GB672365A - A distillation process for the treatment of organic mixtures containing alcohols and organic acids - Google Patents

Abstract

The aqueous and oily fractions from a Fischer Tropsch synthesis are distilled together-through a fractionating column; the head of the column is maintained between 80 DEG and 98 DEG C. and the fractionation is controlled so as to take overhead at least 90 mol. per cent of the alcohols in the feed together with the light hydrocarbons, while at least 90 mol. per cent of the acids in the feed and the remaining hydrocarbons are withdrawn in the bottoms. The presence of the water in the feed prevents loss of alcohols and acids due to esterification. A charging stock consisting of Synthol oil and water solutions in the ratio 25 : 32 was fractionated batchwise using a 4-foot column packed with glass helices. The fractionation was carried out at a reflux ratio of 3 : 1 until the head-temperature reached 95 DEG C. The distillate separated into an oily phase and an aqueous phase. Of the alcohols present in the charging stock, 62.3 mol per cent were present in the aqueous phase of the distillate and 30 mol. per cent in the oil phase. The distillation bottoms also separated into an oily phase and an aqueous phase; the aqueous phase contained 69.5 mol. per cent and the oil phase 27.8 mol. per cent of the acid content of the charging stock. The acids present in the aqueous phase may be recovered by dehydration and fractional distillation, or by solvent extraction and subsequent distillation from the selective solvent. The oil phase contains all the higher (above C4) acids. In a modification, the distillation is first continued until the head-temperature of the column reaches only 80 DEG C.; and then a second cut is made until the temperature reaches 90-98 DEG C. The overhead aqueous phase from this second cut is used to extract the overhead oil phase from the first cut. The aqueous extract is then mixed with the overhead aqueous phase from the first cut to give a mixture rich in alcohols. The distillation may be carried out continuously (see Group III).ALSO:<PICT:0672365/III/1> The aqueous and oily fractions from a Fischer-Tropsch synthesis are distilled together through a fractionating column; the head of the column is maintained between 80 DEG C. and 98 DEG C. and the fractionation is controlled so as to take overhead at least 90 mol per cent of the alcohols in the feed together with the light hydrocarbons, while at least 90 mol per cent of the acids in the feed and the remaining hydrocarbons are withdrawn in the bottoms. The presence of the water in the feed prevents loss of alcohols and acids due to esterification. A charging stock consisting of Synthol oil and water solutions in the ratio 25:32 was fractionated in a 4-foot vacuum-jacketed column (diam. 1 in.) packed with glass helices. The fractionation was carried out batchwise at a reflux ratio of 3:1 until the head-temperature reached 95 DEG C. The distillate separated into an oily phase and an aqueous phase. Of the alcohols present in the charging stock, 62.3 mol per cent were present in the aqueous phase of the distillate and 30 mol per cent in the oil phase. The distillation bottoms also separated into an oily phase and an aqueous phase, the aqueous phase contained 69.5 mol per cent and the oil phase 27.8 mol per cent of the acid content of the charging stock. The acids present in the aqueous phase may be recovered by dehydration and fractional distillation, or by solvent extraction and subsequent distillation from the selective solvent. The oil phase contains all the higher (above C4) acids. In a modification, the distillation is first continued until the head-temperature of the column reaches only 80 DEG C, and then a second cut is made until the temperature reaches 90-98 DEG C. The overhead aqueous phase from this second cut is used to extract the overhead oil phase from the first cut. The aqueous extract is then mixed with the overhead aqueous phase from the first cut to give a mixture rich in alcohols. The distillation may be carried out continuously in the apparatus shown. The synthetic oil and aqueous fractions withdrawn from tanks 6 and 8 respectively are introduced together through line 2 into the mid-portion of column 4 which is heated by reboiler 28. Live steam may be introduced into the column through line 10. The overhead vapours are condensed in condenser 14, and that portion of the condensate not returned as reflux to the column, is passed to separator 20. The bottoms withdrawn from the column through line 26 are passed to separator 30.