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

Abstract

Ni-modified Ag/SiO2 catalysts containing 0~3 wt.% Ni were obtained by impregnating Ni species onto Ag/SiO2 followed by calcination and reduction. The catalysts’ performance in the hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) was tested. Ag-0.5%Ni/SiO2 showed the highest catalytic activity among these catalysts and exhibited excellent catalytic stability. The effects of the Ni content on the structure and surface chemical states of catalysts were investigated by XRF, N2-sorption, XRD, TEM, EDX-mapping, FT-IR, H2-TPR, UV–vis, and XPS. The better catalytic activity and stability of Ni-modified Ag/SiO2 (versus Ag/SiO2) are ascribed to the improved dispersion of active Ag species as well as the higher resistance to the growth of Ag particles due to the presence of Ni species.

Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate over Boron-Modified Ag/SiO2 Catalysts

“…Figure 5 shows TEM images of the two representative catalysts (calcined Ag/SiO 2 and 1B/Ag/SiO 2 ). According to our group's previous study 38,46 and the above XRD results (Figure 3), Ag species mainly exist as metallic Ag on calcined catalysts. Both calcined Ag/SiO 2 and 1B/Ag/SiO 2 appear as agglomerates of irregular SiO 2 support (bright areas) and spherical Ag species particles (darker areas).…”

“…Besides, the addition of B promoted the dispersion of Ag species on SiO 2 , consistent with TEM results (Figure ). Figure shows that the TOF value decreased gradually with the increase of Ag particle size over five catalysts, suggesting that the DMO hydrogenation is a structure-sensitive reaction …”

“…Figure 10 shows that the TOF value decreased gradually with the increase of Ag particle size over five catalysts, suggesting that the DMO hydrogenation is a structure-sensitive reaction. 46 …”

“…Figure 10 shows that the TOF value decreased gradually with the increase of Ag particle size over five catalysts, suggesting that the DMO hydrogenation is a structure-sensitive reaction. 46 As well known, there are many factors that can affect the activity of Ag-based catalysts for vapor-phase DMO hydrogenation. On the basis of the above characterization results, the reasons for the effect of B loading on the performance of the xB/Ag/SiO 2 catalysts can be explained as follows: (1) The XPS results show that the surface Ag content increased in the order of Ag/SiO 2 < 0.5B/Ag/SiO 2 < 5B/Ag/SiO 2 < 3B/Ag/ SiO 2 < 1B/Ag/SiO 2 (Table 2).…”

Ultra-thin silica shell-guarded nanoflares for high-fidelity live cell miRNA-21 imaging by fully avoiding the interference of biothiols

“…Silica is an excellent passivation material that can fully avoid the interaction with biothiols. Moreover, silica exhibits excellent light transmittance, [20][21][22] good water dispersibility, 23 and satisfactory biocompatibility, 24,25 and involves easy preparation and surface modification. It is considered as an ideal carrier material for optical probes.…”