Methanol/amine dehydrogenative

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... 

Oxidative dehydrogenation reactions of alcohols and amines are widespread in enzymatic biochemistry, and are of potential importance with regard to the operation of fuel cells based on simple alcohols such as methanol. The nature of products, and their rates of formation, may vary depending on the reaction conditions, and a role of metal ions has been recognized. The oxidation of amines may lead to a variety of products (nitriles, nitro species, etc.) although dehydrogenated diimine products are obtained quantitatively when the oxidation of the amine occurs via coordination to metal centers. A review is available on the mechanisms of oxidative dehydrogenations of coordinated amines and alcohols (93). 

Hydrogenation and dehydrogenation employ catalysts that form unstable surface hydrides. Transition-group and bordering metals such as Ni, Fe, Co, and Pt are suitable, as well as transition group oxides or sulfides. This class of reactions includes the important examples of ammonia and methanol syntheses, the Fischer-Tropsch and oxo and synthol processes and the production of alcohols, aldehydes, ketones, amines, and edible oils. 

Copper-catalysts promoted with i) other group VIA or VIIIA metals and ii) alcaline or alcaline earth elements (IA or IIA) are used for selective hydrogenation of various organic compounds (1). Moreover Cu(Co) Zn-Al catalysts were extensively studied for the synthesis of methanol and of light alcohols (2,3). More recently, due to the development of fine chemical processes, detailed studies of copper catalysts were carried out in order to show, like for noble metals, the effect of supports (SMSI), of promoters and of activation-on metal dispersion or reduction, on alloy formation... For example modified copper catalysts are known for their utilization in the dehydrogenation of esters (4-6), in the hydrolysis of nitriles (7), in the selective hydrogenation of nitriles (8), in the amination of alcohols (9)... 

Table 1 shows that methyl dodecanoate is easily converted into amine in the presence of CuCr deposited on alumina or on titania. Nevertheless one can observe that the methylation reaction is rather difficult and favoured by alumina. Moreover, a significant increase of N-dimethyl dodecylamine is obtained when the reaction is carried out with a large excess of hydrogen. Due to the mechanism of the reaction this is unexpected indeed it is generally considered that the methylation of primary amine with methanol requires i) the dehydrogenation of alcohol into a carbonyl compound and ii) a further reaction of this compound with primary amine or secondary amine via imine or enamine intermediates. 

More typical for angle strained cycloalkynes is the dehydrogenation of alcohols, amines and thiols208. The reaction of (31) with methanol to yield the alkene (63) and formaldehyde was investigated in detail. On the basis of rate laws and H/D kinetic isotope effects the following reaction mechanism was proposed 208,212>. 

Supported copper-based catalysts are active for a great variety of reactions and there have been many fundamental studies of their catalytic and solid state properties. Among them, the oxidation of hydrocarbons and CO (1), alkanes (2) and alcohols (3) dehydrogenation, hydrogenation of ketones (4), allyl alcohols and a- and 6-unsaturated aldehydes and ketones (5), alcohol amination (6), low temperature water gas shift (7). methanol synthesis (8), oxidative condensation of methanol (9), hydrolysis of acrylonitrile to acrylamide (10), and removal of NOx pollutants (11). 

The heterogeneous catalysis process requires the formulation of a multifunctional catalyst which at a first approximation presents (i) acidic properties (amine adsorption, dehydration,...) and (ii) a hydro-dehydrogenating function (methanol dehydrogenation, hydrogenation of imine and enamine intermediates). 

It has been found that besides reductive amination copper catalysts are also active in the dehydrogenation of methanol to methyl formate. The dehydrogenation of methanol can be considered as a reversible reaction step of the methanol synthesis. In the methanol synthesis over CuO-ZnO-AbOs catalysts both ionic and metallic copper has been suggested as the active site. It has been found that the catalyst containing the maximum amount of ionic copper dissolved in the zinc oxide was the most active in the methanol synthesis. ... 

Literature data discussed above indicate that in the alkylation of a primary amine with an alcohol over a copper-containing catalyst the first and ratedetermining step of the reaction is the dehydrogenation of the alcohol. However, the nature and the oxidation state of the active site, i.e. Cu or Cu" is still debated, although more and more data indicate that ionic copper species may play an important role in the dehydrogenation of methanol. ... 

The use of supported copper has been explored in a number of reactions with good conunercial potential. Some examples are oxidative dehydrogenation (already mentioned), dehydrogenation of esters (Evans et al., 1974 Agarwal et al., 1987 Chen et al., 1989), hydrolysis of nitriles (Lee et al., 1988), amination of esters (Barrault et al., 1991), and one-step synthesis of dissymmetric amines [R2NCH3 or RN(CH3)2] from the corresponding nitriles, methanol, and hydrogen (Barrault et al., 1993). 

Zweifel T, Naubron JV, Griitzmacher H (2009) Catalyzed dehydrogenative coupling of primary alcohols with water, methanol, or amines. Angew Chem frit Ed 48 559... 

Glorius and co-workers reported an alternative approach for the synthesis of formamides by dehydrogenative coupling of methanol with amines. The dehydrogenation of methanol is energetically disfavoured AH=84 kJmol ) compared to ethanol and higher alcohols [AH = 68 kj moP ) and few reports of couplings with methanol exist presumably for this reason. ... 

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