The co-oxidation of As(Ⅲ) and Fe(Ⅱ) in acidic solutions by pressured oxygen was studied under an oxygen pressure between 0.5 and 2.0 MPa at a temperature of 150℃. It was confirmed that without Fe(Ⅱ) ions, As(Ⅲ) i...The co-oxidation of As(Ⅲ) and Fe(Ⅱ) in acidic solutions by pressured oxygen was studied under an oxygen pressure between 0.5 and 2.0 MPa at a temperature of 150℃. It was confirmed that without Fe(Ⅱ) ions, As(Ⅲ) ions in the solutions are virtually non-oxidizable by pressured oxygen even at a temperature as high as 200℃ and an oxygen pressure up to 2.0 MPa. Fe(Ⅱ) ions in the solutions did have a catalysis effect on the oxidation of As(Ⅲ), possibly attributable to the production of such strong oxidants as hydroxyl free radicals (OH ) and Fe(Ⅳ) in the oxidation process of Fe(Ⅱ). The effects of such factors as the initial molar ratio of Fe(Ⅱ)/As(Ⅲ), initial pH value of the solution, oxygen pressure, and the addition of radical scavengers on the oxidation efficiencies of As(Ⅲ) and Fe(Ⅱ) were studied. It was found that the oxidation of As(Ⅲ) was limited in the co-oxidation process due to the accumulation of the As(Ⅲ) oxidation product, As(Ⅴ), in the solutions.展开更多
The successful control of hydrocarbon and CO emissions from low-temperature diesel exhausts requires the use of highly active co-oxidation catalysts.In this study,Sn was used to enhance the catalytic performance of Pd...The successful control of hydrocarbon and CO emissions from low-temperature diesel exhausts requires the use of highly active co-oxidation catalysts.In this study,Sn was used to enhance the catalytic performance of Pd/CeO_(2)in CO and C_(3)H_(6)co-oxidation conditions.CeO_(2)with added stannum(Sn)was prepared as a support using the co-precipitation method,and Pd was loaded onto the support using the impregnation method.After Sn addition(the optimal Ce/Sn ratio is 0.75:0.25),the T_(50)values of CO and C_(3)H_(6)are reduced by 20 and 32℃,respectively.A series of characterization methods indicates that the addition of Sn to the support greatly enhances its lattice oxygen mobility and increases the proportion of PdO.During the co-oxidation process,stronger lattice oxygen mobility allows CO to react faster through the Mars-van Krevelen mechanism,weakening the competition with C_(3)H_(6)for O_(2).A higher PdO content enhances the C_(3)H_(6)oxidation capability.Moreover,CO can more readily reduce PdO than Pd^(2+)in solid solution with the support,which consequently further enhances co-oxidation activity.Therefore,the addition of Sn is a simple and effective strategy for enhancing the performance of Pd/CeO_(2)catalysts in CO and C_(3)H_(6)co-oxidation reactions.Furthermore,the promotional effect of CO achieved in this study contributes to a deeper understanding of the interactions that occur during the co-oxidation of C_(3)H_(6)and CO.展开更多
The co-oxidation of a mixture of phenylsulfinylacetic acid (PSAA) and oxalic acid (OxH2) by Cr(VI) in 20% acetonitrile-80% water (v/v) medium follows third order kinetics, first order, each with respect to PSAA, OxH2 ...The co-oxidation of a mixture of phenylsulfinylacetic acid (PSAA) and oxalic acid (OxH2) by Cr(VI) in 20% acetonitrile-80% water (v/v) medium follows third order kinetics, first order, each with respect to PSAA, OxH2 and Cr(VI). The reaction involves nucleophilic attack of sulfur atom of PSAA on chromium of the oxidizing species, Cr(VI)-OxH2 to form a ternary complex, Cr(VI)-OxH2-PSAA followed by a one-step three-electron reduction of Cr(VI) to Cr(III) and simultaneous oxidation of both the substrates. The reaction is catalysed by Mn2+ ion while retarded by Al3+ ion. Electron releasing substituents in the meta- and para-positions of the phenyl ring of PSAA enhance the rate of co-oxidation while electron withdrawing substituents retards the reaction. The Hammett plots at different temperatures exhibit excellent correlation with negative ρ values. The reaction series obey isokinetic relationship and the observed isokinetic temperature is lying below the experimental range of temperature.展开更多
Twelve samples of Co-Cu/AI2O3 were prepared by impregnating AI2O3 with cobalt salt followed by copper salt or vice versa. The composition of the prepared samples varied in the molar ratios 1:1, 1:2 and 1:3 with respec...Twelve samples of Co-Cu/AI2O3 were prepared by impregnating AI2O3 with cobalt salt followed by copper salt or vice versa. The composition of the prepared samples varied in the molar ratios 1:1, 1:2 and 1:3 with respect to CuO.CoO or CoO:CuO, while Al2O3 content was kept at about 13-15 mol. The prepared solids were calcined at different temperatures and the products were characterized by means of XRD-analysis. The catalytic activity of the calcined solids was tested in H2O2 decomposition. The XRD-analysis revealed that the sequence of impregnation affects much the structure of the samples. The loading of alumina with cobalt followed by copper salts produced sample with structure differs from that for sample firstly treated with copper followed by cobalt salts. XRD- analysis showed the formation of crystalline spinel Co1-x Cux AI2O4 with nearly the same crystal structure as CoAI2O4 even with high copper content. The examination of catalytic activity of these samples showed that catalysts with Co-loaded over Cu were more active than catalysts with Cu loaded over Co. In all cases the double oxides loaded over AI2O3 were more active than the single oxide over AI2O3.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51574285)
文摘The co-oxidation of As(Ⅲ) and Fe(Ⅱ) in acidic solutions by pressured oxygen was studied under an oxygen pressure between 0.5 and 2.0 MPa at a temperature of 150℃. It was confirmed that without Fe(Ⅱ) ions, As(Ⅲ) ions in the solutions are virtually non-oxidizable by pressured oxygen even at a temperature as high as 200℃ and an oxygen pressure up to 2.0 MPa. Fe(Ⅱ) ions in the solutions did have a catalysis effect on the oxidation of As(Ⅲ), possibly attributable to the production of such strong oxidants as hydroxyl free radicals (OH ) and Fe(Ⅳ) in the oxidation process of Fe(Ⅱ). The effects of such factors as the initial molar ratio of Fe(Ⅱ)/As(Ⅲ), initial pH value of the solution, oxygen pressure, and the addition of radical scavengers on the oxidation efficiencies of As(Ⅲ) and Fe(Ⅱ) were studied. It was found that the oxidation of As(Ⅲ) was limited in the co-oxidation process due to the accumulation of the As(Ⅲ) oxidation product, As(Ⅴ), in the solutions.
基金Project supported by the National Key R&D Program of China(2022YFC3701804)the National Natural Science Foundation of China(52225004)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23010201)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2022309)。
文摘The successful control of hydrocarbon and CO emissions from low-temperature diesel exhausts requires the use of highly active co-oxidation catalysts.In this study,Sn was used to enhance the catalytic performance of Pd/CeO_(2)in CO and C_(3)H_(6)co-oxidation conditions.CeO_(2)with added stannum(Sn)was prepared as a support using the co-precipitation method,and Pd was loaded onto the support using the impregnation method.After Sn addition(the optimal Ce/Sn ratio is 0.75:0.25),the T_(50)values of CO and C_(3)H_(6)are reduced by 20 and 32℃,respectively.A series of characterization methods indicates that the addition of Sn to the support greatly enhances its lattice oxygen mobility and increases the proportion of PdO.During the co-oxidation process,stronger lattice oxygen mobility allows CO to react faster through the Mars-van Krevelen mechanism,weakening the competition with C_(3)H_(6)for O_(2).A higher PdO content enhances the C_(3)H_(6)oxidation capability.Moreover,CO can more readily reduce PdO than Pd^(2+)in solid solution with the support,which consequently further enhances co-oxidation activity.Therefore,the addition of Sn is a simple and effective strategy for enhancing the performance of Pd/CeO_(2)catalysts in CO and C_(3)H_(6)co-oxidation reactions.Furthermore,the promotional effect of CO achieved in this study contributes to a deeper understanding of the interactions that occur during the co-oxidation of C_(3)H_(6)and CO.
文摘The co-oxidation of a mixture of phenylsulfinylacetic acid (PSAA) and oxalic acid (OxH2) by Cr(VI) in 20% acetonitrile-80% water (v/v) medium follows third order kinetics, first order, each with respect to PSAA, OxH2 and Cr(VI). The reaction involves nucleophilic attack of sulfur atom of PSAA on chromium of the oxidizing species, Cr(VI)-OxH2 to form a ternary complex, Cr(VI)-OxH2-PSAA followed by a one-step three-electron reduction of Cr(VI) to Cr(III) and simultaneous oxidation of both the substrates. The reaction is catalysed by Mn2+ ion while retarded by Al3+ ion. Electron releasing substituents in the meta- and para-positions of the phenyl ring of PSAA enhance the rate of co-oxidation while electron withdrawing substituents retards the reaction. The Hammett plots at different temperatures exhibit excellent correlation with negative ρ values. The reaction series obey isokinetic relationship and the observed isokinetic temperature is lying below the experimental range of temperature.
文摘Twelve samples of Co-Cu/AI2O3 were prepared by impregnating AI2O3 with cobalt salt followed by copper salt or vice versa. The composition of the prepared samples varied in the molar ratios 1:1, 1:2 and 1:3 with respect to CuO.CoO or CoO:CuO, while Al2O3 content was kept at about 13-15 mol. The prepared solids were calcined at different temperatures and the products were characterized by means of XRD-analysis. The catalytic activity of the calcined solids was tested in H2O2 decomposition. The XRD-analysis revealed that the sequence of impregnation affects much the structure of the samples. The loading of alumina with cobalt followed by copper salts produced sample with structure differs from that for sample firstly treated with copper followed by cobalt salts. XRD- analysis showed the formation of crystalline spinel Co1-x Cux AI2O4 with nearly the same crystal structure as CoAI2O4 even with high copper content. The examination of catalytic activity of these samples showed that catalysts with Co-loaded over Cu were more active than catalysts with Cu loaded over Co. In all cases the double oxides loaded over AI2O3 were more active than the single oxide over AI2O3.
