315 / 2018-07-24 14:21:08

Catalytic Improvement of Biomass Vapors with Metal-Modified Zeolites Based on Cellulose Fast Pyrolysis

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Catalytic fast pyrolysis (CFP) of cellulose, hemi-cellulose, sawdust, and cotton stalk was investigated using a vertical two-stage reactor to evaluate the influence of metal-modified zeolites with different loading amounts for improving the pyrolysis vapor quality. The results indicated that the liquid yield decreased from 54.36% to 37.63%, while the gas and coke yields increased with the introduction of the catalysts. With the modified catalyst, 4Co/HZSM-5 produced the highest gas yield, whereas 4Fe/HZSM-5 and 4Zr/HZSM-5 exhibited similar effects on product yields and showed better catalytic properties than HZSM-5. The 4Zr/HZSM-5 catalyst promoted the formation of benzene and its derivatives, while 4Fe/HZSM-5 produced a higher yield of naphthalene and its derivatives. A reaction network was proposed to describe the catalytic pyrolysis of cellulose. As the Fe loading was increased from 2% to 6%, catalytic deoxygenation and hydrocarbon formation became more effective. The selectivity for naphthalene derivatives increased, and 4% Fe was selected as the optimal loading. In the pyrolysis of different materials over 4Fe/HZSM-5, the total amounts of aromatic hydrocarbons were relatively high and were in the following order: hemi-cellulose > pine sawdust > cellulose > cotton stalk. Catalytic pyrolysis of cellulose and hemi-cellulose afforded the highest selectivities for naphthalene derivatives..