Ethanol oxidative dehydrogenation

Andrade Sales, E., Oliveira de Souza, T., Costa Santos, R., et al. (2005). N2O decomposition coupled with ethanol oxidative dehydrogenation reaction on carhon-supported copper catalysts promoted hy palladium and cobalt, Catal. Today, 107-108, pp. 114—119. 

There are two ways to produce acetaldehyde from ethanol oxidation and dehydrogenation. Oxidation of ethanol to acetaldehyde is carried out ia the vapor phase over a silver or copper catalyst (305). Conversion is slightly over 80% per pass at reaction temperatures of 450—500°C with air as an oxidant. Chloroplatinic acid selectively cataly2es the Uquid-phase oxidation of ethanol to acetaldehyde giving yields exceeding 95%. The reaction takes place ia the absence of free oxygen at 80°C and at atmospheric pressure (306). The kinetics of the vapor and Uquid-phase oxidation of ethanol have been described ia the Uterature (307,308). 

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

The same samples, after a pretreatment in flowing oxygen (10%) at 625 K, were used as catalysts for the oxidative dehydrogenation of ethanol and methanol in the same reactor. The reaction mixture consisted of O2 (3 or 5%), methanol vapor (3%) or ethanol vapor (5%) and He (balance), all delivered by Tylan mass flow controllers or vaporizer flow controllers. Products were analyzed by gas chromatography. The catalysts exhibited no induction period and their activities were stable over many days and over repeated temperature cycles. 

While spectroscopic studies attempt to account for the formation of CH4, CO and C02, they do not show the pathway for the formation of large amounts of H2 in the POE reaction even at lower temperature, around 300 °C.108 It is possible that the acetaldehyde formed by the oxidative dehydrogenation could be partially oxidized to H2 and carbon oxides (see eqns (23) and (24) and Fig. 9). Participation of these reactions could account for the formation of large amounts of H2 in the partial oxidation of ethanol. Based on the experimental observation and thermodynamics of the reactions, a reaction pathway for the partial oxidation of ethanol has been proposed and it is shown in Scheme 5. The proposed pathway accounts for the experimental observation of large amount of H2 and C02 in the partial oxidation of ethanol even at lower temperatures, around 300 °C with traces of acetaldehyde and CO as well as small amount of methane.108... 

Catalysts were prepared by the incipient wetness impregnation. PdZn-alloy formation favors the oxidative dehydrogenation of ethanol to acetaldehyde rather than CH4 thereby producing H2 with high yield in the OSR at low temperatures... 

Oxidative Dehydrogenation of Ethanol to Acetaldehyde Nonporous Ag membranes... 

Figure 1. First order plots based on hydrogen evolution for the oxidative dehydrogenation of ethanolamine (EA), 2-(2-aminoethylamino)ethanol (AEAE), 3-amino-1-propanol (AP), 2-(methylamino)ethanol (MAE) and benzyl alcohol (BA) over chromia-promoted copper.

Acetaldehyde. The industrial production of acetaldehyde by the hydration of acetylene has lost its importance with the introduction of more economical petrochemical processes (dehydrogenation of ethanol, oxidation of ethylene see Section 9.5.2). At present it is practiced only in a few European countries where relatively cheap acetylene is still available.86-88... 

In order to assess the synthetic potential of enzymatic oxidations for organosilicon chemistry, the (hydroxyalkyl)silanes 95, 97 and 99 have been studied for their oxidation (dehydrogenation) with horse liver alcohol dehydrogenase (HLADH E.C. l.l.l.l)79. For this purpose, these compounds were incubated with HLADH in a TRIS-HC1 buffer/THF system in the presence of NAD+. As monitored spectrophotometrically (increase of absorbance of the NADH formed), the (2-hydroxyethyl)silane 97 and the (3-hydroxypropyl)silane 99 were better substrates for HLADH than ethanol, whereas the related (hydroxymethyl)silane 95 was not a substrate under the experimental conditions used. Interestingly, the corresponding carbon analogue 101 was found to be accepted by HLADH. On the other hand, the (2-hydroxyethyl)silane 97 was found to be a better... 

Fig. 15. Deactivation of Fe2(MoQ4)3 and a mechanical mixture (50 50) of Fe2(Mo04>3 + a-Sb2C>4 during the oxidative dehydrogenation of ethanol to acetaldehyde. The amount of Fe2(MoC>4)3 is identical (200 mg) in both experiments. T = 350°C ethanol/02/N2 2/1/20. Gas flow rate 50 ml/min.

Acetaldehyde. Acetaldehyde has been made from ethanol by dehydrogenation and by catalytic hydration of acetylene. Today direct oxidation of ethylene in the liquid phase catalyzed by palladium and copper has replaced these earlier methods. Figure 10.14 shows an ethylene-to-acetaldehyde unit based on this last route. 

It is assumed that also the oxidative dehydrogenation of alcohols like methanol, ethanol and isopropanol with the polyPc goes through hydrogen abstraction at the oxygen bond. The polymers prepared from TCB and CU2CI2 in bulk were treated at 393 K... 

The conversion of ethanol is carried out in the presence of gas-phase oxygen molecules - oxidative dehydrogenation [47,48] - and the oxygen vacancies created in step 3a of Scheme 7.1 are regenerated by gas-phase oxygen. The dehydration of ethanol to ethylene and water does not consume surface oxygen atoms (step 3b). 

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