Palladium-Containing Catalysts Based on Functionalized Carbon Nanofibers for the Dehydrogenation of Methylcyclohexane

The activity of palladium-containing catalysts based on functionalized carbon nanofibers prepared by an incipient wetness impregnation method in the dehydrogenation reaction of methylcyclohexane was investigated. Methylcyclohexane is considered as one of the most promising liquid hydrogen carriers. The dependence of the catalytic characteristics of the samples on the functionalization conditions of carbon nanofibers was studied. Using temperature-programmed desorption, it was shown that an increase in the treatment time of carbon nanofibers in concentrated nitric acid from 1 to 3 h increased the number of hydroxyl groups on their surface, and treatment for 6 h contributed to a rise in the concentration of carboxyl groups and their derivatives (esters and anhydrides). Additional calcination of the functionalized nanofibers in an inert atmosphere at 530°C yielded a sample containing predominantly hydroxyl groups. The presence of hydroxyl groups on the surface of the carbon material had a positive effect on the performance of the catalysts, while the presence of carboxyl groups led to a decrease in the yield of toluene. It was assumed that the observed differences in catalyst activity were due to differences in the dispersion and localization of palladium particles.