Platinum supported on carbon aerogels as catalysts for the n-hexane aromatization

A series of Pt-catalysts were prepared by impregnation of carbon aerogels. The supports were selected on the basis of a different porous texture. The dispersion and sintering resistance of the catalyst were evaluated by varying the Pt-loading and the pre-treatment conditions. XRD, XPS, HRTEM and H2-chemisorption were used to determine the nature and dispersion of Pt-particles. The behavior of these catalysts on the n-hexane conversion was analyzed in different experimental conditions. The performance of catalysts was related to their porous, chemical and dispersion characteristics of the samples. Monofunctional catalysts were obtained in all cases. Isomerisation and cracking take place on the same active sites whereas the aromatization requires different sites. The selectivities for isomerization and hydrogenolysis change with the advance of the reaction while that for aromatization remains constant. Deactivation is related with the loss of the active sites responsible for the hydrogenolysis reactions.

► The mesopores of carbon aerogels favor the Pt-dispersion and sintering resistance.
► The catalytic activity increases with the Pt-dispersion.
► The aromatization selectivity increases with temperature at low Pt-dispersion.
► Cracking and isomerisation develops on the same active sites.
► Hydrogenolysis is favored by the increasing H2 concentration in the stream.