Catalytic upgrading of volatiles in co-pyrolysis of coal and biomass by Mo-MFI molecular sieves

Abstract

Catalytic co-pyrolysis of coal and biomass can improve both solid waste utilization and high value-added product content to obtain higher quality oils, which is significant for the clean and efficient use of coal and the expansion of biomass resource utilization. This study focuses on improving the quality of tar and the content of light fractions by catalytic reforming of coal and biomass co-pyrolysis volatiles. Molybdenum-doped MFI-type molecular sieve catalysts (Mo-MFI) were successfully prepared by a hydrothermal method using TPAOH as a structure-directing agent. The synthesized Mo-MFI molecular sieves were then used in the catalytic reforming of volatile fractions from the co-pyrolysis of low-metamorphic coal and biomass. With the help of biomass and catalyst, the co-pyrolysis tar can increase the content of high-value-added products. It was found that the highest tar yield of 11.4% was achieved when 30 wt% of corn stover was added. The utilization of Mo-MFI catalysts leads to a significant increase of 126% in the light oil content of a blended sample tar consisting of 30 wt% corn stover. The catalyst was also highly selective for low-level phenols, increasing the phenol content in the co-pyrolysis tar by 133.8%, 112.2% for cresols, and 88.1% for xylenol. In addition, a possible reaction pathway for the conversion of hydrocarbons to PXC (phenol, cresol, and xylenol) was proposed based on the changes in the components of the tar product after the addition of the catalyst.