Mesoporous Cu Catalysts for Dimethyl Oxalate Selective Hydrogenation: Impact of the Cu/Al interface on the Textural Properties and Catalytic Behavior

Abstract

AbstractIn this paper, mesoporous monometallic Cu catalysts reinforced by the Al3+ dopants with different chemical features were successfully synthesized by controlling the preparation process. The N2‐Adsorption/Desorption, XRD, H2‐TPR, SEM, TEM, H2‐TPD and XPS were conducted to explore the structure evolution of the as‐synthesized samples focusing on the interface effect between Cu nano‐particles (NPs) and Al3+ dopants. It is found that the precipitants used for preparing precursors show drastically effect on the Al3+ chemical form and Cu/Al bonding manners of the as‐synthesized CuAl catalysts, further determining the resultant physicochemical properties and catalytic behavior in dimethyl oxalate (DMO) hydrogenation. In gas‐phase DMO hydrogenation, 98.0 % ethylene glycol (EG) and 90.0 % ethanol (EtOH) yield from DMO selective hydrogenation can be achieved over the CuAl catalyst by regulating the reaction temperature. The correlation between the catalytic behavior and physicochemical features shows that the surface Cu+ sites generated in the Cu/(hydr)oxide interface should be essential for DMO selective hydrogenation in presence of the adequate Cu0 sites. Additionally, the Cu−O−Al patterns in the Cu/Al interface intend to promote more electron transferred from the Al3+ dopants to Cu species through the O bridging, facilitating the CuAl(O) stronger Cu/Al interaction than that of the CuAl(C) catalyst in form of Cu−Al−OH mode. Thus, the Cu NPs growth of the CuAl(O) catalyst was effectively retarded, favoring enhanced catalytic stability.