Microwave-assisted catalytic fast pyrolysis of spent edible mushroom substrate for bio-oil production using surface modified zeolite catalyst

•Spent edible mushroom substrate is pyrolyzed with microwave heating.•ZSM-5 is modified with three surface modification methods.•The minimum coke yield is obtained via SiO2 deposition modification (SiO2-ZSM-5).•SiO2-ZSM-5 catalyst performs better than other catalysts for bio-oil production.

In order to minimize coke yield and improve hydrocarbon production during microwave-assisted catalytic fast pyrolysis of spent edible mushroom substrate, ZSM-5 zeolite catalyst is modified with pre-coking treatment, chemical vapor deposition of SiO2, and ethylene diamine tetraacetie acid (EDTA) chemical modification method, respectively (labeled PC-ZSM-5, SiO2-ZSM-5 and EDTA-ZSM-5). Experimental results show that all the modification methods result in a loss of external acid sites of ZSM-5. Among the three modified catalysts, the maximum oil fraction yield and the minimum coke yield are obtained with SiO2-ZSM-5. The relative content of hydrocarbons in oil fraction increases in the following order: SiO2-ZSM-5 > EDTA-ZSM-5 > PC-ZSM-5 > original ZSM-5. Moreover, SiO2-ZSM-5 shows the highest relative contents of toluene and xylene, whereas original ZSM-5 produces the lowest ones. Besides, the selectivity of benzene in aromatics follows the order of original ZSM-5 > EDTA-ZSM-5 > PC-ZSM-5 > SiO2-ZSM-5, while the selectivity of toluene + xylene presents the opposite trend.

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