Novel insight into the mechanism of coal hydropyrolysis using deuterium tracer method

Abstract

In this work, the mechanism of coal hydropyrolysis was investigated by using deuterium tracer method. To figure out how hydrogen reacts with coal at the temperature below 400 °C, chars from coal pyrolysis in D2 and N2 atmospheres when the pyrolysis temperature is at 150 to 400 °C were measured by isotope ratio mass spectrometry (IRMS) and electron paramagnetic resonance spectroscopy. The results show that H2 can react with stable radicals in coal during coal pyrolysis without catalyst at temperature as low as 200 °C. To obtain deep insight on which hydrogen transfer pathways affect pyrolysis product distributions of coal, IRMS combined with elemental analyzer and 2H NMR were used to obtain quantitative and qualitative date of deuterium in products. The results suggest that hydrogen atoms are introduced into tar mainly through radicals induce effect during coal pyrolysis without catalyst. And some of non-volatile radicals can abstract hydrogen atoms from H2. Hydrogen atom of H2 can incorporate all structural groups in the tar during coal pyrolysis, and it incorporates preferentially into 1-and 2-ring aromatic carbon and aliphatic carbon in the β or further positions of aromatic ring.