Patent ID: 6323382
Filing Date: 2001-11-27
Classification: B01J,C07C,Y02P

Abstract:
A process for isomerizing a C.sub.8 alkyl aromatic hydrocarbon-containing feedstock comprising the steps of:(a) providing a catalyst including platinum;(b) activating the catalyst by:(1) oxidizing the platinum of said catalyst in a reactor by circulating a stream of nitrogen containing about 1 percent by volume of oxygen across said catalyst while increasing the temperatures from ambient up to about 480.degree. C.;(2) maintaining the circulating stream of nitrogen containing about 1 weight percent oxygen at a temperture of about 480.degree. C. until the platinum of said catalyst is completely oxidized;(3) stopping the circulating stream and depressurizing the reactor;(4) purging the reactor with pure hydrogen at atmospheric pressure;(5) circulating pure hydrogen through the reactor over a range of conditions, slowly increasing temperature and pressure to a limit of less than about 340.degree. C. at ambient pressure; and(6) stabilizing the catalyst by injecting ammonia into the reactor;(c) contacting the feedstock in at least one isomerization zone with the catalyst and being effective to promote C.sub.8 alkyl benzene isomerization at isomerization conditions in the presence of hydrogen at isomerization conditions to isomerize at least a portion of the C.sub.8 alkyl aromatic hydrocarbons and to produce an effluent;(d) separating the effluent to form a hydrogen-rich fraction, a first hydrocarbon-rich fraction containing benzene and toluene and having a lower average molecular weight relative to C.sub.8 alkyl aromatic, and a second fraction enriched in C.sub.8 alkyl aromatic content relative to the effluent;(e) subjecting at least a portion of the first hydrocarbon-rich fraction to the contacting of step (c);(f) increasing system pressure of the hydrogen rich fraction, said hydrogen rich fraction having vaporous light hydrocarbon impurities, said increase in system pressure being high enough to cause a phase change in the vaporous light hydrocarbon impurities from a vapor to a liquid phase, whereby said phase change causes an increase in hydrogen purity in the hydrogen rich fraction; and(g) recovering at least one C.sub.8 alkyl aromatic product from the second fraction.