Separation of glycerine and other lower polyhydric alcohols from the hydrogenolysis products of saccharides

摘要

992,165. Separation of glycerine from the products of the hydrogenolysis of saccharides. ATLAS CHEMICAL INDUSTRIES Inc. July 19, 1963 [July 25, 1962], No. 28633/63. Heading BIB. Glycerine is separated from the products of the hydrogenolysis of saccharides by a threestage distillation process wherein the components of the hydrogenolysis product which boil at a lower temperature than glycerine are distilled over in a "Splitter" column, the bottoms fraction from the "Splitter" is fractionated in a "Tetritol Column" to obtain a heads fraction which contains substantially all the glycerine, and this fraction is then re-fractionated a "First Glycerine Column" and a "Second Glycerine Column" in order to obtain pure glycerine. The flow diagram relates to the treatment of a nickel-catalysed hydrogenolysis product of invert sugar which contains glycerine together with water, ethylene glycol, propylene glycol, 1,2- and 2,3-butanediol, 1,2,3- and 1,2,4-butanetriol, tetritols, and hexitols. The product is diluted with water, filtered, and then passed through an anion and a cation exchange medium to remove ionizable impurities. The product is next freed from water in a "Water Column", operated at a base-temperature of 230 ‹C. and a pressure slightly above atmospheric. The dehydrated product passes to the "Splitter". The top of this column and of the following columns are maintained at an absolute pressure of 100 mm. Hg. and a basetemperature of 230 ‹C., and sufficient open steam is fed into the bottom section of each column to effect distillation. The overhead fraction from the "Tetritol Column" is heated at 145 ‹C. with 0À1% of sulphuric acid for 4 hours at an absolute pressure of 10 mm. Hg., in order to convert polyols having boiling points near glycerine into compounds which can be more readily separated from glycerine. The acidified material is diluted with water to obtain a glycerine concentration of about 90%, and the diluted fraction is neutralized by passing it through an anion exchange medium. The heads fraction from the splitter may be fractionated at atmospheric pressure in order to separate a fraction containing propylene glycol and the butanediols from a fraction containing ethylene glycol. Specification 354,196 is referred to.