Correlation between the surface acidity and activity of bismuth tungstate catalysts

The surface acid strength distribution in bismuth tungstate catalysts with Bi/W ratios of 2/3, 1/1, 2/1 and 6/1 has been investigated. The results are interpreted attributing higher acidities to W–O–W bonds and lower acidities to W=O bonds. An apparent correlation is observed between the surface acidities of the catalysts and their activities in the oxidation and ammoxidation of propylene and 1-butene.

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Bi/W, 2/3, 1/1, 2/1 6/1. , W–O–W W=O. 1-.

     

Dependence of oxidation activity on the structure of bismuth tungstate catalysts

The structures of bismuth tungstate catalysts with Bi/W ratios of 2/3, 1/1, 2/1 and 6/1 have been studied by X-ray diffraction. The presence of corner sharing W–O octahedra in the bulk of Bi/W=2/1 and 1/1 compositions has been established. The Bi/W=2/3 catalyst appears to contain edge-shared W–O octahedra whereas W in the Bi/W=6/1 sample form WO₄ tetrahedra. An apparent correlation has been obtained between the structures of the catalysts and their activities in the oxidation and ammoxidation of propylene and 1-butene.

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Bi/W, 23, 11, 21 61, . , W–O Bi/W=21 11. Bi/W=23 W–O , Bi/W=61 . 1-.

     

钨酸铋对四环素光催化降解性能

采用水热法制备了钨酸铋催化剂,以空气为氧化剂,四环素为底物,考察了制备催化剂时溶液的酸度、降解反应时不同光源、光强度和催化剂量对钨酸铋的光催化降解四环素性能的影响.结果表明,当制备钨酸铋催化剂溶液的pH为1时,催化降解效果较好;当催化剂与四环素的物质的量之比为0.3∶1时,光照时间100 min,光催化降解率达66%;以钨酸铋为催化剂,太阳光光催化降解性能优于红外光和紫外光,太阳光强度越强,催化降解效果越好.     

ESR spectra of47Ti-enriched titanium catalysts for polymerization

For the first time ESR spectra of⁴⁷Ti-enriched Ziegler system Ti-TIBA in toluene have been studied. For the ratio Ti/Al1, more accurate h. f. s. constants have been found. For Ti/Al1/15 no h. f. s. have been observed, which is ascribed to ordering due to the cooperative Jahn-Teller effect.

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TiCl₄+ ⁴⁷Ti. Ti/Al1 . Ti/Al1/15 , -.

     

Correlations between magnetic resonance parameters of ESR and NMR spectra

Empirically established correlations between magnetic resonance parameters of free radicals (g-factors, isotropic hyperfine coupling constans) and isostructural molecules (chemical shifts, isotropic spin-spin coupling constants) or structurally similar ligands in paramagnetic transition metal complexes (isotropic chemical shifts) are systematized and critically discussed. Quantum-chemical analysis of the suggested spin distribution damping coefficients in model systems and structurally similar chemical compounds is performed. Based on the results obtained, physicochemical interpretation of the observed correlations between the parameters of ESR and NMR spectra is given. Dedicated to the memory of Academician V. V. Voevodskii (to the 80th anniversary). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1575–1583, September, 1997     

ESR spectra of gamma-irradiated cellobiose

Conclusions The action of ionizing radiation on cellobiose leads to breakage of the pyranose ring at the C⁵-O bond. A probable mechanism is proposed for the radiation chemical transformations of cellobiose.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2234–2237, October, 1984.     

ESR spectra of arenecyclopentadienyliron dications

ESR spectra of arenecyclopentadienyliron dications have been studied at 77 K. Arenecyclopentadienyliron cations were oxidized with SbCl₅ in CH₂Cl₂ solution at 203 K. The g_∥ and g_⊥ values have been measured and splittings of the degenerate e_2g orbitals have been calculated. The energy differences between the split components proved to be considerably smaller than that of the e^?t_1g level in the corresponding neutral complexes. They are, however, larger than the splittings of the e_2g orbitals observed in ferricinium cations.     

Comparison of activities of cracking catalysts containing ZSM-5 and Y-zeolite

Studies on the catalytic cracking of diesel oil fraction with the boiling range of 493–603 K on H-ZSM-5 and RE, H-Y zeolites has been carried out. The results show that in the presence of H-ZSM-5 zeolite no significant increase in the yield of gasoline is observed. Higher percentage of unsaturated hydrocarbons in the gasoline and gases indicates that the hydrogen transfer activity of H-ZSM-5 containing catalyst is lower than that of RE, H-Y zeolites.

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H-ZSM-5 RE, H-Y , 493–603 . H-ZSM-5 . , , H-ZSM-5 , RE, H-Y .

     

ESR investigation of vanadium-molybdenum oxide catalysts

Upon calcination of vanadium-molybdenum catalysts in air at 500°C two ESR signals are observed. They are attributed to a solid solution of MoO₃ in V₂O₅ (a) and to the incorporation of VO²⁺ into the compound V₂MoO₈ (b).

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500°C - - , MoO₃ V₂O₅, - VO⁺² V₂ MoO₅.

     

钨酸铋/还原氧化石墨烯二氧化氮传感器的研制EI北大核心CSCD

The bismuth tungstate / reduced graphene oxide (Bi2 WO6 / rGO) composite material was synthesized by a simple and one-step hydrothermal method, and the nitrogen dioxide gas sensor was prepared based on this material. The crystal phase, morphology and microstructure of composite were studied by XRD, Raman spectra, SEM and TEM,respectively, which confirmed that composite of Bi2 WO6 and rGO was successfully synthesized, and Bi2 WO6 / rGO composite material with flower-like superstructure was obtained. The composite material was loaded on the interdigital electrode to prepare the nitrogen dioxide gas sensor, while the properties of gas sensor were systemically investigated by using homemade gas-sensing test device. The results indicated that the Bi2 WO6 / rGO composite gas sensor had higher selectivity, higher response value and better long-term stability. The response value of Bi2 WO6 / rGO composite gas sensor was 28. 35% towards 47. 03 mg / m3 NO2, which was 3. 5 times of pure rGO gas sensor. The response time was 55 s with the recovery time of 549 s and the detection limit of 62 μg / m3. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Studies on bismuth tungstate and its use as a lead selective inorganic ion-exchanger

Summary A new inorganic ion-exchanger bismuth tungstate has been synthesized. Its composition, chemical stability and ion-exchange properties have been studied. The material shows high selectivity towards Pb²⁺, which has been separated quantitatively from Zn²⁺, Mg²⁺, Ca²⁺, Mn²⁺, Cu²⁺ and Ni²⁺. It also shows electron exchange behaviour with some strong reducing agents.     

ESR spectra of paramagnetic palladium complexes

Binuclear nitrosopalladium complexes Pd₂(μ-COOR)₂(η²-CH₂C₆H₄NO)₂ (R = Me, CF₃, or Ph) were studied by ESR spectroscopy. Analysis of parameters of ESR spectra of the polycrystalline samples and their toluene solutions suggests partial izomerization of the nitroso ligands to the nitroxide form to result in the oxidation of palladium(II) to palladium(III). __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1746–1751, August, 2005.     

ESR spectra of phosphorus-containing tetrazonyl radicals

Conclusion The oxidation of the products of the reaction of dialkylphosphorylacetaldehydes with aryldiazonium salts gives tetrazonyl radicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1168–1169, May, 1987.     

ESR spectra of irradiated polyacrylic acid

In view of the interest in acrylic acid co-polymerized with other polymers by radiation to promote enhanced crosslinking, a knowledge of the intermediate reaction products is highly desirable. ESR techniques have been used to study the nature and stability of the radicals formed. Acrylic acid was polymerized by exposure to gamma radiation; the nature of the radicals, their decay at various temperatures, and the effect of inhibitors were investigated.The ESR spectrum at room temperature is similar to that described by earlier workers; its dependence on temperature and impurities, as well as its decay, were investigated. From this work, there is reason to believe that the described triplet also contains a central singlet of ΔH_ms19 G; the addition of impurities to the acrylic acid causes the triplet to decay more rapidly, thus leaving the predominant singlet mentioned above. It was also found that the lines in the outer “wings” of the irradiated specimen disappear on heating; at the same time a new line, possibly a singlet of ΔH_ms131 G, either became more intense or more obvious. Some tentative explanations of this behaviour are advanced.