Improvements in or relating to separation of alcohols

摘要

C2 and higher alcohols are separated from mixtures with other organic materials having boiling points in the same temperature range by treating the mixture with trimethyl borate to esterify the alcohols, separating a more volatile methyl alcohol-trimethyl borate fraction from the less volatile residual mixture, separating the more volatile organic material from the less volatile borate esters in the residual mixture, treating the alcohol borate esters with methanol to convert the esters to alcohols, and separating the more volatile methanol-trimethyl borate fraction from the less volatile alcohols. The separation is particularly effective for alcohols in the C7 to C30 range especially for those prepared by the "Oxo" process. In the Figure a mixture of C16-C20 "Oxo" alcohols with hydrocarbon is fed through 1 at a temperature of about 70-90 DEG C. into distillation tower 2 into which vaporous trimethyl borate enters through 3. Methanol-trimethyl borate azeotrope passes through 4 to distillation tower 5 and the "Oxo" alcohol borate esters and the hydrocarbons are withdrawn through 6 to distillation tower 7. A reduced pressure distillation takes place in tower 7, the hydrocarbons being taken overhead through 8 and the "Oxo" alcohol borate ester being withdrawn through 9 to distillation tower 10. Methanol vapour enters the distillation tower 10 through 11 and contacts the "Oxo" alcohol borate ester. The methyl alcohol-trimethyl borate azeotrope is taken overhead to pressure distillation tower 5 which is operated at superatmospheric pressure. Under these conditions a fraction rich in methanol is taken overhead and may be recycled back to distillation tower 10. The methyl borate withdrawn from 5 is recycled to distillation tower 2. Separated "Oxo" alcohol product is withdrawn from the tower 10. Excess methyl borate is used in the esterification reaction and an excess of alcohol is preferably used in the final methanolysis tower. In the example a C12-C20 crude "Oxo" alcohol cut containing aliphatic hydrocarbons as impurities is treated with trimethyl borate and the alcohol borate esters are treated with methanol to give the free alcohols.