GB514342A - Improvements in the manufacture of polyhydric alcohols - Google Patents

Abstract

514,342. Polyhydric alcohols. TAYLOR, A. W. C., WOOLCOCK, J. W., HELLICAR, A. G., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. May 3, 1938, Nos. 13215 and 15378. Drawings to Specification. [Class 2 (iii)] In the production of polyhydric alcohols by hydrogenation of mixtures of hydroxyaldehydes and hydroxy-ketones obtained by the condensation of formaldehyde in the presence of a catalyst and of methanol as diluent, the remaining formaldehyde and preferably also the methanol are removed previous to the hydrogenation, the formaldehyde being removed by conversion into methylal which is then distilled off, or by distillation in the presence of methyl and/or ethyl alcohol. This purification reduced the consumption of catalyst in the hydrogenation. The hydroxy-aldehyde and hydroxyketone mixture may be treated to remove water, and then treated with methanol in excess and 5-10 per cent. sulphuric acid for the production of methylal which is then distilled off after neutralizing the acid. The remaining mixture is treated with centinormal sulphuric acid to hydrolyze acetals and, after removal of the acid as calcium sulphate, is suitable for hydrogenation. Alternatively, the initial mixture may be supplied at the top of a stripping column and a stream of methyl or ethyl alcohol as vapour or liquid is supplied at the bottom, whereby the formaldehyde is removed together with water and alcohol. The hydrogenation may be effected with activated nickel, which may be on a carrier, at 40-50 atmospheres and 120-150‹C. Specification 309,200, [Class 2 (iii)], and 513,708 are referred to.