Enhancement of aromatics from catalytic pyrolysis of yellow poplar: Role of hydrogen and methane decomposition

The present study examined the effects of the pyrolysis environment on BTEX (benzene, toluene, ethylbenzene, and xylenes) production in the catalytic upgrading of yellow poplar pyrolysis vapors. Three different gas environments, N₂, CH₄, and pre-decomposed CH₄ stream (10 wt%-Ni/5 wt%-La₂O₃-5 wt% CeO₂-Al₂O₃), which is a mixture of H₂ (55.62%) and CH₄, were studied using two types of zeolite catalysts, HZSM-5, and 1 wt% Ga/HZSM-5. The BTEX yields were enhanced linearly in the order N₂ < CH₄ < CH₄ ex-situ decomposition. The highest BTEX yield of 9.58 wt% was obtained under the CH₄ ex-situ decomposition environment over 1 wt% Ga/HZSM-5. The methane and hydrocarbons derived from biomass were activated on highly dispersed (GaO)⁺ sites and transformed smoothly to BTEX by aromatization on the BrØnsted acid sites of Ga/HZSM-5. The hydrogen produced from methane decomposition also assisted in aromatics production through the hydrodeoxygenation of methoxyphenols, guaiacols and catechols.