共查询到20条相似文献,搜索用时 17 毫秒
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《印度化学会志》2021,98(8):100116
Co3O4–SrCO3 catalysts with various Sr/Co ratios were synthesized by the coprecipitation method, and their properties were tuned by adjusting the Sr/Co molar ratio. Furthermore, the catalytic combustion of vinyl chloride (VC) was used to evaluate the catalytic activity of the Co3O4–SrCO3 catalysts. The physicochemical properties of the catalysts were studied by X-ray diffraction (XRD), infrared spectroscopy (IR), N2 sorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR) and VC temperature-programmed desorption (VC-TPD). The results showed that the Co3O4–SrCO3 catalysts exhibited composite phases of Co3O4 and SrCO3 and the presence of interactions between them. As a result, the crystallization of the Co3O4 phase for the Co3O4–SrCO3 catalysts was restrained, and the state of Co on the catalyst surface was adjusted. Furthermore, the reducibility and VC adsorption capacity of the Co3O4–SrCO3 catalysts with Sr/Co molar ratios of 0.2 and 0.4 were enhanced compared with those of the Co3O4 catalyst. Otherwise, catalyst SrCo-0.4 exhibited excellent catalytic performance, accompanied by the highest reaction rate and the lowest apparent activation energy. More importantly, the optimized SrCO3–Co3O4 catalyst showed superior catalytic performance compared with other transition metal oxides in previous literature. These results brought a new idea for promoting the activity of transition metal catalysts for the deep oxidation of chlorinated volatile organic compounds (CVOCs) by introducing alkaline-earth metal salts. 相似文献
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This study investigates the feasibility of using ethylene oxide (EO) chain adsorption to determine the surface area of smectite in water. Experimental results indicate that high-molecular-weight poly(ethylene oxide) (PEO) should be used to provide reasonable estimations for monolayer capacity of PEO on smectite. The surface areas of smectites in water are calculated from the monolayer capacity of PEO adsorbed on smectite by taking the area per EO unit as 8.05 A(2). The method measures the actual surface area of smectite exposed when dispersed in water, which is important to applications of smectite under aqueous conditions. 相似文献
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Basma A.A. Balboul 《Thermochimica Acta》2006,445(1):78-81
The reaction between lanthanum oxide and strontium carbonate was studied non-isothermally between 350 and 1150 °C at different heating rates, intermediates and the final solid product were characterized by X-ray diffractometry (XRD). The reaction proceeds through formation of lanthanum oxycarbonate La2O(CO3)2, lanthanum dioxycarbonate La2O2CO3, and non-stoichiometric strontium lanthanum oxide La2SrOx (x = 4 + δ). La4SrO7 was found to be the final product which begins to form at ∼700 °C. Li+ doping enhances the formation of the final product as well as commencement of the reactions at lower temperatures. 相似文献
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O.D. Bonner Charles F. Jordan Ruth K. Arisman Jana M. Bednarek 《The Journal of chemical thermodynamics》1976,8(12):1173-1176
The osmotic and activity coefficients of thiourea and 1,3-dimethylthiourea have been determined from isopiestic measurements in aqueous solutions. Osmotic coefficients of these substances in ethylene carbonate solutions have been calculated from freezing-temperature measurements. The results of this and previously reported work enable the following conclusions. The substitution of alkyl groups for hydrogen atoms or sulfur for oxygen in the urea molecule diminishes the osmotic coefficients in aqueous solutions. Micelle formation is suspected as the cause. Urea tends to dimerize in ethylene carbonate while thiourea does not. 相似文献
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Ivan M. Panayotov Iliyana V. Berlinova Ilya B. Rashkov 《Journal of polymer science. Part A, Polymer chemistry》1975,13(9):2043-2050
The polymerization of ethylene oxide (EO) in tetrahydrofuran (THF) initiated by inclusion compounds of potassium in graphite (C24K) at 50°C was studied. During the initial slow stage of the polymerization the catalyst efficiency increases, while during the second rapid stage the reaction proceeds at a constant concentration of the active centers. The influence of the catalyst and monomer concentrations on the concentration of the active centers and on the catalyst efficiency was studied. The existence of the slow stage is explained by diffusion of ethylene oxide between the graphite planes, where both initiation and initial chain growth take place. The diffusion of the growing chains from the catalyst into the solution brings about the formation of a necessary concentration of active centers in the solution, which ensures the rapid growth of the polymer chains under homogeneous conditions. An x-ray study of the catalyst after polymerization shows a strongly disturbed crystal structure of the graphite. Poly-(ethylene oxide) obtained at a higher degree of conversion, does not contain low molecular weight fractions. 相似文献
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M. K. Krasil'nikova V. I. Lygin K. V. Topchieva 《Theoretical and Experimental Chemistry》1967,2(2):194-197
The adsorption of ethylene and hydrogen on yttrium oxide samples that had been subjected to different thermal treatment in vacuo (500 and 800 C), was studied by infrared spectroscopy. It was found that ethers are formed at the surface when ethylene is chemisorbed. Absorption bands which are characteristic for unsaturated surface compounds are observed for the sample which was dehydrated at 800 C. It was shown that the hydrogenation of these surface compounds is a slow process. 相似文献
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Polymerization of ethylene in the presence of novel single-site titanium phenolate catalytic systems
A. G. Azizov R. V. Alieva G. S. Martynova Sh. R. Bagirova E. S. Kalbalieva 《Polymer Science Series B》2009,51(11-12):444-451
The polymerization of ethylene has been studied in the presence of novel catalytic systems based on various sterically hindered phenol precursor complexes of titanium containing grafted phenoxyammonium ligands. The presence of the grafted ammonium salt in the phenolate ligand leads to an increase in the activity of the catalyst and originates single-site catalytic systems. As evidenced by IR and 13C NMR studies and DSC measurements, the resulting polymers are linear, possess a narrow molecular-mass distribution (M w/M n = 2–4), and are characterized by a wide range of thermal properties. 相似文献
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S. S. Ivanchev M. Yu. Vasil’eva N. I. Ivancheva V. K. Badaev I. I. Oleinik E. V. Sviridova G. A. Tolstikov 《Polymer Science Series B》2009,51(7-8):276-282
The kinetic features of polymerization of ethylene with five methylaluminoxane-activated selfim-mobilizing bis(phenoxyimine) complexes of titanium chloride, namely, bis{2-[(4-allyloxyphenylimino)methyl]-6-tert-butylphenoxy}TiCl2, bis{2-[(4-allyloxyphenylimino)methyl]-4,6-di-tert-butylphenoxy}TiCl2, bis{2-[(4-allyloxyphenylimino)methyl]-6-cumylphenoxy}TiCl2, bis{2-[(4-allyloxyphenylimino)methyl]-4,6-dicumylphenoxy}TiCl2, and bis{2-[(4-allyloxyphenylimino)methyl]-6-1-(4-tert-butylphenyl)ethylphenoxy}TiCl2 have been studied. The activity of these complexes in the polymerization of ethylene in the temperature range 20–80°C and an ethylene pressure of 0.3 MPa has been investigated both in the homogeneous and polymer matrix-bound states. The self-immobilizing catalytic systems possess high activity (up to 40000 kgPE/molcat MPa h) and give rise to ultrahigh-molecular-weight PE (M = (2–7) × 106) with an improved morphology of polymer particles. 相似文献
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The kinetics of ethylene oxide polymerization in THF, with Na, K and Cs-naphthalene complexes as initiators, have been studied in detail. 相似文献
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Chia-Chi Su Yun-Hwei Shen 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,312(1):1-6
The adsorption of polymers on clay is important in many applications. However the mechanisms of poly(ethylene oxide) (PEO) adsorption on smectite and its effect on suspension rheology are not well elucidated at present. The aim of this study was to investigate the mechanisms responsible for PEO sorption on smectite and how this impacts on dispersive behavior of smectite suspension. The results indicated that the hydrophobic interaction between CH2CH2 groups and siloxane surface is the major driven force for PEO adsorption on smectite. In addition, PEO adsorbed preferentially on the surface of low-charge smectite and the delamination of low-charge smectite in water was enhanced due to PEO adsorption presumably due to the hydrophilic ether oxygen of adsorbed PEO. 相似文献
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Effect of copper oxide on the catalytic activity of iron-chromia catalyst for water gas shift reaction 总被引:1,自引:0,他引:1
V. Idakiev D. Mihajlova B. Kunev A. Andreev 《Reaction Kinetics and Catalysis Letters》1987,33(1):119-124
It has been established that copper oxide promotes the catalytic activity of iron-chromia catalyst in the water gas shift reaction due to the formation of catalytically active aggregates. However, due to their gradual recrystallization and sintering into larger copper particles, the promoting effect sharply decreases.
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The adsorption of I? anions on the Bi(111) single-crystal plane from solutions in ethylene carbonate has been investigated by impedance measurement method. The ionic charge due to the specific adsorption has been obtained by integration of differential capacitance curves, and the Gibbs excess has been calculated using the mixed-electrolyte method applied for both electrode charge and electrode potential as the independent electrical variables. The Gibbs energy of I? anion adsorption has been calculated using the virial adsorption isotherm. It was found that under comparable conditions, the results obtained at constant electrode potential and at constant electrode charge were coincident. The Gibbs energy of I? anion adsorption and the calculated electrosorption valency value were found to be very close to these values obtained in propylene carbonate. 相似文献
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Shin-ichiro Fujita Bhalchandra M. Bhanage Hiroshi Kanamaru Masahiko Arai 《Journal of molecular catalysis. A, Chemical》2005,230(1-2):43-48
Several basic metal oxide catalysts were tested for the synthesis of 1,3-disubstituted urea from ethylene carbonate (EC) and amine. Among the catalysts used, CaO has been found to be an excellent recyclable catalyst for the reaction. It has been suggested that strongly basic property of CaO results in its high activity. Disubstituted ureas are obtained from propylamine and butylamine with high yields at 100 °C. Slightly higher reaction temperatures are necessary for obtaining good yields from amines having larger molecular weights and urea is not produced from dibutylamine as a secondary amine. Propylene carbonate can be used instead of EC for the reaction. A reaction mechanism was proposed, which involves reaction between EC and amine giving a carbamate followed by catalytic reaction between the carbamate and amine, yielding 1,3-disubstituted urea. It is suggested that the latter reaction is the rate-determining step. On the basis of this reaction mechanism, the synthesis of unsymmetric urea was also examined. 2-Hydroxyethyl butylcarbamate is selectively produced from EC with butylamine in the absence of the catalyst at a low temperature and reacts with benzylamine producing 1-butyl-3-benzylurea along with symmetric dialkyl ureas. 相似文献
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Role of the surface hydroxyl groups of modified titanium oxide in catalytic ethylene oxide hydration
D. E. Zavelev M. V. Tsodikov G. M. Zhidomirov R. A. Kozlovskii 《Kinetics and Catalysis》2011,52(5):659-671
A quantum-chemical study of the mechanism of ethylene oxide hydration on titanium oxide (anatase) modified with phosphorus
additives was performed. It was demonstrated that the hydroxyl groups of the anatase surface are of importance for the activation
interaction of ethylene oxide with the catalyst surface. The activation of the ethylene oxide molecule and proton transfer
occur with the participation of these hydroxyl groups. It was found that the modification of the titanium oxide surface with
phosphorus additives plays a crucial role in proton transfer. 相似文献
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Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯酯交换反应的研究 《燃料化学学报》2018,46(8):977-984
ZnO、La2O3和Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯反应制备碳酸二甲酯和乙二醇。催化剂采用共沉淀法进行制备,并用BET、XRD、TG-DSC、CO2-TPD和Hammett滴定等对催化剂进行表征。考察了Zn-La物质的量比、焙烧温度,反应条件(反应温度、反应时间、催化剂用量等)对催化剂活性的影响。结果表明,ZnLa复合氧化物物质的量比为2:1,焙烧温度为500℃时,催化剂表现了较好的催化效果。催化剂的活性与催化剂表面的碱性强度和碱量有关,碱量越多催化剂的活性越好。 相似文献