Patent GB-449520-A (GB)
Title: Improvements in or relating to the manufacture of hydroxy acids and lactones
IPC: C07C59/01
Filed: 1934-09-24
Abstract: Hydroxy acids and/or lactones are produced from non-aromatic dicarboxylic acids or esters or mixtures thereof having at least 4 carbon atoms by treatment with hydrogen at an elevated temperature under superatmospheric pressure in the presence of a hydrogenation catalyst, the reaction being stopped when a substantial proportion of the carboxyl groups remains unreduced. The process may be carried out using either the batch method or the continuous method, the former being preferable when reducing a solid or viscous liquid or when using small quantities.  Suitable catalysts are in general those found suitable for the synthesis of methanol from water gas, e.g. reduced metals such as silver, copper, tin, cadmium, lead, iron, cobalt and nickel.  Fused copper oxide is also used, preferably promoted by substances such as the oxides of manganese, zinc, magnesium, or chromium.  When metallic catalysts in the form of powder are used they are supported on a material such as silica, activated carbon, alumina or kieselguhr. When esters are to be hydrogenated the oxides of zinc, manganese, magnesium &c., singly or in admixture are most suitable.  Other materials useful as promoters for the oxides of zinc and manganese are the oxides of chromium, vanadium, tungsten, titanium and molybdenum, of which chromium is preferred, as it tends to inhibit side reactions.  Particularly good results have been obtained by the use of multiple chromite catalysts, i.e. catalysts prepared by precipitation of a mixture of chromates from solution by adding an alkali metal chromate to an aqueous solution of a mixture of hydrogenating metal salts followed by ignition in presence of hydrogen.  The invention is applicable to all multiple basic carboxylic acids and their esters, including citric acid, and aliphatic dibasic acids having more than one carbon atom per carboxyl group such as succinic, glutaric, adipic, suberic, sebacic together with acids having an even larger number of carbon atoms and their esters.  Hydroaromatic acids and esters such as diethylhexahydrophthalate, monobutyl camphorate may also be used. The reaction is controlled by adjusting the time factor, the temperature, and the nature of the catalyst.  The preferred temperatures are 200--400 DEG  C. and the preferred pressures 1500--5000 lbs. per sq. inch.  In examples: (1) a hydrogenation catalyst was prepared by the addition of an ammoniacal solution of ammonium bichromate to a mixed solution of the nitrates of cadmium, copper and zinc, and the precipitate so produced washed, dried, ignited at 400 DEG  C. in a stream of hydrogen, and compressed into tablets.  Adipic acid was passed over the catalyst at 3000 lbs. pressure at 380 DEG  C. for two hours in a stream of hydrogen.  A good yield of the lactone of hydroxy caproic acid was obtained. (2) Ethyl sebacate was passed over a copper chromite catalyst in hydrogen in a shaking autoclave, to yield acetyl o -hydroxydecanoic acid.  (3) Diethyl hexahydrophthalate was treated as in example (2) to give a 40 per cent yield of hexahydrophthalide (lactone of hexahydro-o-hydroxymethylbenzoic acid).ALSO:A mixed chromite catalyst for hydrogenation is prepared by the addition of an ammoniacal solution of ammonium bichromate to a mixed solution of the nitrates of cadmium, copper, and zinc, and the precipitate so produced, washed, dried, ignited in a stream of hydrogen at 400 DEG  C., and compressed into tablets.