Hydrodeoxygenation of karanja oil using ordered mesoporous nickel-alumina composite catalysts

Abstract

Abstract This study presents a systematic investigation of hydrodeoxygenation (HDO) of karanja oil over ordered mesoporous nickel-alumina composite catalysts. These catalysts were prepared by the evaporation-induced self-assembly method. The catalysts showed the ordered mesoporous structure up to 15 wt% nickel content in the catalyst. The mesoporous structure, however, became disorder beyond this nickel content. The catalysts were associated with catalytically active dispersed tetrahedral (or octahedral) coordinated nickel aluminate with strong interaction with alumina and a negligible amount of catalytically poor extra-framework nickel. The mesoporous nickel-alumina composite catalysts thus demonstrated superior catalytic activity compared to mesoporous alumina and γ-Al2O3 supported nickel catalysts. Wide ranges of linear paraffins (C14-C22) were formed in the reaction with C17 alkane as the main product. The conversion of oxygenates was enhanced with the rise in initial hydrogen pressure and nickel content in the catalyst without affecting product distribution much. The cracking of heavy hydrocarbons was, however, significant at elevated reaction temperatures, resulting in high selectivity to C17 alkane. For the optimum nickel loading of 20 wt%, the conversion of oxygenates was almost 100% with about 70 wt% C17 alkane and 15 wt% each lower and higher than C17 alkanes at 633 K and 2 h reaction time.