Structure and oxidation state of silica-supported manganese oxide catalysts and reactivity for acetone oxidation with ozone

Silica-supported manganese oxide catalysts with loadings of 3, 10, 15, and 20 wt % (as MnO2) were characterized with use of X-ray absorption spectroscopy and X-ray diffraction (XRD). The edge positions in the X-ray absorption spectra indicated that the oxidation state for the manganese decreased with increasing metal oxide loading from a value close to that of Mn2O3 (+3) to a value close to that of Mn3O4 (+2(2)/3). The XRD was consistent with these results as the diffractograms for the supported catalysts of higher manganese oxide loading matched those of a Mn3O4 reference. The reactivity of the silica-supported manganese oxide catalysts in acetone oxidation with ozone as an oxidant was studied over the temperature range of 300 to 600 K. Both oxygen and ozone produced mainly CO2 as the product of oxidation, but in the case of ozone the reaction temperature and activation energy were significantly reduced. The effect of metal oxide loading was investigated, and the activity for acetone oxidation was greater for a 10 wt % MnOx/SiO2 catalyst sample compared to a 3 wt % MnOx/SiO2 sample.     

Cobalt promoted copper manganese oxide catalysts for ambient temperature carbon monoxide oxidation

Low levels of cobalt doping (1 wt%) of copper manganese oxide enhances its activity for carbon monoxide oxidation under ambient conditions and the doped catalyst can display higher activity than current commercial catalysts.     

Catalytic decomposition of ozone over cupric oxide catalysts

Kinetic regularities of the catalytic decomposition of ozone over IC-12-1 and ICT-12-9 cupric oxide catalysts in wetted gases have been studied. These catalysts are suggested to be effective for ozone decomposition.

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-12-1 -12-9 . .

     

Propylene oxidation over tin-molybdenum oxide catalysts

The influence of preparation of tin-molybdenum catalysts on their phase composition and activity has been elucidated. The mutual dissolution of Sn and Mo oxides leads to a considerable increase in their activities and selectivities in the partial oxidation of propylene to acetone.

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Oxide talum-containing catalysts of ozone decomposition and methane oxidation

The oxidation of manganese ions is shown to occur in ozone decomposition on manganese-containing catalyst, leading to the deactivation of a sample. The structure of the iron-containing catalyst does not change, ensuring its high stability during ozone decomposition in a dry gas flow at room temperature, conducted in the region of inner diffusion with an activation energy of 15.5 ± 0.7 kJ/mol. The presence of manganese cations in the intermediate stages of reduction is found to increase their activity in the reaction of deep methane oxidation.     

Photocatalytic oxidation of isobutene on immobilized in oxide catalysts

Tin oxide species immobilized on silica have been synthesized. These systems are active in the photocatalytic oxidation of isobutene to acetone and their atomic photocatalytic activity is by almost two orders of magnitude higher than for crystalline SnO₂.

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, . , SnO₂.

     

Mixed-valence manganese calcium oxides as efficient catalysts for water oxidation

Incorporation of calcium to mixed-valence manganese oxides improved the water oxidation activity of these manganese oxides.     

Kinetics and mechanism of 4-acetoxytoluene oxidation by ozone in an acetic anhydride solution in the presence of manganese bromide catalysts

The kinetics of the reaction of ozone with 4-acetoxytoluene in an acetic anhydride solution in the presence of a manganese bromide catalyst is reported. Under these conditions, the major reaction products are 4-acetoxybenzylidenediacetate (68.0%), 4-acetoxybenzyl acetate (18.5%), and 4-acetoxybenzyl bromide (1.6%). The effect of manganese(II) acetate and potassium bromide on the selectivity of oxidation at the methyl group has been investigated. A probable redox catalysis mechanism explaining the experimental data is considered.     

Selective oxidation of benzene to phenol over FeAlPO catalysts using nitrous oxide as oxidant

A tetrahedrally coordinated iron in framework substituted microporous AlPO-5 catalysts are shown to be active and selective for the hydroxylation of benzene to phenol, using nitrous oxide as the oxidant.     

锰负载钛锆和钛锡复合氧化物催化剂烟气脱汞实验研究

采用共沉淀法制备了TiO_2、TiZr和TiSn载体,浸渍锰制备了10%MnO_2的MnTi、MnTiZr和MnTiSn催化剂。采用BET、XRD、H_2-TPR、FT-IR和XPS等对样品进行表征,并对三种催化剂进行固定床脱汞性能实验。结果表明,在100-300℃,MnTiZr和MnTiSn催化剂脱汞性能均优于MnTi催化剂,这归因于Sn和Zr的引入提升了催化剂比表面积和低温氧化还原性能增加了催化剂表面的酸性位点数量、高价态锰离子和O~*含量;在反应温度为150-300℃,MnTiSn催化剂脱汞效率均高于MnTiZr催化剂这是由于前者具有更好的氧化还原性能,表面具有更多含量的高价态锰离子、O~*含量和酸性位点数量;在Hg~0脱除过程中催化剂表面活性组分如高价态锰离子和O~*均消耗,参与了Hg~)氧化为Hg~(2+)的反应且MnTiSn催化剂表面活性组分的消耗量更多。     

Selective oxidation of alcohols by porphyrin-based porous polymer-supported manganese heterogeneous catalysts

A series of porphyrin-based porous polymers to support Mn heterogeneous catalysts (Mn/TFP-DPM, Mn/TFP-DPM-2, Mn/TFP-DPM-3, and Mn/TFP-DPM-4) in the selective oxidation of alcohols were designed. TFP-DPM and TFP-DPM-2 demonstrated micro/nanoscale spherical morphology, whereas TFP-DPM-3 and TFP-DPM-4 exhibited nanosheets structure. According to surface area and porosity analysis results, the specific surface areas of these catalysts were less than 300 m² g^–1. Thermogravimetric analysis indicated that the synthesized catalysts maintain their stability even at 300 °C. Catalysts Mn/TFP-DPM and Mn/TFP-DPM-3, which had the smallest and largest specific surface area among the four catalysts, respectively, were used to perform selective oxidation reaction of alcohols, with experimental results indicating that both have excellent catalytic performance. As these catalysts possess good catalytic performance despite their low specific surface area, we suggest that porphyrin-based porous polymer-supported Mn heterogeneous catalysts are promising materials for selective oxidation of alcohols.     

Titanium-supported nickel-copper oxide catalysts for oxidation of carbon(II) oxide

Nickel-copper compositions for catalytic oxidation of carbon(II) oxide to carbon(IV) oxide were prepared by impregnation of oxide films on titanium surface, obtained by plasma electrolytic oxidation followed by annealing. Plasma electrolysis oxide coatings with a layer thickness of 5 to 50 μm were generated using different electrolytes. The compositions were studied by X-ray powder diffraction, X-ray spectral analysis, and electron microscopy, and moisture absorption of the initial plasma electrolytic structures was estimated. A linear correlation was found between the overall concentration of nickel and copper (4 to 25 mol %) in the surface layer of ∼2–5-μm compositions and their catalytic activity. The overall concentration of nickel and copper was found to increase in parallel with the moisture absorption of plasma electrolytic oxidation coatings. Nickel-copper compositions based on plasma electrolytic oxidation coatings generated in a silicate electrolyte displayed the best catalytic, mechanical, and adhesion properties.     

Methane oxidation on vanadium oxide catalysts synthesized by molecular dispersion on aerosil

It has been found that (Si–O)₂V_2xO_5x–1 catalysts accelerate partial and complete oxidation of CH₄ at 450–550°C. The steps responsible for the rate of the overall reaction with the participation of N₂O at low temperatures involve single V-centers and , whereas in the oxidation by O₂ at higher temperatures V-clusters and O^2–-species take part.

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(Si–O)₂V_2xO_5x–1 CH₄ 450–550°C. , N₂O , V- , O₂ O^2–.

     

Cs-Fe-Co-Bi-Mn-Mo复合氧化物选择性催化氧化异丁烯

Mixed oxide catalyst Cs0.1 Fe2Co6BiMnMo12 Ox was prepared by the interprecipitation method, then the catalyst was calcined at different temperature. Selective oxidation of isobutene was carried out in a fixed-bed reactor. The results showed that the catalyst has high catalytic activity. Under the optimum reaction conditions ( n(-C4^= ) : n(O2) = 1:2-1:4, space velocity = 180h^-1, T = 360℃ ), the yield of methacmlein and methacrylic reached 80%, 8 %,respectively. The total yields of liquid products( methacrolein, methacrylic acid and acetic acid) reached about 90%.     

Selective oxidation of light alkanes over Mo-based oxide catalysts

A highly reduced Keggin-type heteropolymolybdophosphate, H₃PMo₁₂O₄₀(Py), which was formed by the heat-treatment of pyridinium salt of H₃PMo₁₂O₄₀, can catalyze the propane oxidation to acrylic acid and acetic acid selectively. We propose a possible reaction mechanism for alkane oxidation, where protons and electrons on the reduced H₃PMo₁₂O₄₀ catalyst cooperate for activating molecular oxygen to form electrophilic oxygen species for alkane oxidation. It is also reported that Anderson-type heteropolycompounds linked with vanadyl cations VO²⁺ were able to be synthesized by hydrothermal reaction and showed good catalytic activity for the ethene oxidation to acetic acid.     

C-H oxidation using graphite oxide

Graphite oxide was found to be an effective oxidant for use in a broad range of reactions, including the oxidation of olefins to their respective diones, methyl benzenes to their respective aldehydes, diarylmethanes to their respective ketones, and various dehydrogenations. The temperatures used in the reactions were typically mild (100-120 °C), and the heterogeneous nature of the oxidant facilitated isolation and purification of the desired products. In most cases, no by-products were observed and the desired products were isolated in good to excellent yields.