Alcohols, catalytic dehydrogenation

Catalytic dehydrogenation of alcohol is an important process for the production of aldehyde and ketone (1). The majority of these dehydrogenation processes occur at the hquid-metal interface. The liquid phase catalytic reaction presents a challenge for identifying reaction intermediates and reaction pathways due to the strong overlapping infrared absorption of the solvent molecules. The objective of this study is to explore the feasibility of photocatalytic alcohol dehydrogenation. 

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 ... 

KW Rosenmund, F Heise. Oxidative catalytic dehydrogenation of alcohols. V. Catalytic reduction of esters and aldehydes. Ber 54B 2038, 1921. 

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. 

In this chapter we describe recent developments in the catalytic dehydrogenation of alcohols and related reactions as well as the organometalUc chemistry of rhodium and iridium based on the oxygenation of coordinated alkenes. 

All data on the kinetics of the catalytic dehydrogenation of hydrocarbons, amines, and alcohols obtained in our laboratory are expressed by the equation 12) ... 

Recently the author (3, 74) has proposed a duplet model for the catalytic dehydrogenation of open chains (Fig. 18). Here four atoms of the catalyst are active, in the valleys between which are situated four reacting atoms. The intermediate complex is similar to a surface alloy. The reacting atoms do not get into the valleys simultaneously but in stages, for example, for the dehydrogenation of alcohol ... 

The anodic oxidation of secondary alcohols to the corresponding ketones is generally inferior to the catalytic dehydrogenation methods. Electrochemical syntheses are therefore of interest only in special cases. An example of this is the regioselective oxidation of an endo-hydroxyl group in 1,4,3,6-dianhydrohexitols 306) ... 

A more recent process allows the manufacture of ethyl acetate from ethyl alcohol without the use of acetic acid or any other cofeedstocks. In the process (Fig. 1), ethyl alcohol is heated and passed through a catalytic dehydrogenation reactor where part of the ethyl alcohol is dehydrogenated to form ethyl acetate and hydrogen. 

Another commercial aldehyde synthesis is the catalytic dehydrogenation of primary alcohols at high temperature in the presence of a copper or a copper-chromite catalyst. Although there are several other synthetic processes employed, these tend to be smaller scale reactions. For example, acyl halides can be reduced to the aldehyde (Rosemnund reaction) using a palladium-on-barium sulfate catalyst. Formylation of aryl compounds, similar to hydrofomiylation, using HCN and HQ (Gatterman reaction) or carbon monoxide and HQ (Gatterman-Koch reaction) can be used to produce aromatic aldehydes. 

Ethoxyacetaldehyde, an aldehyde ether, is readily prepared in 35% yield from Cellosolve by the vapor-phase dehydrogenation technique. Similar techniques are employed for the catalytic dehydrogenation of secondary alcohols (method 181). 

Primary alcohols are oxidized to aldehydes or acids, and secondary alcohols are oxidized to ketones. Tertiary alcohols resist oxidation, unless they are dehydrated in acidic media to alkenes, which are subsequently oxidized. The conversion of alcohols into carbonyl compounds can be achieved by catalytic dehydrogenation or by chemical oxidation. Catalytic dehydrogenation is especially of advantage with primary alcohols, because it prevents overoxidation to carboxylic acids. Examples are tabulated in equations 223-227 and 265-268. 

Catalytic dehydrogenations of primary alcohols are achieved by passing vapors of the alcohols at 275-350 °C over a catalyst, usually supported on asbestos, silica gel, pumice, etc. Ethyl alcohol is converted into acetaldehyde in 88% yield at 93% conversion by passing it at 275 °C over a mixture of oxides of copper, cobalt, and chromium on asbestos [1135]. 

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