Study of the products of coal hydrogenation and deuteration by electron paramagnetic resonance

Abstract

Products of Loveridge Mine high-volatile bituminous coal (81.8% C daf) after treating with H2, D2, H2-tetralin-d12, were separated into oils (hexane-soluble), asphaltenes (benzene-soluble), benzene) methanol-soluble, and insoluble fractions. The fractions were then studied by electron paramagnetic resonance at 9.5 GHz in which the g-factors, linewidths, and unpaired electron concentrations were measured. The unpaired electron concentrations decreased in the sequence: insoluble fraction > benzene-methanol fraction > asphaltene > oil, while the g-factor decreased in the opposite sequence. Results of these measurements also show that the number of unpaired electrons in the total product is approximately the same as that of the starting coal, although 90% or more remains the insoluble residue, and hydrogenation or hydrogen exchange is largely associated with high unpaired electron content. Measurements at 35 GHz on solids as well as 9.5 GHz on dissolved samples show that the greatest contributions to the homogeneous lineshape arise from both isotropic g-factors and hyperfine splittings. Manganese (II) is also found in the H2 treated insoluble fraction in larger amounts than in the tetralin treated fraction or the initial coal suggesting that H2 diffusion into the solid can cause reduction of the mineral components in the initial coal.