Effect of zeolite structure and Si/Al ratio on cotton stalks hydropyrolysis

Zeolites, being acidic, act as the most promising catalytic materials for deoxygenating reactive oxygenated compounds produced during the pyrolysis of lignocellulosic biomass. Herein, two zeolites, HY and HZSM-5, with different Si/Al ratios, were employed to investigate the effect of zeolite structure on aromatic hydrocarbons (AHs) production during flash hydropyrolysis of cotton stalks (Temperature = 800 ˚C, H₂ pressure = 10 bar). Both the zeolites enhanced AHs production. However, the pore structure and pore size of HZSM-5 marked a pronounced effect on the reduction of oxygenated compounds. With an increase in Si/Al ratio, AHs area% was found to decrease owing to the decrease in acidity. Ni/zeolite catalysts were also investigated to look into the effect of metal loading on the catalytic properties of zeolites. Ni/zeolite catalysts enhanced the aromatic and aliphatic hydrocarbon production by further conversion of phenolics and other oxygenated compounds due to the promotion of direct deoxygenation, decarbonylation and decarboxylation reactions.