The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the propertie...The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the properties of CeO2-supported Co catalysts including the surface area, the crystallite size and the morphology of CeO2, the reduction degree of cobalt species and the adsorption performance of hydrogen and nitrogen. As a consequence, the samples promoted with an appropriate amount of Ba show higher ammonia synthesis rates, while the catalysts with high Ba loading or K promoter all exhibit low catalytic activities.展开更多
The CuO/CeO2 catalysts were investigated by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectronic spectroscopy (XPS), temperature-programmed reduction (TPR), in situ Fourier t...The CuO/CeO2 catalysts were investigated by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectronic spectroscopy (XPS), temperature-programmed reduction (TPR), in situ Fourier transform infrared spectroscopy (FTIR) and NO+CO reaction. The results revealed that the low temperature (〈150℃) catalytic performances were enhanced for CO pretreated samples. During CO pretreatment, the surface Cu+/Cu0 and oxygen vacancies on ceria surface were present. The low va- lence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation. These effects in turn led to higher activities of CuO/CeO2 for NO reduction. The current study provided helpful understandings of active sites and reaction mechanism in NO+CO reaction.展开更多
The NO oxidation reaction was studied over MnOx-CeO2 catalysts prepared by co-precipitation, impregnation and mechanical mixing method, respectively. It was found that the co-precipitation was the most active and a 60...The NO oxidation reaction was studied over MnOx-CeO2 catalysts prepared by co-precipitation, impregnation and mechanical mixing method, respectively. It was found that the co-precipitation was the most active and a 60% NO conversion was achieved at 250 oC. X-ray diffraction (XRD), Brumauer-Emmett (BET), H2-temperature programmed reduction (H2-TPR) and oxygen storage capacity (OSC) techniques were employed to characterize the physical and chemical properties of the catalysts. XRD results showed that amorphous MnOx or Mn-O-Ce solid solution existed in co-precipitation and impregnation prepared sample, while crystalline MnOx was found in mechanical mixing catalyst. A larger surface area was observed on co-precipitation prepared catalyst compared to those prepared by impregnation and mechanical mixing. The strong interaction between MnOx and CeO2 enhanced the reducibility of the oxides and increased the amount of Mn4+ and activated oxygen, which are favorable for NO oxidation to NO2.展开更多
A modified CuO/CeO2 catalyst was prepared by surfactant-assisted impregnation method and showed better catalytic activity for low temperature CO oxidation than that from conventional impregnation method. The physicoch...A modified CuO/CeO2 catalyst was prepared by surfactant-assisted impregnation method and showed better catalytic activity for low temperature CO oxidation than that from conventional impregnation method. The physicochemical properties of different CuO/CeO2 catalysts were characterized by thermogravimetrie and differential scanning calorimetric measurements (TG-DSC), X-ray diffraction (XRD), N2 adsorpti0n-desorption, Raman spectroscopy, H2 temperature-programmed reduction (H2-TPR), tern- perature-programmed desorption of 02 (O2-TPD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The re- sults suggested that the addition of hexadecyl trimethyl ammonium bromide (CTAB) into the impregnation solution could improve the dispersion of CuO species, which could facilitate Cu2+ incorporating into CeO2 lattice and strengthened the synergistic effects between CuO and CeO2, making the lattice oxygen more active, and eventually resulting in enhanced activity for CO oxidation.展开更多
采用浸渍法以Cu(CH3COO)2为前驱体,在N2气氛下于不同温度下焙烧,制备了CuOx/CeO2催化剂。结合XRD,H2-TPR,XPS等表征技术,以及CO-PROX(Preferential Oxidation of CO)反应测试,获得了CuOx/CeO2催化剂中不同Cu物种随焙烧温度变化的分布信...采用浸渍法以Cu(CH3COO)2为前驱体,在N2气氛下于不同温度下焙烧,制备了CuOx/CeO2催化剂。结合XRD,H2-TPR,XPS等表征技术,以及CO-PROX(Preferential Oxidation of CO)反应测试,获得了CuOx/CeO2催化剂中不同Cu物种随焙烧温度变化的分布信息及其对CO-PROX催化活性的影响。结果表明:CuOx/CeO2催化剂CO-PROX催化活性变化的趋势与催化剂表面分散态Cu+物种变化趋势一致,随着焙烧温度从200℃升至500℃,催化剂表面的分散态Cu+先增加后减少,当分散态Cu+在焙烧温度250~400℃达到最多时,其催化活性最好,随后下降,说明分散态Cu+对CO-PROX反应活性起关键作用。展开更多
基金supported by National Natural Science Foundation of China(21776047,21203028)
摘要The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the properties of CeO2-supported Co catalysts including the surface area, the crystallite size and the morphology of CeO2, the reduction degree of cobalt species and the adsorption performance of hydrogen and nitrogen. As a consequence, the samples promoted with an appropriate amount of Ba show higher ammonia synthesis rates, while the catalysts with high Ba loading or K promoter all exhibit low catalytic activities.
基金supported by National Basic Research Program of China(2010CB732300)National Natural Science Foundation of China(21273110,20973091)Natural Science Foundation for the Youth(21203091)
摘要The CuO/CeO2 catalysts were investigated by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectronic spectroscopy (XPS), temperature-programmed reduction (TPR), in situ Fourier transform infrared spectroscopy (FTIR) and NO+CO reaction. The results revealed that the low temperature (〈150℃) catalytic performances were enhanced for CO pretreated samples. During CO pretreatment, the surface Cu+/Cu0 and oxygen vacancies on ceria surface were present. The low va- lence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation. These effects in turn led to higher activities of CuO/CeO2 for NO reduction. The current study provided helpful understandings of active sites and reaction mechanism in NO+CO reaction.
基金supported by National High Technology Research and Development Program of China(863Program,2011AA03A405)grant support from GM Global Research & Development
摘要The NO oxidation reaction was studied over MnOx-CeO2 catalysts prepared by co-precipitation, impregnation and mechanical mixing method, respectively. It was found that the co-precipitation was the most active and a 60% NO conversion was achieved at 250 oC. X-ray diffraction (XRD), Brumauer-Emmett (BET), H2-temperature programmed reduction (H2-TPR) and oxygen storage capacity (OSC) techniques were employed to characterize the physical and chemical properties of the catalysts. XRD results showed that amorphous MnOx or Mn-O-Ce solid solution existed in co-precipitation and impregnation prepared sample, while crystalline MnOx was found in mechanical mixing catalyst. A larger surface area was observed on co-precipitation prepared catalyst compared to those prepared by impregnation and mechanical mixing. The strong interaction between MnOx and CeO2 enhanced the reducibility of the oxides and increased the amount of Mn4+ and activated oxygen, which are favorable for NO oxidation to NO2.
基金supported by the National Natural Science Foundation of China(21273150)‘‘Shu Guang’’Project(10GG23)of Shanghai Municipal Education CommissionShanghai Education Development Foundation
摘要A modified CuO/CeO2 catalyst was prepared by surfactant-assisted impregnation method and showed better catalytic activity for low temperature CO oxidation than that from conventional impregnation method. The physicochemical properties of different CuO/CeO2 catalysts were characterized by thermogravimetrie and differential scanning calorimetric measurements (TG-DSC), X-ray diffraction (XRD), N2 adsorpti0n-desorption, Raman spectroscopy, H2 temperature-programmed reduction (H2-TPR), tern- perature-programmed desorption of 02 (O2-TPD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The re- sults suggested that the addition of hexadecyl trimethyl ammonium bromide (CTAB) into the impregnation solution could improve the dispersion of CuO species, which could facilitate Cu2+ incorporating into CeO2 lattice and strengthened the synergistic effects between CuO and CeO2, making the lattice oxygen more active, and eventually resulting in enhanced activity for CO oxidation.
摘要采用浸渍法以Cu(CH3COO)2为前驱体,在N2气氛下于不同温度下焙烧,制备了CuOx/CeO2催化剂。结合XRD,H2-TPR,XPS等表征技术,以及CO-PROX(Preferential Oxidation of CO)反应测试,获得了CuOx/CeO2催化剂中不同Cu物种随焙烧温度变化的分布信息及其对CO-PROX催化活性的影响。结果表明:CuOx/CeO2催化剂CO-PROX催化活性变化的趋势与催化剂表面分散态Cu+物种变化趋势一致,随着焙烧温度从200℃升至500℃,催化剂表面的分散态Cu+先增加后减少,当分散态Cu+在焙烧温度250~400℃达到最多时,其催化活性最好,随后下降,说明分散态Cu+对CO-PROX反应活性起关键作用。