GB572897A - Improvements in or relating to the treatment by distillation of complex mixtures - Google Patents

Abstract

572,897. Azeotropic distillation. ALUMINIUM PLANT & VESSEL CO., Ltd., RALPH, S. J., and DUMMETT, G. A. March 19, 1943, No. 4484. [Class 32] An acetone-methanol mixture containing at least a trace of water is distilled in the presence of a paraffinoid-aromatic hydrocarbon mixture so that acetone and paraffinoid components are removed as top products and the methanol and aromatic hydrocarbons (and water) are removed in the effluent from the base of the column. The acetone may then be removed from the paraffinoid hydrocarbons, e.g., by washing with water or other preferential solute for acetone, decantation and then concentration in a rectification column;: the methanol may also be separated similarly, thus providing a method of separating the components of the original mixtures. The invention is carried out in a continuous type of distillation apparatus at normal, reduced or increased pressure using comparatively low reflex ratios. When separating acetone and methanol, e.g., in wood spirit, advantageously diluted with water, the hydrocarbons may be fed back to the column immediately after decantation. In the case when the products to be removed from the system are hydrocarbons it is possible to feed the aqueous acetone and methanol resulting from the water washing of the distillate back into the distillation column. A mixture of hydrocarbons obtained, e.g., from the carbonisation of Scottish coal in vertical retorts and distilling at about 112‹C, is fed into fractionating column 3 through pipe line 1 and a solution of acetone and methanol in water is fed in from balance tank 6. Vapours consisting essentially of non-aromatic hydrocarbons and acetone leave the top of the column, are condensed and split into two streams by reflux divider 10. One stream passes in at the base of counter-current scrubber-decanter 13 meeting a stream of dilute methanol, water solution fed from balance tank 14. The top layer of paraffinoid hydrocarbons overflows to 18 while the layer of acetone and methanol in water returns to balance tank 6 and thence back to column 3. At the same time a mixture of aromatic hydrocarbons, methanol and water is continuously removed from the base of column 3 to decanter 21 where the upper layer of aromatic hydrocarbons overflows to storage tank 23 while the lower layer of methanol and water is fed to tank 14. Unsaturated bodies and/or organic sulphur compounds such as those usually present in commercial fractions from coal carbonisation or petroleum products may also be present in the original feed. The majority of the unsaturated bodies will be found in the distillate whereas the sulphur compounds will normally, be found in the bottom product. Examples give details of the separation of hydrocarbon mixtures containing various proportions of non-aromatic and aromatic constituents.