Uniform mesoporous hierarchical nanosized zeolite Y for production of Hydrocarbon-like biofuel under H2-Free deoxygenation

Abstract

Energy is an indispensable part in 21st century and most of our energy demands are supplied by the fossil fuel. However, the environmental and sustainable issues associated with the burning of fossil fuel have motivated the production of biofuel. Zeolite Y is a well-known solid acid catalyst due to its outstanding properties such as large uniform micropore (0.73 nm), high surface area and intrinsic acidity. Unfortunately, the sole micropore of zeolite Y has imposed diffusional limitation for bulky molecules that lead to low catalytic activity and catalyst deactivation due to pore blockage. In this work, we have adopted two synthesis strategies to solve diffusional limitation of conventional zeolite Y. First, mixing the precursor solution and organosilane template at low temperature (4 °C). Secondly, recrystallization of zeolite gel solution at low hydrothermal temperature (80 °C). With these efforts, a series of hierarchical nanosized zeolite Y were prepared with different amount of dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC) (molar ratio of 0.5, 1.5, and 2.5) as a template. The amount of TPOAC added has altered the physicochemical properties of zeolites such as porosity and acidity. The best hierarchical nanosized zeolite Y (MY0.15) was prepared with 0.15 M ratio of TPOAC. It is a 300 nm large aggregate made up of 50 nm zeolite nanocrystals. Besides that, it exhibits a uniform mesopore of 5.8 nm and an acidity of 1.73 mmol/g with a B/L ratio of 0.24. The deoxygenation performance of synthesized zeolites was evaluated through deoxygenation of triolein under H2-free condition at 380 °C for 2 h. The nanosized zeolite Y (MY0) showed a triolein conversion of 47.3% and hydrocarbon selectivity of 60.3%. The presence of uniform mesopore in MY0.15 has improved the conversion and hydrocarbon selectivity to 61.1% and 68.5%, respectively. In terms of initial rate, MY0.15 was 1.7 times faster than that of MY0. In addition, the MY0.15 showed good reusability by retaining 88% of its initial activity after four consecutive runs. Therefore, uniform hierarchical nanosized zeolite Y appears to be an effective catalyst in producing hydrocarbon-like biofuel via H2-free condition and other reactions involving bulky reactants.