Kinetics of isobutane selective oxidation over Mo-V-P-As-Cs-Cu-O heteropoly acid catalyst Original Research Article

Isobutane oxidation was investigated in wide ranges of experimental conditions over Mo-V-P-As-Cs-Cu-O heteropoly acid catalyst. The kinetics could be described by an empirical set of first order equations. Methacrylic acid is produced by a series of consecutive reactions via isobutylene and methacrolein. Neither methacrolein nor methacrylic acid is formed directly from isobutane. Both overoxidation of methacrylic acid and total oxidation of isobutane and intermediates are responsible for the undesired formation of acetic acid and carbonoxides. CO and CO2 are formed via different paths from methacrylic acid, but the formation of CO is associated with the formation of acetic acid and acrylic acid. The activation energies and rate constants for each step of the reaction were determined. Reaction rates of isobutylene and methacrolein are 500 and 120 times faster than the reaction rate of isobutane. Methacrylic acid oxidation is about two times faster than isobutane oxidation. While the presence of isobutane does not influence the reactivity of methacrolein, methacrylic acid oxidation is slowed down due to inhibition of the catalyst active site by isobutane.