Dehydrogenation catalysis

Keywords Alcohols Catalysis Dehydrogenation Formic acid Ruthenium... 

Keywords Alcohols Amides Amines Carbon dioxide Catalysis Dehydrogenative coupling Esters Hydrogen Imines Iridium Metal-ligand cooperation O-H activation Pincer complexes PNN PNP Ruthenium... 

Catalysis (qv) refers to a process by which a substance (the catalyst) accelerates an otherwise thermodynamically favored but kiaeticahy slow reaction and the catalyst is fully regenerated at the end of each catalytic cycle (1). When photons are also impHcated in the process, photocatalysis is defined without the implication of some special or specific mechanism as the acceleration of the prate of a photoreaction by the presence of a catalyst. The catalyst may accelerate the photoreaction by interaction with a substrate either in its ground state or in its excited state and/or with the primary photoproduct, depending on the mechanism of the photoreaction (2). Therefore, the nondescriptive term photocatalysis is a general label to indicate that light and some substance, the catalyst or the initiator, are necessary entities to influence a reaction (3,4). The process must be shown to be truly catalytic by some acceptable and attainable parameter. Reaction 1, in which the titanium dioxide serves as a catalyst, may be taken as both a photocatalytic oxidation and a photocatalytic dehydrogenation (5). 

Ca.ta.lysts, A small amount of quinoline promotes the formation of rigid foams (qv) from diols and unsaturated dicarboxyhc acids (100). Acrolein and methacrolein 1,4-addition polymerisation is catalysed by lithium complexes of quinoline (101). Organic bases, including quinoline, promote the dehydrogenation of unbranched alkanes to unbranched alkenes using platinum on sodium mordenite (102). The peracetic acid epoxidation of a wide range of alkenes is catalysed by 8-hydroxyquinoline (103). Hydroformylation catalysts have been improved using 2-quinolone [59-31-4] (104) (see Catalysis). 

Selectivity among butylene isomers also occurs in vapor-phase heterogeneous catalysis, at least in the case of dehydrogenation of butenes to butadiene, where maximum yields can be obtained by employing slightly different conditions for each isomer (18). In practice, mixtures of isomers are used and an average set of conditions is employed. 

The use of A -enol ethers as substrates for dehydrogenation is often attractive. Aqueous acetone at room temperature gives yields ranging from 70 to 88% other systems with acid catalysis have also been used, e.g. ... 

Progesterone (81) is dehydrogenated by DDQ in dioxane, with acid catalysis. This method and the chloranil reaction (see section VI-A) provide the most direct route from A -3-ketones to -3-ketones. 

EfiSdent hydrogai supply firm decalin at modoate temperatures of below 250°C was acomplished by utilizing the superheated liqirid-film- pe catalysis under reactive distillation conditions in the present study. The composite catalysts in Ak liquid-film states improved dehydrogenation activities for decalin. 

To illustrate how a bifunctional catalyst operates, we discuss the kinetic scheme of the isomerization of pentane [R.A. van Santen and J.W. Niemantsverdriet, Chemical Kinetics and Catalysis (1995), Plenum, New York]. The first step is the dehydrogenation of the alkane on the metal ... 

The Genesis and Principle of Catalysis at Oxide Surfaces Surface-Mediated Dynamic Aspects of Catalytic Dehydration and Dehydrogenation on TiO2(110) by STM and DFT 317... 

Liu YM, Cong PJ, Doolen RD, Guan SH, Markov V, Woo L, Zeyss S, Dingerdissen U. 2003. Discovery from combinatorial heterogeneous catalysis—a new class of catalyst for ethane oxidative dehydrogenation at low temperatures. Appl Catal A Gen 254 59 -66. 

This chapter compares the reaction of gas-phase methylation of phenol with methanol in basic and in acid catalysis, with the aim of investigating how the transformations occurring on methanol affect the catalytic performance and the reaction mechanism. It is proposed that with the basic catalyst, Mg/Fe/0, the tme alkylating agent is formaldehyde, obtained by dehydrogenation of methanol. Formaldehyde reacts with phenol to yield salicyl alcohol, which rapidly dehydrogenates to salicyladehyde. The latter was isolated in tests made by feeding directly a formalin/phenol aqueous solution. Salicylaldehyde then transforms to o-cresol, the main product of the basic-catalyzed methylation of phenol, likely by means of an intramolecular H-transfer with formaldehyde. With an acid catalyst, H-mordenite, the main products were anisole and cresols moreover, methanol was transformed to alkylaromatics. 

Yamada, Y., Ueda, A., Zhao, Z. et al. (2001) Rapid evaluation of oxidation catalysis by gas sensor system total oxidation, oxidative dehydrogenation, and selective oxidation over metal oxide catalysts. Catal. Today, 67, 379. 

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