Structure–activity relationship of CuO–CeO2 in the synthesis of methyl N-phenylcarbamate

Abstract

Methoxycarbonylation of aniline (AN) with dimethyl carbonate (DMC) to produce methyl N-phenylcarbamate (MPC), a key intermediate in non-phosgene diphenylmethane diisocyanate (MDI) synthesis, is facilitated using a newly developed CuO–CeO₂ catalyst. This catalyst demonstrated a high AN conversion rate of 95.1% and an MPC selectivity of 92.7% at an n_DMC/n_AN ratio of 10. The catalyst's effectiveness is attributed to the synergistic interaction between CuO and CeO₂, which enhances oxygen vacancy generation and increases the acid amount, as well as Lewis acid sites. Weak Lewis acid sites are conducive to MPC synthesis. There are three distinct copper species present in the CuO–CeO₂ catalyst, among which the copper species doped into the CeO₂ lattice is beneficial to MPC synthesis. The deactivation of the catalyst, due to the reduction of CuO by methanol, and catalyst regeneration through calcination are discussed. The catalytic mechanism is explored with in situ FT-IR, providing deeper insight into the methoxycarbonylation process.