Catalytic pyrolysis of rice husk over defect-rich beta zeolites for biofuel production

Abstract

The Coats-Redfern method was used to identify the catalytic and non-catalytic pyrolysis of rice husk biomass kinetics by using thermogravimetric analysis. MTES-beta-zeolite and beta-zeolite were synthesized by dry gel conversion method. Both synthesized zeolites and commercial beta-zeolite were mixed with ground rice husk in a 1:0.03 ratio by mass. Thermal degradation for catalytic and non-catalytic pyrolysis of rice husk biomass occurred at 523 K to 823 K. Conversions were majorly observed in Section I (523–633 K) and Section II (723–823 K) temperature ranges. Order and diffusion-based models were in approximation with each other for both temperature ranges. From the Ea trends, it can be understood that MTES beta-zeolite has no significant effect on pyrolysis in Section I and has promising results in Section II. The beta-zeolite and commercial beta-zeolite gave better results for all reaction models in both sections by lowering the activation energies for catalytic pyrolysis of RH compared to those for non-catalytic pyrolysis. By comparing catalytic with non-catalytic pyrolysis of rice husk, activation energy significantly varied for both sections. Thermodynamic parameters (ΔH) and (ΔG) values indicated the activated complex formation and non-spontaneity of the reaction. The negative value of (ΔS) suggested a more ordered state. Furthermore, pyrolysis of rice husk with commercial beta zeolite was performed and biochar produced with a yield of approximately 75%. Different organic compounds were also obtained in the bio-oil which include different aliphatic compounds.