GB467656A - Improvements in or relating to the manufacture of lactones - Google Patents

Abstract

Lactones are prepared by the catalytic hydrogenation of dicarboxylic acid anhydrides at elevated temperature and pressure in the presence of a hydrogenating metal or metal oxide catalyst activated by an acidic oxide of chromium, vanadium, molybdenum, tungsten, titanium or uranium. The dicarboxylic acid anhydrides may belong to the aliphatic, aromatic or heterocyclic series; thus R in the formula <FORM:0467656/IV/1> may represent phenyl or naphthyl, or (CH2)n where n = 2, 3 or 4, or cyclohexyl or cyclopentyl, and the anhydrides of phthalic, camphoric, hexahydrophthalic, 3- and 4-methyl-o-phthalic, 3 : 6-dimethylphthalic and 1 : 8-naphthalic acids are specified. The anhydride may be replaced by the acid in cases in which the anhydride is readily formed within the temperature range. The preferred ranges of temperature and pressure are 100--450 DEG C. and 500--5000 lb. per sq. in., and usually an excess of hydrogen is employed. As hydrogenating metals and metal oxides are mentioned zinc, iron, nickel, cobalt, copper, cadmium, silver, tin, manganese oxide and magnesia. Solvents are preferably present, e.g. hydrocarbons, ethers, esters, or phthalide itself; as hydrocarbons, benzene, toluene, xylene, cyclohexane, methylcyclohexane and dimethylcyclohexane are referred to. The process may be effected in batches or continuously, and may take place in the liquid or vapour phase. Examples are given of the preparation of phthalide and campholide from phthalic and camphoric anhydrides respectively using a copper chromite catalyst prepared by mixing copper nitrate solution with ammonium chromate solution, neutralizing with ammonium hydroxide, filtering off the precipitated copper ammonium chromate, igniting the dry material at 400 DEG C. and extracting the product with dilute acetic acid.