Mechanism of Coal Liquefaction - Reaction of Model Compounds

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Benzyl phenyl ether and dibenzyl as model compounds of coal were hydrogenolyzed under high pressure of hydrogen in the presence of stabilized nickel or synthetic pyrite as the catalyst to elucidate the reaction mechanism of coal liquefaction. The reactions were carried out at 250-500ﾟC, under 3-10MPa of hydrogen for 0-60inin with naphthalene, tetralin and decalin as the solvent.In the case of stabilized nickel used as catalyst, which has strong ability in hydrogenation, the benzene rings of benzyl phenyl ether or dibenzyl were hydrogenated at 250-350ﾟC. Benzyl phenyl ether was split at C-0 bond almost completely at 250ﾟC and converted to phenol and toluene. Phenol was easily hydrogenated to cyclohexanol. At the higher temperature than 370ﾟC, cyclohexane and benzene increased due to dehydroxylation and dehydrogenation. With the increase in hydrogen pressure, hydrogenation and dehydroxylation accelated and gas formation and condensation were reduced.In the case of the synthetic pyrite as catalyst, benzyl phenyl ether produced little the hydrogenated products because of the weak hydrogenation ability. The larger amount of the condensed products such as dibenzyl phenol or tribenzyl phenol were produced in the reaction with decalin as solvent. These condensed products were produced in the early stage of reaction and then decomposed to benzyl phenol, phenol and toluene as the reaction proceeded. Djbenzyl reacted little at the lower temperature than 450ﾟC with the synthetic pyrite, that is difference from the stabilized nickel.