Effect of KOH on the continuous synthesis of cobalt oxide and manganese oxide nanoparticles in supercritical water

The effects of KOH on the supercritical hydrothermal synthesis of cobalt oxide and manganese oxide particles are investigated using a continuous-flow reactor. Significant changes in morphology, particle size, and oxidation state are observed by adding KOH. The spinel Co₃O₄ phase is transformed to a rocksalt CoO phase and the pyrolusite MnO₂ phase is transformed to a hausmannite Mn₃O₄ phase in the presence of 0.5 M KOH. The average particle size of the metal oxides decreased with an addition of KOH. The OH⁻ ions of KOH may act as a reducing agent as well as a supersaturation enhancing agent under supercritical water conditions.     

Complete oxidation of acetone over manganese oxide catalysts supported on alumina- and zirconia-pillared clays

The complete oxidation of acetone has been studied over a series of manganese oxide catalysts supported on the unpillared and the Al- and Zr-pillared forms of two natural clays of the smectite class (a montmorillonite and a saponite). The temperatures required for total combustion of acetone over the several catalysts ranged from 610 to 660 K at the relatively low W_Mn/F_in ratio of 0.40 g_Mn min mmol_acetone⁻¹ used. A significant influence of the clay supports characteristics on the catalytic performance has been found. According to the general behaviour of the various catalysts throughout the light-off tests, the following order of improving catalytic performance can be established with respect to the pillars composition: Al-pillared clays2O₃, MnO₂, Al₂O₃ and ZrO₂, as well as physical mixtures of ZrO₂ with the unpillared clays. The effect on the catalytic performance of the possible competition between the acetone combustion and aldol condensation processes has also been considered.     

Selective oxidation of alcohols using novel crystalline Mo-V-O oxide as heterogeneous catalyst in liquid phase with molecular oxygen

Catalytic selective oxidation of benzyl alcohol with molecular oxygen under mild conditions was carried out over novel crystalline Mo-V-O oxide. The present research is focused on investigation of recycling, reusability and stability of the crystalline oxide in the liquid-phase reaction. The Mo-V-O oxide catalyst was used at least four times with comparable activities to that of fresh catalyst. The separation of the catalyst from reaction medium can stop the conversion of benzyl alcohol, and the addition of the catalyst to the reaction medium can trigger the reaction immediately. The catalytic oxidation of 2,3,6-trimethylphenol as a reference reaction suggested that there were no leached active species in the reaction mixture. The results of the ICP–MS analysis, XRD, and SEM characterization confirmed that the structure and composition of the catalyst were stable. Besides, the Mo-V-O oxide can catalyze the oxidation of a series of alcohols with high selectivities for corresponding carbonyl compounds.     

环氧丙烷的合成及催化剂研究新进展

综述了近年来环氧丙烷合成工艺及催化剂研究的新进展，内容包括对现有环氧丙烷生产工艺的革新、氧气一步气相氧化法、过氧化氢液相氧化法、原位过氧化氢生产和环氧化、光催化氧化等方法，并对各种方法和催化剂的特点和发展前景进行了讨论。     

Fischer–Tropsch synthesis. Conversion of alcohols over iron oxide and iron carbide catalysts

Both iron oxide (Fe₂O₃) and iron carbide catalysts are active for the dehydration of tertiary alcohols; the oxide catalyst is not reduced nor is the bulk carbide oxidized by the steam generated during the dehydration reaction. Secondary alcohols are selectively converted to ketones plus hydrogen by both the iron oxide and carbide catalyst. Fe₂O₃ is reduced to Fe₃O₄ during the conversion of secondary alcohols. Both iron carbide and oxide catalysts dehydrogenate a primary alcohol (C_n) to an aldehyde which undergoes a secondary ketonization reaction to produce a symmetrical ketone with 2n−1 carbons. These results plus those of our earlier ¹⁴C-tracer studies suggest that dehydration of alcohols to produce olefins makes a minor, if any, contribution during Fischer–Tropsch synthesis with an iron catalyst at low and intermediate pressure conditions.     

Simultaneously morphology and phase controlled synthesis of cobalt manganese hydroxides/reduced graphene oxide for high performance supercapacitor electrodes

Cobalt manganese hydroxides with well-defined nanowire morphology (CoMn-HW) is scalable fabricated by adjusting solution contents, Mn/Co ratio and alkaline species. To further improve the conductivity of CoMn-HW, GO is introduced during fabrication process and reduced to rGO according to the high temperature and alkali atmosphere. By optimizing the adding mass of rGO, CoMn-HW/rGO with sandwiched like structure is successfully synthesized for supercapacitor electrode. The composite delivers a high specific capacitance of 784 F g⁻¹ at current density of 0.5 A g⁻¹, good rate capability (84.2% capacitance retention after current density increase 10 times). Moreover, an asymmetric supercapacitor with CoMn-HW/rGO10 as the positive electrode and active carbon as the negative electrode, is assembled and delivers a maximum energy density of 38.3 Wh kg⁻¹ and power density of 8000 W kg⁻¹, representing its potential in energy storage and conversion systems.     

甲醇直接氧化合成二甲氧基甲烷催化剂的研究

二甲氧基甲烷是重要的有机化工原料,在溶剂、化工中间体、制氢和燃料添加剂等领域应用广泛,以甲醇为原料一步合成二甲氧基甲烷是C1化工的研究新热点。以TiO₂为载体,通过负载V₂O₅并采用Ti(SO₄)₂改性制备V₂O₅/TiO₂-SO₄^2-催化剂,在温度（135～150） ℃、V（CH₃OH）∶V（O₂）∶V（N₂）=1∶（1.5～4）∶（7～20）和原料气流量(5 000～8 000) mL·(g·h)^-1条件下,将甲醇直接氧化合成二甲氧基甲烷。结果表明,甲醇转化率为48%,二甲氧基甲烷选择性为80%。     

氢氧直接合成过氧化氢用催化剂的研究进展

过氧化氢（H₂O₂）是一种高效的绿色氧化剂,广泛应用于化学品合成、印染纺织、污水处理等领域。近年来,氢氧直接合成过氧化氢作为一种简单、环保、原子效率高的合成方法,成为一大研究热点。本文系统性地介绍了近年来氢氧直接合成过氧化氢催化剂的催化反应机理,负载金属的不同结构和性质对直接合成过氧化氢的催化性能与作用机理,重点讨论了与催化剂载体相关的载体结构、载体酸性、载体添加物、载体与金属相互作用等方面对反应活性和选择性的影响。最后对比了近年来直接合成过氧化氢用催化剂的催化性能,认为合成高选择性、高产率的催化剂仍是未来直接合成过氧化氢工业化应用的发展方向。     

Effect of the nature and structure of pillared clays in the catalytic behaviour of supported manganese oxide

In the present work, the complete oxidation of acetone has been studied over a series of supported manganese oxide catalysts on the unpillared and the Al- and Zr-pillared forms of two natural clays, a montmorillonite and a saponite. A significant influence of the clay supports characteristics on the catalytic performance has been found. The following order of improving catalytic performance is established with respect to the pillars composition: Al-pillared clays < unpillared clays < Zr-pillared clays.     

Electrochemical and spectral studies on the catalytic oxidation of nitric oxide and nitrite by high-valent manganese porphyrins at an ITO electrode

Catalytic oxidation of nitric oxide and nitrite by water-soluble manganese(III) meso-tetrakis(N-methylpyridinium-4-yl) porphyrin (Mn(III)(4-TMPyP) was first studied at an indium-tin oxide (ITO) electrode in pH 7.4 phosphate buffer solutions. A stepwise oxidation of Mn(III)(4-TMPyP) through high-valent manganese porphyrin species has been observed by electrochemical and spectroelectrochemical (OTTLE) techniques. The formal potential of 0.63 V for the formation of OMn(IV)(4-TMPyP) has been estimated from OTTLE data. The product, oxoMn(IV) porphyrin, was relatively stable decaying slowly to Mn(III)(4-TMPyP) with a first-order rate constant of 3.7 × 10⁻³ s⁻¹. OMn(IV)(4-TMPyP) has been found to oxidize NO catalytically at potentials about 70 mV more negative than that previously reported for OFe(IV)(4-TMPyP) with good selectivity against nitrite. Nitrite was catalytically oxidized at potentials higher than 1.1 V presumably by OMn(V)(4-TMPyP). OMn(IV)(4-TMPyP) was observed as an intermediate species. Nitrate has been confirmed to be a final product of the electrolysis at 1.2 V, while at 0.8 V nitrite left unchanged, demonstrating that OMn(IV)(4-TMPyP) could not oxidize nitrite. A possible schemes of the catalytic oxidation of NO by OMn^IV(4-TMPyP) and NO₂⁻ by OMn(V)(4-TMPyP) have been proposed.     

锰氧八面体分子筛的制备及应用研究进展

锰氧八面体分子筛具有多孔结构、温和的表面酸碱性、混合价态的锰离子和优异的离子交换性,被广泛应用于多相催化、电池材料和吸附材料等领域。本文介绍了锰氧八面体分子筛的化学组成,对其孔结构、氧化还原性能及酸碱性等理化性质予以总结,简述了水热法、回流法、微波法、溶胶-凝胶法和固相法等常用制备方法。锰氧八面体分子筛可应用于CO催化氧化、有机物催化氧化、CO₂活化利用和费托合成等催化领域,尤其对CO和挥发性有机物有较高的氧化活性,在电池材料和吸附材料等非催化领域也有重要的应用前景。最后指出了当前锰氧八面体分子筛研究中存在的问题,未来工作应探索更高效的合成方法,深入认识其催化作用机理,进一步拓宽该材料的应用范围。     

Catalytic activity of manganese oxide supported on alumina in the synthesis of quinoxalines

Two catalysts, alumina and manganese oxide supported on alumina, have been prepared by calcination and precipitation-impregnation methods, respectively. The catalysts are characterised by the following techniques: Brunner-Emmett-Teller-N₂ adsorption-desorption for surface area, temperature programmed desorption of NH₃ and n-butyl amine back titration methods for surface acidity, powder X-ray diffraction for textural properties, and Fourier transform infrared spectroscopy for the anionic radicals. The catalytic activity has been determined under heterogeneous conditions in the condensation reaction between o-phenylenediamine and benzil. The product purity is checked by thin-layer chromatography and melting point. The products are also analysed by LC-MS and ¹H-NMR techniques. The yields of the products have been found to be good and catalysts exhibited excellent recyclability. The effect of changing the reaction parameters such as temperature, reaction time, amount of the catalyst, nature of solvent and molar ratio of reactants on the yield of the product has been studied. The surface acidity of the catalysts plays an important role in activating the reaction.     

Sulfur resource recovery based on electrolytic manganese residue calcination and manganese oxide ore desulfurization for the clean production of electrolytic manganese

An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed, in which the electrolytic manganese residue(EMR) was initially calcined for cement buffering;then the generated SO_2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA) desulfurization; at last, the desulfurized slurry was introduced to the electrolytic manganese production(EMP). Results showed that 4.0 wt% coke addition reduced the sulfur of calcined EMR to 0.9%, thereby satisfying the cement-buffer requirement. Pilot-scale desulfurization showed that about 7.5 vol% of high SO_2 containing flue gas can be cleaned to less than 0.1 vol% through a five-stage countercurrent MOOA desulfurization. The desulfurized slurry had 42.44 g·L~(-) Mn~(2+) and 1.92 g·L~(-1) S_2 O_6~(2-), which was suitable for electrowinning after purification, and the purity of manganese product was 99.93%, satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7% of sulfur reutilization from the EMR and 94.1% was effectively used to the EMP. The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge, which promoted the cleaner production of EMP industry.     

Characterization and performance of hydrous manganese oxide prepared by electrochemical method and its application for supercapacitors

Hydrous manganese oxide was deposited on graphite substrates at anodic potentials of 0.5-0.95 V versus saturated calomel electrode (SCE) in 0.25 M Mn(CH₃COO)₂ solution at 25 °C. Morphology of manganese oxide prepared was examined by scanning electron microscopy (SEM). Manganese oxide deposited at various anodic potentials was evaluated by cyclic voltammetry with various potential scan rates in different electrolytes. Results indicated that the pseudocapacitive behaviors of manganese oxide were excellent both in 2 M KCl and 2 M (NH₄)₂SO₄ solutions at room temperature. Manganese oxide deposited at 0.5 V versus SCE showed better capacitive behaviors, the specific capacitances were 275 F/g in 2 M KCl solution and 310 F/g in 2 M (NH₄)₂SO₄ solution, respectively. Besides, better electrochemical reversibility could be obtained in 2 M KCl solution.     

Gold catalysts for the direct oxidation of aminoalcohols to aminoacids

Gold catalysts on different supports, prepared by sol immobilization and deposition–precipitation, were tested in aminoalcohol oxidation for the direct preparation of aminoacids. Nitrogen substitution appeared to be crucial for avoiding parallel reaction pathway, but also the reaction conditions play an important role. Basic conditions and moderate temperature (40 °C) represent a good compromise for enhancing selectivity to aminoacids. TiO₂ represents the most versatile support.     

Preparation of copper-containing mesoporous manganese oxides and their catalytic performance for CO oxidation

Copper-containing mesoporous manganese oxides were prepared by the sol–gel method. The samples obtained were characterized by XRD, N₂ adsorption–desorption, ICP, CO-TPD, redox measurement and XPS. After calcination at 300 °C, amorphous structure was shown by XRD for all the samples. All the samples had mesopores of about 6 nm and high surface areas of 170–230 m² g⁻¹. Using these samples as catalysts, CO oxidation was carried out as a model reaction. Copper-containing mesoporous manganese oxide prepared by the sol–gel method showed a very high activity. On the other hand, copper-supported manganese oxide prepared by the impregnation method using copper sulfate showed a low activity. Differences in activities were correlated with the mobility of lattice oxygen.     

Process systems engineering studies for the synthesis of catalytic biomass-to-fuels strategies

The goal of this paper is to show how chemical process synthesis and analysis studies can be coupled with experimental heterogeneous catalysis studies to identify promising research directions for the development of strategies for the production of renewable fuels. We study five catalytic biomass-to-fuels strategies that rely on production of platform chemicals, such as levulinic acid and fermentable sugars. We first integrate catalytic conversion subsystems with separation subsystems to generate complete conversion strategies, and we then develop the corresponding process simulation models based on experimental results. Our analyses suggest that catalytic biomass-to-fuel conversion strategies could become economically competitive alternatives to current biofuel production approaches as a result of iterative experimental and computational efforts.     

Effects of electrochemical-deposition method and microstructure on the capacitive characteristics of nano-sized manganese oxide

The amorphous nano-structured manganese oxide was electrochemically deposited onto a stainless-steel electrode. The structure and surface morphology of the obtained manganese oxide were studied by means of X-ray diffraction analysis and scanning electron microscopy. The capacitive characteristics of the manganese oxide electrodes were investigated by means of cyclic voltammetry and constant current charge-discharge cycling. The morphological and capacitive characteristics of the hydrous manganese oxide was found to be strongly influenced by the electrochemical deposition conditions. The highest specific capacitance value of ca. 410 F g⁻¹ and the specific power of ca. 54 kW kg⁻¹ were obtained at 400 mV s⁻¹ sweep rate of potentiodynamic deposition condition. The cyclic-life data showed that the specific capacitance was highly stable up to 10,000 cycles examined. This suggests the excellent cyclic stability of the obtained amorphous hydrous manganese oxide for supercapacitor application.     

Effect of manganese oxide on the sintered properties and low temperature degradation of Y-TZP ceramics

The sinterability of yttria-tetragonal zirconia polycrystals (Y-TZP) containing small amounts of MnO₂ as sintering aid was investigated over the temperature range of 1250–1500 °C. Sintered samples were evaluated to determine bulk density, Young's modulus, Vickers hardness and fracture toughness. In addition, the tetragonal phase stability of selected samples was evaluated by subjecting the samples to hydrothermal ageing in superheated steam at 180 °C/10 bar for up to 24 h. The results showed that the addition of MnO₂, particularly ≥0.3 wt% was effective in aiding densification, improving the matrix stiffness and hardness when compared to the undoped Y-TZP sintered at temperatures below 1350 °C. On the other hand, the fracture toughness of Y-TZP was unaffected by MnO₂ addition except for the 1 wt% MnO₂-doped Y-TZP samples sintered above 1400 °C. The hydrothermal ageing resistance of Y-TZP was significantly improved with the additions of MnO₂ in the Y-TZP matrix.     

多金属氧酸盐催化合成缩醛（酮）的研究进展

作为具有出色催化性能的绿色催化剂多金属氧酸盐,在催化合成缩醛（酮）反应领域展现出了广阔的应用前景。首先简要地介绍了多金属氧酸盐的性质及其应用;然后综述了近几年来多金属氧酸盐及负载多金属氧酸盐催化剂在催化合成缩醛（酮）反应中的研究现状,包括活性炭、硅胶、二氧化钛、分子筛等载体;并对其未来的发展方向进行了展望。