, acetates; germanium oxides, oxalates, chlorides; lead halides, nitrates, acetate in aqueous or organic solution.

The support can be of various types. as already mentioned hereinabove. One support which is particularly suitable has specific properties such as a specific area as determined using the BET method of between 10 and 500 M2 per gram and a total porous volume of 0.2 to 1.3 cm3 per gram of support.

Once the metals have been fixed on the support, the catalyst may be subjected to an activation treatment in hydrogen at between 50 and 6000C. This step is not always necessary, however.

The following, non-limitative examples illustrate the invention.

- 6 EXAMPLE 1 (comparative test) The catalyst is prepared by impregnating the chloropentamine rhodium chloride in ammoniacal solution on a silica, the specific surface area of which is equal to 200 m2 per gram and the total porous volume of which is equal to 0.8 cm 1 per gram, followed by filtration, washing in distilled water, calcination in air at 4500C and reduction in hydrogen at 4500C. The end catalyst contains 1.13% rhodium and will be called catalyst A. Protected from air, catalyst A, under a flow of argon, is fed into the Grignard-type reactor containing an organic solvent (nheptane). The reactor is then closed, and purged of the argon which it contains. A solution of acetophenone is then injected, under hydrogen, which has a concentration of 0.3 mol/1 acetophenone, that is to say a proportion of about 220 moles of acetophenone per gram atom of rhodium. The hydrogen pressure is then increased to 8 MPa and the temperature is increased to 660C. The evolution of the composition of the reaction medium is followed by gas chromatography.

The results obtained are given in Table 1.

Table 1

Time Molecules of Methyl phenyl (hours) acetophenone Carbinol Selectivity transformed per gram atom rhodium 0 0 0.25 131 42 0.5 200 26 0.75 226 14 It can be seen that if the activity of catalyst A is high (the number of acetophenone moles transformed is high), the methyl phenyl carbinol selectivities are low. The other reaction products which it has been 7 possible to identify are methyl cYclohexyl ketone and methyl cyclohexyl carbinol.

EXAMPLE 2 (according to the invention) Catalyst A (0.25 g), prepared in Example 1, is charged into a Grignardtype reactor containing an organic solvent, normal heptane, with the precautions mentioned in Example 1 being taken. Tetrabutyl tin (0.02 g) is then injected into the solvent. The reactor is then closed and purged with hydrogen. The hydrogen pressure is then increased to 4 MPa and the temperature is increased to 950C. These conditions are kept for 0. 3 hours accompanied by stirring (400 revs/min).

The end catalyst has an atomic ratio of tin to rhodium of 1 and will be called catalyst B (containing 1.13% by weight Rh and 1.3% by weight Sn). The pressure and temperature are then brought to 2 MPa and 300C respectively. A solution of acetophenone in n-heptane is then injected into the reagent in a proportion of about 220 moles acetophenone per gram atom rhodium. The same operating conditions are employed as in Example 1.

The results obtained are given in Table 2.

8 Table 2

Time Molecules of Methyl phenyl (hours) acetophenone carbinol selectivity transformed per gram atom rhodium 0 0 1 145 92 1.75 182 95 2 208 97 3 220 91 Despite the fact that catalyst B is less active than catalyst A, it is possible to obtain yields of methyl phenyl carbinol of 92w10 for comparable activities. Moreover, for up to 95% of the conversion, the methyl phenyl carbinol is produced with selectivities of 970,,,,,.

EXAMPLE 3

Catalyst A (0.25 g), prepared in Example 1, is fed into a Grignard-type reactor containing an organic solvent (normal heptane), with the precautions mentioned in Example 1 being taken. Tetrabutyl tin (0.003 g) is then injected into the solvent. The reactor is then closed and purged purged with hydrogen. The hydrogen pressure is then increased to 4 MPa and the temperature is increased to 950C. These conditions are kept for 14 hours accompanied by stirring (400 revs/min).

The end catalyst has an atomic ratio of tin to rhodium of 0.3 and will be called catalyst C (containing 1.13% by weight Rh and 0.4% by weight Sn).

The pressure and temperature are then brought to 2 MPa and 300C respectively. A solution of acetophenone in n-heptane is then injected 9 into the reagent in a proportion of about 220 moles acetophenone per gram atom rhodium. The operating conditions are the same as in Example 1.

The results obtained are given in Table 3.

Table 3

Time Molecules of Methyl phenyl (hours) acetophenone carbinol selectivity transformed per gram atom rhodium 0 0 1 72 84 2 109 88 3 160 75 Catalyst C is much less active than catalyst B since catalyst C only permits the conversion of 72 moles acetophenone per gram atom rhodium and per hour, whereas catalyst B permits the conversion of 145 moles of acetophenone per gram atom rhodium for the same reaction time.

Example 4 ml of a suspension of Raney nickel in n-heptane containing 70 mg nickel is charged into a Grignard-type reactor. The reactor is then purged with hydrogen.

The pressure and temperature are then brought to 2 MPa and to 300C respectively. A solution of acetophenone in n-heptane is then injected into the reagent in a proportion of about 220 moles of acetophenone per gram atom of nickel. The operating conditions are the same as in Example 1.

- The results obtained are given in Table 4.

Table 4

Time Molecules of Methyl Phenyl (hours) acetophenone carbinol Selectivity transformed per atom gramme nickel 0 0 0 1 123 33 2 160 30 3 165 17 4 168 is Catalyst D has a significant initial activity, but it quickly becomes poisoned with time. The methyl phenyl carbinol selectivities observed are low.

EXAMPLE 5 ml of a Raney nickel suspension in n-heptane containing 70 mg nickel is charged into a Grignard-type reactor. 0.05 g tetrabutyl tin is then injected into the solvent. The reactor is then closed, and purged with hydrogen. The hydrogen pressure is then increased to 4 MPa accompanied by stirring (400 revs/min). The end catalyst has an atomic ratio of tin to nickel of 0.08 and will be called catalyst E (containing 85% nickel and 13% tin) (example 4). The results obtained are shown in Table 5.

Table 5

Time Molecules Methyl phenyl (hours) acetophenone carbinol selectivity transformed per gram atom nickel 0 0 0 1 92 95 2 136 98 3 163 97 4 195 94 The initial activity of catalyst E is less than that of catalyst D, but its activity is more stable with time. The methyl phenyl carbinol selectivities observed are in the order of those obtained with catalyst B. 1

Claims

1. - A process for the production of aromatic alcohol by selective hydrogenation of mono-aromatic ketone in the presence of a catalyst comprising:

(a) at least one group VIII metal selected from iridium, nickel, palladium, platinum, rhodium, ruthenium; (b) and at least one additional group Wa metallic element selected from tin, germanium and lead.

and wherein, supposing that the catalyst is supported, the content by weight of (a) is between 0. 1 and 5% and the content by weight of (b) is between 0.01 and 5% and supposing that (a) is Raney nickel, the content by weight of (b) is between 0. 5 and 15%.

2 - A process according to Claim 1, wherein the support is selected from the refractory oxides, charcoal and graphite.

3 - A process according to Claim 2, wherein the refractory oxide is selected from silica, alumina and silica-aluminas.

4 - A process according to one of the preceding claims, wherein the catalyst contains 0.

5 to 1.5% by weight of a group VIII metal.

- A process according to one of the preceding claims, wherein the molar ratio between the group VIII metal(s) and the additional element(s) is between 0.3 and 3.

13 -

6 - A process according to one of the preceding claims, wherein the molar ratio between the group VIII metal(s) and the additional element(s) is between 0.8 and 2.5.

7 - A process according to one of the preceding claims, wherein the catalyst contains 80 to 99% by weight Raney nickel.

8 - A process for the production of methyl phenyl carbinol from acetophenone according to one of the preceding claims, wherein the pressure is between 1 and 10 MPa and the temperature is between 0 and 1000C.

9 - A process for the production of methyl phenyl carbinol from acetophenone according to one of the preceding claims, wherein the pressure is between 2 and 8 MPa and the temperature is between 20 and 700C.

10. - A methyl phenyl carbinol prepared by the process of any one of claims 1-9.

11. - A process according to claim 1 substantially/,, hereinbefore described with reference to the Examples.

12. - A methyl phenyl carbinol according to claim 10 substantially as hereinbefore described with reference to the Examples.