Synthesis of ZSM-5 using different silicon and aluminum sources nature for catalytic conversion of lignite pyrolysis volatiles to light aromatics

Abstract

ZSM-5 zeolites with different physicochemical property were synthesized using different silicon (Si) and aluminum (Al) sources by hydrothermal method with controlling Al and Si addition. Different crystal shapes were observed from three Si sources. Al sources can influence crystal formation during crystallinity. Al nature causes different amorphous species which affect zeolite activity by blocking the accessible pores. A feasible mechanism of Si and Al sources for crystallization of zeolite was proposed. The activity for lignite volatiles-to-aromatics (LVTA) reaction was investigated to obtain light aromatics. Zeolite using tetraethylortho silicate and aluminum sulfate octahydrate as Si and Al sources shows large surface area and more accessible pores which cause excellent BTEXN yield (23.7 mg/g). The tar yield in the process of LVTA reaction is associated with both porous and acid properties while excessive acidity may cause the formation of coke on the zeolite which causes the blockage. ZSM-5 with optimum and accessible acid sites and abundant pores give a high tar yield and low coke yield. This work provides a ZSM-5 catalyst with suitable acidity and pore property for LVTA reaction.