Kinetic Investigation of the Pyrolysis of Isobutyric Anhydride and Isobutyric Acid

Low-carbon ketenes are produced by the pyrolysis of corresponding anhydrides or acids. In this work, the pyrolysis experiments of isobutyric anhydride (IBAN) and isobutyric acid (IBA) were carried out to investigate the pyrolysis kinetics. Results showed that the pyrolysis temperature of IBA is far higher than that of IBAN, and dimethylketene (DMK, the main product) selectivity during IBA pyrolysis is much lower than that during IBAN pyrolysis. Furthermore, compared with the four-centered transition state of acid pyrolysis, a more stable six-centered transition state of anhydride pyrolysis was obtained by computational chemistry, which is the reason for the lower pyrolysis temperature of anhydrides. The reaction network of IBAN pyrolysis and the corresponding kinetics were discussed as well. Finally, the effect of different functional groups (methyl, vinyl, and ethynyl groups) on the activation energies of anhydride pyrolysis was investigated, providing references for low-carbon anhydride pyrolysis.