The effect of synergy between Cr2O3-CeO2 and USY zeolite on the catalytic performance and durability of chromium and cerium modified USY catalysts for decomposition of chlorinated volatile organic compounds

Cu and Co modified beta zeolite catalysts for the trichloroethylene oxidation

“…We propose that the combination of acid and redox properties is the key factor to design active catalysts in the TCE oxidation reaction. In this basis, we support the hypothesis that this reaction takes place in different steps [23,44]: first the TCE molecule is adsorbed on the acid sites of the zeolite and then it reacts with the active oxygen species of the zeolite surface leading to the formation of reaction intermediates, which can be further oxidized in the presence of active oxygen species until being converted into CO x , HCl, Cl 2 and H 2 O. In this way, a redox cycle occurs on the catalyst surface between the oxygen vacancies and the oxygen of the gas phase, and this determines both the activity and the selectivity of the reaction.…”

“…In this way, Divakar et al [22] studied the catalytic activity of ZSM-5 and Beta zeolites with Fe and they found that all the catalysts were active for the trichloroethylene oxidation, but the results obtained depended on the catalyst preparation procedure. Huang et al [23] studied the synergy between Cr 2 O 3 -CeO 2 and USY zeolite on the catalytic performance, showing that the interaction between chromium and cerium improves the mobility of oxygen species, favouring the oxidation of the chlorinated volatile organic compounds. These results show that the interaction of the transition metal and the zeolite improves the catalytic activity of the material.…”

Highly Selective Catalytic Dechlorination of Dichloromethane to Chloromethane over Al−Ti Mixed Oxide Catalysts

“…The Lewis acid sites are assumed to be the active sites of dechloriantion of DCM because Lewis acid sites are consumed during the reaction, [19] and intermediates are formed on them. [21] The TOF of dechlorination over AlÀ Ti mixed oxide catalysts was calculated as the formation rate of CM per acid site as summarized in Table 5. By comparing with the TOF values under the mentioned reaction conditions, the order of the selective catalytic dechlorination reaction is as follow:…”

“…The oxidative decomposition of CVOCs by reacting them with dioxygen can convert CVOCs to harmless substances such as carbon dioxide, in which a number of efficient catalysts have been studied for the catalytic oxidation of CVOCs, including zeolites, [8][9][10] perovskites, [11][12][13][14] noble metals [15][16][17][18][19] and metal oxides. [20][21][22][23][24][25][26][27][28][29] The complete oxidation of CVOCs to CO 2 would be efficient approach to solve the environmental problems of CVOCs, but another potential way to convert the CVOCs into value-added intermediates could be considered. Selective partial dechlorination of multi-chlorinated methane compounds to convert to a mono-chlorinated methane, i. e., chloromethane (CM), is desired since the CM can be used as extractant, refrigerant or chemical intermediate for the production of value-added products.…”

“…[19] 2CH 2 Cl 2 þ H 2 O ! CO þ CH 3 Cl þ 3HCl (5) The conventional metal oxides such as Al 2 O 3 [19] and TiO 2 [30,31] were reported to show catalytic activity for this reaction since Lewis acidity is beneficial to the formation of intermediates [21] and the surface hydroxyl groups in these metal oxides could react with DCM to produce CM. [19] However, low overall efficiencies over the conventional Al 2 O 3 and TiO 2 catalysts should be significantly improved to develop a practical catalytic process for the selective dechlorination to chloromethane.…”