Reactivity of a Simplest Conjugated Diolefin in Liquid-Phase Oxidation: Mechanisms and Products

Abstract

Ethylene is the simplest member of olein series, but butadiene-1,3 (BD) is the simplest conjugated diolein. In this chapter, we describe liquid-phase oxidations of BD with an emphasis on comparison of the diolein with monooleins. BD interacts with oxygen to form polyperoxide, whose thermal decomposition or hydrogenation leads to the formation of 2-butene-1,4-diol, 3-butene-1,2-diol, or butanediols together with furan and acrolein. BD can be oxidized in polar solvents by radical chain route to form directly the dioxygenates. Metal catalysts are able to control the oxidation by promoting formation of 2-butene-1,4-diol, 4-hydroxybut-2-enal, and furan. PdTe/C catalyst is applied in industry to produce 2-butene-1,4-diol diacetates with selectivity of 98%. The outstanding selectivity of the catalyst is caused by combined action of components in nonradical route and esteriication of inal product in acetic acid. Similar reaction in methyl alcohol yields 1,4-dimethoxy-2-butene, but with lower eiciency. The nonradical mechanism is irmly established for epoxidation of BD with hydrogen peroxide catalyzed by phosphotungstates. The selectivity of BD and hydrogen peroxide conversion to 3,4-epoxy-1-butene around 100% is atained. Analysis of published information and our own studies show many similarities in oxidation of BD and light oleins, which are very useful for understanding the mechanisms.