Jet fuel range hydrocarbons production through competitive pathways of hydrocracking and isomerization over HPW-Ni/MCM-41 catalyst

Abstract

To promote hydrocracking and isomerization activities of bifunctional catalyst for the conversion of methyl palmitate into jet biofuel, phosphotungstic acid (HPW) loaded on Ni/MCM-41 catalyst enhanced strong acidity to strengthen conversion pathways of hydrocracking and isomerization. In the bifunctional catalytic system, Ni catalyzed hydrodeoxygenation and dehydrogenation of methyl palmitate to produce 1-pentadecene, while acid sites catalyzed further conversion of 1-pentadecene to produce jet fuel range hydrocarbons. Quantum chemistry calculation showed that activation energy in chemisorption process of 1-pentadecene onto acid sites significantly reduced from 203.9 kJ/mol with MCM-41 to 81.6 kJ/mol with HPW. Since bond order of β-scission site in 1-pentadecene over HPW was 0.93% lower than that over MCM-41, and Hirshfeld atomic charge of carbenium ion in 1-pentadecene over HPW (0.0722) was much higher than that over MCM-41 (0.0473), HPW showed better catalytic activities than MCM-41 in both hydrocracking and isomerization processes. The overall selectivity of jet biofuel increased to 86.1% with 47.1% n-alkane selectivity and 8.3% iso-alkane selectivity, due to improved strong acid density from 0.563 to 0.730 mmol/g over 20% HPW-Ni/MCM-41 catalyst.