| 摘要 |
1,142,543. Extractive distillation. HEINRICH KOPPERS, G.m.b.H. 24 April, 1967 [13 Oct., 1966], No. 18700/67. Heading C5E. Aromatic hydrocarbons are separated from non-aromatic hydrocarbons by an extractive distillation process characterized by the following features :- (a) the extraction agent, e.g. propylene carbonate, contains as additives compounds similar to, but not the same as, those being extracted (e.g. if only benzene is to be extracted, then the additive may be xylene or Cg aromatics); (b) at least two extractivedistillation columns, shown as 14 and 19 in the Figure, are installed one behind the other in series, the downstream column 19 being operated at a lower pressure than the upstream column 14; and (c) the extract is treated in a number of column systems in series, each system corresponding to a desired product (e.g. column systems 23 and 29 for production of benzene and toluene respectively), each system consisting of an extractive stripper section (e.g. 23a), an extractive rectifying section (23b), a distillative rectifying section (23c) and a distillative stripping section (23d), the two extractive sections and the two distillative sections each constituting a pair of sections between which vapour and liquid interchange may take place, and the head of the extractive rectifying section (23b) being connected to the head of the distillate stripper section (23d), the bottom product of the preceding column system being fed between the a and b sections and the extraction agent being fed to the b section, while at the same time a pure aromatic extraction product is removed overhead from the c section, while a non-aromatic fraction is obtained as bottoms product in the d section. Sections a, b, c and d may be arranged differently from as shown in Fig. 3, e.g. a and b in one column and c and d in another. In a modification, the b section may be omitted if the next higher boiling product is not required in quantitative yield, e.g. as shown in column system 36, and it is also possible for the d section to be omitted in any system in which the heads product is not required in a pure state. The additive to the extraction agent may be already present therein, or may be added thereto, and part of the additive may be added directly to columns 14 and 19 at 41 and 42 above the feed-point of the extraction agent. In the Figure, benzene, toluene and xylene are recovered at 24, 31 and 37 respectively, and non-aromatics at 16, 21, 27, 34 and 39 all of which are combined in manifold 17. |
