Design of a ternary 3D composite from hydrochar, zeolite and magnetite powder for direct conversion of biomass to gasoline

Abstract

Recyclable zeolite-based composites were prepared using a simple one-step hydrothermal liquefaction (HTL) process. The synthesis process introduced magnetite and commercial zeolite into/onto the meso-macro structured algal hydrochar. The composites were analyzed for their N2 adsorption porosity, surface functional groups, total acid sites, and scanning electron microscopy morphology. The crystalline phase-change during the HTL and chemical interaction of hydrochar/zeolite and hydrochar/magnetic powder were confirmed by XRD and SEM-EDS analyses. The preparation of five catalytic systems along with possible reaction mechanisms were investigated in HTL of a local freshwater green alga topic using Design Expert 11 software to plan the experiments. Py-GCMS of the obtained bio-oil indicated that using two-dimensional (A2D) and three-dimensional (A3D) catalysts could catalyze the reactions toward the production of heavy gasoline (C7-C12) and biodiesel (C8-C21), respectively. It was shown that in 2D architecture, ketones undergo a series of aldol condensation reactions, and alkenes experience oligomerization, whereas in the 3D structure, the increase of the local pressure, expels monomers in the form of gasoline from the catalyst pores. Our newly developed 3D ternary composite not only had no negative effect on total acid sites of commercial zeolite but also, boosted the strong acidic sites due to the accommodation of Zn4.00Fe16.00Ni4.00O32.00 inside the composite.