GB1321465A - Process for the separation of a starting mixture by means of liquid-liquid extraction - Google Patents

Abstract

1321465 Separation of the components of a liquid mixture by solvent extraction and distillation SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ BV 24 Sept 1970 [26 Sept 1969] 45526/70 Heading BIB [Also in Division C5] Following a process wherein a liquid starting mixture is submitted to liquid-liquid extraction with a solvent which boils at a higher temperature than the mixture and in which some of the components of the starting mixture are more readily soluble than others, the less soluble of the dissolved components are removed from the extract phase by distilling it in the presence of a liquid mixture which boils within a lower temperature range than the starting mixture and which contains components which are more readily soluble in the solvent than others. The lower boiling mixture is preferably derived from an original mixture from which the starting mixture is also obtained, e.g. by distillation or extractive distillation. In an example, a mixture of benzene, toluene, xylene, paraffins and naphthenes, obtained by thermal treatment of gasoline, is separated by distillation in column 52 into a C 6 -C 9 fraction boiling in the range 115‹-165‹C, and a C 5 -C 8 fraction boiling in the range 65‹-135‹C. The higher boiling fraction, which contains 91% of aromatics, is passed through line I into column 2 where it is extracted with sulpholane supplied through line 3; and the raffinate, which contains 70.5 paraffins, is discharged through line 4. The extract phase is passed through line 5 into column 6 where it is distilled in the presence of the lower boiling fraction from column 52, additional sulpholane being supplied to column 6 through line 53. Column 6 is operated at a pressure of 1.2 atm. abs. and a top temperature of 113‹C: and the overhead fraction is condensed and passed into the lower section of extraction column 2. The bottoms fraction from column 6 is passed to column 10 where it is stripped with steam supplied through line 12. Sulpholane, withdrawn from the base of column 10, is recycled to column 2; and a sulpholane-rich stream, withdrawn through line 53, is passed to column 6. The overhead fraction obtained from the head of column 10 comprises only aromatic hydrocarbons, and is separated by subsequent distillation into a benzene-, a toluene- and a xylene-fraction.