The hydro-modification mechanism of subbituminous coal

Abstract

The hydro-modification mechanism of subbituminous coal was investigated by the isotope trace method. The results show that the yield and caking index (GRI) of modified coal increase to 95.96 wt% and 81 under H2-THN, respectively. Both of them are higher than that under H2-1-MN or N2-THN, which also is consistent with the hydrogen consumption. Meanwhile, the linear regression between the GRI of modified coal and the yield of extracts is 0.9841, which indicates the presence of bonding components in the extracts. Furthermore, the IRMS analysis of modified coal under different conditions further confirmed that more hydrogen atoms from H2 and THN enter into the modified coal with high GRI. Through the 2H NMR and IRMS analyses of the extracts and calculation of hydrogen contribution rate, more hydrogen atoms enter into the possible bonding components, and most of them arrive in that in THF soluble. The hydrogen atoms from H2, transferred by THN, are combined with the macromolecular structure of coal, and the hydrogen atoms from THN enter into possible bonding components. Moreover, the hydrogen atoms in α positions of THN are abstracted at first, and then β positions, which are found from the 2H NMR analyses of THN-D4 before and after reaction. Based on the above, the hydro-modification mechanism of subbituminous coal is proposed.