Gas-phase hydrogenolysis of benzene and derivatives at elevated pressure; Methane formation

Benzene, in 20-30 bar of hydrogen, reacts smoothly in a quartz tubular flow reactor between 1163-1262 K, to give high yields of methane. With dwell times of 3-23 s, degrees of conversion ranged from 10 to 95%. Substituents such as Cl and CH3 are displaced more easily: ca, 350 times more rapidly at 1250 K. Mechanisms are discussed on a quantitat- ive thermochemical-kinetic basis. Of the alternatives considered, only a pathway through H atom addition, (reversible) isomerisation of C8H7. species, H-transfer from H-2 to give for example - methylcyclopentadiene (F), followed by splitting into . CH3 and cyclopentadienyl radical (G), would fully explain the observed rates of conversion of benzene.