Catalytic depolymerization of coal char over iron-based catalyst: Potential method for producing high value-added chemicals

This study examined the feasibility of catalytic depolymerization of coal char obtained from the pyrolysis of low-rank coal at low temperature over iron-based catalyst to produce valuable chemicals. The depolymerization with or without the addition of ferric nitrate in a Gray-King assay reactor from 150 to 600 °C was performed. Compared with 0.2% of organic liquid products generated from the depolymerization without catalyst, the liquid yield increased to 1.61% (more than 7 times) when 1 wt% of catalyst was added. The GC×GC-MS analyses of the de-watered liquid products from depolymerization with catalyst showed that nitro-substituted phenols and alkyl-substituted naphthalene occupied the main contents, which were approximately 54.67% and 36.53%, respectively, and the rests were aliphatic hydrocarbons. An obvious DTG peak was observed from depolymerization with catalyst at 150-400 °C interval. The FTIR spectra analysis showed that the percentage of ether bond of the remained char with catalyst decreased compared with that of raw char without catalyst, reflected that the catalyst facilitates the breaking of ether bond of the raw char to produce more smaller fragments so that more liquid organic products were produced. This research provides a novel method for clean and efficient utilization of coal char and a potential way to produce high value-added chemicals.