Effects of acidity and microstructure on the catalytic behavior of cesium salts of 12-tungstophosphoric acid for oxidative dehydrogenation of propane

Abstract

A series of Cs x H 3− x PW 12O 40 ( x = 0.9–3.0) samples with regularly dependent acidity values and gradually transformed microstructures was synthesized by a precipitation method. Along with the increase in Cs content in the Cs x H 3− x PW 12O 40 samples, the concentration of acid sites decreased monotonically, and their morphologies changed gradually from compact large lumps to nano-sized particles. Mesoporous channels were formed probably because of the stacking of nanoparticles in the samples with x > 2.1. When the Cs x H 3− x PW 12O 40 samples were used as catalysts for oxidative dehydrogenation (ODH) of propane, higher conversions of propane were achieved over the catalysts with higher acidity. The formation of mesoporous structure improved propane conversion evidently. The best yield of propylene was achieved over the Cs 1.5H 1.5PW 12O 40 catalyst, which possessed a high concentration of acid sites and non-porous structure. Our studies demonstrate that not only the acidity but also the porous structure of the Cs x H 3− x PW 12O 40 play key roles in the ODH of propane.