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

Abstract

In this paper, mesoporous monometallic Cu catalysts reinforced by the Al 3 + dopants with different chemical features were successfully synthesized by controlling the preparation process. The N 2 -Adsorption/Desorption, XRD, H 2 -TPR, SEM, TEM, H 2 -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 Al 3 + dopants. It is found that the precipitants used for preparing precursors show drastically effect on the Al 3 + 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 gasphase 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 Cu 0 sites. Additionally, the CuÀ OÀ Al patterns in the Cu/Al interface intend to promote more electron transferred from the Al 3 + 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 CuÀ AlÀ OH mode. Thus, the Cu NPs growth of the CuAl(O) catalyst was effectively retarded, favoring enhanced catalytic stability.

Role of the Cu dopant in the textural and catalytic features of the Co/ZnO catalyst for dimethyl oxalate selective hydrogenation

“…5,6 Accordingly, developing the optimal catalyst for DMO selective hydrogenation has become vital to achieving the syngas-DMO-EG route. [7][8][9] It is well-established that copper (Cu) nanoparticles (NPs) have been widely applied in DMO selective hydrogenation, owing to the specificity of the active Cu sites in carbon-oxygen (C-O) bond hydrogenation, but inactive in C-C bonds, favoring high EG yield. 10,11 Nonetheless, dispersive Cu NPs tends to aggregate under exothermic reactions.…”

“…In particular, the feedstock can be gained from various feedstocks including natural gas, coal, renewable biomass and even organic waste, guaranteeing adequate supply 5,6 . Accordingly, developing the optimal catalyst for DMO selective hydrogenation has become vital to achieving the syngas–DMO–EG route 7‐9 …”