Hierarchical ZSM-5/SiC nano-whisker/SiC foam composites: Preparation and application in MTP reactions

Abstract A hierarchical composite catalyst composed of a ZSM-5 coating on SiC nano-whiskers that grew on SiC foam supports was designed and synthesized to simultaneously improve the zeolite loading and mass transfer of both the reactants and products in the methanol-to-propylene (MTP) reaction. SiC nano-whiskers were first grown on SiC foam supports by a chemical vapor deposition method to construct a hierarchical porous structure on the struts. ZSM-5 type zeolite crystals with high coverage were then hydrothermally grown on the SiC nano-whiskers after their surface was properly modified with zeolite precursor gel. In this way, the mass loading of the zeolite coating and mass transfer property, the two key factors that hinder the catalytic properties of the ZSM-5/SiC foam composite reported in our previous work, were enhanced, which in turn substantially improved the stability and selectivity of the obtained ZSM-5/SiC nano-whisker/SiC foam composites in MTP reaction as compared with those of the ZSM-5/SiC foam composites and ZSM-5 pellets.