Effects of alkali and alkaline earth metals on the formation of light aromatic hydrocarbons during coal pyrolysis

Light aromatic hydrocarbons from coal pyrolysis such as benzene, toluene, xylene, and naphthalene have been found wide applications as industrial raw materials. The alkali and alkaline earth metals (AAEMs) are of considerable effect on the yield and distribution of coal tar during pyrolysis. In this study, the yield and distribution of the pyrolysis products of three raw coals with different ranks, demineralized coals prepared by acid washing, and metal-loaded coals were investigated using pyrolysis-gas chromatograph/mass spectrometer (Py-GC/MS). The results show that the yields of benzene, xylene, toluene, and naphthalene are significantly different before and after acid washing, and the generation of light aromatic hydrocarbons has an obvious dependency on AAEMs in coal. AAEMs have good catalytic activity on the decomposition of phenols and condensed aromatics to light aromatic hydrocarbons. (C) 2016 Elsevier B.V. All rights reserved.