Some Aspects of the Mechanisms of Catalytic Reforming Reactions

Abstract

A brief review is given of the evolution of our ideas on the mechanism of catalytic reforming reactions over the last 40 years. The early bifunctional reaction mechanism, though criticized much, led first to an understanding and optimization of the reforming process and later to several other catalyst and process innovations. Kinetic and tracer studies on model catalysts using single hydrocarbons as reactants and the surface-science approach revealed the finer nuances of the mechanism involved. Simultaneously, the roles of S, Cl, coke, and hydrogen and of a second metal component like Re, Ir, or Sn in the industrial catalyst were also understood to a greater or lesser extent. All these results make the mechanism of reforming reactions a field of fascinating complexity in fundamental and industrial catalysis.

Naphtha Reforming and Upgrading of Diesel Fractions

“…The metal site reactions were considered to be the fast reactions; the acid site reactions the slow, rate-determining steps. This mechanism led first to better understanding and process optimization and later on to several catalyst and process innovations [13]. So far, the chemistry of reforming has not resolved into a set of widely recognized reaction mechanisms that can explain experimental results as a function of several parameters and lacks well-established interpretations.…”

“…Water enhances the Broensted acidity of alumina but also strips off chlorine, particularly during regeneration. Commercially chlorine is restored by the addition of organic chloride, at the start of cycle or continuously [13].…”

“…In commercial manufacture, the catalyst support for fixed-bed processes may be extrudate cylinders. Alumina supports for moving-bed processes are spherical to reduce attrition and are usually produced by the ''oil dropping'' method [13,25].…”

Recovery of Platinum and Palladium from the Spent Petroleum Catalysts by Substrate Dissolution in Sulfuric Acid

“…The petroleum catalysts containing platinum or palladium are discarded when its catalytic function deteriorates. 2,5) In the catalysts, small amounts of platinum or palladium are contained in large volume of support materials, typically alumina. 6) Platinum and palladium in spent petroleum catalysts can be recovered through various hydrometallurgial [7][8][9][10][11][12][13] or pyrometallurgical routes.…”

Effect of pressure on H/D exchange during n-octane conversion with Pt-SiO2 catalysts

“…However, at the higher hydrogen partial pressure, the relative conversion of the labeled cyclohexane seemed to decrease with increasing total conversion of the mixture. Later, Paál and Menon [6] indicated that the higher hydrogen www.elsevier.com/locate/apcata Applied Catalysis A: General 289 (2005) 28-36 partial pressure might promote hydrogenation of the cyclic surface precursors of benzene (cyclohexene or cyclohexadiene) to cyclohexane.…”