Dehydrogenation, methanol over copper

Dehydrogenation of methanol over copper containing catalysts at the temperature range 200—400° C is achieved by two Hnearly indepen dent stepwise channels... 

Minyukova TP, Simentsova II, Khasin AV et al (2002) Dehydrogenation of methanol over copper-containing catalysts. Appl Catal A Gen 237 171-180... 

The conversion of ethanol to acetaldehyde can be effected by dehydrogenation over copper at 250-300°C or by (partially) oxidative dehydrogenation over silver at 450-500°C. However, this route was largely superseded by the Wacker process for the direct oxidation of ethylene in aqueous solutions of Pd/Cu chlorides. Rhone-Poulenc and BP have also patented potential processes for the homologation of methanol to acetaldehyde ... 

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. 

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. 

Introduction.—The oxidative dehydrogenation of alcohols to aldehydes and ketones over various catalysts, including copper and particularly silver, is a well-established industrial process. The conversion of methanol to formaldehyde over silver catalysts is the most common process, with reaction at 750—900 K under conditions of excess methanol and at high oxygen conversion selectivities are in the region 80—95%. Isopropanol and isobutanol are also oxidized commercially in a similar manner. By-products from these reactions include carbon dioxide, carbon monoxide, hydrogen, carboxylic acids, alkenes, and alkanes. 

A test case is the investigation of selective oxidation of methanol to formaldehyde over metallic copper. This process occurring as dehydrogenation and/or oxydehydrogenation was studied extensively by in-situ NEXAFS and earlier by surface science. These studies brought about the relevance of unique oxygen species termed as sub oxide ° for the selective catalytic reaction. Conventional copper oxides were identified to catalyse the total oxidation and bare metal was found to be inactive. A target for in-situ XPS was thus the search for a sub oxide, the confirmation of its relevance for selective oxidation and the... 

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. ... 

All of the above results indicate that ionic copper species are active in the methanol synthesis over Cu-ZnO-AbOs catalysts. Contrary to that, in the dehydrogenation of cyclohexanol to cyclohexanone over reduced Cu-ZnO-AbOa catalysts a correlation was found between activity and reversible carbon monoxide uptake measured by IR spectroscopy, therefore, it was proposed that metallic copper species are the probable active sites in this dehydrogenation reaction. ... 

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. ... 

---