Tailored hierarchical zeolites via greener synthesis for the pyrolytic conversion of peanut shell waste

Abstract

Peanut shell is a high volume globally produced waste. Catalytic pyrolysis is proposed for its valorization. Hierarchical ZSM-5 zeolites were evaluated as solid catalysts to improve bio oil composition. Starch, cheap, renewable and safe polymeric carbohydrate was employed as a bio-mesotemplate for the synthesis. Good results were obtained in terms of structure, crystallinity and mesoporosity. Microwave heating was also evaluated in terms to reach a greener synthesis method. Crystallization time was reduced to 30 min instead of 48 h of the conventional hydrothermal procedure. From XRD analysis, it was determined that the samples prepared with a maximum content of 1.68 starch/Si molar ratio possess the crystalline structure of ZSM-5 zeolites. When higher starch content was evaluated, an amorphous pattern was obtained. A ZSM-5 micro/meso crystalline structure, as result of starch incorporation, was obtained by a simple and fast synthesis method. Hierarchical zeolites exhibited excellent performance in catalytic fast pyrolysis of biomass, resulting in improved selectivity towards 2,5-dimethylfuran.