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881.
S. Yez Vilar A. Castro‐Couceiro B. Rivas‐Murias A. Fondado J. Mira J. Rivas M. A. Searís‐Rodríguez 《无机化学与普通化学杂志》2005,631(11):2192-2196
The dielectric properties of mixed‐oxide CaMn7O12 are reported. This compound exhibits a high dielectric constant at room temperature (ε′r> 104), for frequencies up to 104 Hz, values that make it very attractive for potential applications provided that its rather high losses can be minimized. Complex plane analysis of the obtained data reveal an important extrinsic contribution to these high ε′r values; and also that the intrinsic dielectric constant of this material is ε′r,∞ ≈ 30, a value rather high for this type of compounds, that could be related to the electronic process of charge‐ordering present in this oxide below 440 K. 相似文献
882.
锰基催化剂上CO2加氢反应性能的研究 总被引:1,自引:0,他引:1
研究了Mn基催化上CO2的加氢反应性能,结果表明:CO2活化吸附量的增加有利于CO2转化率的提高。Mn具有较好的CO2加氢生成CO的催化活性,CuO,Fe2O3的ZnO的加入使催化剂活性得到进一步的提高;NiO的加入增加了催化剂的H2活化吸附量,从而使催化剂对CH4的选择性得到提高,同时使CO2的转化率与Ni/γ-Al2O3相比略有下降。 相似文献
883.
A. V. Mashkina V. N. Yakovleva T. P. Voskresenskaya 《Reaction Kinetics and Catalysis Letters》1997,60(1):157-162
Surface acidity/Basicity of mixed oxides of La and Zn activated at three different temperatures were determined. The data
have been correlated with the catalytic activity for liquid phase reduction of cyclohexanone in isopropanol. 相似文献
884.
Orlik S. N. Pop G. Ganea R. Ostapyuk V. A. Alekseenko L. M. 《Theoretical and Experimental Chemistry》2004,40(3):187-191
We used X-ray phase analysis, IR, X-ray photoelectron, and NMR spectroscopy to characterize a synthesized mesoporous material (Fe,Al)-MCM-41. As a result of a certain combination of structural, acidic, and oxidation–reduction properties of the surface, (Fe,Al)-MCM-41 exhibits catalytic activity in reactions with participation of nitrogen oxides, in particular partial oxidation of propane by nitrogen(I) oxide to isopropanol. 相似文献
885.
E. V. Ishchenko V. K. Yatsimirskii S. V. Gaidai 《Theoretical and Experimental Chemistry》2005,41(5):340-345
We have used thermal desorption (TD) with mass spectrometric detection of the desorbed species to study the state of the surface
of oxide catalysts for oxidation of CO. Detection of weakly bound forms of water and the species H3O+ and HO
2
⋅
in the thermal desorption spectra correlates with the existence of temperature hysteresis in these samples. The data obtained
are explained by the reaction occurring in a highly active state via a heterogeneous-homogeneous mechanism, and also by the
effect of local superheating.
__________
Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 323–327, September–October, 2005. 相似文献
886.
Dr. Alberto Verdini Dr. Prashant Shinde Dr. Gian Luca Montanari Dr. Simone Tommaso Suran‐Brunelli Dr. Marco Caputo Dr. Giovanni Di Santo Dr. Carlo A. Pignedoli Dr. Luca Floreano Prof. Daniele Passerone Dr. Andrea Goldoni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14672-14677
Herein the formation of water molecules in the intermediate step of the redox reaction of porphyrins self‐metalation on O/Cu(111) is demonstrated. Photoemission measurements show that the temperature on which porphyrins pick‐up a substrate metal atom on O/Cu(111) is reduced by about 185±15 K with respect to the pure Cu(111). DFT calculations clearly indicate that the formation of a water molecule is less expensive than the formation of H2 on the O/Cu(111) substrate and, in some cases, it can be also exothermic. 相似文献
887.
High surface area porous W/Sn oxide nanomaterials were prepared via water/oil based (W/O) emulsion. Tungstic acid solution was generated by cation exchange of sodium tungstate in acidic Dowex resin. The acid was then mixed with a clear homogeneous aqueous N-cetyl trimethyl ammonium bromide (CTAB) solution followed by a slow addition of 0.2 M SnCl4 solution. The mixture was stirred for 24 h and then subjected to slow calcination at 500 °C. The prepared materials were characterized using SEM-EDX, BET surface area, and sorption of nitrogen and water. Fourier transform infrared spectroscopy (FTIR) was used to characterize the surface acidic properties using pyridine vapor as a probe. The materials were then tested toward the Dimethyl methylphosphonate (DMMP) adsorption at various temperatures using infrared spectroscopy. At elevated temperatures, the desorption of DMMP from WO3 and SnO2 surfaces results in forming methyl phosphonate that strongly bounds on the metal oxide surfaces. In contrast, the FTIR spectra showed that the adsorbed dimethyl methylphosphonate (DMMP) on the mixed W/Sn oxide powders can be molecularly desorbed without any decomposition. 相似文献
888.
Dr. Hao Zhu Chen Hou Yijing Li Dr. Guanghui Zhao Dr. Xiao Liu Ke Hou Prof. Dr. Yanfeng Li 《化学:亚洲杂志》2013,8(7):1447-1454
A facile one‐pot synthesis of highly water‐dispersible size‐tunable magnetite (Fe3O4) nanocrystal clusters (MNCs) end‐functionalized with amino or carboxyl groups by a modified solvothermal reduction reaction has been developed. Dopamine and 3,4‐dihydroxyhydroxycinnamic acid were used for the first time as both a surfactant and interparticle linker in a polylol process for economical and environment‐friendly purposes. Morphology, chemical composition, and magnetic properties of the prepared particles were investigated by several methods, including FESEM, TEM, XRD, XPS, Raman, FTIR, TGA, zeta potential, and VSM. The sizes of the particles could be easily tuned over a wide range from 175 to 500 nm by varying the surfactant concentration. Moreover, ethylene glycol/diethylene glycol (EG/DEG) solvent mixtures with different ratios could be used as reductants to obtain the particles with smaller sizes. The XRD data demonstrated that the surfactants restrained the crystal growth of the grains. The nanoparticles showed superior magnetic properties and high colloidal stability in water. The cytotoxicity results indicated the feasibility of using the synthesized nanocrystals in biology‐related fields. To estimate the applicability of the obtained MNCs in biotechnology, Candida rugosa lipase was selected for the enzyme immobilization process. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with the free enzyme. This novel strategy would simplify the reaction protocol and improve the efficiency of materials functionalization, thus offering new potential applications in biotechnology and organocatalysis. 相似文献
889.
Thermo‐analytical Investigations on the Superoxides AO2 (A = K,Rb, Cs), Revealing Facile Access to Sesquioxides A4O6
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Rb4O6 and Cs4O6 represent open shell p electron systems, featuring charge, spin, orbital and structural degrees of freedom, which makes them unique candidates for studying the ordering processes related, otherwise exclusively encountered in transition metal based materials. Probing the physical responses has been restrained by the intricacy of synthesizing appropriate amounts of phase pure samples. Tracing the thermal decomposition of respective superoxides has revealed that at least the rubidium and cesium sesquioxides exist in thermodynamic equilibrium, appropriate p‐T conditions given. These insights have paved the way to highly efficient and convenient access to Rb4O6 and Cs4O6. 相似文献
890.
Meilana Dharma Putra Saeed M. Al-Zahrani Ahmed E. Abasaeed 《Journal of Energy Chemistry》2013,22(5):778-782
Incorporation of strontium into V-Mo alumina-supported catalyst enhanced its performance (increased conversion and selectivity, decreased reducibility and improved stability) in propane oxydehydrogenation to propylene. 12.5% Sr loading was shown to be the optimum content to the V-Mo catalyst. The results were supported by various characterization techniques, namely, BET, XRD, SEM, FTIR and TPD. 相似文献