Perspectives on the Active Sites and Catalyst Design for the Hydrogenation of Dimethyl Oxalate

Abstract

What should people do with the huge amount of CO 2 captured? CO 2 to CO is a promising way for using carbon resources because CO is one component of syngas for the production of many important synthesis intermediates such as dimethyl oxalate (DMO). Hydrogenation of DMO provides an economical and eco-friendly approach for the synthesis of methyl glycolate, ethylene glycol (EG), and ethanol, which is often determined by the reaction conditions and catalysts with different active sites. Thus, DMO or EG is also an important carbon carrier or CO 2 utilization product. Also, DMO hydrogenation is a representative reaction for studying the structure−activity relationship in CO/C−O bond hydrogenation. Therefore, this work provides a comprehensive review of the progress in DMO hydrogenation from the perspective of constructing and stabilizing the active sites. The silver and copper based catalysts with different structures and morphologies used for DMO hydrogenation have been discussed with regard to their catalytic performance and reaction mechanism. The synergy of Cu 0 and Cu + in DMO hydrogenation has been questioned, and new active sites are proposed with more experimental evidence. New reaction routes, hybrid active sites, and the effect of catalyst structure on the active sites for DMO hydrogenation have been achieved and reviewed. Moreover, a strategy of introducing organic additives to improve EG yield and stabilize copper species has been described. This work may help advance the understanding of active sites in DMO hydrogenation and guide the future rational design and fabrication of highly stable and low-cost DMO hydrogenation catalysts.

Boron Modified Bifunctional Cu/SiO2 Catalysts with Enhanced Metal Dispersion and Surface Acid Sites for Selective Hydrogenation of Dimethyl Oxalate to Ethylene Glycol and Ethanol

“…The asymmetric and broad Auger peak in the Cu LMM XAES spectrum could be deconvoluted into two overlapped peaks at 913.8-914.4 eV and 918.3-918.6 eV, representing Cu + and Cu 0 species, slightly higher than the value of the pure Cu/SiO 2 catalyst [16,32]. The synergetic effect between Cu + and Cu 0 species on the surface of Cu-based catalysts was extensively acknowledged in the hydrogenation of DMO [5,6,11]. As summarized in Table 3, the surface Cu + /(Cu + + Cu 0 ) ratio was gradually increased from 59.5% to 69.2% with the increase of boron content, which corresponded with the results reported by Zhu et al [25].…”

“…The characterization results of EDS, H 2 -TPR, XPS, and XAES implied that the strong electronic interactions existed between the active component copper and boron promoter, affecting the distributions of copper species with different valence states. The synergetic effect between Cu + and Cu 0 species on the surface of Cu-based catalysts was extensively acknowledged in the hydrogenation of DMO [5,6,11,[39][40][41][42][43][44][45][46]. In detail, the Cu 0 sites dissociate and activate H 2 molecule, and Cu + sites adsorbed the carbonyl group.…”

“…According to the literature, Cu-based catalysts are extensively investigated owing to the outstanding activity in C-O and C=O bonds and relative inactivity for C-C bonds in DMO hydrogenation [4][5][6]. Among them, the Cu/SiO 2 catalysts presented good catalytic performance, low cost and environmentally friendly in DMO vapor-phase hydrogenation reaction [7][8][9].…”

Ni-Modified Ag/SiO2 Catalysts for Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate

“…The hydrogenation of DMO contains the successive hydrogenation of DMO to MG, MG to ethylene glycol (EG), and EG to ethanol (EtOH) [ 11 ]. To make sure that the hydrogenation of DMO stops at the formation of MG, catalysts with relatively weak hydrogenolysis ability should be used.…”

Fabrication Method‐Engineered Cu–ZnO/SiO2 Catalysts with Highly Dispersed Metal Nanoparticles toward Efficient Utilization of Methanol as a Hydrogen Carrier

“…[14] The CuSi-based catalysts have also been extensively used in hydrogenation of carbon-oxygen bonds, for instance, hydrogenation of CO 2 [15] and dimethyl oxalate. [16] In the year of 2015, an excellent Cu/SiO 2 catalyst with predominance of Cu þ species was reported for CO 2 hydrogenation to methanol with satisfactory performance. [17] Then, the CuZn@SiO 2 and CuIn@SiO 2 catalysts with core-shell structure displayed appealing catalytic stability and high methanol selectivity.…”