In situ encapsulation of platinum clusters within H-ZSM-5 zeolite for highly stable benzene methylation catalysis

摘要

The catalytic conversion of benzene and methanol to alkyl aromatic products is a promising way of converting nonpetroleum sources to fine chemicals. Ethylbenzene is the major by-product, which is still difficult to suppress. Besides, coke deposition on ZSM-5 catalysts is of serious concern on account of its impact on the catalyst deactivation and consequent loss in the production yield. In this study, Pt@ZSM-5 catalysts were synthesized using in situ hydrothermal synthesis techniques. The resultant catalysts exhibit a higher activity (60.1%) in comparison with impregnated Pt/ZSM-5 catalysts (56.3%), which is ascribed to the preservation of the pore volume and surface area in the resulting material. Notably, thanks to the high dispersion of Pt particles within the ZSM-5 nanocrystals, the Pt@ZSM-5 catalysts show superior anti-coking performance without deactivation after 300 h on stream, along with a high suppression ability towards the formation of ethylbenzene (<0.01%). Meanwhile, the confinement within the ZSM-5 crystals protects the Pt clusters from sintering and coalescence during thermal regeneration treatments. Such novel Pt@ZSM-5 catalysts exhibit excellent activity, remarkable stability and outstanding recyclability, thus providing an opportunity for benzene alkylation with methanol towards industrial production.