Kinetics of one-stage Wacker-type oxidation of C2-C4 olefins catalysed by an aqueous PdCl2-heteropoly-anion system

Article abstract of DOI:10.1016/S0021-9517(02)93720-6

The steady-state kinetics of the one-stage Wacker oxidation of gaseous olefins, e.g., ethylene, propylene, and 1-butene by oxygen catalyzed by the Pd(II)/heteropoly anions-3 redox system to form, respectively, acetaldehyde, acetone, and methyl ethyl ketone in aqueous solution was studied. The catalytic system involved an aqueous solution of Pd(II) chloride (0.05-2 mM Pd(II), [Pd(II)]/[Cl^-] = l: 50) and Keggin-type heteropoly anions [PMo₉V₃O₄₀]^6-(50 mM), at 20°-50°C. The reactivity of olefins increases in the following order: ethylene ≤ 1-butene < propylene; but the total range was only a factor of 3. The oxidation of ethylene and propylene occurred without any complication. The oxidation of 1-butene was accompanied by double-bond migration to form 2-butene, apparently proceeding through relatively stable π-allyl Pd(II) complexes. Use of a flow reactor with continuous removal of the products from the catalyst solution could reduce their overoxidation.