Gas-phase nitration of toluene with zeolite beta

The gas-phase nitration of toluene was studied over a solid-acid zeolite beta catalyst with two different nitrating agents, HNO3 and N2O4, in a setup for continuous nitration. The selectivity of the reactions to 4-nitrotoluene was good, but the catalysts deactivated within a few hours. HNO3 gave higher yields than N2O4, but both HNO3 and N2O4 required a temperature lower than 160 °C to obtain acceptable yields and less oxidation products. At higher temperatures, catalyst deactivation was accelerated and the yield of nitrotoluene decreased. Lowering the feed rate of toluene led to a slower deactivation of catalyst. The deactivation of the catalyst was caused by pore blocking due to liquid reaction products as well as coke formation. Unlike in liquid-phase nitration, dealumination did not play a role in the deactivation of the catalyst, which could be regenerated by calcination in air.

The gas-phase nitration of toluene was studied with HNO3 and N2O4 in a setup for continuous nitration. The difference between these two nitrating agents, the mechanism of nitration, the reasons for catalyst deactivation and the optimum reaction conditions are discussed in the paper.Figure optionsDownload as PowerPoint slide