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

Isobutane oxidation was investigated in wide ranges of experimental conditi ons 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 methacro lein. Neither methacrolein nor methacrylic acid is formed directly from iso butane. Both overoxidation of methacrylic acid and total oxidation of isobu tane and intermediates are responsible for the undesired formation of aceti c acid and carbonoxides. CO and CO2 are formed via different paths from met hacrylic acid, but the formation of CO is associated with the formation of acetic acid and acrylic acid. The activation energies and rate constants fo r each step of the reaction were determined. Reaction rates of isobutylene and methacrolein are 500 and 120 times faster than the reaction rate of iso butane. Methacrylic acid oxidation is about two times faster than isobutane oxidation. While the presence of isobutane does not influence the reactivi ty of methacrolein. methacrylic acid oxidation is slowed down due to inhibi tion of the catalyst active sire by isobutane. (C) 2001 Elsevier Science B. V. All rights reserved.