In situ FTIR spectroscopy study to reveal Ga-modified ZSM-5 for boosting isobutene amination

Abstract

Direct amination of isobutene to tert-butylamine is industrially attractive but extremely challenging. Understanding the mechanism and modifying the acid site properties are important for developing highly efficient amination catalysts. Here we developed Ga-modified ZSM-5 to boost the direct amination of isobutene and investigated the mechanism via in situ FTIR spectroscopy. Kinetic evaluation of isobutene protonation indicated that the addition of Ga facilitated the protonation of isobutene. By combining DFT calculations and in situ FTIR experiments, we inferred that the displacement of NH₄⁺ on active sites by isobutene and the subsequent activation of isobutene to the corresponding intermediates limited the catalytic activity. The addition of Ga to Al-ZSM-5 modified the adsorption strength of the reaction species and provided synergistic effect sites and thus enhanced the isobutene amination activity.