Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<s...Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<sup>2+</sup>) by temperature-programmed desorption of CO<sub>2</sub> (CO<sub>2</sub>-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO<sub>2</sub> molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO<sub>2</sub> obtained on the reference zeolite NaX (13.5 kJ·mol<sup>-1</sup>) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol<sup>-1</sup> respectively). In the chemisorbed CO<sub>2</sub> region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO<sub>3</sub>2-</sup>) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol<sup>-1</sup>, higher than the desorbed species (bicarbonates: HCO<sub>3</sub>2-</sup>) on the reference R-NaX (62 kJ·mol<sup>-1</sup>). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol<sup>-1</sup> lower to desorption energies of bicarbonates noted on the reference zeolite NaX.展开更多
The effects of different crystal structures of copper chloride hydroxide on the catalytic synthesis of diethyl carbonate by the oxidative carbonylation of ethanol was discussed. The catalytic activity was improved sig...The effects of different crystal structures of copper chloride hydroxide on the catalytic synthesis of diethyl carbonate by the oxidative carbonylation of ethanol was discussed. The catalytic activity was improved significantly and the active component of γ-Cu2（OH）3Cl was partially converted into Cu（OH）Cl when KCl was added in the catalyst. CO-TPD analysis of the catalyst showed that the adsorption of CO increased and the desorption temperature shifted to the right. Morphological analysis by SEM of the catalyst showed that the active component of the catalyst was highly dispersed on the carrier promoting the catalytic activity of the catalyst in the synthesis of DEC. Reaction mechanism analysis showed that the fact that Cu（OH）Cl was more active than γ-Cu2（OH）3Cl in the oxidative carbonylation of ethanol to DEC was attributed to the John-Teller effect.展开更多
A series of ultrafine Mo Co K catalysts with different Co/Mo ratios but constant potassium content were characterized by TPD technique and their catalytic performance for higher alcohol synthesis was investigated The ...A series of ultrafine Mo Co K catalysts with different Co/Mo ratios but constant potassium content were characterized by TPD technique and their catalytic performance for higher alcohol synthesis was investigated The results indicated that there are two kinds of adsorption sites, ie, low temperature adsorption sites (LTAS) around 90?℃ and high temperature adsorption sites (HTAS) above 400?℃ for H 2 and CO on the surface of the catalysts The desorption temperature of HTAS for H 2 and CO as well as the desorption amount of HTAS for H 2 were strongly influenced by the Co/Mo ratio of the catalysts It was found that the addition of Co into the ultrafine Mo K catalyst resulted in a decrease of the HTAS desorption temperature and an increase of the HTAS desorption amount for H 2 As the Co/Mo ratio increased further, the HTAS desorption amount for H 2 increased accordingly while the HTAS desorption temperature remained constant However, the HTAS desorption temperature for CO was found to be mainly influenced by the Co/Mo ratio, and the HTAS desorption temperature got its minimum at the Co/Mo ratio of 1∶7 It was found that a weaker adsorption of H 2 and CO on the HTAS and an appropriate H 2 adsorption amount were favourable for the formation of higher展开更多
采用BET、XPS和TPD表征手段对超细Mo Co K催化剂的织构、表面结构和吸附行为进行了研究,结合催化剂的合成低碳醇性能,论证了Co在超细Mo Co K催化剂合成低碳醇中的作用。Co的加入提高了催化剂合成低碳醇的活性和选择性,同时也提高了催化...采用BET、XPS和TPD表征手段对超细Mo Co K催化剂的织构、表面结构和吸附行为进行了研究,结合催化剂的合成低碳醇性能,论证了Co在超细Mo Co K催化剂合成低碳醇中的作用。Co的加入提高了催化剂合成低碳醇的活性和选择性,同时也提高了催化剂的比表面并促进了微孔的形成,催化剂的催化性能与其织构之间呈现出很好的顺变关系。Co对催化剂中可能作为合成低碳醇活性中心的低价Mo物种的电子结合能值影响较小。Co的加入降低了H2和CO在催化剂表面的强吸附中心的吸附强度,从而有利于合成低碳醇反应的发生。研究结果表明,Co仅仅是作为结构助剂,通过调变催化剂的织构和催化剂表面的H2及CO的强吸附中心而影响其合成低碳醇性能的。展开更多
文摘Study of physisorbed and chemisorbed carbon dioxide (CO<sub>2</sub>) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca<sup>2+</sup> and Ba<sup>2+</sup>) by temperature-programmed desorption of CO<sub>2</sub> (CO<sub>2</sub>-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO<sub>2</sub> molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO<sub>2</sub> obtained on the reference zeolite NaX (13.5 kJ·mol<sup>-1</sup>) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol<sup>-1</sup> respectively). In the chemisorbed CO<sub>2</sub> region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO<sub>3</sub>2-</sup>) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol<sup>-1</sup>, higher than the desorbed species (bicarbonates: HCO<sub>3</sub>2-</sup>) on the reference R-NaX (62 kJ·mol<sup>-1</sup>). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol<sup>-1</sup> lower to desorption energies of bicarbonates noted on the reference zeolite NaX.
文摘The effects of different crystal structures of copper chloride hydroxide on the catalytic synthesis of diethyl carbonate by the oxidative carbonylation of ethanol was discussed. The catalytic activity was improved significantly and the active component of γ-Cu2（OH）3Cl was partially converted into Cu（OH）Cl when KCl was added in the catalyst. CO-TPD analysis of the catalyst showed that the adsorption of CO increased and the desorption temperature shifted to the right. Morphological analysis by SEM of the catalyst showed that the active component of the catalyst was highly dispersed on the carrier promoting the catalytic activity of the catalyst in the synthesis of DEC. Reaction mechanism analysis showed that the fact that Cu（OH）Cl was more active than γ-Cu2（OH）3Cl in the oxidative carbonylation of ethanol to DEC was attributed to the John-Teller effect.
文摘A series of ultrafine Mo Co K catalysts with different Co/Mo ratios but constant potassium content were characterized by TPD technique and their catalytic performance for higher alcohol synthesis was investigated The results indicated that there are two kinds of adsorption sites, ie, low temperature adsorption sites (LTAS) around 90?℃ and high temperature adsorption sites (HTAS) above 400?℃ for H 2 and CO on the surface of the catalysts The desorption temperature of HTAS for H 2 and CO as well as the desorption amount of HTAS for H 2 were strongly influenced by the Co/Mo ratio of the catalysts It was found that the addition of Co into the ultrafine Mo K catalyst resulted in a decrease of the HTAS desorption temperature and an increase of the HTAS desorption amount for H 2 As the Co/Mo ratio increased further, the HTAS desorption amount for H 2 increased accordingly while the HTAS desorption temperature remained constant However, the HTAS desorption temperature for CO was found to be mainly influenced by the Co/Mo ratio, and the HTAS desorption temperature got its minimum at the Co/Mo ratio of 1∶7 It was found that a weaker adsorption of H 2 and CO on the HTAS and an appropriate H 2 adsorption amount were favourable for the formation of higher
文摘首次采用聚乙二醇凝胶法制备了Co系类钙钛矿LnS rCoO4(Ln=L a,P r,N d,Sm,Eu)复合氧化物,研究了稀土对催化剂的结构和催化性能的影响,考察了它们对CO和C3H8的氧化反应活性,并运用XRD、BET、TPD等方法对催化剂进行了表征。结果表明:该类复合氧化物具有K2N iF4结构,它们的结构和催化性能随稀土不同而变化,其中以L aS rCoO4催化活性最好,这是由L aS rCoO4的晶格氧更易移动、Co3+离子含量更高,氧空位和反应时化学吸附氧更多所致。
文摘采用BET、XPS和TPD表征手段对超细Mo Co K催化剂的织构、表面结构和吸附行为进行了研究,结合催化剂的合成低碳醇性能,论证了Co在超细Mo Co K催化剂合成低碳醇中的作用。Co的加入提高了催化剂合成低碳醇的活性和选择性,同时也提高了催化剂的比表面并促进了微孔的形成,催化剂的催化性能与其织构之间呈现出很好的顺变关系。Co对催化剂中可能作为合成低碳醇活性中心的低价Mo物种的电子结合能值影响较小。Co的加入降低了H2和CO在催化剂表面的强吸附中心的吸附强度,从而有利于合成低碳醇反应的发生。研究结果表明,Co仅仅是作为结构助剂,通过调变催化剂的织构和催化剂表面的H2及CO的强吸附中心而影响其合成低碳醇性能的。
