Influence of phosphate addition on activity of Ag and Cu catalysts for partial oxidation of alcohols

Effect of phosphorus on the activity of Cu/SiO 2 catalysts in the hydrogenolysis of glycerol

“…The Cu(18.4)/SiO 2 catalyst displayed a main peak at around 300 • C, while a low-intense shoulder can also be observed around 340 • C. The peak at 300 • C can be attributed to the reduction of highly dispersed CuO species from Cu 2+ to Cu 0 [26,27], while the shoulder at 340 • C can be attributed to the reduction Cu + to Cu 0 [28,29], suggesting that this is an intermediate species in the reduction step. In contrast, the Cu(x)/P(y)-SiO 2 catalysts presented less intense peaks at 300 • C attributed to the reduction of highly dispersed CuO [26,27], while the principal peak observed at 350 • C was assigned to the reduction of Cu 2+ -like O Cu-P interaction [30]. Finally, the formation of phosphates or Cu polyphosphates was not detected from TPR analyses.…”

Ag-Based Catalysts in Heterogeneous Selective Oxidation of Alcohols: A Review

“…Interactions between the silica surface, polyphosphate modifier and Ag was studied in our previous works [87,90,91]. Based on the TPR, UV-vis DRS, and IR spectroscopy data, we suggested a mechanism for active species organization (highly dispersed silver particles) on the surface of the investigated Ag-containing materials.…”

“…The next generation of the catalysts for the selective EG oxidation is connected with the development of the idea about the application of Ag clusters/NPs as active species able to adsorb oxygen in a strongly bounded form. Such an approach was implemented in our previous works [85][86][87][88][89], where the Ag-containing materials (5 wt%) were applied as catalysts instead of polycrystalline Ag. The active component in the form of Ag NPs was distributed in the mesoporous space of the silica matrix ( Figure 10) together with the polyphosphate modifier.…”

“…in the catalyst composition allowed transforming all silver into ionic state participating in the reversible redox process. It is noteworthy that silver coordinated by the polyphosphate was not able to participate in the deep oxidation of EG [87]. In Figure 11 the TPR profiles for Ag/SiO 2 and Ag/P 2 O 5 /SiO 2 catalysts in CO/He mixture are presented.…”

Role of PdAg interface in Pd-Ag/SiO2 bimetallic catalysts in low-temperature oxidation of carbon monoxide

“…The activity of the reduced sample was lower: a 5% con version CO was achieved at a temperature of 80°C, and the conversion of CO in a range of 210-240°C was comparable with the activity of the 4Pd catalyst. An increase in the activity of the bimetallic catalysts in CO oxidation can be caused by the cooperative participa tion of the active sites of silver particles (highly active in the activation of О 2 even at room temperature [44]) with the phases of Pd o or PdO. In this case, it is likely that the cooperation at the Ag-PdO interface is more effective because the activity of the oxidized sample, in which palladium occurs in an oxidized state (the reduction of palladium in CO in the (2Pd + 2Ag) catalyst was BONDARCHUK, MAMONTOV observed in a temperature range of 200-340°C, Fig.…”