Interplay between copper nanoparticle size and oxygen vacancy on mg-doped ceria controls partial hydrogenation performance and stability

Abstract

A series of CunCeMgOx catalysts with various copper nanoparticle sizes and surface defect densities were synthesized and tested for partial hydrogenation of 1,3-butadiene (1,3-BD). The data demonstrated a reaction pathway involving the dissociation of molecular hydrogen on the peripheral oxygen vacancies (O-v-Cu+) before reacting with 1,3-BD adsorbed on the corresponding Cu+ atoms. Analysis of the performance data indicated that the turnover frequency of these Cu+ sites is approximately five times higher than those of the surface Cu-0 sites. Among the catalysts considered, Cu0.5CeMgOx with the smallest copper nanoparticle size provided a stable performance for at least 15 h time-on-stream, while the others were easily deactivating because of carbon deposition. Furthermore, unlike the conventional copper-based catalysts, the Cu0.3CeMgOx catalyst achieved a complete suppression of total hydrogenation even at space velocities offering a complete 1,3-BD conversion. The findings offer a broad potential for the rational design of noble metal-free, highly selective, and stable copper-based partial hydrogenation catalysts for reactions that are prone to coke formation.