Dehydrogenates methanol

Some methylotrophic bacteria dehydrogenate methanol to formaldehyde. The latter undergoes an aldol condensation to form a hexulose-6-phos-phate ... 

Such selectivity changes by a poison are shown very nicely by the work of Madix and co-workers on Ni(lf)O) which showed that clean Ni totally dehydrogenates methanol, whereas with S poisoning the partial dehydrogenation to formaldehyde is favoured (fig. 48 Johnson and Madix, 1981). Thus the ellect of the selective poisoning is to make the Ni surface behave more like a copper surface, and reflects the kind of behaviour described above for Rh in the presence of a high field. 

This enhanced activity is due to the fact that Pt, Ru and WO3 are present on adjacent sites on codeposited (Pt-Ru-WOsyC electrode. Availability of WO3 at near vicinity of Pt enables the release of hydrogen from methanol or partially dehydrogenated methanol fragments by forming bronzes [5], which enhances oxidation of methanol. 

Degradation, polyethylene Degradation, polymers, catalytic Dehydration, Cd-FAU Dehydration, clinoptilolite Dehydration, isopropanol Dehydration, K-LSX Dehydration, MOR Dehydrocyclodimerisation, butadiene Dehydrogenation, ethylbenzene Dehydrogenation, methanol Dehydroisomerisation, n-butane Dehydroxylation, phenol Delaminated zeolites De novo simulation DeNOx catalyst... 

Metal cations Metal cation reduction Metal cations in MeAPO synthesis Metal corrosion prevention Metallocene, supported catalyst 24-0-05 Metallosilicates, microporous Methanol adsorption Methanol amination Methanol conversion Methanol dehydrogenation Methanol formation Methanol in alkylation 15-0-03 25-0-03 Methanol to hydrocarbons Methanol, reagent Methanol, steam reforming Methylamine in MFI synthesis N-Methylation, aniline Methylation, 4-methylbiphenyl Methylation, toluene, model 4-methylbiphenyl, methylation Methylcyclohexane cracking Methylcyclopentane hydroconversion Methylene silanes... 

Dehydrogenation - Methanol can also be oxidized to formaldehyde by passing its vapor over copper heated to 300°C. Two atoms of hydrogen are eliminated from each molecule to form hydrogen gas and hence this process is termed dehydrogenation. 

Experiments during the nineteenth century had shown that certain oxides could be used as dehydrogenation catalysts. For example, Jahn dehydrogenated methanol by passing the vapour over finely divided zinc or zinc oxide to produce a stoichiometric mixture of hydrogen and carbon monoxide. ... 

Another possible route for producing formaldehyde is by the dehydrogenation of methanol (109—111) which would produce anhydrous or highly concentrated formaldehyde solutions. Eor some formaldehyde users, minimization of the water in the feed reduces energy costs, effluent generation, and losses while providing more desirable reaction conditions. 

Other potential processes for production of formic acid that have been patented but not yet commerciali2ed include Hquid-phase oxidation (31) of methanol to methyl formate, and hydrogenation of carbon dioxide (32). The catalytic dehydrogenation of methanol to methyl formate (33) has not yet been adapted for formic acid production. 

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. 

Arguably the key step in the MGC process is the conversion of a-hydroxyisobutyramide to methyl a-hydroxyisobutyrate using methyl formate as the methylating agent. Methyl formate is made commercially by MGC via vapor-phase dehydrogenation of methanol (72). 

Methanol undergoes reactions that are typical of alcohols as a chemical class (3). Dehydrogenation and oxidative dehydrogenation to formaldehyde over silver or molybdenum oxide catalysts are of particular industrial importance. 

In the petroleum (qv) industry hydrogen bromide can serve as an alkylation catalyst. It is claimed as a catalyst in the controlled oxidation of aHphatic and ahcycHc hydrocarbons to ketones, acids, and peroxides (7,8). AppHcations of HBr with NH Br (9) or with H2S and HCl (10) as promoters for the dehydrogenation of butene to butadiene have been described, and either HBr or HCl can be used in the vapor-phase ortho methylation of phenol with methanol over alumina (11). Various patents dealing with catalytic activity of HCl also cover the use of HBr. An important reaction of HBr in organic syntheses is the replacement of aHphatic chlorine by bromine in the presence of an aluminum catalyst (12). Small quantities of hydrobromic acid are employed in analytical chemistry. 

In the presence of metallic copper, metallic silver, or a copper-silver alloy used in the form of gauze or as metal deposited on a low surface area inert support, methanol can be dehydrogenated to formaldehyde at 400—500°C. 

Although this pure dehydrogenation reaction is not practiced commercially, at least two processes exist in which methanol is dehydrogenated to formaldehyde in the presence of air. 

Although ethylene is produced by various methods as follows, only a few are commercially proven thermal cracking of hydrocarbons, catalytic pyrolysis, membrane dehydrogenation of ethane, oxydehydrogenation of ethane, oxidative coupling of methane, methanol to ethylene, dehydration of ethanol, ethylene from coal, disproportionation of propylene, and ethylene as a by-product. 

Dehydrogenation processes in particular have been studied, with conversions in most cases well beyond thermodynamic equihbrium Ethane to ethylene, propane to propylene, water-gas shirt reaction CO -I- H9O CO9 + H9, ethylbenzene to styrene, cyclohexane to benzene, and others. Some hydrogenations and oxidations also show improvement in yields in the presence of catalytic membranes, although it is not obvious why the yields should be better since no separation is involved hydrogenation of nitrobenzene to aniline, of cyclopentadiene to cyclopentene, of furfural to furfuryl alcohol, and so on oxidation of ethylene to acetaldehyde, of methanol to formaldehyde, and so on. 

Reaction of nitro-2f/-chromene derivatives 134 with 135 in methanol at room temperature afforded a mixture of the Z-isomer 136 and tricyclic compound 137, which could be formed by denitrocyclization reaction of the corresponding primarily formed E-isomer and the following dehydrogenation (Eq. 15). The structural identification was based on the MS and H-NMR, however, it is not sufficiently documented and similar examples are not known (91IJC(B)297). 

Formaldehyde, produced by dehydrogenation of methanol, is used almost exclusively in die syndiesis of phenolic resins (Fig. 7.2). Iron oxide, molybdenum oxide, or silver catalysts are typically used for preparing formaldehyde. Air is a safe source of oxygen for this oxidation process. 

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