Dehydrogenation of methyl alcohol

Formaldehyde is a gas, b.p. — 21°, and is usually prepared by the dehydrogenation of methyl alcohol m the presence of heated copper or silver. By admitting air with the methyl alcohol vapour, part of the hydrogen is oxidised to give the heat necessary for the reaction ... 

Rb+- and Cs+-impregnated X zeolites were found to exhibit the highest activity and selectivity in these transformations. A CsX zeolite treated with boric acid, for example, gave better than 50% overall selectivity in the formation of styrene and ethylbenzene (410°C, 60% conversion).275 Treatment of these catalysts with copper or silver nitrate resulted in further improvements in catalyst performance.276 The promoting role of these metals was suggested to be their involvement in dehydrogenation of methyl alcohol. 

Brown and Henke, 1), and silver may be substituted for copper in the oxidative dehydrogenation of methyl alcohol to formaldehyde. 

In order to dehydrogenate one mole of methyl alcohol 0-5 mole of oxygen is required, and hence for one volume of the alcohol half as much oxygen or two and a half times as much air. The stoicheiometrical mixture must therefore contain methyl alcohol and air in the proportions (by volume) 1 2-5, i.e. 28-5 per cent of methyl alcohol. Since the volumes vary as the partial pressures the temperature of evaporation (of the alcohol) must be so chosen that its vapour pressure shall be 28-5 per cent of the atmospheric pressure, i.e. about 210 mm. of mercury. The vapour pressures of better known substances atvarious temperatures are to be found in Landolt-Bomstein, Physikalrchem. Tabetien, 5th Edition, 1923, and supplementary volumes i., 1927, ii. 1931, iii. 1935,1936. 

Ketones.have the characteristic -C- signature group imbedded in them. Acetone, CH3COCH3, comes from two different routes. It is a by-product in the cumene to phenol/acetone process. It is the on-purpose product of the catalytic dehydrogenation of isopropyl alcohol. Acetone is popular as a solvent and as a chemical intermediate for the manufacture of MIBK, methyl methacrylate, and Bisphenol A. 

Catalytic dehydrogenation of methyl vinyl carbinol at temperatures above 250 C in presence of a brass spelter catalyst is claimed to give a 33 per cent yield of methyl vinyl ketone, CHs-CO CH=CH2. Catalytic vapo>phase oxidation of the unsaturated alcohols to form unsaturated carbonyl compounds has been found to give considerably higher yields. Temperatures in the range of 360-550 C and use of a metallic silver catalyst are described. 

Alternatively, aliphatic alcohols may be converted directly to the respective dimethyl alkylamines by catalytic amination in the presence of dimethylamine and low-pressure hydrogen over copper catalyst. The mechanism is believed to involve catalytic dehydrogenation of the alcohol to an aldehyde, addition of DMA with concomitant water elimination to form the enamine, and then subsequent reduction to the alkyldimethylamine. This route is particularly favored with longer-chain alcohols, which are derived through hydrogenation of tallow, or palm fatty acids, or methyl esters... 

Alternatively, Dixneuf and co-workers reported the Ru-catalyzed alkylation of the sp C-H bonds of alcohols using an alkene via the dehydrogenation of the alcohol substrate (Scheme 41) [234]. In a representative example of this transformation, benzyl 2-pyridyl alcohol (0.25 mmol) was reacted with methyl acrylate (1.0 mmol) in the presence of [RuCl2(p-cymene)]2 (5 mol%) combined with Cu(OAc) H20 (0.8 equiv) in dichloroethane to give the corresponding a-alkylated product in 80 % yield (Scheme 41). 

The main use of copper oxide/zinc oxide catalysts has been in dehydrogenation and hydrogenation reactions. These include the dehydrogenation of isopropyl alcohol to acetone as well as the hydrogenation of oxo-alcohols and fatty acid methyl esters. Although in many processes copper chromite catalysts are preferred to copper oxide/zinc oxide, the environmental problems involved in disposing of chromium wastes may reverse the situation. 

Methyl /-Butyl Ether. MTBE is produced by reaction of isobutene and methanol on acid ion-exchange resins. The supply of isobutene, obtained from hydrocarbon cracking units or by dehydration of tert-huty alcohol, is limited relative to that of methanol. The cost to produce MTBE from by-product isobutene has been estimated to be between 0.13 to 0.16/L ( 0.50—0.60/gal) (90). Direct production of isobutene by dehydrogenation of isobutane or isomerization of mixed butenes are expensive processes that have seen less commercial use in the United States. 

Direct oxidation yields biacetyl (2,3-butanedione), a flavorant, or methyl ethyl ketone peroxide, an initiator used in polyester production. Ma.nufa.cture. MEK is predominandy produced by the dehydrogenation of 2-butanol. The reaction mechanism (11—13) and reaction equihbtium (14) have been reported, and the process is in many ways analogous to the production of acetone (qv) from isopropyl alcohol. 

PCSs obtained by dehydrochlorination of poly(2-dilorovinyl methyl ketones) catalyze the processes of oxidation and dehydrogenation of alcohols, and the toluene oxidation207. The products of the thermal transformation of PAN are also catalysts for the decomposition of nitrous oxide, for the dehydrogenation of alcohols and cyclohexene274, and for the cis-tnms isomerization of olefins275. Catalytic activity in the decomposition reactions of hydrazine, formic acid, and hydrogen peroxide is also manifested by the products of FVC dehydrochlorination... 

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. 

Data for the initial reaction rate for the catalytic dehydrogenation of sec-butyl alcohol to methyl ethyl ketone are given in Table 16.13 (Thaller and Thodos, 1960 Shah, 1965). The following two models were considered for the initial rate ... 

Thaller, L.H., and G. Thodos, "The Dual Nature of a Catalytic-Reaction The Dehydrogenation of sec-Buty Alcohol to Methyl Ethyl Ketone at Elevated Pressures", AIChE Journal, 6(3), 369-373, 1960. 

Methyl pyruvate has been prepared from the silver salt of pyruvic acid and methyl iodide,3 and from the free acid by the alcohol-vapor method without a catalyst.4 Pyruvic esters have also been prepared by the dehydrogenation of lactic acid esters.5... 

Uses Copolymerized with methyl acrylate, methyl methacrylate, vinyl acetate, vinyl chloride, or 1,1-dichloroethylene to produce acrylic and modacrylic fibers and high-strength fibers ABS (acrylonitrile-butadiene-styrene) and acrylonitrile-styrene copolymers nitrile rubber cyano-ethylation of cotton synthetic soil block (acrylonitrile polymerized in wood pulp) manufacture of adhesives organic synthesis grain fumigant pesticide monomer for a semi-conductive polymer that can be used similar to inorganic oxide catalysts in dehydrogenation of tert-butyl alcohol to isobutylene and water pharmaceuticals antioxidants dyes and surfactants. 

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