BE675582A - - Google Patents

Description

       

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  "PROCEDL FOR" HYDROGENATIOI; OF BENZOIC ACID IN CYCLOHEXANE-CARBOX'SiLIRO'E ACID "
The invention relates to the hydrogenation of benzolic acid to cyclohexane-carboxylic acid.



   Heretofore, the hydrogenation of benzoic acid to cyclohexanecarboxylic acid has not been applied in practice. Glacial acetic acid, recommended for this purpose, is an unattractive dispensing agent.



   It has been found that the hydrogenation of benzoic acid, resp. of metal salts of benzoic acid, leads to the formation of cyclohexanecarboxylic acid, resp. of metal salts of cyclohexanecarboxylic acid, almost without the formation of side products, if benzoic acid and / or a metal salt of benzolic acid is contacted, in the presence of water and together with hydrogen with a catalyst, containing in metallic form at least one of the metals palladium, rhodium, ruthenium, platinum and iridium, nickel and / or cobalt also being able to be applied with regard to the metal salts of benzol acid.



   By carrying out the hydrogenation in this way, the amount of water can be varied very widely. Thus one can apply e.g. amounts of 5, 15, 20,30, 50 or 100% by weight of water relative to the amount of acid

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 benzoic or salt. There is already an increase in the rate of hydrogenation and an extension of the longevity of the catalyst if small amounts of a few percent of water are used.



   By applying larger amounts of water, eg an amount by weight of water which is double, triple, quintuple or tenfold in relation to the amount of benzoic acid or salt, we have the advantage of an easily transportable suspension, emulsion or solution of the material to be hydrogenated which can be contacted in a simple manner with the catalyst.



   The process according to the invention can be carried out at atmospheric pressure, but it is also possible to apply pressures lower or higher than this, eg 10, 25, 50 or 100 atm. or even more.



  The application of a high pressure requires that the hydrogenation plant be resistant to this pressure.



   The measures to be taken with regard to the adduction of the reaction components, the regulation of the temperature and the pressure, the evacuation of the reaction mixture, as well as those relating to the realization in @ntinu process, are those usual for the realization of hydrogenation process that we do not have to specify. During a continuous process the benzoic acid or the unconverted salt and the unused hydrogen can be recycled.



   The catalysts which are applied in metallic form can be provided on a support, e.g. e. thorium oxide, aluminum oxide, magnesium oxide, zirconium oxide, silicon dioxide, silica gel, kieselguhr yes carbon.



   As opposed to metal salts, the ammonium salt of benzoic acid cannot be hydrogenated in this way to the corresponding salt of cyclohexanecarboxylic acid.



  Example 1
In a cylindrical autoclave with a capacity of 0.5 l, fitted with a stirrer, 30 g of calcium benzoate and 2 g of catalyst (5% ruthenium

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 on charcoal) are suspended in 300 cc of water in a hydrogen atmosphere. Then the pressure is maintained at a temperature of 160 ° C. at 100 atm. by the introduction of hydrogen.



   After 1.5 hours the calcium benzoate was hydrogenated.



  Exempt?
In a cylindrical autoclave with a capacity of 50 l, fitted with a stirrer, 40 g of Ra.cey nickel are suspended in a nitrogen atmosphere in a solution of 8 kg of sodium benzoate. in 20 1 of water. Then hydrogenated at a pressure of 5 atm. and at a temperature of 200 C, using hydrogen. After 1 hour the hydrogenation is complete. The aqueous solution obtained from sodium cyclohexanecarboxylic acid is separated
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 of the catalyst by ceotrif ugatiosu After evaporation of the solution, 8.2 kg of sodium salt of cyclohexane-carboxylic acid are obtained, which corresponds to a yield of 98.4%.



  Example 3,
In a cylindrical autoclave with a capacity of 1 liter, equipped with a stirrer, a mixture is kept consisting of 122 g of benzoic acid, 300 g of water and 3 g of catalyst, (5% rhodium on charcoal) at a temperature of 130 C under a hydrogen pressure of 12 atm. After 1.5 hours the benzoic acid was hydrogenated to cyclohexanecarboxylic acid.



   The reaction mixture is carried out by absorbing the cyclohexane-carboxylic acid into hexane and by evaporating the solution obtained after filtration. 17 g of cyclohexanecarboxylic acid are thus recovered (yield 99.2%).



  Example
In a manner analogous to that described in Example 3, hydrogenation is carried out using a mixture consisting of 250 g of benzoic acid, 45 g of water and 4 g of catalyst (5% ruthenium on aluminum oxide).



  The temperature is held at 125 - 130 C.

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 After 40 hours, the hydrogenation is completed, which progresses slowly.



    @ It is observed that the reaction product contains 131 g of acid
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 Cyclohexane-carboxy11Que (yield 50%).


    

Claims (1)

CLAIMS 1. Process for the hydrogenation of benzoic acid resp. do metal salts of benzoic acid to cyclohexanecarboxylic acid, resp. in metal salts of cyclohexanecarboxylic acid, characterized in that the benzoic acid and / or a metal salt of benzoic acid is brought into contact, in the presence of water and together with hydrogen, with a catalyst, containing in mets Clique form at least one of the metals palladium, rhodium, ruthenium, platinum and iridium, nickel and / or cobalt also being applicable as regards the metal salts of benzoic acid. 2. Process for the hydrogenation of benzoic acid, as indicated in the description and explained by the examples. 3. Cyclohexanecarboxylic acid and / or metal salts of cyclohexanecarboxylic acid obtained according to the process of conclusion 1 or 2.