Patent GB-686022-A (GB)
Title: Purifying synthetic alcohols by distillation
IPC: C07C29/74
Filed: 1950-04-21
Abstract: An impure alcohol or mixture of isomeric alcohols, produced by hydrogenation of the corresponding carbonyl compounds, which alcohol or mixture contains high-boiling thermally-labile impurities, is purified by distillation in the presence of an inert thermally-stable liquid boiling from 20 DEG  to 200 DEG  F. above the alcohol or mixture, the temperature of the distilland being <PICT:0686022/IV (b)/1> maintained substantially below the decomposition temperature of the thermally-labile impurities.  The required alcohol is obtained as distillate, leaving the thermally-labile impurities together with a substantial proportion of the inert stable liquid as bottoms in the still.  The process is of particular application in the purification of iso-octyl alcohol obtained by " Oxo " synthesis.  The inert thermally-stable liquid, which preferably forms 10 to 50 per cent by volume of the total distilland, may be an added hydrocarbon fraction, or, in the purification of an " Oxo " alcohol, it may be an alcohol of higher molecular weight, formed in the synthesis by using a feed-mixture containing, in addition to the olefine required to give the desired alcohol, an olefine of higher molecular weight.  The purified alcohols obtained by the process, are suitable for the preparation of colourless plasticizers of the di-ester type (phthalates and adipates).  A mixture containing 80 per cent C7 olefine and 20 per cent C8 olefine is fed through line 1 into reactor 2 where it reacts with carbon monoxide and hydrogen to give aldehydes, which are then hydrogenated to give C8 and C9 alcohols. The alcohol mixture contains high-boiling ethers, esters and acetals as impurities, and it also contains unreacted olefines.  The impure alcohol mixture is passed through line 3 into the side of topping tower 4, from the head of which the unreacted olefines are recovered. The alcohol mixture withdrawn from the base of tower 4 is passed through line 11 into the side of column 12.  The bottoms temperature in column 12 is not allowed to exceed 260 DEG  C.  A C8 alcohol fraction is taken-off overhead from column 12, and condensed.  Part of the condensate is returned to column 12 as reflux, and the remainder is withdrawn through line 16 as product (B.R. 175-193 DEG C.).  The bottoms from column 12 are passed through line 21 to column 22, the base of which is maintained at 260 DEG  C. or higher.  The C9 alcohol is obtained as overhead product (B.R. 193-210 DEG  C) from column 22, while the ethers, esters and acetals are withdrawn as bottoms.  In another example, isooctyl alcohol, obtained by " Oxo " synthesis, is topped and then purified from high-boiling impurities by distillation in the presence of an added hydrocarbon cut boiling from 205 DEG  to 260 DEG  C.ALSO:<PICT:0686022/III/1> An impure alcohol or mixture of isomeric alcohols, produced by hydrogenation of the corresponding carbonyl compound, which alcohol or mixture contains high-boiling thermally-labile impurities, is purified by distillation in the presence of an inert thermally-stable liquid boiling from 20 DEG F to 100 DEG F above the alcohol or mixture, the temperature of the distilland being maintained substantially below the decomposition temperature of the thermally-labile impurities. The required alcohol is obtained as distillate, leaving the thermally-labile impurities together with a substantial proportion of the inert thermally-stable liquid as bottoms in the still.  The process is of particular application in the purification of iso-octyl alcohol obtained by "Oxo" synthesis.  The inert thermally-stable liquid, which preferably forms 10 to 50 per cent by volume of the total distilland, may be an added hydrocarbon fraction, or, in the purification of an "Oxo" alcohol, it may be an alcohol of higher molecular weight, formed in the synthesis by using a feed-mixture containing, in addition to the olefine required to give the desired alcohol, an olefine of higher molecular weight. A mixture containing 80 per cent C7 olefine and 20 per cent C8 olefine is fed through line 1 into reactor 2 where it reacts with carbon monoxide and hydrogen to give aldehydes, which are then hydrogenated to give C8 and C9 alcohols.  The alcohol mixture contains high-boiling ethers, esters and acetals as impurities, and it also contains unreacted olefines. The impure alcohol mixture is passed through line 3 into the side of topping tower 4, from the head of which the unreacted olefines are recovered.  The alcohol mixture withdrawn from the base of tower 4 is passed through line 11 into the side of column 12.  The bottoms temperature in column 12 is not allowed to exceed 260 DEG C.  A C8 alcohol fraction is taken-off overhead from column 12, and condensed. Part of the condensate is returned to column 12 as reflux and the remainder is withdrawn through line 16 as product (B.R. 175 DEG -193 DEG C).  The bottoms from column 12 are passed through line 21 to column 22, the base of which is maintained at 260 DEG C or higher. The C9 alcohol is obtained as overhead product (B.R. 193 DEG -210 DEG C) from column 22, while the ethers, esters and acetals are withdrawn as bottoms.  In another example, iso-octyl alcohol obtained by "Oxo" synthesis, is topped and then purified from high-boiling impurities by distillation in the presence of an hydrocarbon cut boiling from 205 DEG C to 260 DEG C.