Hydrodeoxygenation and hydrocracking of microalgae biodiesel to produce jet biofuel over H3PW12O40-Ni/hierarchical mesoporous zeolite Y catalyst

To improve jet biofuel quality with increased iso-alkane content, a bi-functional catalyst with strong acidity was proposed to promote hydrodeoxygenation and hydrocracking of microalgae biodiesel through loading heteropoly acid H3PW12O40 (HPW) on Ni-based hierarchical mesoporous zeolite Y (meso-Y). It was found by quantum chemistry calculation that hydrodeoxygenation process of microalgae biodiesel was inclined to the decarboxylation pathway other than the decarbonylation pathway, because the total enthalpy of pentadecane and by-products obtained through decarboxylation of methyl palmitate (C16: 0) was lower by 187.7 kJ/mol than that through decarbonylation. The selectivities of hydrocracking products with odd carbons (2n-1, n=5, 6, 7, 8) were higher than those with even carbons (2n), because the covalent bonds hydrocracked to remove even carbons were 0.001-0.149% longer in bond length and 0.012-1.697% lower in bond order than those hydrocracked to remove odd carbons. The experimental results of hydrodeoxygenation and hydrocracking conversion of microalgae biodiesel into jet biofuel carried out in a fixed bed reaction system agreed well with the quantum chemistry calculation results. The BET surface area of 10% Ni/meso-Y catalyst loaded with 4% HPW decreased by 14.3% to 453.9m(2)/g, but its strong acid density increased by 30.6% to 1.62 mmol/g. Accordingly, the selectivity of jet biofuel in liquid products converted from microalgae biodiesel at 255 degrees C and 2 MPa hydrogen increased to 63.1%, in which iso-alkane selectivity markedly increased to 20.5% and arene selectivity was reasonable at 11.1%.