Journal of Membrane Science, Vol.496, 70-77, 2015
Synergetic effect of H-ZSM-5/Silicalite-1@Pt/Al2O3 core-shell catalyst to enhance the selective hydrogenation of p-xylene
A H-ZSM-5/Silicaliie-1@PL/Al2O3 core-shell catalyst that combined para-directed isomerization and shape-selective hydrogenation was synthesized by coating MFI membranes onto the surface of Pt/Al2O3 pellet. The binary p/m xylene mixture was performed as the teed to evaluate the enhanced selective hydrogenation property of this bi-layered core-shell catalyst. In the hydrogenation of xylene isomers, the hydrogenation efficiency and selectivity of p-xylene over the H-ZSM-5/Silicalite-1@Pt/Al2O3 core-shell catalyst exceeded those over the monolayer H-ZSM-5@Pt/Al2O3 and Silicalite-1@Pt/Al2O3 core-shell catalysts, while maintaining the tiny formation of the unexpected hydrogenation products of m- or oxylene. The effect of reaction temperature was also investigated on the H-ZSM-5/Silicalite-1@Pt/Al2O3 catalyst. The p-xylene hydrogenation conversion and 1.4-dimethylcyclohexane selectivity of as high as 90.8% and 97.2%, respectively. were achieved at 300 degrees C. The isomerization on the H-ZSM-5 shell and the selective hydrogenation on the Silicalite-1@Pt/Al2O3 cooperated concertedly and promoted mutually. This bi-layered core-shell catalyst. with the synergetic effect of equilibrium shift and shape-selectivity, might have great potential to develop into a novel approach for xylenes separation. (C) 2015 Elsevier B.V. All rights reserved.