Hydrodesulfurization (HDS) of light gas oil was investigated using sulfided Co-Mo/Al 2 O 3 catalyst. The behavior of dibenzothiophene, monomethyldibenzothiophenes (C1-DBTs) and dimethyldibenzothiophenes (C2-DBTs) in HDS was traced under the following conditions: temperature, 280-400 °C; LHSV, 2-10 h -1 ; and gas/oil, 1000 and 125 NL (L-(NTP))/L. The HDS of these compounds was treated as a pseudo-first-order reaction. The ratio of the rate constants of 4-methyldibenzothiophene (4-MDBT) and DBT to that of 4,6-dimethyldibenzothiophene (4,6-DMDBT) diminished relative to those of the model reactions. The activation energies of DBTs increased in the order DBT < 4-MDBT < 4,6-DMDBT, while the differences between values diminished relative to those of HDS reactions using a single component among DBT, 4-MDBT, and 4,6-DMDBT. The retarding effect of H 2 S on HDS decreased in the order DBT > 4-MDBT, and further, 4,6-DMDBT was not inhibited. The results indicated that the selectivity for biphenyls in the HDS of DBT was higher than in the HDS of 4-MDBT or 4,6-DMDBT and that DBT and 4-MDBT were adsorbed by the catalyst more weakly than 4,6-DMDBT. An aromatic hydrocarbon of larger ring number has a stronger retarding effect on the HDS rate. The addition of phenanthrene decreased the HDS rate of DBTs in the order DBT > 4-MDBT > 4,6-DMDBT, while 1-methylnaphthalene did not affect the HDS rate. The effect of phenanthrene on the HDS rate appeared to be related to the differences in the adsorption ability of DBTs. To the contrary, the addition of acridine decreased HDS rate in the order 4,6-DMDBT > 4-MDBT > DBT. The results indicate that the retarding effect of acridine is different from that of phenanthrene.

The hydrogen exchange of coals with water was investigated using a tritium tracer method to estimate the mobility of hydrogen in coals. The reactions at several temperatures between 50 and 300 °C were carried out using a glass batch reactor and a pulse flow reactor, respectively. At lower temperatures, the ratio of hydrogen exchange of coal with water increased with a decrease in rank of coals and tended to change with respect to the content of functional groups such as hydroxyl group, thiol, amino group, and carboxylic acid in coal. From the results obtained from the hydrogen exchange of model compounds of the functional groups present in coal, it is proposed that the hydrogen only in the functional group was exchangeable at lower temperature while the hydrogen in aromatic ring substituted by functional groups also became exchangeable at 300 °C. It was found that the use of the pulse flow reactor as well as the glass batch reactor was very useful facile and convenient methods to trace the hydrogen exchange between coal and water.

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