Catalytic pyrolysis of rice straw for high yield of aromatics over modified ZSM-5 catalysts and its kinetics

Abstract

The fabrication of ZSM-5 for the catalytic pyrolysis of biomass into highly selective valuable aromatics remains a challenge. This study investigates the product selectivity of rice straw pyrolysis without and with P-ZSM-5, alkali (0.4 M ZSM-5) and metal (8 wt% Ni-ZSM-5) modified catalysts via Py-GC/MS. Results revealed that the addition of catalysts significantly affected product distribution, with maximum selectivity of aromatics (47%) over 8 wt% Ni-ZSM-5 followed by P-ZSM-5 (44%) and 0.4 M ZSM-5 (42%). 8 wt% Ni-ZSM-5 exhibited the additive effect for monoaromatics with a maximum yield of BTX (67.23 mg/g) due to improved acidity responsible for the promotion of acid catalyzed reactions. Furthermore, the thermo-kinetics of rice straw without and with catalysts were investigated using thermogravimetric analysis. Thermogravimetric analysis shows that the degradation rate of rice straw reduced after the addition of catalysts. From the kinetic analysis, the value of activation energy of rice straw (114.43 kJ mol−1) decreased after the addition of catalysts, which was 102.48 kJ mol−1 (P-ZSM-5), 93.11 kJ mol−1 (0.4 M ZSM-5) and 61.89 kJ mol−1 (8 wt% Ni-ZSM-5). Thermodynamic parameters (ΔHandΔG) show that catalytic pyrolysis of rice straw is an endothermic and nonspontaneous process.