Pt-Zn clusters encapsulated in hierarchical MFI zeolite for efficient propane dehydrogenation

Propylene is the second most important chemicals in the petrochemical industry. Propane dehydrogenation as the on-purpose propylene production route, has attracted much attentions due to great success in the exploitation of shale gas. Recently, Pt@zeolite is proven to the most promising catalyst for propane dehydrogenation, because Pt clusters encapsulated in zeolite channel show high resistance to Pt particles sintering. However, the micropore of zeolite imposes severe diffusion limitation of propylene, and thus the coke formation easily takes place which leads to a fast deactivation. Herein, we report efficient Pt/Zn-MFIhierarchical catalysts for PDH with auxiliary mesopore for accelerating mass transfer, and these Pt/Zn-MFIhierarchical exhibit not only high thermal stability but also excellent resistance to coking. The Pt/Zn-MFIhierarchical catalyst is obtained by an introduction of Pt species into the hierarchically porous Zn-MFI that is prepared from one-step hydrothermal synthesis. The formed Pt-Zn clusters are exclusively located in the micropore of MFIhierarchical, and the migrating of Pt-Zn clusters is largely prevented under the harsh reaction conditions. Mesopores in MFIhierarchical greatly enhances the diffusion rate of propylene, which significantly alleviates the coke formation arising from polymerization of propylene. The most efficient Pt/Zn-MFI-120hierarchical catalyst delivers propane conversion of around 46 % and propylene selectivity of above 98 %. This catalyst undergoes a slow loss of activity with a deactivation rate kd of as low as 0.005 h−1, and its catalytic performance can be fully restored via a simple calcination.