Preparation of Metal-Acid bifunctional catalyst Ni/ZSM-22 for palmitic acid catalytic deoxygenation

Abstract

In this work, methods employing ethanol for dispersion as well as precursor combination by rotary evaporation were combined to produce Ni-based ZSM-22 catalysts. The catalytic activity in palmitic acid deoxygenation over Ni/Z22@E was enhanced compared with that of the wet-impregnated method. The conversion of palmitic acid reached 98.9 %, in which C16/C15 alkane was as high as 4.07. The Ni species on the surface of catalysts showed strong stability so that not susceptible to inactivation by coking or leaching. In addition, the mechanism and kinetics of the palmitic acid deoxygenation reaction were analyzed. The results showed that the ethanol dehydration reaction was the most difficult to occur, and the high C16 alkanes selectivity can be attributed to the low activation energy of the hydrodeoxygenation (HDO) pathway. Both experimental and kinetics calculation results suggested that there may be a mechanistic change in the fatty acid deoxygenation reaction at around 240 °C that resulted in a large increase in the hydrodecarboxylation (HDX) pathway. Based on this, selected adjustments of the products were proposed for fatty alcohols below 220 °C, C16 alkanes between 260 and 280 °C, and C15 alkanes above 280 °C.