Simulated moving bed reactor for isomerization and separation of p-xylene

A novel simulated moving bed reactor (SMBR) application for p-xylene production, which combines xylene isomerization and selective adsorption operating in liquid phase, at temperatures between 453 and 573 K is proposed. The SMBR unit configuration and principle of operation are explained. Experimentally determined xylenes adsorption equilibrium and kinetics parameters are used in the description of the xylene adsorption step. The reaction kinetics reported in the literature is used in the modelling of a fixed bed isomerization reactor. The equivalent true moving bed reactor (TMBR) modelling strategy is applied in modelling of the SMBR unit for p-xylene production. The steady state model assumes axial dispersion, coupled external and internal mass transfer resistances, and multicomponent Langmuir isotherms. The influence of the switching time, operating temperature and length of the reactors on process performance is presented for two different feed compositions: (A) xylenes composition is the same as in the feed used in a PAREX unit; (B) xylenes composition is the same as in the raffinate stream from the PAREX unit (both cases calculated on ethylbenzene and desorbent free basis).