Gas phase, oxidation processes

Isobutjiene [115-11-7] or tert-huty alcohol can be converted to methacrylic acid in a two-stage, gas-phase oxidation process via methacrolein as an intermediate. The alcohol and isobutjiene may be used interchangeably in the processes since tert-huty alcohol [75-65-0] readily dehydrates to yield isobutjiene under the reaction conditions in the initial oxidation. Variations of this process have been commercialized by Mitsubishi Rayon and by a joint venture of Sumitomo and Nippon Shokubai. Nippon Kayaku, Mitsui Toatsu, and others have also been active in isobutjiene oxidation research. 

After several years and millions of dollars were spent to develop a homogenous gas-phase oxidation process to produce propylene oxide, the development was terminated. This was a reaction classified as a... 

The important role Transmission Electron Microscopy (TEM) can play in this process is demonstrated on the development of an oxidation catalyst for the production of acrylic acid. Acrylic acid is produced by BASF in quantities of several 100.000 tons per year in a two step gas phase oxidation process starting from propene, which is oxidised to acrolein in the first step and then further oxidised to acrylic acid in a second step, each step requiring a special developed catalyst. Acrylic acid is used as a base material for the production of superabsorbents for nappies, dispersions and emulsions for adhesives and construction materials. 

This paper is concerned with the effect of amines on intermediates formed during the oxidation of simple organic molecules. Amines were added first to two systems in which peroxides are known to be formed in high yield to see whether they have any effect on the kinetics of the later reactions between the fuel and oxygen secondly, amines were added to two peroxides under conditions where the amines act as inhibitors of gas-phase oxidation processes. 

The oxidation of aromatic hydrocarbons originating from coal is one of the first organic gas phase oxidation processes carried out on an industrial scale. The development of these processes was initiated by the discovery that the V2Os catalyst used for the oxidation of sulphur dioxide was also applicable to the partial oxidation of benzene to maleic anhydride and naphthalene to phthalic anhydride. Remarkably, V2Os-based catalysts are still used in these processes today as they appear superior to any other type of catalyst. 

H. Niki, in Homogeneous Gas Phase Oxidation Processes in the Troposphere, E. D. Goldberg, Ed., Springer-Verlag, Berlin, 1982, pp. 301-312. 

The overwhelming majority of biomimetics operate in liquid. Their activity depends on the origin of solvents, reaction mixture and cell effects. Gas-phase oxidation processes are less dependent on these effects and in the first approximation can be considered as oxidation under quasi-ideal conditions. It goes without saying that enzymatic reactions do not proceed in gases. However, it is possible to simulate catalytic functions in the gas phase. This simplifies the decoding of the reaction mechanism, not complicated by factors accompanying the liquid-phase oxidation [1],... 

The propene oxidation process is globally conducted on a 5 million t/a scale. A new gas-phase oxidation process of propene to propene oxide using hydrogen peroxide would save the use of solvents and is expected to have higher selectivity. 

However, the mechanism through which this anomaly is sequestered inside the solids is not clear. It is postulated that, as the nebular disk evolved, this isotopically enriched ice migrates inward (and mixes with the isotopically normal water) and volatilizes in the inner nebula, driving gas-phase oxidation processes to form solids, during which the isotopic anomaly is passed to condensates (Yurimoto Kuramoto 2004). A major issue is that the silicate materials do not show the required level of heavy-oxygen fractionation, so another mass-independent mechanism is required. 

Lerou, J.J. Harold, M.P. Mills, P.L. Industrial heterogeneous gas-phase oxidation processes. Proceedings of the First Annual NIOK Conference, van Santen, R. World Scientific Publishing Amsterdam, 1994. 

In selective gas-phase oxidation processes the conversion often does not reach 100%, in order to reduce total oxidation. This means that some starting material and/or intermediate products are present in the reaction mixture. Following separation, these may be recycled into the reaction to avoid yield losses. Although the above may seem obvious, an economical and efficient recycling procedure is not always simple, depending on the volatility of the components involved and the concentration of any unwanted by-products. In practice, a purge is included in the recycle to maintain an equilibrium concentration of by-products. 

In gas-phase oxidation processes at temperatures above 300 °C, as used for the production of phthalic anhydride, maleic anhydride and naphthalic anhydride, careful selection of a suitable catalyst ensures that the smallest possible amount of by-product arises. 

The electrocatalytic oxidation of alkenes has similarly been the subject of extensive study, as part of the development of fuel cell technology. The overall reaction is thought to be similar to gas phase oxidation processes, involving both adsorption of the olefin and oxidative adsorption of water molecules, the latter forming intermediate species which react with the... 

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