Impact of Deactivation Phenomena on Kinetics of the C-N Coupling Reaction over Supported Cu2O Catalysts in Continuous-Flow Conditions

摘要

Heterogeneous C-N coupling of bromobenzene with aniline was investigated in flow conditions, with emphasis on kinetic evolution of the catalyst (1% Cu2O/support) deactivation. A kinetic model including parallel and sequential steps leading to the formation of three reaction products (diphenylamine, triphenylamine, and aminodiphenyl) has been established. It was found that the support is not inert in this reaction, and changing its composition induced the following order of catalytic activity: 1% Cu2O/Al2O3 > 1% Cu2O/TiO2 > 1% Cu2O/ZnO. Conversely, the resistance to deactivation varied in the reverse order. This was merely assigned to the nature of the interaction of copper with the catalyst support. Among these, Cu2O/TiO2 highlighted the best compromise between catalytic activity and resistance to deactivation. It was also found that a larger excess of aniline improved the selectivity in diphenylamine and enhanced catalyst (1% Cu2O/TiO2) resistance to deactivation. Structural characterization of these catalysts by X-ray diffraction, X-ray photoelectron spectroscopy, and 142 temperature-programmed reduction provided support for the evidenced kinetic results.