Manufacture of primary alcohols

摘要

Primary alcohols are made by passing an epoxide of formula in which R1 and R2 are alkyl, aryl or alicyclic radicals, in the vapour phase at elevated temperatures over an isomerization catalyst until substantially complete conversion to the corresponding aldehyde has taken place and subsequently conducting the mixture from the isomerization step with hydrogen over a hydrogenation catalyst at elevated temperatures. Substantially complete conversion is defined as such as results in the vapours leaving the isomerization reactor having no more than 5 per cent of the initial amount of epoxide. Isomerization is preferably effected with inert gases, hydrogen being preferred since it may be used in the subsequent hydrogenation. Many epoxides are specified representative being isobutene oxide and alpha-methylstyrene oxide and the oxides of propylene dimer 2,3,4-trimethyl pentene-1 and cyclohexyl-methyl-ethylene. The reaction mixture obtained by treating alpha-di-isobutene in the liquid phase with molecular oxygen in the presence of oxidation catalysts, cf. Specification 682,067, may also be used. Alumina, expecially when activated, is the preferred isomerization catalyst and silica gel and phosphoric acid on carriers are also mentioned. Isomerization temperatures mentioned are 200-350 DEG C. and preferably the diluent gas is present in amounts to maintain the temperature at about 350 DEG C. Copper catalysts are preferred in the hydrogenation and temperatures specified are 180-350 DEG C. Hydrogen, which may be used in excess, e.g. 5-10 fold, may be recycled. In examples: (1) 1,2-epoxy-2,4,4-trimethyl pentane is passed with nitrogen over activated alumina and the pentanol obtained hydrogenated over copper on kieselguhr to the pentanol; (2) air oxidized di-isobutene is passed with hydrogen over activated alumina and the products over copper on kieselguhr to yield 2,4,4-trimethyl pentanol which is separated from methyl p neo-pentyl carbinol and ketone which are also obtained and (3) is similar to (2) save that extra hydrogen is provided for the hydrogenation.