Aromatic hydrocarbons heterogeneous catalysis

G. Giannetto, J..A, Perez, R. Sciamanna, L. Garcia, R. Gallasso, and R. Monque, Symposium on Alkylation, aromatization, oligomerization and isomerization of short chain hydrocarbons over heterogeneous catalysis, American Chemical Society, New York, (1991)659. 

Type of Active Sites. - In heterogeneous catalysis the following type of actives sites can be distinguished (i) metallic, (ii) acid-base, (iii) red-ox type, and (iv) anchored metal-complex. The catalytic sites may contain one of the above types of active sites or can include several types of sites. In case of different type of sites the catalysts are bifunctional or multifunctional. For instance, Pt/Al203 and Pt/mordenite are typical bifunctional catalysts containing both metallic and acidic types of active sites. On the other hand, Pt or Pd supported on silicon carbide, nitride, or Pt/L-zeolite are mono-functional catalysts. There are important industrial reactions, such as isomerization and aromatization of linear hydrocarbons, which requires bifunctional catalysts, such as chlorinated... 

O Connor has written surveys of both homogeneous and heterogeneous catalysis while the reviews of Skupinska and Al-Jarallah et focus particularly on homogeneous catalysis. Recently, Minachev et al. have written about their work on the catalytic and physicochemical properties of the zeolites based on pentasils for oligomerizing lower olefins and paraffins into a mixture of aliphatic hydrocarbons of the composition Ce-Cio or into a concentrate of aromatic hydrocarbons, depending on the reaction conditions. 

Herman Pines for over fifty years has made significant contributions to heterogeneous catalysis. He has emphasized hydrocarbon reactions. Among the areas he has researched are acid catalysis, base catalysis, aluminas, aromatization and dehydrogenation catalysts and metal hydrogenation catalysts. His students and colleagues over the years recall his industrial and his academic career. 

Clerici, M.G. and Kholdeeva, O.A. (eds) (2013) Liquid Phase Oxidation via Heterogeneous Catalysis Organic Synthesis and Industrial Applications, John Wiley Sons, Inc., Hoboken. Bruckner, A. and Baems, M. (1997) Selective gas-phase oxidation of polycyclic aromatic hydrocarbons on vanadium oxide-based catalysts. Appt Catal. A- Gen., 157 (1-2), 311-334. Corma, A., Esteve, P., and Martinez, A. (1996) Solvent effects during the oxidation of olefins and alcohols with hydrogen peroxide on Ti-beta catalyst the influence of the hydrophilicity-hydrophobicity of the zeolite. /. Catal, 161 (1), 11-19. 

Supported metal clusters play an important role in nanoscience and nanotechnology for a variety of reasons [1-6]. Yet, the most immediate applications are related to catalysis. The heterogeneous catalyst, installed in automobiles to reduce the amount of harmful car exhaust, is quite typical it consists of a monolithic backbone covered internally with a porous ceramic material like alumina. Small particles of noble metals such as palladium, platinum, and rhodium are deposited on the surface of the ceramic. Other pertinent examples are transition metal clusters and atomic species in zeolites which may react even with such inert compounds as saturated hydrocarbons activating their catalytic transformations [7-9]. Dehydrogenation of alkanes to the alkenes is an important initial step in the transformation of ethane or propane to aromatics [8-11]. This conversion via nonoxidative routes augments the type of feedstocks available for the synthesis of these valuable products. 

Within the last few years there has been a growing tendency to draw the analogy between the chemistry of organometallic complexes and that of hydrocarbons adsorbed on metal atoms in surfaces. For example, it is postulated that the isotopic exchan between deuterium and alkanes, catalysed by thin films of nickel, palladium or rhodium, occurs via an equilibrium between a- and 7r-bonded metal-organic species [109, 110, 111, 112]. i-Bonded olefins are postulated in Zie er catalysis, see above, in the catalytic deuteration of aromatic complexes [113], and in a variety of isomerization reactions [112, 114, US]. Other intermediate metal-carbon systems which have been proposed in heterogeneous catalytic systems include carbenes , e.g. M= H2 [109], Ji-enyl systems [114] and of course the metal-carbonyl M—CO and bridging carbonyl M- O—M. 

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