Dehydrogenation of methanol

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. 

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). 

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. 

Normalization by Oxygen Uptake of the Rates of Oxidative Dehydrogenation of Methanol and Ethanol... 

The oxidative dehydrogenation of methanol to formaldehyde is a model reaction for performance evaluation of micro reactors (see description in [72]). In the corresponding industrial process, a methanol-air mixture of equimolecular ratio of methanol... 

Figure 3.36 Arrhenius plot for the oxidative dehydrogenation of methanol to formaldehyde performed in a micro reactor [72].

The oxidative dehydrogenation of methanol to formaldehyde was choosen as model reaction by BASF for performance evaluation of micro reactors [1, 49-51, 108]. In the industrial process a methanol-air mixture of equimolecular ratio of methanol and oxygen is guided through a shallow catalyst bed of silver at 150 °C feed temperature, 600-650 °C exit temperature, atmospheric pressure and a contact time of 10 ms or less. Conversion amounts to 60-70% at a selectivity of about 90%. 

Desai SK, Neurock M, Kourtakis K. 2002. A periodic density functional theory study of the dehydrogenation of methanol over Pt(lll). J Phys Chem B 106 2559-2568. 

Okamoto Y, Sugino O, Mochizuki Y, Ikeshoji T, Morikawa Y. 2003. Comparative study of dehydrogenation of methanol at Pt(lll)/water and Pt(lll)/vacuum interfaces. Chem Phys Lett 377 236-242. 

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. 

The photocatalytic activity of [Ir(SnCl3)5FI]3 in the dehydrogenation of methanol to give dimethoxymethane and dihydrogen is described.80,81 Tra .s-[IrClF[(SnCl3 )4]3 and trans-... 

This benzyl-methyl transfer reaction appears to be general in these systems. This process could involve the dehydrogenation of methanol on the surface of palladium, which produces formaldehyde. The formaldehyde could than add to the nitrogen atom to produce a quaternary carbinolamine (Scheme 4.92). 

Partial dehydrogenation of methanol can yield formaldehyde and this can potentially react with itself or unconverted methanol to yield another commonly reported by-product of methanol decomposition, methyl formate 1,12... 

Oxidative Dehydrogenation of Methanol Porous AI203 membranes... 

Oxidative dehydrogenation of methanol. Silver catalyst deposited in the pores of the membrane (66 wt% Ag). 

Lefferts, L., J. G, van Ommen and J. R. H. Ross, 1986, The oxidative dehydrogenation of methanol to formaldehyde over silver catalysts in relation to the oxygen-silver interaction. Appl. Catal. 23 385-401... 

Methanol dehydrogenation to ethylene and propylene. In some remote ioca-tions, transportation costs become very important. Moving ethane is almost out of the question. Hauling propane for feed or ethylene itself in pressurized or supercooled vessels is expensive. Moving naphtha or gas oil as feed requires that an expensive olefins plant with unwanted by-products be built. So what s a company to do if they need an olefins-based industry at a remote site One solution that has been commercialized is the dehydrogenation of methanol to ethylene and propylene. While it may seem like paddling upstream, the transportation costs to get the feeds to the remote sites plus the capital costs of the plant make the economics of ethylene and its derivatives okay. 

Dehydrogenation of methanol, dehydrogenation of propane, metathesis of ethylene and butylene, and cat crackers. (Other crackers in refineries produce olefins too.)... 

Two major pathways for CSRM have been suggested using copper-based catalysts (i) a decomposition-WGSR sequence and (ii) dehydrogenation of methanol to methyl formate (Equation 6.7). 

Ab initio pseudopotential study of dehydrogenation of methanol on oxygen-modified Ag(llO) surface has been described by Sun et al. [277]. 

It includes the steam reforming of methane over a nickel catalyst to synthesis gas followed by the copper-catalyzed transformation of the latter to methanol (see Section 3.5.1). Finally, formaldehyde is produced by oxidative dehydrogenation of methanol. 

As significant amounts of hydrogen are formed, it has long been assumed that formaldehyde is essentially formed by dehydrogenation of methanol, accelerated by the combustion of a large part of the liberated hydrogen. Recently, however, several authors explain the kinetics on the basis of direct interaction of methanol with oxygen. 

A fundamental issue in selective oxidation is the activation of C—H bonds that is always required for ODH (oxidative dehydrogenation) and oxo-functionalization and is detrimental for epoxidation. A particular case is silver [70] as catalyst, which can achieve highly selective epoxidation of ethene as well as highly selective dehydrogenation of methanol to formaldehyde although it is notably in both cases only the same metallic catalyst. We will return to this case in the next section, which deals with the multiplicity of active oxygen species. 

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