PtZn Intermetallic Compound Nanoparticles in Mesoporous Zeolite Exhibiting High Catalyst Durability for Propane Dehydrogenation

A PtZn alloy nanoparticle catalyst for propane dehydrogenation was synthesized by simple coimpregnation of Pt(NH3)4(NO3)2 with Zn(NO3)2 onto a mesoporous material, which was built with siliceous MFI zeolite nanosheets. This mesoporous zeolite-supported PtZn catalyst exhibited high activity and selectivity with remarkably long catalytic lifetime compared with other PtZn catalysts loaded on γ-alumina, MCM-48 mesoporous silica, silica gel, and bulk MFI zeolite. When measured under a high-purity propane flow at 580 °C, the PtZn/mesoporous zeolite catalyst with metal loadings of 0.7 wt % Pt and 0.7 wt % Zn lasted for more than 20 days before the propane conversion decreased to half of its initial value. In comparison, other PtZn catalysts were deactivated almost completely within a few days. Atomic-resolution scanning transmission electron microscopic analysis revealed that the mesoporous zeolite contained finely dispersed Pt1Zn1 intermetallic compound-type alloy nanoparticles, which could effectively suppress catalyst deactivation. The mesoporous structure and the surface silanol groups of the MFI zeolite are suggested to play an important role in promoting the formation of intermetallic alloy nanoparticles.