Decomposition of nitrous oxide on AlFe-PILC catalyst

Summary Two AlFe-PILC catalysts were prepared with different OH/metal ratio and applied in nitrous oxide (N₂O) decomposition reactions. The 100% conversion of N₂O with NH₃into N₂and H₂O was achieved below 500^oC with both applied catalysts. However, the activity of catalysts in direct conversion of N₂O into N₂and O₂did not exceed 40 % below 500^oC. In this reaction the activity of AlFe-PILC catalyst synthesized at higher OH/metal ratio (4) is higher compared to the activity of AlFe-PILC catalyst with OH/metal ratio (2). Free FeO·Fe₂O₃particles were registered in the AlFe-PILC catalyst with higher OH/metal ratio (4).     

Polymerization of alkylene oxides by dialkylzinc–lewis base systems

Dialkylzinc–Lewis base systems are found to be active catalysts for the polymerization of alkylene oxides. The diethylzinc–dimethyl sulfoxide system is especially effective in the preparation of high polymers of ethylene oxide and propylene oxide. Diethylzine does not react with dimethyl sulfoxide, but there is strong association between the compounds. The proton magnetic resonance spectrum of a poly(ethylene oxide) prepared by the catalyst system suggests that the n-butoxyl group is attached to the end of the polymer chain. Polymerization of ethylene oxide seems to be initiated by the ethyl–zinc bond. The active species of the system seems to be diethylzinc coordinated with dimethyl sulfoxide. The efficiency of the catalyst system for the formation of high molecular weight polymer is 10^?1?10^?2. The other part of the catalyst is responsible for the formation of low polymers.     

Effect of ultra-fine gold particle addition to metal oxides in ethylene oxidation

Oxidation of ethylene was carried out over alumina-supported metal oxide catalysts and highly dispersed gold catalysts, respectively, under atmospheric pressure. The ethylene was completely oxidized to produce carbon dioxide and water with both metal oxide and gold catalysts. The activity of gold catalyst prepared by deposition method was much higher than that of supported metal oxide catalysts. Ultra-fine gold particles on Co₃O₄ were more active than on Al₂O₃. Fe₂O₃/Al₂O₃ and MnO₂/Al₂O₃ catalysts were more active than MoO₃/Al₂O₃ catalyst. The activity of the supported metal oxide catalysts was greatly enhanced by addition of gold particles. It was therefore considered that gold particles promote dissociative adsorption of oxygen and the adsorbed oxygen reacts with adsorbed ethylene on support adjacent to the active site.     

Oxidation ofn-butane and propene on exhydrotalcite Mg, Al, Fe mixed oxides

Oxidative dehydrogenation ofn-butane and propene has been studied on six Mg−Al−Fe oxide catalysts prepared by thermal decomposition of layered double hydroxides with a hydrotalcite-like structure, possessing Mg²⁺ and Al³⁺ ions in the brucite-like layers, and hexacyanoferrate in the interlayers. In all cases, CO₂ and H₂O are formed, together with minor amounts of ethylene and methane. On the solids prepared from hexacyanoferrate(II), formation of benzene is also observed.     

Monolayer V2O5/TiO2–ZrO2 catalysts for selective oxidation of o-xylene: preparation and characterization

A series of TiO₂?CZrO₂ supported V₂O₅ catalysts with vanadia loadings ranging from 4 to 12 wt% were synthesized by a wet impregnation technique and subjected to various thermal treatments at temperatures ranging from 773 to 1,073?K to understand the dispersion and thermal stability of the catalysts. The prepared catalysts were characterized by X-ray powder diffraction (XRD), BET surface area, oxygen uptake, and X-ray photoelectron spectroscopy (XPS) techniques. XRD results of 773?K calcined samples conferred an amorphous nature of the mixed oxide support and a highly dispersed form of vanadium oxide. Oxygen uptake measurements supported the formation of a monolayer of vanadium oxide over the thermally stable TiO₂?CZrO₂ support. The O 1s, Ti 2p, Zr 3d, and V 2p core level photoelectron peaks of TiO₂?CZrO₂ and V₂O₅/TiO₂?CZrO₂ catalysts are sensitive to the calcination temperature. No significant changes in the oxidation states of Ti⁴⁺ and Zr⁴⁺ were noted with increasing thermal treatments. Vanadium oxide stabilized as V⁴⁺ at lower temperatures, and the presence of V⁵⁺ is observed at 1,073?K. The synthesized catalysts were evaluated for selective oxidation of o-xylene under normal atmospheric pressure in the temperature range of 600?C708?K. The TiO₂?CZrO₂ support exhibits very less conversion of o-xylene, while 12 wt% V₂O₅ loaded sample exhibited a good conversion and a high product selectivity towards the desired product, phthalic anhydride.     

Catalytic oxidation of CO,hydrocarbons, and ethyl acetate over perovskite-type complex oxides

The catalytic activity of M^IM^IIO₃] perovskite-type complex oxides (M^I = La, Y, Nd, Yb; M^II = Co, Mn, Ni) in the oxidation of CO, propylene, benzene, ethylbenzene,o-xylene, and ethyl acetate was investigated. The Co-containing catalysts were shown to be more active in the oxidation than the Mn-containing catalysts. A relationship between the catalytic and adsorption properties was established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 602–605, April, 1994.     

Reduction of nitrogen oxides with ammonia over complex vanadium and chromium oxides

Catalytic properties of -Al₂O₃ -supported complex vanadium and chromium oxides V_2–x Cr _x O_5– (0 < × s 1.3), amorphous to X-rays, in the reduction of nitrogen oxides with ammonia were studied. Vanadium exists in these catalysts mostly in a pentavalent state and chromium exists as Cr³⁺ and Cr⁶⁺. As the content of chromium in the catalysts increases, the optimal temperature of the process decreases, and the degree of conversion of nitrogen oxides increases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 339–342, February, 1996.     

The impact of alkaline earth oxides on Bi2O3 and their catalytic activities in photodegradation of Bisphenol A

The BPA into wastewater has posed a threat to environment and human health. Hence, we aimed to eliminate BPA in a short time and with a rapid degradation rate from food wastewater. Herein, the effects of different alkaline-earth oxide doped with Bi₂O₃ nanoparticles on the photocatalytic degradation of bisphenol A were investigated. SrO-Bi₂O₃, CaO-Bi₂O₃, and MgO-Bi₂O₃ binary oxides were prepared by wet-impregnation method. The structural and optical features of catalysts were clarified BET, XRD, DRS, FT-IR, PL, and SEM techniques. The photocatalytic activities of catalysts were compared for different light sources. Considering that the characterization analysis and experimental results, the highly improved photocatalytic activity was mainly attributed to the effective structure of the SrO-Bi₂O₃ binary oxide and the strong alkali properties in the nanocomposite. Obviously, 5wt% SrO-Bi₂O₃ photocatalyst showed more excellent degradation performance and highest degradation reaction rate (0.21 mg l^–1 min^–1) within 30 min. It was observed that the photocatalytic activity improved by the additive of alkaline oxide on Bi₂O₃.     

Reactions of nitrogen oxides (NO,N2O) with the surface of a copper-chromium oxide catalyst

Weight-space and IR spectroscopic methods have been used to investigate the reaction of NO and N₂O with the surface of a copper-chromium oxide catalyst in the form of copper chromite with a 20% excess of Cr₂O₃. Comparisons have been made between the relative reactivities of the different oxides (NO, N₂O, O₂) in oxidation of the Cu⁺ and Cu^o surface centers. The role of these centers in oxidation of CO by oxygen and by nitrogen oxides is discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 3, pp. 338–343, May–June, 1985.     

Mesoporous Mn promoted Co3O4 oxides as an efficient and stable catalyst for low temperature oxidation of CO

Mesoporous Mn-doped Co₃O₄ catalysts were successfully prepared via a dry soft reactive grinding method based on solid state reaction, and their catalytic performances on CO oxidation were evaluated at a high space velocity of 49,500 mL g⁻¹ h⁻¹. A significant promoted effect was observed once the atomic ratios of Mn/(Co+Mn) were lower than 10%, for instance, the temperature for 50% conversion decreased to about −60 °C, showing superior catalytic performance compared to the single metal oxide. Especially, the Mn-promoted Co₃O₄ catalyst with a Mn/(Co+Mn) molar ratio of 10% could convert 100% CO after 3000 min of time-on-steam without any deactivation at room temperature. As prepared catalysts were characterized by XRD, N₂-adsorption/desorption, TEM, H₂-TPR, O₂-TPD and CO-titration analysis. The significant enhancement of performance for oxidation of CO over Mn-Co-O mixed oxides was associated with the high active oxygen species concentrations formed during the pretreatment in O₂ atmosphere.     

Catalytic performance of silica-supported chromium oxide catalysts in ethane dehydrogenation with carbon dioxide

The oxidative dehydrogenation of ethane into ethylene by CO₂ over a series of silica-supported chromium oxide catalysts was investigated. The results showed that the catalysts were effective for the reaction and CO₂ in the feed promoted the catalytic activity. The 5%Cr/SiO₂ catalyst exhibited the excellent performance with 30.7% ethane conversion and 96.5% ethylene selectivity at 700^oC. ESR and UV-DRS were used to probe the active sites and the species with high valent states (Cr⁵⁺ and/or Cr⁶⁺) were found to be important for the reaction.     

Nickel catalysts based on porous nickel for methane steam reforming

The influence of synthesis conditions on the phase composition and texture of porous nickel supports as plates with a magnesium oxide underlayer were investigated by X-ray diffraction, low-temperature nitrogen absorption, and electron microscopy combined with X-ray microanalysis. Nickel catalysts supported on these plates were studied. Thermal treatment of Mg(NO₃)₂ in nitrogen yields a magnesium oxide underlayer with a small specific surface area (support I). The replacement of nitrogen with hydrogen leads to a larger surface area (support II). The formation of MgO is accompanied by the incorporation of Ni²⁺ cations from the oxide film into the underlayer. Upon subsequent reduction with hydrogen or under the action of the reaction medium, these cations form fine crystallites of nickel. The supports having an oxide underlayer show a higher activity in methane steam reforming than the initial metallic nickel. Nickel catalysts on supports I and II show similar activities. The activity of the catalysts was stable throughout 50-h-long tests; no carbon deposits were detected by TEM.     

Polymerization of oxiranes by polymeric organoantimony oxides

Polymeric arylantimony(V) oxides [poly(ArSbO₂), Ar = phenyl, p-chlorophenyl (CPh), and p-methylphenyl (Tol)] were employed as catalysts for the polymerization of oxirane [ethylene oxide (EO)] and also substituted oxiranes [propylene oxide (PO), 1,2-butylene oxide (BO), and epichlorohydrin (ECH)]. The polymerization of EO by ArSbO₂s proceeded 3–60 times faster than that by the other organoantimony and -tin compounds such as triphenylstibine oxide (Ph₃SbO) and arenestannoic acids (ArSnO₂H), respectively. Apparent activation energy for the polymerization of EO was estimated as 13.7, 13.3, and 13.6 kcal/mol for PhSbO₂, TolSbO₂, and CPhSbO₂, respectively. The results of the polymerization as well as ¹H-, ¹³C-, and ¹⁷O-NMR spectroscopy suggested that the polymerization was initiated by ArSbO₂ or Ar₂Sb₂O₄ fragments, which was derived from a nucleophilc solvation of the polymeric ArSbO₂ by oxiranes in situ.     

Sn-Mo混合氧化物的缺陷结构及催化性能的研究

本文以1-丁烯在水蒸汽存在下选择性氧化制甲乙酮为典型反应, 利用XRD, ESR,IR, XPS, TEM和SEM研究了Sn-Mo氧化物的结构与活性的关系。制备了8个样品, A, B,C,D,E,F,G和H的Mo/(Mo+Sn)分别为0,0.1,0.2,0.4,0.6,0.8,0.9,1.0。     

Copper-cerium oxide catalysts for the selective oxidation of carbon monoxide in hydrogen-containing mixtures: I. Catalytic activity

A series of copper-cerium oxide catalysts were prepared, and their properties toward the reaction of CO oxidation in hydrogen-containing gas mixtures were studied. It was found that the copper-cerium oxide catalysts are stable, active, and selective in this reaction. The conditions under which these catalysts decreased the concentration of CO from 1 to <10^?3 vol % in hydrogen containing water vapor and carbon dioxide were determined.     

介孔氧化铝负载Ni-Co氧化物催化剂上丙烷氧化脱氢制丙烯

以非离子型三嵌段共聚物作为模板剂, 异丙醇铝为氧化铝的前驱物, 采用一锅法合成了一系列介孔氧化铝负载镍氧化物、钴氧化物以及镍-钴双金属氧化物催化剂, 并以介孔氧化铝为载体, 采用浸渍法制备了负载Ni-Co 氧化物催化剂. 采用N₂吸附-脱附、高分辨透射电镜(HRTEM)、X射线粉末衍射(XRD)、H₂程序升温还原(H₂-TPR)以及激光拉曼光谱(LRS)等技术对催化剂的结构与性质进行表征, 并考察了催化剂的丙烷氧化脱氢反应性能. 结果表明: 一锅法制备的各催化剂均有大的比表面积和规整的孔道结构, 且负载的金属氧化物高度分散; 而浸渍法制备的催化剂, 其载体的介孔结构被破坏并有Co₃O₄晶相生成. 在考察的催化剂中, 一锅法合成的介孔氧化铝负载Ni-Co 氧化物催化剂表现出最佳的丙烷氧化脱氢性能. 在450 °C、C₃H₈:O₂:N₂的摩尔比为1:1:4和空速(GHSV)为10000 mL·g^-1·h^-1条件下, 该催化剂上丙烯产率为10.3%, 远高于浸渍法制备的催化剂上所获得的丙烯产率(2.4%). 关联催化剂表征和反应结果, 讨论了催化剂结构与性能之间的关系.     

Characterization of new catalysts based on uranium oxides

Catalysts based on uranium oxides were systematically studied for the first time. Catalysts containing various amounts of uranium oxides (5 and 15%) supported on alumina and mixed Ni-U/Al₂O₃ catalysts were synthesized. The uranium oxide catalysts were characterized using the thermal desorption of argon, the low-temperature adsorption of nitrogen, X-ray diffraction analysis, and temperature-programmed reduction with hydrogen and CO. The effects of composition, preparation conditions, and thermal treatment on physicochemical properties and catalytic activity in the reactions of methane and butane oxidation, the steam and carbon dioxide reforming of methane, and the partial oxidation of methane were studied. It was found that a catalyst containing 5% U on alumina calcined at 1000°C was most active in the reaction of high-temperature methane oxidation. For the Ni-U/Al₂O₃ catalysts containing various uranium amounts (from 0 to 30%), the introduction of uranium as a catalyst constituent considerably increased the catalytic activity in methane steam reforming and partial oxidation.     

Generation and characterization of supported films of transition metal and rare earth metal oxide catalysts

Summary The generation of catalytically relevant metal and/or metal oxide compounds supported on silica fibres is described. The systems investigated are Ni^o, Cu^o, Cu^o/ZnO, as well as perovskite-type La/Fe, La/Ni and La/Mn oxide phases. Ultrasound-aided generated vapours containing dissolved metal salt precursors are transferred onto preheated quartz fibres and transformed into the catalytically relevant phases by subsequent calcination. Analytical SEM and X-ray diffraction reveals the presence of differently crystalline, rough surfaces. The influence of the precursor salt and the conditions of calcination on the formation of the supported catalysts is discussed.     

Dehydrocyclization of Diphenylamine to Carbazole over Platinum-Based Bimetallic Catalysts

 Gas phase dehydrocyclization of diphenylamine (DPA) to carbazole over monometallic and bimetallic 0.4 wt% Pt-based catalysts in a fixed bed reactor was studied in the presence of hydrogen at a temperature of 550 ^oC. Alumina and carbon supported Pt catalysts showed very high initial activity (> 95%). The selectivity for carbazole over carbon supported Pt catalysts was slightly lower. Doping of the catalyst with potassium led to an increase in the selectivity for carbazole by 15%. Bimetallic Pt-Sn catalysts prepared by co-impregnation were less selective than catalysts prepared by successive impregnation. The selectivity for carbazole over bimetallic Pt-Sn catalysts prepared by successive impregnation was 75%, but their activity decreased with increased Sn loading. Highly active and reasonably selective catalysts were Ir-doped bimetallic Pt-based catalysts. The conversion of diphenylamine over Pt-Ir catalysts was above 98% and the selectivity for carbazole was nearly 55%, while the lifetime was much longer.     

Heat of immersion of iron(III) oxides in water at 25°C

The heat of immersion in water was measured at 25°C for three iron(III) oxides using a twin-type microcalorimeter. One of the samples was commercial α-Fe₂O₃ (sample C) and the other two (samples M and F) were prepared by calcining magnetite and iron(III) hydroxide in air at various temperatures, T_p, from 300 to 700°C. The samples were evacuated at outgassing temperature, T_o, between room temperature and 500°C at a pressure of 1 × 10^?2?2.7 × 10^?2N m^?2 for 6 h. The heat of immersion, h_i(J m^?2), of samples C and M increased with an increase in T_o and showed the maximum h_i at T_o =400°C, while sample F did not show the maximum up to T_o =500°C. The systematic correlation was not observed between h_i and T_p of sample F. The heat of reproduction of the surface hydroxyl group on sample F was approximately estimated as 6.6 × 10⁴ J mole^?1 H₂O.