Electron spectroscopic studies of copper in catalysts for methanol synthesis

The state of Cu²⁺ ions in Cu–Zn–Al catalysts for methanol synthesis has been studied by electron spectroscopy (5000–50000 cm^–1). It has been established that low-temperature ZnO stabilizes copper in a distorted octahedral coordination as cluster structures resembling (but not similar to) CuO. The presence of Al promotes the formation of these clusters and inhibits the formation of CuO.

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(5000–50000 ^–1) Cu²⁺ Cu–Zn–Al . , ZnO , ( ) CuO. , CuO.

     

Bifunctionality of Cu/ZnO catalysts for alcohol-assisted low-temperature methanol synthesis from syngas:Effect of copper content

Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO_X catalysts while varying the copper content(X). Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction intermediate in this reaction, creating a different reaction pathway. The formation of crystalline phases and characteristic morphology of the co-precipitated precursors during the co-precipitation step were important factors in obtaining an efficient Cu/ZnO catalyst with a high dispersion of metallic copper,which is one of the main active sites for methanol synthesis. The acidic properties of the Cu/ZnO catalyst were also revealed as important factors, since alcohol esterification is considered the rate-limiting step in alcohol-assisted low-temperature methanol synthesis. As a consequence, bifunctionality of the Cu/ZnO catalyst such as metallic copper and acidic properties was required for this reaction. In this respect, the copper content(X) strongly affected the catalytic activity of the Cu/ZnO_X catalysts, and accordingly, the Cu/ZnO_0.5 catalyst with a high copper dispersion and sufficient acid sites exhibited the best catalytic performance in this reaction.     

Titania supported copper catalysts for methanol synthesis from carbon dioxide

The effect of co-catalyst (ZnO or ZrO₂) has been tested for hydrogenation of CO₂ on CuO/TiO₂ and CuO/Al₂O₃. CuO−ZnO/TiO₂ catalyst showed the highest activity for methanol synthesis. Kinetic parameters were also determined.     

不同改性组分对Cu-ZnO基催化剂低温甲醇合成性能的影响

通过共沉淀法制备了Al、Zr和Ce改性的Cu-ZnO基低温甲醇合成催化剂,采用氮气物理吸附、H2-TPR、CO2-TPD、N2O滴定、XRD和TEM等技术对其进行了表征,并考察了改性组分和煅烧温度对其在170℃下合成气制甲醇催化性能的影响。结果表明,经Zr改性的Cu-ZnO基催化剂,其低温甲醇合成性能较好;随着煅烧温度的降低,Cu在催化剂表面的分散度逐渐变大、颗粒逐渐变小,所得到的催化剂其活性也较高;其中,未经煅烧的Cu-ZnO/ZrO2催化剂的活性最佳,其甲醇时空产率为106.02 g/(kg·h),选择性达87.04%。     

Genesis of catalysts for methanol synthesis

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Promoting effect of polyoxyethylene octylphenol ether on Cu/ZnO catalysts for low-temperature methanol synthesis

Cu/ZnO catalysts were prepared by the co-precipitation method with the addition of OP-10 (polyoxyethylene octylphenol ether) and were chemically and structurally characterized by means of XRD, BET, H₂-TPR, CO-TPD and N₂O-titration. The effect of OP-10 addition on the activity of Cu/ZnO for the slurry phase methanol synthesis at 150 °C was evaluated. The results showed that Cu/ZnO prepared with addition of 8% OP-10 (denoted as C8) exhibited the promoted activity for the methanol synthesis. The conversion of CO and the STY (space time yield) of methanol were 42.5% and 74.6% higher than those of Cu/ZnO prepared without addition of OP-10 (denoted as C0), respectively. The precursor of C8 contained more aurichalcite and rosasite, and the concerted effect of Cu-Zn in C8 was found to be stronger than that in C0. Compared with C0, C8 showed smaller particle size, lower reduction temperature and larger BET and Cu surface areas.     

State of copper in Cu?Zn?Al oxide catalysts for methanol synthesis

Nature of the catalytically active component in Cu–Zn–Al oxide catalysts for methanol synthesis and water-gas shift reaction and the peculiarities of copper ions, responsible for the high rates of methanol synthesis, are discussed.

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Variations in electronic state of silver catalysts for methanol oxidation

Variations in the electronic state of silver catalysts for methanol oxidation under the effect of the reaction medium have been studied, using diffuse reflectance spectroscopy. The nature of active centers-Ag⁺ cations, Ag _n ⁺ complexes and clusters of various sizes for bulk and supported catalysts are shown to be identical.

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. - Ag⁺, Ag _n ⁺ .

     

Sonochemical synthesis of silver nanoparticles coated copper wire for low-temperature solid state bonding on silicon substrate

The rapid and efficient preparation of silver-copper wire by sonochemical assisted reduction method for high antioxidant performance and low melting temperature. Good ohmic contact between Ag-Cu wire and Si substrate can be achieved at temperature as low as 320℃.     

Kinetics of methanol synthesis in the presence of low-temperature catalyst

The kinetics of methanol synthesis performed in a flow circulation installation in the presence of low-temperature copperzinc-aluminium catalyst has been investigated. The application of a power kinetic equation describing the surface chemical interaction on an exponentially inhomogeneous surface is established. The effect of the volume rate and the temperature is studied and the presence of a compensation effect is proved. A possibility of determination of the temperature and the volume rate, under which conditions the side-reactions do not affect the main one, is shown on the basis of the kinetic investigations.

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Active state of molybdenum in molybdenum-alumina catalysts for propylene oxidation

Catalytic properties of molybdenum-alumina catalysts for propylene oxidation are shown to be determined by water-soluble molybdenum compounds, being apparently aluminomolybdenum heteropoly acids bonded to the catalyst surface.

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Kinetic studies of methanol synthesis from CO_2+H_2 over copper based catalysts

The catalytic activity for the synthesis of methanol from carbon dioxide and hydrogen wasmeasured on various binary and ternary catalysts containing copper oxide under a pressure of 10 atm.Among these samples the catalysts, CuO/ZnO/γ-Al_2O_3, demonstrated the highest activity andselectivity to methanol; MnO, as third component, had no promotional effect on the activity of meth-anol formation. Based on a simple power rate law the apparent activation energy estimation and par-tial pressure dependence measurement were accomplished over eight catalysts. The activation energiesvaried from 40 to 120 kJ / mol depending on the composition of catalysts. The rates of methanol for-mation to be 0.3 -- 0.9 order in H_2 and about 0.1 -- 0.2 order in CO_2 were reported.     

On the path to catalysts for the low-temperature ammonia synthesis

A nontraditional approach to the development of catalysts for low-temperature ammonia synthesis is considered. The approach is characterized by application of catalysts representing heterogeneous analogs of the known homogeneous nitrogen-fixing systems based on transition metal compounds and strong electron donors. The use of this approach led to the development of catalysts that considerably surpass in their activity (at atmospheric pressure) the industrial catalyst for the ammonia synthesis. Some of the developed catalysts are active in the formation of ammonia from dinitrogen and dihidrogen even at 110–150°C. The mechanisms of activation and hydrogenation of dinitrogen over these new catalysts are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 796–806, May, 1998.     

Formation of methane in methanol synthesis on zinc-chromium catalysts

The rate of methane formation on zinc-chromium catalysts is described by zero-order rate law, If the catalyst is activated by copper, the rate of methane formation increases due to a decrease in the activation energy of the reaction. Presumably the formation of methane and methanol takes place on different active centers.

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ZrO2在合成甲醇催化剂CuO-ZnO-ZrO2中的作用

采用并流共沉淀法制备了一系列ZrO2的原子比不同的CuO-ZnO-ZrO2甲醇合成催化剂.在固定床反应器中进行合成气制甲醇的研究,考察了ZrO2在催化剂中的作用.结果表明,ZrO2的加入能显著提高催化剂的性能,当ZrO2的原子比达到0.10时,催化剂的活性最高并且耐热性能最强;过量的ZrO2会降低催化剂的活性.利用TPR、XRD、BET技术对催化剂进行了表征,发现适量ZrO2的加入不仅有助于提高Cu活性组分在催化剂表面的分散,提高催化剂的比表面积,使催化剂不容易高温烧结,而且有利于促进催化剂还原.     

溶胶凝胶法制备甲醇裂解铜系催化剂

甲醇具有能量密度高、易于储存运输及价格低廉等优点,以甲醇作为氢气载体裂解制H2,可以解决氢气难以储存运输的困难。用于该反应的催化剂较多,铜系催化剂以其价格便宜、毒性小等特点而受到研究者的广泛关注。但是该催化剂在低温下活性不高。本文用溶胶一凝胶法制备技术研制了一系列加助剂的铜系催化剂,进行热重和TPR表征,讨论其在甲醇裂解制氢模型反应中的应用。     

Active component of supported vanadium catalysts in the selective oxidation of methanol

The structure of catalysts based on vanadium oxide supported on different oxides (SiO₂, γ-Al₂O₃, ZrO₂, and TiO₂) was investigated. Their catalytic properties in the selective oxidation of methanol in a temperature range of 100–250°C were studied. It was shown that the nature of the support determines the structure of the oxide forms of vanadium. The supporting of vanadium on SiO₂ and γ-Al₂O₃ leads to the preferred formation of crystalline V₂O₅; the surface monomeric and polymeric forms of VO_x are additionally formed on ZrO₂ and TiO₂. It was established that the crystalline V₂O₅ oxide is least active in the selective oxidation of methanol; the polymeric forms are more active than monomeric ones. The mechanism of the selective oxidation of methanol to dimethoxymethane and methyl formate on the vanadium oxide catalysts is considered.     

Bifunctional copper catalysts for an atom efficient ether synthesis

A direct etherification of aromatic ketones and aliphatic alcohols into the corresponding asymmetrical ethers by the use of a bifunctional heterogeneous copper catalyst is described. The reaction protocol reveals to be versatile and convenient respect to the traditional ether synthesis for both environmental and practical concerns.     

锆助剂对低温液相合成甲醇用铜铬硅催化剂性能的影响

考察了含锆的铜铬硅催化剂低温液相合成甲醇性能，并进行了BET、TPR-H2、TPD-H2、TPD-CO、XRD和XPS表征。结果表明，锆作为结构助剂及电子助剂对催化剂在低温液相合成甲醇反应中具有显著的促进作用，反应活性可提高32.25 ％。锆助剂能有效提高催化剂的比表面积，促进催化剂中铜铬组分的分散及表面富集。ZrO2加入在催化剂表面产生的Cu+与催化活性的改善密切相关，Zr4+、Cr3+、Cu+可形成复合中心，为价态的稳定性提供微环境，在H2活化及C O键的断裂等反应步骤中起重要作用。