Microwave pyrolysis of low rank coal to light aromatics catalyzed by Ni/Mo/P modified bifunctional biochar

Efficient pyrolysis of low-rank coal is very important for the country to achieve energy saving and emission reduction. This process not only improves the green utilization and conversion efficiency of energy, but also provides strong support for the optimization and upgrading of energy structure. Bifunctional biochar (BAC) catalyst modified by nickel, molybdenum and phosphorus with both chemical catalysis and physical absorption was prepared by impregnation method. The catalytic effects of BAC catalyst, microwave and hydrogen solvent on the formation of light aromatic hydrocarbons during the pyrolysis of low rank coal were investigated. The results show that the modification of traditional biochar and the successful introduction of phosphate-containing groups not only increase the acidic active site of the catalyst, but also, after loading Ni and Mo, the catalyst can significantly reduce the activation energy of low-rank coal cracking reaction, effectively improve the conversion rate of low-rank coal and the selectivity of light aromatics, and promote the oriented preparation of light aromatics by cracking and aromatization of low-rank coal. The addition of transition metal molybdenum not only improves the heat resistance of nickel-based catalyst, effectively prevents the sintering of catalyst, but also enhances the interface bonding strength between nickel and molybdenum and biochar, and significantly improves the stability and service life of catalyst in microwave field. In addition, the prepared Ni/Mo/P-BAC bifocal catalyst not only has excellent chemical catalysis, but also shows good wave absorption performance, significantly improves the microwave electric field intensity in the reaction zone, and effectively promotes the rapid polarization and bond breaking of low-rank coal molecules themselves, thus improving the selectivity of light aromatic hydrocarbons in the pyrolysis process of low-rank coal. Light aromatic hydrocarbons have been prepared by microwave pyrolysis of low-rank coal. By introducing hydrogen-supplying solvent to further promote the pyrolysis of low-rank coal, the yield of light aromatics can reach 58.42%.