High aromatic content in diesel fuel has been recognized both to lower the fuel quality and to contribute significantly to the formation of undesired emissions in exhaust gases [1, 2]. Because of the health hazards associated with these emissions, environmental regulations governing the composition of diesel fuels are being tightened in both Europe and the United States, leading to limitations on aromatics [3, 4].

Aromatic Hydrogenation Catalysis: A Review

Organic catalysis over zeolites: A perspective on reaction paths within micropores

The unique environment of the Bransted acidic protons in the micropores of zeolites controls the overall catalytic behavior of zeolites to a significant extent. One of the most obvious consequences for reactivity is the resulting stereoselectivity of zeolitic catalysts. Molecules too large to enter the zeolite will not be converted. Also, large molecules that are formed in the microcavities of the zeolite but are unable to pass through the smallest micropore diameter on their path outward of a zeolite particle will not appear as a product. Molecules that move through the micropores of a zeolitic particle can have a significant interaction with the walls of the zeolite micropores. The strength of this interaction can be deduced from heats of adsorption measurements. I t appears to be a sensitive function of zeolite micropore diameter or shape.lj2 The interaction energy tends to increase as the zeolite micropores get smaller. The smaller the micropore diameters, the shorter the average distance between the molecular adsorbate atoms and the micropore

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Reactivity Theory of Zeolitic Broensted Acidic Sites

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Platinum nanoparticles in the size range of 1.7-7.1 nm were produced by alcohol reduction methods. A polymer (poly(vinylpyrrolidone), PVP) was used to stabilize the particles by capping them in aqueous solution. The particles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM investigations demonstrate that the particles have a narrow size distribution. Mesoporous SBA-15 silica with 9-nm pores was synthesized by a hydrothermal process and used as a catalyst support. After incorporation into mesoporous SBA-15 silica using low-power sonication, the catalysts were calcined to remove the stabilizing polymer from the nanoparticle surface and reduced by H2. Pt particle sizes determined from selective gas adsorption measurements are larger than those determined by bulk techniques such as XRD and TEM. Roomtemperature ethylene hydrogenation was chosen as a model reaction to probe the activity of the Pt/SBA-15 materials. The reaction was shown to be structure insensitive over a series of Pt/SBA-15 materials with particle sizes between 1.7 and 3.6 nm. The hydrogenolysis of ethane on Pt particles from 1.7 to 7.1 nm was weakly structure sensitive with smaller particles demonstrating higher specific activity. Turnover rates for ethane hydrogenolysis increased monotonically with increasing metal dispersion, suggesting that coordinatively unsaturated metal atoms present in small particles are more active for C 2H6 hydrogenolysis than the low index planes that dominate in large particles. An explanation for the structure sensitivity is suggested, and the potential applications of these novel supported nanocatalysts for further studies of structure -activity and structure-selectivity relationships are discussed.

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Pál Tétényi

Papers

The mechanism of aromatization on platinum black catalyst; dehydrocyclization of hexadienes and hexatrienes

Kinetics and mechanism of ethane hydrogenolysis on silica-supported platinum and platinum-iron catalysts

Comparative study of various platinum catalysts in skeletal reactions of C6-hydrocarbons

Catalytic transformations of cyclohexanol on Group VIII metal catalysts

Hydrogen control of platinum-catalyzed skeletal reactions of alkanes: Selectivities and surface species