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Yaoqiang Chen - One of the best experts on this subject based on the ideXlab platform.
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pd or pdo catalytic active site of methane oxidation operated close to stoichiometric air to fuel for Natural Gas Vehicles
Applied Catalysis B-environmental, 2017Co-Authors: Fujin Huang, Jianjun Chen, Shandong Yuan, Lin Zhong, Yaoqiang ChenAbstract:Abstract A Pd catalyst supported on La-modified Al2O3 (La-Al) with and without doping CeO2-ZrO2 (CZ) is prepared via incipient wetness impregnation method. The catalysts are used as model catalyst for Natural Gas Vehicles (NGVs) to investigate the active sites of methane oxidation within the range of air/fuel ratios (λ values) close to stoichiometric value (λ = 1). Both the two catalysts show high activity for methane oxidation under rich conditions. Under lean conditions, the methane oxidation activity over the dopant-free catalyst depend on the direction of λ change, and this catalyst displays relatively lower activity when the λ changes from richer values to lean ones. By contrast, the catalyst with dopant under the same lean conditions can nearly maintain its high activity regardless of the change direction. The results of X-ray powder diffraction (XRD) and temperature programmed reduction under H2 (H2-TPR) indicate the existence of the interactions between the dopant and Pd species, and these interactions are beneficial to retain Pd in oxidized state. Ex situ X-ray photoelectron spectra (XPS) experiments are explored to correlate the catalytic activity of the methane oxidation with the oxidized valent state of Pd. The results confirm that the dopant can preserve most of the Pd species in PdO even under the rich conditions. The results also suggest that both metallic Pd and PdO can act as the active sites for methane oxidation under much richer conditions, and that under lean conditions, PdO instead of metallic Pd plays a role in methane oxidation.
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catalytic performance of pt rh cezryla laal with stoichiometric Natural Gas Vehicles emissions
Chinese Journal of Catalysis, 2015Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yajuan Cui, Ruimei Fang, Yaoqiang ChenAbstract:Abstract The composite support CeZrYLa+LaAl was prepared by a co-precipitation method, and Pt–Rh bimetallic catalysts were fabricated on this support using different preparation procedures. The catalytic activities of these materials were tested in a Gas mixture simulating the exhaust from a stoichiometric Natural Gas vehicle. The as-prepared catalysts were also characterized by X-ray photoelectron spectroscopy, X-ray diffraction, N 2 adsorption-desorption and H 2 -temperature-programmed reduction. It was found that the order of activities for CH 4 , CO and NO conversion was Cat3 ≈ Cat2 > Cat1, where Cat3 had the lowest light-off temperature ( T 50 ) for CO (114 °C) and NO (149 °C), the lowest complete conversion temperature ( T 90 ) for CH 4 (398 °C) and CO (179 °C), and the lowest Δ T ( T 90 – T 50 ) for CH 4 (34 °C) and CO (65 °C). Cat2 showed the lowest T 50 for CH 4 (342 °C), the lowest T 90 for NO (174 °C), and the lowest Δ T for NO (17 °C). Cat1 had the highest T 50 and T 90 and the largest Δ T out of all three catalysts. Indicating that Pt–Rh bimetallic catalysts (Cat2 and Cat3) prepared by physically mixing Pt and Rh powders exhibited much better catalytic activity than those (Cat1) prepared by co-impregnation, since homogeneous Pt and Rh sites made a significant contribution to CH 4 /CO/NO conversions. In contrast, strong Pt–Rh interactions in the co-impregnation materials affected the oxidation states of Pt, and the Pt-enriched surface blocked active Rh sites. Moreover, Cat3 was prepared by adding additives (La 3+ , Zr 4+ and Ba 2+ ) into the physically mixed Pt–Rh catalysts. XRD results demonstrated that the additive cation (Zr 4+ ) was incorporated into the CeO 2 –ZrO 2 lattice, thus creating a higher concentration of defects and improving the O 2 -mobility. XPS results showed that the Cat3 had the highest Ce 3+ /Ce ratio, suggesting the presence of a significant quantity of oxygen vacancies and cerium in the Ce 3+ state. All of these further promoted the three-way catalytic activity and widened the air-to-fuel working-window.
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excellent complete conversion activity for methane and co of pd tio2 zr0 5al0 5o1 75 catalyst used in lean burn Natural Gas Vehicles
Journal of Energy Chemistry, 2014Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Palladium catalysts are supported on TiO 2 , ZrO 2 , Al 2 O 3 , Zr 0.5 Al 0.5 O 1.75 and TiO 2 -Zr 0.5 Al 0.5 O 1.75 prepared by co-precipitation method, respectively. Catalytic activities for methane and CO oxidation are evaluated in a Gas mixture that simulated the exhaust from lean-burn Natural Gas Vehicles (NGVs). Pd/TiO 2 -Zr 0.5 Al 0.5 O 1.75 performs the best catalytic activity among the tested five catalysts. For CH 4 , the light-off temperature ( T 50 ) is 254 °C, and the complete conversion temperature ( T 90 ) is 280 °C; for CO, T 50 is 84 °C, and T 90 was 96 °C. Various techniques, including N 2 adsorption-desorption, X-ray diffraction (XRD), H 2 -temperature-programmed reduction (H 2 -TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) are employed to characterize the effect of supports on the physicochemical properties of prepared catalysts. N 2 adsorption-desorption and SEM show that TiO 2 -Zr 0.5 Al 0.5 O 1.75 expresses uniform nano-particles and large meso-pore diameters of 26 nm. H 2 -TPR and XRD indicate that PdO is well dispersed on the supports and strongly interacted with each other. The results of XPS show that the electron density around PdO and the proportion of active oxygen on TiO 2 -Zr 0.5 Al 0.5 O 1.75 are maxima among the five supports.
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Pd catalysts supported on modified Zr05Al05O1.75 used for lean-burn Natural Gas Vehicles exhaust purification
Journal of Natural Gas Chemistry, 2012Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La 2 O 3 , ZnO, Y 2 O 3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction (XRD), NH 3 temperature-programmed desorption (NH 3 -TPD), H 2 temperature-programmed reduction (H 2 -TPR), N 2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust Gas from lean-burn Natural Gas Vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrAl. The addition of ZnO or Y 2 O 3 promoted the conversion of CH 4 . In the absence of water vapor, Pd/ZnZrAl exhibited the best activity for CH 4 conversion with the light-off temperature ( T 50 ) of 275 °C and the complete conversion temperature ( T 90 ) of 314 °C, respectively. However, in the presence of water vapor, Pd/YZrAl was the best one over which the light-off temperature ( T 50 ) of methane was 339 °C and the complete conversion temperature ( T 90 ) was 371 °C. These results indicated that Pd catalyst supported on the modified composite ZrAl support showed excellent catalytic activity at low temperature and high resistance to H 2 O poisoning for the exhaust purification of lean-burn Natural Gas Vehicles.
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effect of cobalt oxide on performance of pd catalysts for lean burn Natural Gas Vehicles in the presence and absence of water vapor
Journal of Natural Gas Chemistry, 2010Co-Authors: Enyan Long, Yun Wang, Maochu Gong, Xiaoyu Zhang, Zhimin Liu, Yaoqiang ChenAbstract:Abstract Pd-based catalysts modified by cobalt were prepared by co-impregnation and sequential impregnation methods, and characterized by X-ray powder diffraction (XRD), N2 adsorption/desorption (Brunauer-Emmet-Teller method), CO-chemisorption and X-ray photoelectron spectroscopy (XPS). The activity of Pd catalysts was tested in the simulated exhaust Gas from lean-burn Natural Gas Vehicles. The effect of Co on the performance of water poisoning resistance for Pd catalysts was estimated in the simulated exhaust Gas with and without the presence of water vapor. It was found that the effect of Co significantly depended on the preparation process. PdCo/La-Al2O3 catalyst prepared by co-impregnation exhibited better water-resistant performance. The results of XPS indicated that both CoAl2O4 and Co3O4 were present in the Pd catalysts modified by Co. For the catalyst prepared by sequential impregnation method, the ratio of CoAl2O4/Co3O4 was higher than that of the catalyst prepared by co-impregnation method. It could be concluded that Co3O4 played an important role in improving water-resistant performance.
Jose Maria Baldasano - One of the best experts on this subject based on the ideXlab platform.
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emissions variation in urban areas resulting from the introduction of Natural Gas Vehicles application to barcelona and madrid greater areas spain
Science of The Total Environment, 2009Co-Authors: Maria Goncalves, Pedro Jimenezguerrero, Jose Maria BaldasanoAbstract:On-road traffic is the major contributor to pollutant emissions in urban areas. Nowadays different emission abatement strategies are being tested in order to improve urban air quality (e.g. the European Commission currently promotes the use of Natural Gas as an alternative fuel). Several feasible scenarios regarding the introduction of Natural Gas Vehicles (NGV) are studied in the two main cities of Spain (Barcelona and Madrid) by using the HERMES emission model. The most suitable emission factors to NGV are selected among those available in the literature. The account of emissions in the base case scenario estimated for a typical summertime polluted day of the year 2004 reflects that in Barcelona 86% of primary pollutants come from on-road traffic compared to 93% in Madrid, because of the heavier industrial activity in the former. The introduction of NGV in urban zones would have a positive effect on emissions, whose extent largely depends on the substituted fleets and the conurbation characteristics. Maximum reductions in NO(x) emissions in Madrid are attributed to the substitution of 10% of the oldest diesel and petrol cars, while in Barcelona the change of 50% of the oldest commercial light Vehicles becomes more effective. PM(2.5) and SO(2) emissions can be significatively reduced with the introduction of NGV instead of the oldest commercial light Vehicles. The substitution of conventional fuels by Natural Gas must reach around 4% to achieve significative reductions in traffic emissions (larger than 5%). This work focuses on air quality issues, therefore GHG emissions are not included, nevertheless this kind of associated impact has to be considered by the decision makers. Assessing the efficacy of environmental improvement strategies entails a realistic design of emission scenarios and their evaluation. The detailed emission account provides a fundamental basis for the air quality modelling and its comparison among scenarios.
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high resolution modeling of the effects of alternative fuels use on urban air quality introduction of Natural Gas Vehicles in barcelona and madrid greater areas spain
Science of The Total Environment, 2009Co-Authors: Maria Goncalves, Pedro Jimenezguerrero, Jose Maria BaldasanoAbstract:The mitigation of the effects of on-road traffic emissions on urban air pollution is currently an environmental challenge. Air quality modeling has become a powerful tool to design environment-related strategies. A wide range of options is being proposed; such as the introduction of Natural Gas Vehicles (NGV), biofuels or hydrogen Vehicles. The impacts on air quality of introducing specific NGV fleets in Barcelona and Madrid (Spain) are assessed by means of the WRF-ARW/HERMES/CMAQ modeling system with high spatial-temporal resolution (1 km(2), 1 h). Seven emissions scenarios are defined taking into account the year 2004 vehicle fleet composition of the study areas and groups of Vehicles susceptible of change under a realistic perspective. O(3) average concentration rises up to 1.3% in Barcelona and up to 2.5% in Madrid when introducing the emissions scenarios, due to the NO(x) reduction in VOC-controlled areas. Nevertheless, NO(2), PM10 and SO(2) average concentrations decrease, up to 6.1%, 1.5% and 6.6% in Barcelona and up to 20.6%, 8.7% and 14.9% in Madrid, respectively. Concerning SO(2) and PM10 reductions the most effective single scenario is the introduction of 50% of NGV instead of the oldest commercial Vehicles; it also reduces NO(2) concentrations in Barcelona, however in Madrid lower levels are attained when substituting 10% of the private cars. This work introduces the WRF-ARW/HERMES/CMAQ modeling system as a useful management tool and proves that the air quality improvement plans must be designed considering the local characteristics.
Maochu Gong - One of the best experts on this subject based on the ideXlab platform.
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catalytic performance of pt rh cezryla laal with stoichiometric Natural Gas Vehicles emissions
Chinese Journal of Catalysis, 2015Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yajuan Cui, Ruimei Fang, Yaoqiang ChenAbstract:Abstract The composite support CeZrYLa+LaAl was prepared by a co-precipitation method, and Pt–Rh bimetallic catalysts were fabricated on this support using different preparation procedures. The catalytic activities of these materials were tested in a Gas mixture simulating the exhaust from a stoichiometric Natural Gas vehicle. The as-prepared catalysts were also characterized by X-ray photoelectron spectroscopy, X-ray diffraction, N 2 adsorption-desorption and H 2 -temperature-programmed reduction. It was found that the order of activities for CH 4 , CO and NO conversion was Cat3 ≈ Cat2 > Cat1, where Cat3 had the lowest light-off temperature ( T 50 ) for CO (114 °C) and NO (149 °C), the lowest complete conversion temperature ( T 90 ) for CH 4 (398 °C) and CO (179 °C), and the lowest Δ T ( T 90 – T 50 ) for CH 4 (34 °C) and CO (65 °C). Cat2 showed the lowest T 50 for CH 4 (342 °C), the lowest T 90 for NO (174 °C), and the lowest Δ T for NO (17 °C). Cat1 had the highest T 50 and T 90 and the largest Δ T out of all three catalysts. Indicating that Pt–Rh bimetallic catalysts (Cat2 and Cat3) prepared by physically mixing Pt and Rh powders exhibited much better catalytic activity than those (Cat1) prepared by co-impregnation, since homogeneous Pt and Rh sites made a significant contribution to CH 4 /CO/NO conversions. In contrast, strong Pt–Rh interactions in the co-impregnation materials affected the oxidation states of Pt, and the Pt-enriched surface blocked active Rh sites. Moreover, Cat3 was prepared by adding additives (La 3+ , Zr 4+ and Ba 2+ ) into the physically mixed Pt–Rh catalysts. XRD results demonstrated that the additive cation (Zr 4+ ) was incorporated into the CeO 2 –ZrO 2 lattice, thus creating a higher concentration of defects and improving the O 2 -mobility. XPS results showed that the Cat3 had the highest Ce 3+ /Ce ratio, suggesting the presence of a significant quantity of oxygen vacancies and cerium in the Ce 3+ state. All of these further promoted the three-way catalytic activity and widened the air-to-fuel working-window.
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excellent complete conversion activity for methane and co of pd tio2 zr0 5al0 5o1 75 catalyst used in lean burn Natural Gas Vehicles
Journal of Energy Chemistry, 2014Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Palladium catalysts are supported on TiO 2 , ZrO 2 , Al 2 O 3 , Zr 0.5 Al 0.5 O 1.75 and TiO 2 -Zr 0.5 Al 0.5 O 1.75 prepared by co-precipitation method, respectively. Catalytic activities for methane and CO oxidation are evaluated in a Gas mixture that simulated the exhaust from lean-burn Natural Gas Vehicles (NGVs). Pd/TiO 2 -Zr 0.5 Al 0.5 O 1.75 performs the best catalytic activity among the tested five catalysts. For CH 4 , the light-off temperature ( T 50 ) is 254 °C, and the complete conversion temperature ( T 90 ) is 280 °C; for CO, T 50 is 84 °C, and T 90 was 96 °C. Various techniques, including N 2 adsorption-desorption, X-ray diffraction (XRD), H 2 -temperature-programmed reduction (H 2 -TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) are employed to characterize the effect of supports on the physicochemical properties of prepared catalysts. N 2 adsorption-desorption and SEM show that TiO 2 -Zr 0.5 Al 0.5 O 1.75 expresses uniform nano-particles and large meso-pore diameters of 26 nm. H 2 -TPR and XRD indicate that PdO is well dispersed on the supports and strongly interacted with each other. The results of XPS show that the electron density around PdO and the proportion of active oxygen on TiO 2 -Zr 0.5 Al 0.5 O 1.75 are maxima among the five supports.
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Pd catalysts supported on modified Zr05Al05O1.75 used for lean-burn Natural Gas Vehicles exhaust purification
Journal of Natural Gas Chemistry, 2012Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La 2 O 3 , ZnO, Y 2 O 3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction (XRD), NH 3 temperature-programmed desorption (NH 3 -TPD), H 2 temperature-programmed reduction (H 2 -TPR), N 2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust Gas from lean-burn Natural Gas Vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrAl. The addition of ZnO or Y 2 O 3 promoted the conversion of CH 4 . In the absence of water vapor, Pd/ZnZrAl exhibited the best activity for CH 4 conversion with the light-off temperature ( T 50 ) of 275 °C and the complete conversion temperature ( T 90 ) of 314 °C, respectively. However, in the presence of water vapor, Pd/YZrAl was the best one over which the light-off temperature ( T 50 ) of methane was 339 °C and the complete conversion temperature ( T 90 ) was 371 °C. These results indicated that Pd catalyst supported on the modified composite ZrAl support showed excellent catalytic activity at low temperature and high resistance to H 2 O poisoning for the exhaust purification of lean-burn Natural Gas Vehicles.
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effect of cobalt oxide on performance of pd catalysts for lean burn Natural Gas Vehicles in the presence and absence of water vapor
Journal of Natural Gas Chemistry, 2010Co-Authors: Enyan Long, Yun Wang, Maochu Gong, Xiaoyu Zhang, Zhimin Liu, Yaoqiang ChenAbstract:Abstract Pd-based catalysts modified by cobalt were prepared by co-impregnation and sequential impregnation methods, and characterized by X-ray powder diffraction (XRD), N2 adsorption/desorption (Brunauer-Emmet-Teller method), CO-chemisorption and X-ray photoelectron spectroscopy (XPS). The activity of Pd catalysts was tested in the simulated exhaust Gas from lean-burn Natural Gas Vehicles. The effect of Co on the performance of water poisoning resistance for Pd catalysts was estimated in the simulated exhaust Gas with and without the presence of water vapor. It was found that the effect of Co significantly depended on the preparation process. PdCo/La-Al2O3 catalyst prepared by co-impregnation exhibited better water-resistant performance. The results of XPS indicated that both CoAl2O4 and Co3O4 were present in the Pd catalysts modified by Co. For the catalyst prepared by sequential impregnation method, the ratio of CoAl2O4/Co3O4 was higher than that of the catalyst prepared by co-impregnation method. It could be concluded that Co3O4 played an important role in improving water-resistant performance.
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influence of ceo2 and la2o3 on properties of palladium catalysts used for emission control of Natural Gas Vehicles
Journal of Natural Gas Chemistry, 2009Co-Authors: Xiaoyu Zhang, Maochu Gong, Enyan Long, Li Cai, Yaoqiang ChenAbstract:Abstract Pd/YZ-Al2O3 (Y and Zr modified Al2O3, and hereafter, labelled as Al) catalysts with 4 wt% additive CeO2 and/or La2O3 were prepared and characterized by X-ray photoelectron spectroscopy (XPS), NO-temperature programmed desorption (NO-TPD), N2-adsorption/desorption (Brunauer-Emmet-Teller BET method), X-ray diffraction (XRD) and CO-chemisorption. Catalytic activities for CH4, CO and NO conversion were tested in a Gas mixture simulated the emissions from Natural Gas Vehicles (NGVs) operated under stoichiometric conditions. The results indicated that all catalysts exhibited excellent catalytic performances for CH4 and CO oxidation and the promoting effect of CeO2 or La2O3 was significant for NO conversion. XPS results showed that the electron density around Pd was increased by CeO2 and/or La2O3, the binding energy of Pd 3d decreased as the order: Pd/Al > Pd/Ce/Al > Pd/La/Al > Pd/CeLa/Al. The electron-rich Pd showed Rh-like catalytic properties which exhibited good activity for the reduction of NO. NO-TPD results showed that the addition of CeO2 and/or La2O3 increased NO adsorption on surface, and promoted the conversion of NO.
Yun Wang - One of the best experts on this subject based on the ideXlab platform.
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catalytic performance of pt rh cezryla laal with stoichiometric Natural Gas Vehicles emissions
Chinese Journal of Catalysis, 2015Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yajuan Cui, Ruimei Fang, Yaoqiang ChenAbstract:Abstract The composite support CeZrYLa+LaAl was prepared by a co-precipitation method, and Pt–Rh bimetallic catalysts were fabricated on this support using different preparation procedures. The catalytic activities of these materials were tested in a Gas mixture simulating the exhaust from a stoichiometric Natural Gas vehicle. The as-prepared catalysts were also characterized by X-ray photoelectron spectroscopy, X-ray diffraction, N 2 adsorption-desorption and H 2 -temperature-programmed reduction. It was found that the order of activities for CH 4 , CO and NO conversion was Cat3 ≈ Cat2 > Cat1, where Cat3 had the lowest light-off temperature ( T 50 ) for CO (114 °C) and NO (149 °C), the lowest complete conversion temperature ( T 90 ) for CH 4 (398 °C) and CO (179 °C), and the lowest Δ T ( T 90 – T 50 ) for CH 4 (34 °C) and CO (65 °C). Cat2 showed the lowest T 50 for CH 4 (342 °C), the lowest T 90 for NO (174 °C), and the lowest Δ T for NO (17 °C). Cat1 had the highest T 50 and T 90 and the largest Δ T out of all three catalysts. Indicating that Pt–Rh bimetallic catalysts (Cat2 and Cat3) prepared by physically mixing Pt and Rh powders exhibited much better catalytic activity than those (Cat1) prepared by co-impregnation, since homogeneous Pt and Rh sites made a significant contribution to CH 4 /CO/NO conversions. In contrast, strong Pt–Rh interactions in the co-impregnation materials affected the oxidation states of Pt, and the Pt-enriched surface blocked active Rh sites. Moreover, Cat3 was prepared by adding additives (La 3+ , Zr 4+ and Ba 2+ ) into the physically mixed Pt–Rh catalysts. XRD results demonstrated that the additive cation (Zr 4+ ) was incorporated into the CeO 2 –ZrO 2 lattice, thus creating a higher concentration of defects and improving the O 2 -mobility. XPS results showed that the Cat3 had the highest Ce 3+ /Ce ratio, suggesting the presence of a significant quantity of oxygen vacancies and cerium in the Ce 3+ state. All of these further promoted the three-way catalytic activity and widened the air-to-fuel working-window.
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excellent complete conversion activity for methane and co of pd tio2 zr0 5al0 5o1 75 catalyst used in lean burn Natural Gas Vehicles
Journal of Energy Chemistry, 2014Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Palladium catalysts are supported on TiO 2 , ZrO 2 , Al 2 O 3 , Zr 0.5 Al 0.5 O 1.75 and TiO 2 -Zr 0.5 Al 0.5 O 1.75 prepared by co-precipitation method, respectively. Catalytic activities for methane and CO oxidation are evaluated in a Gas mixture that simulated the exhaust from lean-burn Natural Gas Vehicles (NGVs). Pd/TiO 2 -Zr 0.5 Al 0.5 O 1.75 performs the best catalytic activity among the tested five catalysts. For CH 4 , the light-off temperature ( T 50 ) is 254 °C, and the complete conversion temperature ( T 90 ) is 280 °C; for CO, T 50 is 84 °C, and T 90 was 96 °C. Various techniques, including N 2 adsorption-desorption, X-ray diffraction (XRD), H 2 -temperature-programmed reduction (H 2 -TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) are employed to characterize the effect of supports on the physicochemical properties of prepared catalysts. N 2 adsorption-desorption and SEM show that TiO 2 -Zr 0.5 Al 0.5 O 1.75 expresses uniform nano-particles and large meso-pore diameters of 26 nm. H 2 -TPR and XRD indicate that PdO is well dispersed on the supports and strongly interacted with each other. The results of XPS show that the electron density around PdO and the proportion of active oxygen on TiO 2 -Zr 0.5 Al 0.5 O 1.75 are maxima among the five supports.
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Pd catalysts supported on modified Zr05Al05O1.75 used for lean-burn Natural Gas Vehicles exhaust purification
Journal of Natural Gas Chemistry, 2012Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La 2 O 3 , ZnO, Y 2 O 3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction (XRD), NH 3 temperature-programmed desorption (NH 3 -TPD), H 2 temperature-programmed reduction (H 2 -TPR), N 2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust Gas from lean-burn Natural Gas Vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrAl. The addition of ZnO or Y 2 O 3 promoted the conversion of CH 4 . In the absence of water vapor, Pd/ZnZrAl exhibited the best activity for CH 4 conversion with the light-off temperature ( T 50 ) of 275 °C and the complete conversion temperature ( T 90 ) of 314 °C, respectively. However, in the presence of water vapor, Pd/YZrAl was the best one over which the light-off temperature ( T 50 ) of methane was 339 °C and the complete conversion temperature ( T 90 ) was 371 °C. These results indicated that Pd catalyst supported on the modified composite ZrAl support showed excellent catalytic activity at low temperature and high resistance to H 2 O poisoning for the exhaust purification of lean-burn Natural Gas Vehicles.
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effect of cobalt oxide on performance of pd catalysts for lean burn Natural Gas Vehicles in the presence and absence of water vapor
Journal of Natural Gas Chemistry, 2010Co-Authors: Enyan Long, Yun Wang, Maochu Gong, Xiaoyu Zhang, Zhimin Liu, Yaoqiang ChenAbstract:Abstract Pd-based catalysts modified by cobalt were prepared by co-impregnation and sequential impregnation methods, and characterized by X-ray powder diffraction (XRD), N2 adsorption/desorption (Brunauer-Emmet-Teller method), CO-chemisorption and X-ray photoelectron spectroscopy (XPS). The activity of Pd catalysts was tested in the simulated exhaust Gas from lean-burn Natural Gas Vehicles. The effect of Co on the performance of water poisoning resistance for Pd catalysts was estimated in the simulated exhaust Gas with and without the presence of water vapor. It was found that the effect of Co significantly depended on the preparation process. PdCo/La-Al2O3 catalyst prepared by co-impregnation exhibited better water-resistant performance. The results of XPS indicated that both CoAl2O4 and Co3O4 were present in the Pd catalysts modified by Co. For the catalyst prepared by sequential impregnation method, the ratio of CoAl2O4/Co3O4 was higher than that of the catalyst prepared by co-impregnation method. It could be concluded that Co3O4 played an important role in improving water-resistant performance.
Hongyan Shang - One of the best experts on this subject based on the ideXlab platform.
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catalytic performance of pt rh cezryla laal with stoichiometric Natural Gas Vehicles emissions
Chinese Journal of Catalysis, 2015Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yajuan Cui, Ruimei Fang, Yaoqiang ChenAbstract:Abstract The composite support CeZrYLa+LaAl was prepared by a co-precipitation method, and Pt–Rh bimetallic catalysts were fabricated on this support using different preparation procedures. The catalytic activities of these materials were tested in a Gas mixture simulating the exhaust from a stoichiometric Natural Gas vehicle. The as-prepared catalysts were also characterized by X-ray photoelectron spectroscopy, X-ray diffraction, N 2 adsorption-desorption and H 2 -temperature-programmed reduction. It was found that the order of activities for CH 4 , CO and NO conversion was Cat3 ≈ Cat2 > Cat1, where Cat3 had the lowest light-off temperature ( T 50 ) for CO (114 °C) and NO (149 °C), the lowest complete conversion temperature ( T 90 ) for CH 4 (398 °C) and CO (179 °C), and the lowest Δ T ( T 90 – T 50 ) for CH 4 (34 °C) and CO (65 °C). Cat2 showed the lowest T 50 for CH 4 (342 °C), the lowest T 90 for NO (174 °C), and the lowest Δ T for NO (17 °C). Cat1 had the highest T 50 and T 90 and the largest Δ T out of all three catalysts. Indicating that Pt–Rh bimetallic catalysts (Cat2 and Cat3) prepared by physically mixing Pt and Rh powders exhibited much better catalytic activity than those (Cat1) prepared by co-impregnation, since homogeneous Pt and Rh sites made a significant contribution to CH 4 /CO/NO conversions. In contrast, strong Pt–Rh interactions in the co-impregnation materials affected the oxidation states of Pt, and the Pt-enriched surface blocked active Rh sites. Moreover, Cat3 was prepared by adding additives (La 3+ , Zr 4+ and Ba 2+ ) into the physically mixed Pt–Rh catalysts. XRD results demonstrated that the additive cation (Zr 4+ ) was incorporated into the CeO 2 –ZrO 2 lattice, thus creating a higher concentration of defects and improving the O 2 -mobility. XPS results showed that the Cat3 had the highest Ce 3+ /Ce ratio, suggesting the presence of a significant quantity of oxygen vacancies and cerium in the Ce 3+ state. All of these further promoted the three-way catalytic activity and widened the air-to-fuel working-window.
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excellent complete conversion activity for methane and co of pd tio2 zr0 5al0 5o1 75 catalyst used in lean burn Natural Gas Vehicles
Journal of Energy Chemistry, 2014Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Palladium catalysts are supported on TiO 2 , ZrO 2 , Al 2 O 3 , Zr 0.5 Al 0.5 O 1.75 and TiO 2 -Zr 0.5 Al 0.5 O 1.75 prepared by co-precipitation method, respectively. Catalytic activities for methane and CO oxidation are evaluated in a Gas mixture that simulated the exhaust from lean-burn Natural Gas Vehicles (NGVs). Pd/TiO 2 -Zr 0.5 Al 0.5 O 1.75 performs the best catalytic activity among the tested five catalysts. For CH 4 , the light-off temperature ( T 50 ) is 254 °C, and the complete conversion temperature ( T 90 ) is 280 °C; for CO, T 50 is 84 °C, and T 90 was 96 °C. Various techniques, including N 2 adsorption-desorption, X-ray diffraction (XRD), H 2 -temperature-programmed reduction (H 2 -TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) are employed to characterize the effect of supports on the physicochemical properties of prepared catalysts. N 2 adsorption-desorption and SEM show that TiO 2 -Zr 0.5 Al 0.5 O 1.75 expresses uniform nano-particles and large meso-pore diameters of 26 nm. H 2 -TPR and XRD indicate that PdO is well dispersed on the supports and strongly interacted with each other. The results of XPS show that the electron density around PdO and the proportion of active oxygen on TiO 2 -Zr 0.5 Al 0.5 O 1.75 are maxima among the five supports.
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Pd catalysts supported on modified Zr05Al05O1.75 used for lean-burn Natural Gas Vehicles exhaust purification
Journal of Natural Gas Chemistry, 2012Co-Authors: Hongyan Shang, Yun Wang, Maochu Gong, Yaoqiang ChenAbstract:Abstract Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La 2 O 3 , ZnO, Y 2 O 3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction (XRD), NH 3 temperature-programmed desorption (NH 3 -TPD), H 2 temperature-programmed reduction (H 2 -TPR), N 2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust Gas from lean-burn Natural Gas Vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrAl. The addition of ZnO or Y 2 O 3 promoted the conversion of CH 4 . In the absence of water vapor, Pd/ZnZrAl exhibited the best activity for CH 4 conversion with the light-off temperature ( T 50 ) of 275 °C and the complete conversion temperature ( T 90 ) of 314 °C, respectively. However, in the presence of water vapor, Pd/YZrAl was the best one over which the light-off temperature ( T 50 ) of methane was 339 °C and the complete conversion temperature ( T 90 ) was 371 °C. These results indicated that Pd catalyst supported on the modified composite ZrAl support showed excellent catalytic activity at low temperature and high resistance to H 2 O poisoning for the exhaust purification of lean-burn Natural Gas Vehicles.
