Vapor phase oxidation reactions

Prior to 1916, acetaldehyde was manufactured by the oxidation of alcohol in the liquid phase with bichromate and sulfuric add.1 Since that time it has been ade quite largely by the hydration of acetylene in sulfuric acid solutions activated with mercury salts. However, the relatively low price of ethanol in America has made the formation of acetaldehyde by vapor phase dehydrogenation or limited oxidation of the alcohol attractive commercially. To this end several methods have been proposed for conducting the transformation industrially. Developments of processes employing vapor phase oxidation reactions have all been based largely on the prindples disclosed by the early work, a considerable portion of which had been undertaken purely for the purpose of research and not industrialization. 

Vapor Phase Oxidation Reactions of the Fuel Generate Heat)... 

Phthalic anhydride, produced in Germany as early as 1916 and in other parts of the world in the 1920s, was nsed initially in the synthesis of indigo dyes. At first naphthalene was oxidized by chromic acid or olenm bnt, by a convenient accident, it was found that mercury catalyzed the oxidation reaction. Later work by BASF in Germany and H. D. Gibbs and C. Condover in the United States developed catalysts for the vapor phase oxidation reaction. 

The catalytic vapor-phase oxidation of propylene is generally carried out in a fixed-bed multitube reactor at near atmospheric pressures and elevated temperatures (ca 350°C) molten salt is used for temperature control. Air is commonly used as the oxygen source and steam is added to suppress the formation of flammable gas mixtures. Operation can be single pass or a recycle stream may be employed. Recent interest has focused on improving process efficiency and minimizing process wastes by defining process improvements that use recycle of process gas streams and/or use of new reaction diluents (20-24). 

Formaldehyde is readily reduced to methanol by hydrogen over many metal and metal oxide catalysts. It is oxidized to formic acid or carbon dioxide and water. The Cannizzaro reaction gives formic acid and methanol. Similarly, a vapor-phase Tischenko reaction is catalyzed by copper (34) and boric acid (38) to produce methyl formate ... 

Above about 250°C, the vapor-phase oxidation (VPO) of many organic substances becomes self-sustaining. Such oxidations are characterized by a lengthy induction period. During this period, peroxides accumulate until they can provide a source of new radicals to sustain a chain reaction. Once a critical threshold peroxide concentration is reached, the reaction accelerates very rapidly. 

Reactions of /l-Butane. The most important industrial reactions of / -butane are vapor-phase oxidation to form maleic anhydride (qv), thermal cracking to produce ethylene (qv), Hquid-phase oxidation to produce acetic acid (qv) and oxygenated by-products, and isomerization to form isobutane. 

Finally, selective hydrogenation of the olefinic bond in mesityl oxide is conducted over a fixed-bed catalyst in either the Hquid or vapor phase. In the hquid phase the reaction takes place at 150°C and 0.69 MPa, in the vapor phase the reaction can be conducted at atmospheric pressure and temperatures of 150—170°C. The reaction is highly exothermic and yields 8.37 kJ/mol (65). To prevent temperature mnaways and obtain high selectivity, the conversion per pass is limited in the Hquid phase, and in the vapor phase inert gases often are used to dilute the reactants. The catalysts employed in both vapor- and Hquid-phase processes include nickel (66—76), palladium (77—79), copper (80,81), and rhodium hydride complexes (82). Complete conversion of mesityl oxide can be obtained at selectivities of 95—98%. 

For the manufacturing of sulfosuccinic acid esters, which belong to a special class of surfactants, maleic acid anhydride is needed. Maleic acid anhydride is an important intermediate chemical of the chemical industry. Its worldwide output amounts to about 800,000 tons (1990) [64]. Maleic acid is produced by catalytic vapor phase oxidation process of benzene or n-C4 hydrocarbons in fixed bed or fluidized bed reactors according the following reaction equations. The heat of reaction of the exothermic oxidation processes is very high. 

There are several other routes to acetone of minor importance air oxidation of IPA reaction between IPAand acrolein for the production of allyl alcohol, with acetone as the by-product vapor phase oxidation of butane coproduction when IPA is oxidized yielding acetone and H2O2, hydrogen peroxide, the principal ingredient of bleach and by-product production from the manufacture of methyl ethyl ketone. 

In the 1960s, like almost all acetylene technology, the HCN/C2H2 route to acrylonitrile gave way to ammoxidation of, propylene. Thar word, ammoxidation, looks suspiciously like the contraction of two more familiar terms, ammonia and oxidation, and it is. When Standard of Ohio (Sohio) was still a company they developed a one-step vapor phase catalytic reaction of propylene with ammonia and air to give acrylonitrile. 

Ammonoxidation. The contraction of two terms, ammonia and oxidation, ammonoxidation is a one-step process involving vapor phase, catalytic reaction of propylene with ammonia and the,oxygen portion of air to give acrylonitrile. The ammonoxidation reaction is carried out at about 800°F and 30 psi. 

Pd and Cu ion containing zeolites catalyze the vapor phase oxidation of methylpyridines [129]. Thus, on PdCuNa-mordenite, 2-methylpyridine was oxidized to 2-pyridinecarbaldehyde with 40% yield. The reduced reactivity ratio of 2,6-dimethylpyridines to monomethylpyridines on zeolite catalysts compared to oxide catalysts, demonstrates the presence of steric control in these reactions. 

At a later stage of volcanism, volatile components are supplied from the magma and crystals of sulfur or hematite crystallize around volcanic fumaroles or in fissures of surrounding rocks. Compared with crystallization in pegmatite, the environment is much more open, and the crystals of sulfur and hematite grow due to the chemical reaction occurring when the components supplied in the vapor phase oxidize at the Earth s surface. This crystallization therefore corresponds to... 

Phenol can also be prepared by the decomposition of benzoic acid prepared by the oxidation of toluene.927,978 The process is an oxidative decarboxylation catalyzed by copper(II). An interesting feature of this reaction is that the phenolic hydroxyl group enters into the position ortho to the carboxyl group as was proved by 14C labeling.979 In the Dow process980 molten benzoic acid is transformed with steam and air in the presence of Cu(II) and Mg(II) salts at 230-240°C. A copper oxide catalyst is used in a vapor-phase oxidation developed by Lummus.981... 

Vapor-phase oxidation of toluene to benzaldehyde was studied with various Mo-, U—, and Sb-based mixed-oxide catalysts. The selectivity to benzaldehyde fell with increasing the toluene conversion. The best performances were obtained with Mo-P and U-Mo oxide catalysts the one-pass yield of benzaldehyde reached 40 mol% with a selectivity of about 60 mol%. The catalytic activity of the U-Mo oxides was more stable than that of the Mo-P oxides. The effects of the reaction variables on both the rate and selectivity were also studied. 

Catalytic Oxidation of Ethene to Acetaldehyde and Acetic Acid. -Evnin et al120 studied Pd-doped V2 Os catalysts for the vapor-phase oxidation of ethene to acetaldehyde in a heterogeneous type of Wacker process. From a mechanistic study they establish a redox mechanism with Pd both as the site of the ethene oxidation and of the reoxidation of the catalyst. On the basis of the role of the V4+ ions proposed by these authors, Forni and Gilardi121 substantiated this mechanism by adding tetra- and hexa-valent dopants to the V2 05 and studying the effects on the catalytic reaction. 

By their very nature, the vapor-phase oxidation processes result in the concentration of reaction heat in the catalyst zone, from which it must be removed in large quantities at high-temperature levels. Removal of heat is essential to prevent destruction of apparatus, catalyst, or raw material, and maintenance of temperature at the proper level is necessary to ensure the correct rate and degree of oxidation. With plant-scale operation and with reactions involving deep-seated oxidation, removal of heat constitutes a major problem. With limited oxidation, however, it may become necessary to supply heat even to oxidations conducted on a plant scale. 

Ethylene oxide is prepared industrially by the vapor phase oxidation of ethylene over a supported silver catalyst at elevated temperatures.49la c Application of this reaction to higher olefins results in complete oxidation of the olefin to carbon dioxide and water. In general, autoxidations of olefins are notoriously unselective because of the many competing reactions of the intermediate peroxy radicals in these systems. 

Hodevar et al. investigated the action of Ce. Cu 02-M (0-05 < x < 0.20) for phenol oxidation (reaction temperature I50°C) encouraged by the fact that this kind of catalyst is active in the vapor-phase oxidation of organic pollutants and also by the fact that de Leitenburg et al. [33] used Cc02 Zr02-Cu0 catalyst in the wet-oxidation of acetic acid [58]. The activity and stability of this catalyst depend much... 

For each mole of acetaldehyde formed, one mole of palladium chloride was reduced to metallic palladium. To make this process industrially attractive, it must be conducted so that palladium chloride acts as a catalyst rather than as an oxidant—i.e., so that the metallic palladium formed is reoxidized to palladium chloride and can be reused for the principal reaction. This was the second fundamental recognition, which helped make this process commercial. The search for proper oxidants for metallic palladium was facilitated by the observation of Smidt et al. (34) that if cupric or ferric chloride were added to palladium chloride in the vapor-phase oxidation of ethylene to acetaldehyde, the acetaldehyde yield was increased. Therefore, these compounds were also used in the liquid-phase oxidation. In such a system, the following reactions will occur in the presence of oxygen and hydrochloric acid, the latter being formed by the reaction above (34). 

Ni0-Fe203 catalysts were used for the vapor phase oxidation of benzoic acid to phenol. This reaction took place in a stream of air at 400°C. A catalyst having a Ni Fe atomic ratio of one gave phenol in 88% selectivity at 100% conversion. 0 ... 

With a yield in the order of 75 percent, maleic acid can be made from furfural by a catalytic vapor phase oxidation with air at 270 °C [107]. The overall reaction is... 

Dynamic or kinetic Monte Carlo methods have been used to simulate the catalytic surface chemistry for various different reaction systems. The vapor-phase oxidation of CO to form CO2, however, has been the most widely studied due to its simplicity as well as its general applicability. Pioneering work by Ziff [82] and Zhdanov [83] shows the formations of interesting phase transitions as a function of the kinetics and lateral interactions. Many subsequent studies by various other groups extend the basic models to cover more general features. 

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