PROCESS FOR THE PRODUCTION OF HIGH PURITY META-XYLENE

摘要

1436584 Separating xylenes UOP Inc 6 Aug 1973 [7 Aug 1972] 37172/73 Heading C5E A process for the simultaneous production of high purity meta-xylene and high purity para-xylene from a fresh feed stream containing mixed C 8 aromatics which process comprises: (a) separating, in a selective adsorption zone, an isomerized stream containing mixed C 8 aromatics and produced by the isomerization referred to hereinafter to produce a high purity paraxylene stream and a para-xylene-deficient stream containing para-xylene in a proportion below para-xylene/meta-xylene eutectic proportions; (b) fractionating said para-xylenedeficient stream in a fractionating zone to produce a meta-xylene overhead fraction containing ortho-xylene in a proportion below ortho-xylene/meta-xylene eutectic proportions and a bottoms fraction comprising ortho-xylene; (c) separating the overhead fraction by crystallization in a crystallization zone to produce high purity meta-xylene and a recycle stream; (d) contacting in an isomerization zone said bottoms fraction and said recycle stream with an isomerization catalyst to effect isomerization and thereby to produce the feed stream as hereinbefore referred to containing the said mixed C 8 aromatics in proportions approaching a thermodynamic equilibrium composition; and, (e) introducing a fresh feed stream containing mixed C 8 aromatics into either or both of the selective adsorption zone and the isomerization zone. The selective adsorbent may be a zeolite X or Y containing one or more cations of the following metals: K, Ba, Ag, Cs, Pr, Nd and Sm. The process may be modified to obtain only a pure m-xylene stream.