Ethanol, catalytic oxidation

Two possible interesting acetals are diethoxy ethane or butane. They can be synthesized by the catalyzed reaction of acetaldehyde (obtained by ethanol catalytic oxidation) with two molecules of ethanol, or by the catalyzed reaction of butanal (obtained by catalytic conversion of two molecules of acetaldehyde) with two molecules of ethanol. To achieve a one-pot synthesis, a key aspect for a possible commercial development, it is necessary to develop suitable multifunctional catalysts. Research on these aspects is in progress [63]. 

Manufactured by the liquid-phase oxidation of ethanal at 60 C by oxygen or air under pressure in the presence of manganese(ii) ethanoate, the latter preventing the formation of perelhanoic acid. Another important route is the liquid-phase oxidation of butane by air at 50 atm. and 150-250 C in the presence of a metal ethanoate. Some ethanoic acid is produced by the catalytic oxidation of ethanol. Fermentation processes are used only for the production of vinegar. 

Another metal that has attracted interest for use as electrode material is rhodium, inspired by its high activity in the catalytic oxidation of CO in automotive catalysis. It is found that Rh is a far less active catalyst for the ethanol electro-oxidation reaction than Pt [de Souza et al., 2002 Leung et al., 1989]. Similar to ethanol oxidation on Pt, the main reactions products were CO2, acetaldehyde, and acetic acid. Rh, however, presents a significant better CO2 yield relative to the C2 compounds than Pt, indicating a... 

At this stage, it should be pointed out that modihcation of a Pt-Sn catalyst by Ru atoms increases cell performance (and hence catalytic activity with regard to ethanol electro-oxidation), but has no effect on the OCV or on product distribution [Rousseau et al., 2006]. It seems, then, that the oxidation mechanism is the same on Pt-Sn and Pt-Sn-Ru, which supports the proposition that Ru allows OH species to be produced when the anode potential is increased and noncatalytically active tin oxides are formed. 

The catalytic oxidation of ethanol is catalyzed by Pd-Al203 at 30 °C, and is considered to be of first order with respect to oxygen (Hopper et al., 2001 Ramachandran and Chaudhari, 1980). The rate constant for this reaction is km = 0.0177 cm3/(g s). The complete oxidation of ethanol is represented by the following reaction ... 

Traditionally, ethanol has been made from ethylene by sulfation followed by hydrolysis of the ethyl sulfate so produced. This type of process has the disadvantages of severe corrosion problems, the requirement for sulfuric acid reconcentration, and loss of yield caused by ethyl ether formation. Recently a successful direct catalytic hydration of ethylene has been accomplished on a commercial scale. This process, developed by Veba-Chemie in Germany, uses a fixed bed catalytic reaction system. Although direct hydration plants have been operated by Shell Chemical and Texas Eastman, Veba claims technical and economic superiority because of new catalyst developments. Because of its economic superiority, it is now replacing the sulfuric acid based process and has been licensed to British Petroleum in the United Kingdom, Publicker Industries in the United States, and others. By including ethanol dehydrogenation facilities, Veba claims that acetaldehyde can be produced indirectly from ethylene by this combined process at costs competitive with the catalytic oxidation of ethylene. 

Since 1990, the present authors and coworkers have observed CTL during the catalytic oxidation of various organic vapors ethanol, butanol, acetone, n-... 

The present authors and coworkers observed intense CTL emission during the catalytic oxidation of ethanol or acetone vapor on a heated aluminum oxide powder [8]. This phenomenon was applied to the consumption-free CTL-based sensor for detecting combustible vapors. The CTL response was fast and reproducible for a change in concentration of a sample vapor in air. CTL emission has three distinct features ... 

The second CTL mechanism is luminescence from the excited species produced in the course of catalytic oxidation. One of the excited species, formaldehyde (HCHO), is produced during the catalytic oxidation of ethanol, and the reaction process is depicted schematically in Fig. 5. The HCHO is finally oxidized to CO2 and H2O in an atmosphere containing oxygen. 

Figure 6 shows the CTL spectra observed during the catalytic oxidation of ethanol on y-alumina, calcium carbonate, and barium sulfate. The profiles of these broad spectrum components are similar to each other, and they peak in the vicinity of 420 nm. The profiles of the CTL spectra from the excited species depend on the kind of catalyst. Fine spectra are observed in the non-porous BaSC>4 catalyst. In Fig. 6b, the thin curves denote the fine spectrum components obtained by the peak-fitting technique. 

Fig. 6 CTL spectra by the catalytic oxidation of ethanol on a y-ALCh, b CaCC>3, c BaS04 catalysts at 500 °C [20]. d Comparison of the CTL spectrum with the theoretical emission lines from the excited HCHO [27]...

Ethanol is decomposed to form ether and ethylene on the alumina catalyst. Formaldehyde and formic acid are produced by the catalytic oxidation of ethanol in an atmosphere containing oxygen. In the course of this catalytic oxidation on a certain kind of catalyst, the excited HCHO is produced and the CTL emission is observed in its relaxation process. 

Fig. 9 Temperature dependence of CTL intensity (circles) and relative partial pressure of the reaction product CO2 (triangles) by catalytic oxidation on the y-AI2O3 catalyst in a ethanol/air b acetone/air...

Similar to the catalyst of the catalytic thermometry sensor, the catalytic activity of the CTL-based sensor depends not only on the kind of catalyst material and the surface-to-volume ratio of the powder but also on the preparation procedure of the powder. In considering these conditions, a detailed comparison of the CTL catalytic activity has not been reported so far. The present authors and coworkers observed the CTL emission by ethanol vapor on y-aluminum oxide, barium sulfate, calcium carbonate, and zirconium oxide at a few hundred degrees. On the other hand, CTL emission is not observed during the catalytic oxidation on metal and semiconductive materials, e.g., tin oxide, zinc oxide, and copper oxide. 

CDPIO-Ag Suggest a rate law and mechanism for the catalytic oxidation of ethanol over tantalum oxide when adsorption of ethanol and oxygen take place on different sites. [2nd ed. P6-17]... 

C2H,0H Vapor phase catalytic oxidation Heterogeneous Ethanol and preheated air are passed over Ag gauze at — 300°-575 C. and atmospheric pressure... 

Yu Z, Chuang SSC (2007) In situ IR study of adsorbed species and photo-generated electrons during photo-catalytic oxidation of ethanol on TiO. J Catal 246 118... 

This process was elaborated as a heterogeneously catalyzed variation by Asahi Chemicals (Japan) in order to open a new route to diisocyanates, not depending on the use of phosgene [120, 134]. Ethyl phenylcarbamate, which in a first step is obtained by catalytic oxidative carbonylation of aniline, CO, oxygen, and ethanol (eq. (17)), is condensed with aqueous formaldehyde to yield methylene diphenyl diurethane. Thermal decomposition leads to methylene diphenyl diisocyanate (MDI), which is one of the most important intermediates for the industrial manufacture of polyurethanes (eq. (18)). The yields and selectivities of the last reaction step seem to be the main reasons why this process is still inferior to the existing ones. 

Recently, Sen has reported two catalytic systems, one heterogeneous and the other homogeneous, which simultaneously activate dioxygen and alkane C-H bonds, resulting in direct oxidations of alkanes. In the first system, metallic palladium was found to catalyze the oxidation of methane and ethane by dioxygen in aqueous medium at 70-110 °C in the presence of carbon monoxide [40]. In aqueous medium, formic acid was the observed oxidation product from methane while acetic acid, together with some formic acid, was formed from ethane [40 a]. No alkane oxidation was observed in the absence of added carbon monoxide. The essential role of carbon monoxide in achieving difficult alkane oxidation was shown by a competition experiment between ethane and ethanol, both in the presence and absence of carbon monoxide. In the absence of added carbon monoxide, only ethanol was oxidized. When carbon monoxide was added, almost half of the products were derived from ethane. Thus, the more inert ethane was oxidized only in the presence of added carbon monoxide. 

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