Sustainable production of acrolein: Preparation and characterization of zirconia-supported 12-tungstophosphoric acid catalyst for gas-phase dehydration of glycerol

摘要

ZrO2-supported H3PW_(12)O_(40) (HPW) catalysts were used to catalyze the dehydration of glycerol to produce acrolein at 315 °C under a high space velocity (GHSV_(Glycerol) = 400h~(-1)). The catalysts were prepared by varying the loading of HPW on two ZrO(OH)2 supports of different preparations, followed by calcination in flowing nitrogen. The use of alcogel-derived ZrO(OH)2-AN for the support, compared with conventional hydrogel-derived ZrO(OH)2-CP, produced HPW/ZrO2 catalysts that showed higher surface areas and better catalytic performance for the selective formation of acrolein from glycerol dehydration. Independent of the preparation history of ZrO2, the Keggin-anion density (HPW nm~(-2)) at the catalyst surface appeared as a key to the selectivity and mass-specific activity of HPW for acrolein production. Acrolein selectivity as high as 70 mol% was obtained over the catalysts having the intermediate densities (0.18-0.65 HPW nm~(-2)), at which most of the Keggin HPW remained intact after calcination up to 650 °C. At higher densities, destruction of the Keggin HPW would occur during the calcination, which led to lower acrolein selectivity. High selectivity (71 mol%) and high yield (≥54%) for acrolein production were found sustainable over the best performing HPW/ZrO2-AN catalyst for reaction times up to 10 h.