Zeolites ZSM-5 with different Si/Al ratios were in-situ synthesized on the surface ofhoneycomb-shaped cordierite support for the first time. Characterizations of XRD and SEM wereperformed and it has been proved that t...Zeolites ZSM-5 with different Si/Al ratios were in-situ synthesized on the surface ofhoneycomb-shaped cordierite support for the first time. Characterizations of XRD and SEM wereperformed and it has been proved that the zeolite ZSM-5 was grown on the surface of the cordieritehomogeneously. NO decomposition on the Cu exchanged ZSM-5/cordierite monolith catalysts wasalso studied. It was found that the monolith catalysts have a fine initial activity at 673K and GHSVof 10,000h-1. Such method should be a good way to make auto exhaust converter with monolithcatalyst for NOx removal.展开更多
A series of single-phase T-structured NdSrCu 1-x Co x O 4-δ with oxygen vacancies and T -structured Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ (x: 0–0.4) with oxygen excess were prepared using ultrasound-assisted citric ac...A series of single-phase T-structured NdSrCu 1-x Co x O 4-δ with oxygen vacancies and T -structured Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ (x: 0–0.4) with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-programmed desorption (NO-TPD). The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCu 1-x Co x O 4-δ catalysts were of oxygen vacancies whereas the Sm 1.8 Ce 0.2 Cu 1?x Co x O 4-δ ones possessed excessive oxygen (i.e., over-stoichiometric oxygen); with a rise in Co doping level, the oxygen vacancy density of NdSrCu 1-x Co x O 4-δ decreased while the over-stoichiometric oxygen amount of Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO 3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr -1 , and 600–900°C, the catalytic activity of NO decomposition followed the order of NdSrCuO 3.702 〉 NdSrCu 0.8 Co 0.2 O 3.736 〉 NdSrCu 0.6 Co 0.4 O 3.789 〉 Sm 1.8 Ce 0.2 Cu 0.6 Co 0.4 O 4.187 〉 Sm 1.8 Ce 0.2 Cu 0.8 Co 0.2 O 4.104 〉 Sm 1.8 Ce 0.2 CuO 4.045 , in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu 3+ /Cu 2+ redox ability of NdSrCu 1-x Co x O 4-δ account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.展开更多
The decomposition of NO has been studied in a steady flow reactor on fresh carbon nanotubes (CNTs), purified CNTs, Rh/p-CNTs and Rh/gamma -Al2O3 between 573 K and 973 K. NO decomposition at 573 K was initially complet...The decomposition of NO has been studied in a steady flow reactor on fresh carbon nanotubes (CNTs), purified CNTs, Rh/p-CNTs and Rh/gamma -Al2O3 between 573 K and 973 K. NO decomposition at 573 K was initially complete over a reduced surface. The amount of NO absorption increased at temperature below 773 K. 100% NO conversion and more than 100% N-2 activity was achieved at 973 K for 150 min on p-CNTs and f-CNTs.展开更多
The effect of the addition of small amounts of rare earths (Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was inves...The effect of the addition of small amounts of rare earths (Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/CuCo/AI catalyst were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), scanning electron mieroscopy-energy dispersive spectroscopy (SEM-EDS), H2-temperature-programmed reduc- tion (H2-TPR), electron paramagnetic resonanee (EPR) spectroscopy and low temperature nitrogen adsorption, The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial re- duction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/CuCo/A1 catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/CuCo/A1 and Nd/CuCo/A1 were the most active catalysts. The catalyst Ce/CuCo/AI was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu+/Cu2+ and Ce3+/Ce4+. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2.展开更多
A series of LnSrNiO_4(A_2BO_4, Ln=La, Pr, Nd, Sm, Gd) mixed oxides with K_2NiF_4 structure, in which Asite(Sr) was partly substituted by individual light rare earth element, was prepared. The solid state physicochemic...A series of LnSrNiO_4(A_2BO_4, Ln=La, Pr, Nd, Sm, Gd) mixed oxides with K_2NiF_4 structure, in which Asite(Sr) was partly substituted by individual light rare earth element, was prepared. The solid state physicochemical properties including crystal structure, defect structure, IR spectrum, valence state of Bsite ion, nonstoichiometric oxygen, oxygenous species, the properties of oxidation and reduction etc. as well as the catalytic behavior for NO decomposition on these mixed oxides were investigated. The results show that all of these mixed oxide catalysts have high activity for the direct decomposition of NO(at 900 ℃ the conversion of NO is more than 90%). The effect of the substitution of light rare earth elements at Asite on catalytic behavior for NO decomposition was elucidated.展开更多
Catalytic direct decomposition of NO by perovskite-type catalysts has attracted much attention for the various possible components and the unique structure. LaCoO_3 nanoparticles were precipitated on a-Al_2O_3 micro p...Catalytic direct decomposition of NO by perovskite-type catalysts has attracted much attention for the various possible components and the unique structure. LaCoO_3 nanoparticles were precipitated on a-Al_2O_3 micro powders by rotary chemical vapor deposition(rotary CVD) and its catalytic performance for the decomposition of NO was investigated. LaCoO_3 nano-particles with 100 nm in average diameter and 1.5% in mass were uniformly dispersed on a-Al_2O_3 powder. The conversion of NO increased with increasing temperature from 400 to 950 ℃, and reached 28.7% at 950 ℃. The gas velocity of transformed NO on LaCoO_3 nano-particles catalyst per mass unit was 7.7 mL/(g min), showing a good catalytic activity over the calculated results of pure catalysts. After five times of aging performance experiments, the NO conversion kept the same value, showing a good aging performance and thermal stability.展开更多
Catalysts of Co1.5Mg1.5/Al0.9Ti0.1O and Co1.5Mg1.5/AlO were successfully prepared by calcinations of corresponding hydrotalcite-like compounds at 800°C for 4 hr. The derived oxides were of spinel phase and a smal...Catalysts of Co1.5Mg1.5/Al0.9Ti0.1O and Co1.5Mg1.5/AlO were successfully prepared by calcinations of corresponding hydrotalcite-like compounds at 800°C for 4 hr. The derived oxides were of spinel phase and a small quantity of Ti substitution did not change the crystal purity. Their catalytic performance for the NO storage/decomposition was investigated. Ti incorporation enhanced the NO decomposition activity while has an opposite effect on the storage capacity of catalyst. In situ FT-IR spectra of the catalysts showed that the final adsorption species on the catalysts was coordinated nitrates/nitrites. In addition, NO storage/decomposition mechanism has been discussed on the basis of these observations.展开更多
文摘Zeolites ZSM-5 with different Si/Al ratios were in-situ synthesized on the surface ofhoneycomb-shaped cordierite support for the first time. Characterizations of XRD and SEM wereperformed and it has been proved that the zeolite ZSM-5 was grown on the surface of the cordieritehomogeneously. NO decomposition on the Cu exchanged ZSM-5/cordierite monolith catalysts wasalso studied. It was found that the monolith catalysts have a fine initial activity at 673K and GHSVof 10,000h-1. Such method should be a good way to make auto exhaust converter with monolithcatalyst for NOx removal.
基金supported by the Natural Science Foundation of Beijing Municipality Key Class B Project (No.KZ200610005004)the Beijing Municipal Commission of Education (No. PHR200907105)the Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality(PHR (IHLB))
文摘A series of single-phase T-structured NdSrCu 1-x Co x O 4-δ with oxygen vacancies and T -structured Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ (x: 0–0.4) with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-programmed desorption (NO-TPD). The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCu 1-x Co x O 4-δ catalysts were of oxygen vacancies whereas the Sm 1.8 Ce 0.2 Cu 1?x Co x O 4-δ ones possessed excessive oxygen (i.e., over-stoichiometric oxygen); with a rise in Co doping level, the oxygen vacancy density of NdSrCu 1-x Co x O 4-δ decreased while the over-stoichiometric oxygen amount of Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO 3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr -1 , and 600–900°C, the catalytic activity of NO decomposition followed the order of NdSrCuO 3.702 〉 NdSrCu 0.8 Co 0.2 O 3.736 〉 NdSrCu 0.6 Co 0.4 O 3.789 〉 Sm 1.8 Ce 0.2 Cu 0.6 Co 0.4 O 4.187 〉 Sm 1.8 Ce 0.2 Cu 0.8 Co 0.2 O 4.104 〉 Sm 1.8 Ce 0.2 CuO 4.045 , in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu 3+ /Cu 2+ redox ability of NdSrCu 1-x Co x O 4-δ account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.
文摘The decomposition of NO has been studied in a steady flow reactor on fresh carbon nanotubes (CNTs), purified CNTs, Rh/p-CNTs and Rh/gamma -Al2O3 between 573 K and 973 K. NO decomposition at 573 K was initially complete over a reduced surface. The amount of NO absorption increased at temperature below 773 K. 100% NO conversion and more than 100% N-2 activity was achieved at 973 K for 150 min on p-CNTs and f-CNTs.
基金Project supported by the European Social Fund(ESF)(BG051PO001-3.3.06-0050)
文摘The effect of the addition of small amounts of rare earths (Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/CuCo/AI catalyst were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), scanning electron mieroscopy-energy dispersive spectroscopy (SEM-EDS), H2-temperature-programmed reduc- tion (H2-TPR), electron paramagnetic resonanee (EPR) spectroscopy and low temperature nitrogen adsorption, The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial re- duction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/CuCo/A1 catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/CuCo/A1 and Nd/CuCo/A1 were the most active catalysts. The catalyst Ce/CuCo/AI was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu+/Cu2+ and Ce3+/Ce4+. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2.
文摘A series of LnSrNiO_4(A_2BO_4, Ln=La, Pr, Nd, Sm, Gd) mixed oxides with K_2NiF_4 structure, in which Asite(Sr) was partly substituted by individual light rare earth element, was prepared. The solid state physicochemical properties including crystal structure, defect structure, IR spectrum, valence state of Bsite ion, nonstoichiometric oxygen, oxygenous species, the properties of oxidation and reduction etc. as well as the catalytic behavior for NO decomposition on these mixed oxides were investigated. The results show that all of these mixed oxide catalysts have high activity for the direct decomposition of NO(at 900 ℃ the conversion of NO is more than 90%). The effect of the substitution of light rare earth elements at Asite on catalytic behavior for NO decomposition was elucidated.
基金Funded by the National Natural Science Foundation of China(Nos.51372188 and 51521001)the 111 Project(B13035)+3 种基金the International Science&Technology Cooperation Program of China(2014DFA53090)the Natural Science Foundation of Hubei Province,China(2016CFA006)the National Key Research and Development Program of China(2017YFB0310400)the Fundamental Research Funds for the Central Universities(WUT:2017II43GX,2017III032)
文摘Catalytic direct decomposition of NO by perovskite-type catalysts has attracted much attention for the various possible components and the unique structure. LaCoO_3 nanoparticles were precipitated on a-Al_2O_3 micro powders by rotary chemical vapor deposition(rotary CVD) and its catalytic performance for the decomposition of NO was investigated. LaCoO_3 nano-particles with 100 nm in average diameter and 1.5% in mass were uniformly dispersed on a-Al_2O_3 powder. The conversion of NO increased with increasing temperature from 400 to 950 ℃, and reached 28.7% at 950 ℃. The gas velocity of transformed NO on LaCoO_3 nano-particles catalyst per mass unit was 7.7 mL/(g min), showing a good catalytic activity over the calculated results of pure catalysts. After five times of aging performance experiments, the NO conversion kept the same value, showing a good aging performance and thermal stability.
基金supported by the Chinese National Science Fund for Distinguished Young Scholars (No. 20725723)the National Natural Science Foundation of China (No.20877088, 20907065)
文摘Catalysts of Co1.5Mg1.5/Al0.9Ti0.1O and Co1.5Mg1.5/AlO were successfully prepared by calcinations of corresponding hydrotalcite-like compounds at 800°C for 4 hr. The derived oxides were of spinel phase and a small quantity of Ti substitution did not change the crystal purity. Their catalytic performance for the NO storage/decomposition was investigated. Ti incorporation enhanced the NO decomposition activity while has an opposite effect on the storage capacity of catalyst. In situ FT-IR spectra of the catalysts showed that the final adsorption species on the catalysts was coordinated nitrates/nitrites. In addition, NO storage/decomposition mechanism has been discussed on the basis of these observations.