Development of a catalytically green route from diverse lignocellulosic biomasses to high-density cycloalkanes for jet fuels

Abstract

This study reports a novel route to manufacture high-density cycloalkanes for jet fuels from diverse lignocellulosic biomasses. The consecutive processes for manufacturing high-density cycloalkanes primarily included the catalytic microwave-induced pyrolysis of diverse lignocellulosic biomasses (hybrid poplar, loblolly pine and Douglas fir) over a well-promoted ZSM-5 and a hydrogenation process in the presence of a RANEY® nickel catalyst. Two variables (catalytic temperature and catalyst-to-biomass ratio) were employed to determine the optimal conditions for the production of C₈–C₁₆ aromatics in the catalytic microwave-induced pyrolysis. The maximum carbon yield of the desired aromatics was 24.76%, which was achieved from the catalytic microwave-induced pyrolysis of hybrid poplar at 500 °C with the catalyst-to-biomass ratio of 0.25. We observed that the aromatics derived from catalytic microwave-induced pyrolysis in the n-heptane medium were completely hydrogenated into renewable high-density cycloalkanes for jet fuels. In the hydrogenation process, increasing the catalyst loading and reaction temperature could promote the selectivity to high-density cycloalkanes. The results indicated that hybrid poplar was the optimal feedstock for obtaining the highest selectivity (95.20%) towards high-density cycloalkanes. The maximum carbon yield of cycloalkane-enriched hyrogenated organics based on hybrid poplar was 22.11%. These high-density cycloalkanes with high selectivity can be directly used as additives in jet fuels, such as JP-5, JP-10 and RJ-5.