Methanol heterogeneous oxidation

Some control over the spHt between methyl radical oxidation (to HCHO) and dimerization in heterogeneous oxidation can be achieved by varying conditions (116). For homogeneous oxidation, an efficiency of 70—80% to methanol has been claimed at 8—10% conversions (110). This is the high end of the reported range and is controversial. Even so, such technology appears unlikely to be competitive for regular commercial use until further advances are made (117). The critical need is to protect the products from further oxidation (118). [Pg.341]

Fig. 51.1. Schematic of the feedback method of measuring heterogeneous standard rate constant at titantium nitride thin film. The UME is poised at a potential where ferrocene methanol is oxidized at a diffusion-controlled rate (Et = 0.4 V). The substrate is biased at a potential so that it reduces the species being produced at the UME, thus controlling the feedback effect.

Metallic components have also been added to a variety of heterogeneous oxide catalysts, to introduce additional hydrogenation, dehydrogenation and hydrogen transfer processes during aldolization, ketonization or Tishchenko reactions. Examples include acetone (propanone) to 4-methyl-pentan-2-one, ethanol to acetone and methanol to methyl formate (methyl methanoate), e.g. [Pg.337]

The extensively studied reaction of methanol oxidation exemplifies both types of processes, dissociative dehydrogenation and heterogeneous oxidation. [Pg.727]

A well-pronounced dependence of the yield of DMTM products on the reactor surface material (quartz vs. stainless steel) at a short residence time ( 2s), especially strong at lower pressures, was observed in [91] (Fig. 3.14). Only at high pressures, close to 80 atm, the difference becomes insignificant. At this pressure, both materials provided nearly the same maximum yield of methanol, which was achieved, however, at different oxygen concentrations 3.5% O2 for the stainless steel reactor and 6—8% O2 for the quartz reactor (Fig. 3. 40). Such a sharp distinction can be explained not only by different rates of the heterogeneous activation of methane and decomposition of the products on these surfaces, but also by different rates of the heterogeneous oxidation of methane to deep-oxidation products, CO2 and H2O. [Pg.96]

It is well known that Rh(I) complexes can catalyze the carbonylation of methanol. A heterogenized catalyst was prepared by ion exchange of zeolite X or Y with Rh cations.126 The same catalytic cycle takes place in zeolites and in solution because the activation energy is nearly the same. The specific activity in zeolites, however, is less by an order of magnitude, suggesting that the Rh sites in the zeolite are not uniformly accessible. The oxidation of camphene was performed over zeolites exchanged with different metals (Mn, Co, Cu, Ni, and Zn).127 Cu-loaded zeolites have attracted considerable attention because of their unique properties applied in catalytic redox reactions.128-130 Four different Cu sites with defined coordinations have been found.131 It was found that the zeolitic media affects strongly the catalytic activity of the Cd2+ ion sites in Cd zeolites used to catalyze the hydration of acetylene.132... [Pg.257]

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