A series of praseodymium added CeO2(ZrO2)/TiO2 catalysts separately prepared by methods of sol-gel and impregnation were tested for selective catalytic reduction of NO, and characterized by X-ray diffraction (XRD)...A series of praseodymium added CeO2(ZrO2)/TiO2 catalysts separately prepared by methods of sol-gel and impregnation were tested for selective catalytic reduction of NO, and characterized by X-ray diffraction (XRD), N2-brumauer-emmett-teller (N2-BET), NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), PL spectra, Ra-man spectra, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), respectively. Influence of prepara-tion method on catalytic performance was studied. Results showed that the influence of Pr addition on catalytic performance of the CeO2(ZrO2)/TiO2 catalysts was different between the sol-gel method and the impregnation method. The Pr addition tended to interact with TiO2 and formed the structure of Ti-O-Pr in the sol-gel method while it was more likely to interact with CeO2 forming the struc-ture of Ce-O-Pr in the impregnation method. The total acid amount and redox properties of the catalysts prepared by sol-gel method decreased with the addition of Pr element, which resulted in decrease of catalytic activity. In contrast, the Pr-added catalyst prepared by impregnation method was found to possess easier reducibility, more total acid amount and higher proportion of Ce3+ species, which was favourable for higher catalytic activity.展开更多
A series CeO2(ZrO2)/TiO2 catalysts were modified with Er using a sol-gel method.The catalytic activity of the obtained catalysts in the selective catalytic reduction(SCR) of NO with NH3 was investigated to determi...A series CeO2(ZrO2)/TiO2 catalysts were modified with Er using a sol-gel method.The catalytic activity of the obtained catalysts in the selective catalytic reduction(SCR) of NO with NH3 was investigated to determine the appropriate Er dosage.The catalysts were characterized using X-ray diffraction,N2 adsorption,NH3 temperature-programmed desorption,H2 temperature-programmed reduction,photoluminescence spectroscopy,electron paramagnetic resonance spectroscopy,and X-ray photoelectron spectroscopy.The results showed that the optimum Er/Ce molar ratio was 0.10;this catalyst had excellent resistance to catalyst poisoning caused by vapor and sulfur and gave more than 90% NO conversion at 220–395 ℃ and a gas hourly space velocity of 71 400 h^-1.Er incorporation increased the Ti^3+ concentrations,oxygen storage capacities,and oxygen vacancy concentrations of the catalysts,resulting in excellent catalytic performance.Er incorporation also decreased the acid strength and inhibited growth of TiO2 and CeO2 crystal particles,which increased the catalytic activity.The results show that high oxygen vacancy concentrations and oxygen storage capacities,large amounts of Ti^3+,and low acid strengths give excellent SCR activity.展开更多
Effects of Zr/Ti molar ratio in SO42-/ZrO2-TiO2 solid acid catalyst calcined at different temperatures on its surface properties and catalytic activity were thoroughly investigated in this paper. The physicochemical c...Effects of Zr/Ti molar ratio in SO42-/ZrO2-TiO2 solid acid catalyst calcined at different temperatures on its surface properties and catalytic activity were thoroughly investigated in this paper. The physicochemical characteristics of prepared samples were determined by N2 adsorptiondesorption, XRD, NH3-TPD and XPS techniques, respectively. It was found that the crystallization temperature of the samples increased after the combination of ZrO2 and TiO2; and phase transformations from the anatase to the rutile of TiO2 species and the tetragonal to the monoclinic of ZrO2 species were effectively suppressed at higher temperature. The sample with a Zr/Ti molar ratio of 3/1 calcined at 450℃ showed the highest surface area and the most acid sites among all the tested samples. The acid site densities of samples were relatively closed to each other if they were calcined at the same temperature, however, decreased with the calcination temperature. The result indicates that the sulfur content in samples is a crucial factor to control the acid site density. Calcining the sample at 650℃ and higher temperatures resulted in a significant desorption of sulfate ion on the samples. The synthesized samples were evaluated as a potential catalyst for glucose conversion under the near-critical methanol conditions (200℃/4 MPa). The results suggested that the relatively weaker acid sites of the catalyst were more favorable for the accumulation of methyl glucosides, while the moderate acid sites were responsible for the formation of methyl levulinate. The catalytic activity for methyl levulinate production almost increases linearly with the catalyst acid site density. The catalyst deactivation is due to the loss of sulfate ion and the two catalysts with Zr/Ti molar ratios of 3/1 and 1/3 could effectively alleviate the deactivation caused by sulfate solution in the reaction medium and can be reused after calcination with the reuse rate of over 90% in terms of the methyl levulinate selectivity.展开更多
基金supported by National Key Research and Development Program of China(2016YFC0205500)National Natural Science Foundation of China(51272105)+1 种基金Jiangsu Provincial Science and Technology Supporting Program(BE2013718)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
摘要A series of praseodymium added CeO2(ZrO2)/TiO2 catalysts separately prepared by methods of sol-gel and impregnation were tested for selective catalytic reduction of NO, and characterized by X-ray diffraction (XRD), N2-brumauer-emmett-teller (N2-BET), NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), PL spectra, Ra-man spectra, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS), respectively. Influence of prepara-tion method on catalytic performance was studied. Results showed that the influence of Pr addition on catalytic performance of the CeO2(ZrO2)/TiO2 catalysts was different between the sol-gel method and the impregnation method. The Pr addition tended to interact with TiO2 and formed the structure of Ti-O-Pr in the sol-gel method while it was more likely to interact with CeO2 forming the struc-ture of Ce-O-Pr in the impregnation method. The total acid amount and redox properties of the catalysts prepared by sol-gel method decreased with the addition of Pr element, which resulted in decrease of catalytic activity. In contrast, the Pr-added catalyst prepared by impregnation method was found to possess easier reducibility, more total acid amount and higher proportion of Ce3+ species, which was favourable for higher catalytic activity.
基金supported by the National Natural Science Foundation of China(51272105)Jiangsu Provincial Science and Technology Supporting Program(BE2013718)+1 种基金Research Subject of Environmental Protection Department of Jiangsu Province of China(2013006)Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)~~
摘要A series CeO2(ZrO2)/TiO2 catalysts were modified with Er using a sol-gel method.The catalytic activity of the obtained catalysts in the selective catalytic reduction(SCR) of NO with NH3 was investigated to determine the appropriate Er dosage.The catalysts were characterized using X-ray diffraction,N2 adsorption,NH3 temperature-programmed desorption,H2 temperature-programmed reduction,photoluminescence spectroscopy,electron paramagnetic resonance spectroscopy,and X-ray photoelectron spectroscopy.The results showed that the optimum Er/Ce molar ratio was 0.10;this catalyst had excellent resistance to catalyst poisoning caused by vapor and sulfur and gave more than 90% NO conversion at 220–395 ℃ and a gas hourly space velocity of 71 400 h^-1.Er incorporation increased the Ti^3+ concentrations,oxygen storage capacities,and oxygen vacancy concentrations of the catalysts,resulting in excellent catalytic performance.Er incorporation also decreased the acid strength and inhibited growth of TiO2 and CeO2 crystal particles,which increased the catalytic activity.The results show that high oxygen vacancy concentrations and oxygen storage capacities,large amounts of Ti^3+,and low acid strengths give excellent SCR activity.
基金supported by the National Key Basic Research Program (2010CB732201) from the Ministry of Science and Technology of Chinathe Natural Science Foundation of China (U0733001, 50776035)the Basic Research Foundation from the Ministry of Education for Universities (2010121077)
摘要Effects of Zr/Ti molar ratio in SO42-/ZrO2-TiO2 solid acid catalyst calcined at different temperatures on its surface properties and catalytic activity were thoroughly investigated in this paper. The physicochemical characteristics of prepared samples were determined by N2 adsorptiondesorption, XRD, NH3-TPD and XPS techniques, respectively. It was found that the crystallization temperature of the samples increased after the combination of ZrO2 and TiO2; and phase transformations from the anatase to the rutile of TiO2 species and the tetragonal to the monoclinic of ZrO2 species were effectively suppressed at higher temperature. The sample with a Zr/Ti molar ratio of 3/1 calcined at 450℃ showed the highest surface area and the most acid sites among all the tested samples. The acid site densities of samples were relatively closed to each other if they were calcined at the same temperature, however, decreased with the calcination temperature. The result indicates that the sulfur content in samples is a crucial factor to control the acid site density. Calcining the sample at 650℃ and higher temperatures resulted in a significant desorption of sulfate ion on the samples. The synthesized samples were evaluated as a potential catalyst for glucose conversion under the near-critical methanol conditions (200℃/4 MPa). The results suggested that the relatively weaker acid sites of the catalyst were more favorable for the accumulation of methyl glucosides, while the moderate acid sites were responsible for the formation of methyl levulinate. The catalytic activity for methyl levulinate production almost increases linearly with the catalyst acid site density. The catalyst deactivation is due to the loss of sulfate ion and the two catalysts with Zr/Ti molar ratios of 3/1 and 1/3 could effectively alleviate the deactivation caused by sulfate solution in the reaction medium and can be reused after calcination with the reuse rate of over 90% in terms of the methyl levulinate selectivity.