Mild conversion of coal for producing valuable chemicals

Exploiting new concepts, as well as practical methods, is essential for utilizing coal more effectively and cleanly. In this paper, special attention is paid to new pyrolysis methods: liquid phase oxidation at low temperatures, and solvent extraction using conventionally-used solvents as means to recover raw materials for valuable chemicals, clean fuels, and carbon materials from coal under rather mild operating conditions. Trials performed to obtain aromatic compounds and tar from coal in high yields through each method are briefly reviewed, and several attempts made by the authorʹs group aiming at mild conversion of coal are introduced. These include the flash pyrolysis of solvent swollen coal, pyrolysis of coal solubilized in a conventionally used solvent, liquid phase oxidation of coal with H2O2 at 60°C, and extraction of coal in a flowing non-polar solvent at 350°C. These methods were developed based on the recent progress in the understanding of coal structure.