Propene oxide, from heterogeneous oxidation

The interest of Eastern European chemists in oxirans has been evident for many years, and from such sources have come a number of reviews on the production of these important raw materials. While concentrating mainly on ethene and propene oxides, one review deals more specifically with the types of heterogeneous catalysts employed in the processes." The latest edition of the Kirk-Othmer Encyclopedia contains an entry on epoxidation. ... 

Zeolite catalysts may also be regarded as mixed oxides, but the crystallographic structures differ from the solids discussed above in that active sites for catalysis occur within the open lattice framework. In consequence, rate data are not directly comparable with similar observations for other heterogeneous reactions since the preexponential factors are calculated and reported on a different basis. For completeness, however, it is appropriate to mention here that instances of compensation behavior on zeolite catalysts are known. Taylor and Walker (282) described such an effect for the decomposition reactions of formic acid and of methyl forma te on cation-exchanged 13X molecular sieves, and comparable trends may be found in data reported for reactions of propene on similar catalysts (283). 

More than 5 million tons of acrylonitrile are made annually. It is synthesized industrially by the gas-phase heterogeneous ammoxidation of propene. New catalysts based on Bi-Mo or V-Sb oxides may lead to manufacture of this important compound from propane. Although the new process has a considerably lower selectivity to acrylonitrile, the lower cost of the alkane makes it economically interesting (the propane method can cut at least 20 % from the production costs of the propene route). Nevertheless, increases in the selectivity of the catalysts, especially at higher conversions, will be necessary for this process to compete with the usual process of acrylonitrile synthesis [24]. 

For the commercial production of vinyl acetate, a procedure with a heterogeneous fixed-bed catalyst is exclusively applied today. The catalysts usually consist of palladium salts, mostly the acetate, or palladium metal together with alkali acetate supported on a carrier such as alumina, silica, or carbon without any additional oxidant. This process avoids the formation of larger amounts of by-products. Thus, from ethylene vinyl acetate and from propene, allyl acetate is obtained exclusively. 

Among the industrially relevant cyclic ethers tetrahydrojuran (THF) is by far the most important. THF is produced by condensation of 1,4-butandiol that is obtained from several feedstock basis (acetylene, propene, butadiene, and butane, see Scheme 5.3.4). 1,4-Dioxane is obtained by condensation of diethylene glycol that itself is obtained by the addition of water to ethylene oxide. The reaction is catalyzed by sulfuric acid (homogeneous catalysis) or by acidic ion-exchange resins (heterogeneous catalysis) and proceeds at about 160 °C with continuous distillative removal of water. 

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