Kinetics for Co catalyzed oxidative cyanation of biomass-based furfural

Abstract

Oxidative cyanation of furfural (1a) to 2-furancarbonitrile (3a) by using NH₃ as a nitrogen source and O₂ as an oxidant is an effective strategy for biomass-based nitrile synthesis. Herein, Co catalyst supported on a nanocomposite of nitrogen-doped carbon and TiO₂ (Co/NC-TiO₂) was developed for the oxidative cyanation. The multiphase interface architecture of the catalyst enriched oxygen vacancies; moreover, the electron-rich NC nanocomponent facilitated Co²⁺/Co³⁺ valence transformation, thus promoting O₂ activation. The kinetic analysis demonstrated the condensation of 1a/NH₃-to- (2-furanyl)methanimine (2a) as the rate-determining step, which was consecutively promoted by 2a/O₂-to-3a dehydrogenation over the catalyst surface. A Langmuir-Hinshelwood mechanism was suggested for the oxidative dehydrogenation of the 2a/O₂-to-3a step, in which O₂ is activated by an associative adsorption on the Co surface yielding a superoxide radical (O₂^•–) species for 2a dehydrogenation with the release of H₂O₂. This research highlights a kinetic and mechanic understanding of the catalytic oxidative cyanation.