Studies on styrene oxidation reaction catalyzed by ruthenium substituted polyoxotungstates: kinetics and phase transfer effect

• Published in: Journal of molecular catalysis. A, Chemical Vol. 161; no. 1; pp. 163 - 169
• Main Authors: Xinrong, Lin, Jinyu, Xu, Huizhang, Liu, Bin, Yue, Songlin, Jin, Gaoyang, Xie
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 06-11-2000; Elsevier
• Subjects: Benzaldehyde; Catalysis; Catalyst; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Polyoxotungstates; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Polyoxotungstates; Catalyst; Benzaldehyde; Benzoic acid; Heteropolysalt; Ruthenium; Hydrocarbon; Reaction product; Selectivity; Concentration effect; Styrene; Benzenic compound; Oxidation; Activation energy; Ethylenic compound; Modified material
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/S1381-1169(00)00331-9

A series of ruthenium substituted polyoxotungstates were used to catalyze the cleavage oxidation of styrene. Under all experimental conditions investigated, reaction products were benzaldehyde and benzoic acid. Kinetic studies showed that these reactions were consecutive reactions consisting of first oxidizing styrene into benzaldehyde and then oxidizing the benzaldehyde into benzoic acid. In this work, the first oxidation step was carefully studied. It has been shown to be first order with respect to substrate and catalysts but zero order with respect to NaIO
4 under the conditions studied. The activation energies of the first oxidation catalyzed by different polyanions are closely similar to one another, but the value of pre-exponential factors, differed by orders of magnitudes. Such differences could possibly be accounted for by the phase transfer effect as experiments showed that lowering the concentration of phase transfer reagent for low distribution ratio (
C
aq/
C
org) catalysts would enhance the pre-exponential factor value and selectivity of the reaction.