Role of solid- and gas-phase interactions in the coaction of the oxides in MnO2 + PbO and MnO2 + V2O5 compositions activating the thermal oxidation of GaAs

Spatial separation of the oxides in MnO₂ + PbO and MnO₂ + V₂O₅ binary compositions activating the thermal oxidation of GaAs has made it possible to locate the interactions between these oxides that are responsible for the nonlinear effects observed in their coaction. The solid-phase interactions enhance the chemostimulating activities of both oxides (a positive nonlinear effect takes place). The gas-phase interactions cause a marked negative deviation from the additive chemical stimulation effect.     

Role of an inert component in compositions with manganese(II) and manganese(IV) oxides in studying nonlinear effects in GaAs thermal oxidation

GaAs thermal oxidation by mixtures containing manganese(II) and manganese(IV) oxides and gallium arsenide-inert components was studied.     

Contribution from two types of peroxyl radicals to cyclohexanol oxidation and their reactivity

The oxygen uptake kinetics in the liquid-phase oxidation of cyclohexanol initiated by cumyl peroxide in the presence of inhibitors (ionol and nitrobenzene) has been investigated (373 K, ortho-dichlorobenzene as the solvent). The relative contributions from the hydroperoxyl and α-hydroxycyclohexylperoxyl radicals to chain propagation has been determined. The rate constants for the reactions of these radicals with the alcohol have been determined.     

The effect of metal oxides on the oxidation of polybutadiene

Carboxy-terminated polybutadiene (CTPB) was oxidised as a coating on various metal oxides by heating in air on a thermobalance. The oxidation was found to be free from diffusion control and was catalysed by certain of the oxides. The catalysis was shown to be independent of semiconductor type and to be associated with those oxides for which the width of the forbidden zone between the valence and conduction bands (U) is less than 1.9 eV. In general, low values of U result in high catalytic activity. It is proposed that catalysis occurs by a redox mechanism, viz. RO₂H + p → RO₂^. + H⁺, RO₂H + e → RO^. + OH^?.     

Formation of oxides and their role in the growth of Ag nanoplates on GaAs substrates

Simple galvanic reactions between highly doped n-type GaAs wafers and a pure aqueous solution of AgNO 3 at room temperature provide an easy and efficient protocol to directly deposit uniform Ag nanoplates with tunable dimensions on the GaAs substrates. The anisotropic growth of the Ag nanoplates in the absence of surfactant molecules might be partially ascribed to the codeposition of oxides of gallium and arsenic, which are revealed by extensive data from electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, during the growth of the Ag nanoplates. The electron microscopic characterization shows that each Ag nanoplate has a "necked" geometry, that is, it pins on the GaAs lattices through only a tiny neck (with sizes of <10 nm). In addition, the as-grown Ag nanoplates exhibit strong enhancement toward Raman scattering of materials on (or around) their surfaces.     

过渡金属氧化物掺杂对铜锰氧化物催化CO氧化性能的影响

以乙酸铜和乙酸锰为铜锰前驱体,以NH₄HCO₃为沉淀剂,相应金属硝酸盐为掺杂剂,采用共沉淀法制备了不同过渡金属氧化物掺杂的铜锰氧化物催化剂.?采用N₂物理吸附、X射线衍射,氢气-程序升温还原和原位红外漫反射光谱等方法对催化剂进行了表征,考察了系列催化剂上CO反应性能.?结果表明,掺杂过渡金属氧化物可以调变催化剂对CO的吸附能力,进而影响催化剂性能.     

Contribution to the study of the sorption of radionuclides on hydrated oxides

The mechanism of¹⁰⁶Ru(III),¹⁰⁶RuNO(II),¹⁴⁴Ce(III),¹⁴⁷Pm(III),⁸⁵Sr(II),¹³¹I⁻,³⁵SO ₄ ²⁻ , and H₂ ³²PO ₄ ²⁻ radionuclide sorption on hydrated ferrous, ferric, aluminium and chromic hydrated oxides was studied. The dependence of sorption on the pH has shown that in a certain range of pH values it is the ion exchange of the radionuclide for a proton or a hydroxyl group of the oxide that probably plays a decisive role in the sorption process. The sorption depends considerably on the pH in the whole range of studied, but its decrease with cations in alkaline media and its increase with I⁻ ion in acidic media does not agree with the above sorption mechanism. Similarly, the course of the dependence of sorption on the sorbent concentration does not indicate ion exchange to be the only mechanis, but it indicates a more complicated sorption process. Probably the sorption of colloidal forms of the radionuclides proceeds, too.     

GaAs thermal oxidation with participation of spatially separated activator oxides (MnO + PbO and MnO + V2O5)

Spatial separation of activator oxides in MnO₂ + PbO and MnO₂ + V₂O₅ binary compositions helps to locate the interactions between the oxides that lead to nonlinear joint effects of the compositions on GaAs thermal oxidation. The mutual enhancement of the chemostimulating activity (a positive nonlinear effect) was discovered in the solid phase, whereas vapor-phase processes led to a considerable negative nonadditivity of the joint chemostimulating effect.     

The catalytic effect of rare earth oxides on the thermal decomposition of ammonium perchlorate

The kinetics of the decomposition of ammonium perchlorate (AP) in the presence of rare earth oxides, yttrium oxide (Y₂O₃) and lanthanum oxide (La₂O₃) as catalysts have been investigated. The Prout-Tompkins and contracting-cube equations have been found to fit the isothermal thermogravimetry data of catalysed AP decomposition. Gases evolved during catalytic decomposition of AP were analysed by infrared spectroscopy by matrix isolation technique. The mechanism of the catalysed thermal decomposition of AP has also been discussed in terms of an electron transfer process.

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Zusammenfassung Es wurde die Reaktionskinetik der thermischen Zersetzung von Ammoniumperchlorat (AP) in Gegenwart der Seltenerdenoxide Yttriumoxid (Y₂O₃) und Lanthanoxid (La₂O₃) als Katalysatoren untersucht. Zum Fitting der isothermen thermogravimetrischen Daten der katalysierten Zersetzung von AP läßt sich die Prout-Tompkins- und die Schrumpfwürfelgleichung erfolgreich anwenden. Die bei der katalytischen Zersetzung von AP freigesetzten Gase wurden durch IR-Spektroskopie untersucht. Der Mechanismus der katalytischen thermischen Zersetzung wurde auch vom Gesichtspunkt eines Elektronentransferprozesses aus besprochen.

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Contribution of solid-phase hexapeptide ligand libraries to the repertoire of human bile proteins

Proteins in bile may have important physiological functions and serve as disease biomarkers. Here, the protein composition of human gallbladder bile was analyzed using a recently described chromatography-like technology capable to enhance the signal of low-abundance species. First, proteins present in bile fluid were treated with immobilized peptide ligand libraries to concentrate dilute and very dilute species while concomitantly diluting the high-abundance proteins. The analysis of resulting protein mixture was then performed using LC-MS/MS after having classically separated proteins by a mini preparative gel electrophoresis. Overall 222 gene products were found; 143 of them were not reported before in proteomics studies. Ligand libraries by themselves contributed to find 81 new gene products distributed throughout different categories. The described chromatographic approach provides a significant contribution to the bile protein repertoire and opens new perspectives for the discovery of markers for specific biliary tract diseases.     

Contribution of activation analysis with low energy charged particles to studies on GaAs

It is shown that the instrumental analysis of carbon and oxygen in GaAs, at trace level, can be achieved by irradiation with low energy deuterons and tritons (3 MeV). The experimental sensitivities are 6 ppb/weight for the¹⁶O( ₁ ³ H,n)¹⁸F reaction and 25 ppb/weight for the¹²C( ₁ ² H,n)¹³N reaction. Applications related to the metallurgy of GaAs are described.     

Study of the mutual influence of hydrogen and carbon monoxide in their joint oxidation on palladium

The joint oxidation of hydrogen and carbon monoxide in excess oxygen on palladium was investigated in a reactor for separate calorimetry and a gradientless microreactor at atmospheric pressure. An initiating influence of hydrogen m the oxidation of carbon monoxide, as well as inhibitory effect of carbon monoxide on the heterogeneous-homogeneous oxidation of hydrogen, was detected. The conditions of transition of the reactions into the volume according to a heterogeneous-homogeneous mechanism were determined. It is suggested that the joint oxidation of CO and H₂ occurs with the participation of the same active intermediate products formed from hydrogen and oxygen.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 504–508, July–August, 1985.     

Electrochemical study on the adsorption of carbon oxides and oxidation of their adsorption products on platinum group metals and alloys

CO(2) reduction and CO adsorption on noble metals (Pt, Rh, Pd) and their alloys (Pt-Rh, Pd-Pt, Pd-Rh, Pd-Pt-Rh) prepared as thin rough deposits have been studied by chronoamperometry (CA), cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). The influence of alloy surface composition on the values of surface coverage, eps (electron per site) and potential of the oxidation of CO(2) reduction and CO adsorption products is shown. The oxidation of the adsorbate on Pt-Rh alloys proceeds more easily (at lower potentials) than on pure metals. On the other hand, in the case of Pd-Pt and Pd-Rh alloys the adsorbate oxidation is more difficult and requires higher potentials than on Pt or Rh. The analysis of the EQCM signal is presented for the case of adsorption and oxidation of carbon oxide adsorption products on the electrodes studied. The comparison of adsorption parameters and the EQCM response obtained for platinum group metals and alloys leads to the conclusion that reduced CO(2) cannot be totally identified with adsorbed CO.     

铈基复合氧化物中晶格氧用于甲烷部分氧化制合成气

采用共沉淀法制备了Ce-M-O氧载体（M＝Fe、Mn、Cu）,并进行了XRD表征。研究了Ce-M-O中晶格氧部分氧化甲烷制合成气的反应。考察了再生时间、再生温度对氧载体部分氧化甲烷性能的影响。研究结果表明, Ce-Fe-O固溶体中的晶格氧适于部分氧化甲烷制合成气。在新鲜的Ce Fe O氧载体上存在少量的强氧化物种,导致开始阶段大部分甲烷被完全氧化,然后该氧载体能均匀地释放出具有高选择性的体相晶格氧将甲烷氧化为CO和H2。通过对氧载体再生条件的控制,可以有效提高目标产物的选择性,当再生温度为850℃,再生时间为7min时, 获得了最大的CO（96.68%）和H2（97.56%）选择性,同时H2与CO摩尔比达到2.02。在无气相氧存在下,用Ce-Fe-O中晶格氧实现甲烷部分氧化制合成气的方法是可行的。     

Studies on the thermal reactions of aluminium oxides and hydroxides

The gibbsite -alumina decomposition (in air) and the-alumina boehmite transformation (under hydrothermal conditions) were investigated isothermally. Reaction products were characterized by TG and X-ray diffraction.The rate of the gibbsite -alumina reaction below 250 °C appears to be nucleation and growth controlled. That of the hydrothermal transformation of-alumina to boehmite depends on the time of grinding and the particle size of the gibbsite from which the-oxide has been prepared. During this reaction, partial re-formation of gibbsite was observed at lower temperatures, but the final product was always boehmite.

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Zusammenfassung Die Zersetzung von Hydrargillit zu-Aluminiumoxid in Luft und die Umwandlung von-Aluminiumoxid zu Böhmit unter hydrothermalen Bedingungen bei isothermer Versuchsführung wurden untersucht. Die Reaktionsprodukte wurden mittels Thermogravimetrie und Röntgenbeugung charakterisiert. Die Geschwindigkeit der Umsetzung von Hydrargillit zu-Aluminiumoxid unterhalb 250 °C wird durch Keimbildung und Wachstum bestimmt. Die Geschwindigkeit der hydrothermalen Umsetzung-Al₂O₃Böhmit hängt von der Mahldauer und der Teilchengrössen des Hydrargillits ab, aus dem das-Al₂O₃ präpariert worden war. Während letztere Reaktion wird bei tieferer Temperatur partiell Hydrargillit gebildet, das Endprodukt war stets Böhmit.

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The effect of oxidation and reduction on thermal expansion of magnetite from 298 to 1173 K at different vacuum conditions

Three thermal expansion curves of natural and synthetic magnetite (Fe₃O₄) have been measured under different vacuum conditions (10⁻⁴ and 10⁻⁶ mbar). The different behavior in thermal expansion depends on vacuum level, which controls the partial oxidation of the sample. If the vacuum is poor, that is in mildly oxidizing conditions, the thermal expansion curve presents a discontinuity at 875 K and the samples oxidizes. In non-oxidizing conditions the discontinuity is not present and the thermal expansion coefficient is markedly smaller. The experimental curves indicate that virtually all thermal expansion data on magnetite in the literature were measured on oxidized or partially oxidized samples.     

Selective catalytic oxidation of ethanol to acetic acid on dispersed Mo-V-Nb mixed oxides

The direct oxidation of ethanol to acetic acid is catalyzed by multicomponent metal oxides (Mo-V-NbO(x)) prepared by precipitation in the presence of colloidal TiO(2) (Mo(0.61)V(0.31)Nb(0.08)O(x)/TiO(2)). Acetic acid synthesis rates and selectivities (~95 % even at 100 % ethanol conversion) were much higher than in previous reports. The presence of TiO(2) during synthesis led to more highly active surface areas without detectable changes in the reactivity or selectivity of exposed active oxide surfaces. Ethanol oxidation proceeds via acetaldehyde intermediates that are converted to acetic acid. Water increases acetic acid selectivity by inhibiting acetaldehyde synthesis more strongly than its oxidation to acetic acid, thus minimizing prevalent acetaldehyde concentrations and its intervening conversion to CO(x). Kinetic and isotopic effects indicate that C-H bond activation in chemisorbed ethoxide species limits acetaldehyde synthesis rates and overall rates of ethanol conversion to acetic acid. The VO(x) component in Mo-V-Nb is responsible for the high reactivity of these materials. Mo and Nb oxide components increase the accessibility and reducibility of VO(x) domains, while concurrently decreasing the number of unselective V-O-Ti linkages in VO(x) domains dispersed on TiO(2).     

Improving effect of boron carbide on the combustion and thermal oxidation characteristics of amorphous boron

Boron carbide (B₄C) is one of the main products from the primary combustion of boron (B)-based propellants and has a significant influence on the secondary combustion of B. To systematically evaluate its effects on the secondary combustion of B, mixtures of B₄C and B in different mass ratios were prepared. To study the ignition temperatures and combustion flames of the samples, a xenon lamp ignition experimental system and a flame shape test system were designed, respectively. A thermogravimetry–differential scanning calorimetry–Fourier transform infrared spectroscopy combined thermal analysis system was used to study the thermal oxidation characteristics and analyze the gaseous products of the samples. The results indicate that B₄C reduces the heat absorption at the beginning of the ignition, but subsequently prevents the rapid rise of sample temperature. During the stable combustion stage, the maximum flame length under optical density 10⁻⁴ (OD4) filter was 20.4 mm, and the maximum flame length under 580 nm + OD4 filters (represents the combustion of B element) was 16.7 mm. The samples contained a small amount of HBO₂ and H₃BO₃, which led to slight mass loss during the low temperature section of the thermal oxidation process. During the high temperature section, the oxidation of B and B₄C caused considerable mass gain. The gaseous products of the thermal oxidation process include CO₂, CO, and H₂O. In general, the B content of 60% was the most beneficial to decrease the oxidation temperature, increase the combustion intensity, and improve the heat-releasing ability of the samples.

     

球形氧化铝负载锰基双金属氧化物催化剂催化臭氧深度氧化NO

在工业锅炉烟气处理领域,由于锅炉容量低,烟气温度往往无法满足传统选择性催化还原(SCR)所需温度窗口.工业锅炉烟气成分的复杂性也给氮氧化物治理带来了严峻考验.臭氧深度氧化NO结合湿法洗涤同时脱硫脱硝技术具有独特的应用优势.传统臭氧氧化技术中,NO被臭氧氧化为NO2,进而在脱硫塔中实现一体化脱硫脱硝.但由于NO2溶解度相对较低,需要在脱硫浆液中加入添加剂提高脱硝效率,造成运行成本增加.NO经臭氧深度氧化后,NO2进一步转化为溶解度高的N2O5,传统脱硫石膏浆液即可实现高效吸收N2O5,从而有效提高氮氧化物吸收效率.但由于N2O5生成反应速率低,深度氧化存在臭氧投入量大、反应时间长及臭氧残留多的缺点.臭氧耦合催化剂深度氧化NO可有效解决以上问题.首先,本文采用溶胶-凝胶法合成一系列单金属氧化物(Mn,Co,Ce,Fe,Cu,Cr)作为臭氧深度氧化NO的催化剂.结果发现锰氧化物表现出最高的催化活性,在70oC下,O3/NO摩尔比为2.0时经过0.12 s的反应时间催化剂即可实现80%以上的转化效率.但根据N2O5生成的总包反应(2NO+3O3=N2O5+3O2)可以看出,O3/NO摩尔比为1.5时即可实现N2O5的完全转化.由于催化臭氧氧化反应温度较低,中间产物在催化剂表面聚集,占据大量活性位,进而导致无法实现1.5摩尔比的高效转化.通过采用球形氧化铝作为载体,避免粉末状催化剂紧凑型布置,增加换热面积,可有效降低催化剂表面中间产物聚集;同时延长了气体与催化剂的接触时间,提高反应效率.在球形氧化铝载体上负载锰基双金属氧化物(Ce-Mn,Fe-M,Cr-Mn,Cu-Mn和Co-Mn),在初始NO浓度为410 mg/m3,反应温度100oC,O3/NO摩尔比1.5,催化反应时间0.12 s的工况下,催化剂最终实现95%(Fe-Mn)和88%(Ce-Mn)的转化效率,剩余NO和NO2的浓度分别低于20 mg/m3(Fe-Mn)和50 mg/m3(Ce-Mn),臭氧残留浓度低于25 mg/m3.同负载单一锰氧化物(83%转化率)相比,双金属氧化物进一步提高了N2O5生成效率.因此,臭氧耦合催化剂深度氧化NO结合湿法吸收在工业锅炉超低排放(NOx<50 mg/m3)领域具有广泛应用前景.通过XRD、氮气吸附、H2-TPR和XPS等手段研究了催化剂的晶体结构、孔结构参数、氧化还原性能和表面原子价态.催化臭氧深度氧化NO主要与催化剂对臭氧的分解性能和对NO的氧化性能有关.较大的比表面积和孔容有利于催化剂的吸附.氧空位有利于臭氧的吸附和分解.Mn4+和Mn3+的均衡分布既有利于NO的吸附氧化又有利于臭氧的吸附分解,最终提高了N2O5生成效率.