C2H6/CO2 oxidative dehydrogenation (ODH) reaction on nanostructured CrAPSO-34 catalyst: One-pot hydrothermal vs. conventional hydrothermal/impregnation catalyst synthesis

Abstract

A series of Cr incorporated SAPO-34 catalysts varying in Cr content and a Cr supported SAPO-34 catalyst were prepared by one-pot hydrothermal and incipient-wetness impregnation methods, respectively. The synthesized materials were characterized by XRD, FESEM, TEM, BET, EDX dot mapping, TPD-NH3 and FTIR, and tested in ethane dehydrogenation with CO2 reaction. The incorporation of Cr3+ into the SAPO-34 framework and impregnation of Cr species were proved by TEM technique. With increase in the incorporated Cr content, smaller cubic crystals and amorphous particles were obtained. However, the extra-framework species probably appeared. Chromium impregnation led to micropore blockage and surface coverage partly, resulting in morphology change somewhat, significant decrease of surface area and acidity as evidenced by FESEM, TEM, BET and TPD-NH3 analysis. However, one-pot synthesis not only preserved the structure of SAPO-34 but also allowed higher surface area, more effective surface acidity and better chromium dispersion to be achieved, features that account for superior catalytic performance and stability of directly synthesized Cr rich catalyst. The Cr incorporated SAPO-34 catalyst containing rich amount of Cr exhibited the best catalytic activity, showing 38% ethylene yield at 700 °C even after 5 h on-stream operation.