Simulated moving bed reactor for p-xylene production: Dual-bed column

• Dual-bed column for adsorption and production of p-xylene in SMBR unit.
• Dynamic optimization to estimate appropriate adsorbent and catalyst proportion.
• Analysis of different adsorbent/catalyst ratios and first-bed lengths.
• Integrated method combining TMBR and SMBR results to develop dual-bed SMBR

A dual-bed Simulated Moving Bed Reactor (SMBR) is developed under the framework of a proposed aromatics complex where the extract product, with 70 wt% p-xylene, is further purified by a crystallization unit to obtain the final product. Each column within the unit contains an adsorbent/catalyst homogeneous mixture as first bed followed by another bed of just adsorbent. A method of dynamic optimization is applied to estimate the optimum adsorbent/catalyst proportion within the first bed so p-xylene production is equal to its adsorption. Afterwards, the unit is optimized through successive simulations using the SMBR model giving a productivity of 226.27 kg/m3 h (produced p-xylene per volume of adsorbent and catalyst within the columns), a desorbent consumption of 0.07 m3/kg (volume of desorbent per produced p-xylene), and a produced p-xylene to fed p-xylene ratio of 1.75 at 200 °C. Finally, using the commercial software gPROMS, an integrated method that combines less time-consuming results from True Moving Bed Reactor (TMBR) approach with the rigorous SMBR calculations to develop the dual-bed SMBR unit is presented.

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