Hydrogenation of Pyrene and Catalytic Interconversion of Hydropyrenes

Abstract Reexamination on the hydrogenation of pyrene (1) with Raney nickel catalyst under atmospheric pressure afforded a mixture of 4,5-di- (2), 4,5,9,10-tetra- (3), 1,2,3,6,7,8-hexa- (4), and 1,2,3,3a,4,5-hexahydropyrene (5). The relative amount of each product at the initial reaction stage was determined by time–yield relation of the products. The formation sequence of the products is discussed with reference to the hydrogenations of 2–5: 4 may be formed independent of 2, and 2 is converted to 3. Hydropyrene 5 may be produced from 1 mainly through the same σ-adsorbed species which also leads to 2. The hydrogenation of 1 with palladium and platinum catalysts gave similar results as with nickel. With nickel and palladium catalysts the hydrogenation of 1 was faster than that of 4H-cyclopenta[def]phenanthrene (9). However, with platinum the hydrogenation of 1 was slower than that of 9. Catalytic interconversion of 2–5 was examined at 240 °C under an argon pressure of 90 kg cm−2. Hydroarene 2 was easily dehydrogenated, and 3 and 5 were interconverted to a fair extent. Therefore, 2, 3, and 5 may be good hydrogen donor solvents for coal liquefaction.