Use of Pd/activated carbon fiber catalyst to dehydrogenate cyclohexane

In this work, activated carbon fibers (ACFs) were prepared from polyacrylonitrile fibers, Pd catalyst was loaded onto the ACFs. The BET surface areas noted before activation were in the range of 120-140 m2/g. Activation of the fibers with carbon dioxide increased the surface areas of the fibers to about 150-190 m2/g. Diameters of metallic Pd particles loaded along the fibers ranged from 50 nm to 100 nm. The shape of the Pd particles was generally spherical albeit some non-spherical Pd particles were also noted. The catalytic activity of the Pd/ACF system in dehydrogenating cyclohexane at 350oC under liquid-phase conditions was investigated. Utilizing the Pd/ACF system in the micro-autoclave of a differential scanning calorimetric system was described for the liquid-phase catalytic dehydrogenation of cyclohexane. The DSC thermogram of the non-catalytic system yielded fewer endothermic events compared to the catalytic dehydrogenation of cyclohexane in the presence of Pd/ACF. The dehydrogenation of cyclohexane at 350oC was a first-order reaction with a rate constant, k = 3.5 x 10-4 s-1. GC-MS analyses of the products of catalytic dehydrogenation revealed a wide distribution of saturated and unsaturated hydrocarbons that were not present in the corresponding non-catalytic experiment. The presence of high molecular weight products could be explained by the recombination of carbon radicals during reaction.