Production of Benzene by the Hydrodemethylation of Toluene with Carbon-Supported Potassium Hydride.

The hydrodemethylation (HDM) of toluene to benzene is an industrial process performed at elevated temperatures (≈500 °C and higher). Here, it was reported that heating graphite-supported potassium hydride (KH/C) with toluene under H2 atmosphere provided benzene already at 125-250 °C. Depending on the H2 pressure, the reaction was either substoichiometric ( ≤11 bar) or catalytic ( ≥50 bar) with respect to KH, indicating that KH may serve as a radical chain initiator. At 250 °C, the selectivity to benzene was 98 and 63 % when using 6 and 80 bar of H2 , respectively, owing to the competing formation of cyclohexane and methylcyclohexane at high H2 pressure. The used KH/C material was amenable to recycling without a notable loss in the yield of benzene.