Highly active behaviors of CeO2–CrOx mixed oxide catalysts in deep oxidation of 1,2-dichloroethane

Synergistic performance between oxidizability and acidity/texture properties for 1,2-dichloroethane oxidation over (Ce,Cr)xO2/zeolite catalysts

“…Although the impregnation of transition metal oxides or noble metals is always considered, the synergy between oxides/noble metals and zeolites can hardly reach the best, and thus, the similar problems still exist (Guisnet et al, 2009;Aranzabal et al, 2009;López-Fonseca et al, 2005;Gutiérrez-Ortiz et al, 2003;Chatterjee et al, 1992). CeO 2 -based catalysts, especially CeO 2 -transition metal mixed oxides, have also attracted considerable interest (Harmsen et al, 2001;Wang et al, 2009;de Rivas et al, 2011de Rivas et al, , 2012Yang et al, 2015aYang et al, , 2014Yang et al, , 2015b, since CeO 2 can undergo a rapid and reversible redox cycle of Ce 4 þ '-Ce 3 þ , coupled with its strong interaction with other active metal, which is helpful to stabilize the active components and improve the redox property. Among the CeO 2 -based catalysts, (Ce,Cr) x O 2 mixed oxide exhibits outstanding catalytic performances for deep oxidation of Cl-VOCs with quite different molecule structures, because of its very high oxidizing ability.…”

Elimination of 1,2-dichloroethane over (Ce, Cr) O2/Nb2O5 catalysts: synergistic performance between oxidizing ability and acidity

“…Besides, more Cr 6+ species would appear with increasing (Ce,Cr)xO2 content, as peak α also grows bigger with increasing (Ce,Cr)xO2 content. Our previous studies [11,13,14] have demonstrated that the highly oxidizing Cr 6+ species is beneficial for the deep oxidation of the C2H3Cl byproduct, and thus, the maximum C2H3Cl concentration decreases obviously with increasing (Ce,Cr)xO2 to Nb2O5 mass ratio. However, more Cr 6+ species does not necessarily mean better activities (see TOF values), which is another clear evidence of the fact that both the redox and the acidic properties contribute to the elimination of DCE and that a synergistic effect between (Ce,Cr)xO2 and Nb2O5 is essential for improving the catalytic performance.…”

“…For (Ce,Cr)xO2, three H2 consumption peaks are observed: peak α (at ∼344 °C), which can be related to the reduction of Cr 6+ to Cr 3+ ; peak γ, which is attributed to the reduction of either surface/subsurface O or small Cr2O3 particles; whereas, the peak observed at a high temperature (above 700 °C) can be assigned to the reduction of CeO2 lattice O [28]. The redox properties of (Ce,Cr)xO2 have been detailly discussed in our previous studied [11,13,28]. It is revealed that the formation of small Cr2O3 particles can increase the amount of oxygen vacancies in CeO2, which would contribute to the mobility of active oxygen species and is beneficial for the destruction of the byproducts produced in the process of DCE oxidation.…”

“…Although supported noble metal catalysts generally exhibit higher oxidation activities, they react more easily with chlorine species, leading to the poisoning of the catalysts and the formation of polychlorinated byproducts during the oxidation process. Therefore, metal oxide catalysts, especially CeO2-based mixed oxides (such as CeO2-MnOx, CeO2-ZrO2, and CexPr1−xO2) [9][10][11][12] have been investigated and used extensively, owing to their lower cost and better resistance to chlorine poisoning. Among them, (Ce,Cr)xO2 exhibits outstanding catalytic performance for the deep oxidation of Cl-VOCs owing to its high oxidizing ability, but it is still necessary to increase its selectivity to HCl rather than towards Cl2, in order to reduce the toxicity of the final products [11,[13][14][15].…”

“…Therefore, metal oxide catalysts, especially CeO2-based mixed oxides (such as CeO2-MnOx, CeO2-ZrO2, and CexPr1−xO2) [9][10][11][12] have been investigated and used extensively, owing to their lower cost and better resistance to chlorine poisoning. Among them, (Ce,Cr)xO2 exhibits outstanding catalytic performance for the deep oxidation of Cl-VOCs owing to its high oxidizing ability, but it is still necessary to increase its selectivity to HCl rather than towards Cl2, in order to reduce the toxicity of the final products [11,[13][14][15]. On the other hand, various researchers [16][17][18][19] have reported that H-type zeolites exhibit high selectivities to HCl formation for the degradation of Cl-VOCs owing to their proper strong/weak acid properties.…”