GB795650A - Method of distilling vinyltoluene - Google Patents

Abstract

Vinyltoluene is separated from the reaction products of the thermal dehydrogenation of ethylbenzene by submitting the reaction products to fractional distillation in the presence of a small proportion (e.g. 0.01 to 0.1 per cent) of 2-nitrophenol or 2-nitrothiophene or a mixture thereof to inhibit the formation of polymeric material. The purified vinyltoluene is obtained as distillate, while divinylbenzene and the inhibitor are retained in the distillation residues. In an example, a vinyltoluene feedstock containing 0.5 per cent of divinylbenzene, to which 0.2 per cent of dinitrocresol had been added, was fed through inlet 2 into the reboiler 1 of a column 4, which was 26 feet long and was filled with ceramic saddles. The upper part of the column was connected to condenser 6, receiver 8, distillate-withdrawal pipe 11, and reflux <PICT:0795650/III/1> return pipes 9, 14. The fractionation was carried out at an absolute pressure of 85 to 95 mm., employing a reflux ratio of 3 : 1, while feeding 2-nitrophenol dissolved in a small amount of the reflux from vessel 12 into the column at a point 8 feet below the top in an amount corresponding to 0.04 per cent by weight of the feedstock supplied to the reboiler. The distillation was carried out continuously over a period of 31 days without any apparent formation of polymer in the apparatus.