Effect of Fe-modified α-Al2O3 on the properties of Pd/α-Al2O3 catalysts in selective acetylene hydrogenation

The use of nanocrystalline Fe-modified α-Al₂O₃ prepared by sol–gel and solvothermal method as supports for Pd catalysts resulted in an improved catalyst performance in selective acetylene hydrogenation. Moreover, the amount of coke deposits was reduced due to lower acidity of the Fe-modified α-Al₂O₃ supports.     

Conversion of alkylmercaptans in the presence of γ-Al2O3

In the presence of -Al₂O₃ at 200–500°C methylmercaptans quantitatively transform into dimethyl sulfides with almost equilibrium degrees of conversion. 100% selectivity towards diethyl sulfide is observed when ethylmercaptan conversion amounts to about 50% of its equilibrium value. In more severe conditions, dimethyl- and diethyl sulfides convert with eliminating hydrocarbons and H₂S. Selectivity towards diisopropylsulfide is as high as 30% with isopropylmercaptane conversion up to 25%; the reaction follows a parallel-consecutive scheme.

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-Al₂O₃ 200–500°C . 100% 50% . - H₂S. 30% 25%, - .

     

The effect of preparation method on the defect structure and luminescence properties of γ-Al2O3

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Dehydrogenation of Isobutane Over V2O5/γ-Al2O3 Catalyst

The effect of the type of the support and the amount of V₂O₅ loading on the activity of V₂O₅/γ-Al₂O₃ catalyst for the dehydrogenation of isobutane have been investigated. Based on the experimental results of TPR, XRD and ESR spectroscopy, it is suggested that there are strong interactions between vanadia and carrier and that the V⁴⁺ species on the surface is the active site of V₂O₅/γ-Al₂O₃ for this reaction. This revised version was published online in June 2006 with corrections to the Cover Date.     

NiO在γ-Al2O3及 TiO2/γ-Al2O3载体上的表面存在状态

本文采用LRS,XRD,UV－DRS考查了γ－Al2O3上TiO2的分散容量,分散态Ti^4 离子的配位环境;NiO在经TiO2改性后的γ－Al2O3载体上的分散容量,结果表明,（1)TiO2在γ－Al2O3表面的分散容量约为0．65mmol/100m^2γ－Al2O3,当TiO2含量低于该分散容量时Ti^4 在γ－Al2O3载体表面以嵌入形式呈离子态分布,而含量离于分散容量时还有结晶态的TiO2出现,（2）NiO在TiO2/γ－Al2O3载体表面的分散容量约为1．1mmol/100m^2γ－Al2O3,比之在γ－A2O3载体表面的分散容量（1．5mmol/100m^2γ－Al2O3）要低,这是由于γ-AlO3表面上部分空位被Ti^4 离子占据,用表面相互作用的“嵌入模型”（Incorporation Model)讨论的这些结果。     

Influence of MgO loading on the structure and catalytic performance of Pd/γ-Al2O3, I. Effect of interaction between MgO and γ-Al2O3

The influence of MgO dispersed on -Al₂O₃ in different amounts on the structure and performances of Pd/-Al₂O₃ catalysts has been studied by means of XRD, H₂–O₂ titration, BET and catalytic activity test for CO oxidation. It was found that introduction of MgO enhanced greatly the CO oxidation activity of catalyst. It seems that the enhanced activity stems from the stronger interaction between MgO and -Al₂O₃ at a given temperature (e.g. 450 °C).     

La2O3/γ-Al2O3催化剂用于二甲醚二氧化碳重整制氢

采用等体积浸渍法制备了不同负载量的La₂O₃/γ-Al₂O₃催化剂,并考察了负载量和反应温度对催化剂用于二甲醚二氧化碳重整制氢反应的性能影响。结果表明,反应温度为550℃、La₂O₃负载量为15%时,催化剂表现出最好的性能：二甲醚的转化率为100%,二氧化碳的转化率达到85.4%,产物氢气的选择性高达93.3%,一氧化碳的选择性为76.04%,副产物甲烷的选择性仅为6.3%。550 ℃时其平均积炭速率为1.387 5 mg/（g·h）。研究还利用XRD、BET、TEM、TG等方法对催化剂进行了表征。     

Carbon nanotubes decorated α-Al2O3 containing cobalt nanoparticles for Fischer-Tropsch reaction

A new hierarchical composite consisted of multi-walled carbon nanotubes (CNTs) layer anchored on macroscopic α-Al2O3 host matrix was synthesized and used as support for Fischer-Tropsch synthesis (FTS). The composite constituted by a thin shell of a homogeneous, highly entangled and structure-opened carbon nanotubes network and it exhibited a relatively high and fully accessible specific surface area of 76 m 2 g-1 , compared with that of 5 m 2 g-1 of the original α-Al2O3 support. The metal-support interaction between carbon nanotubes surface and cobalt precursor and high effective surface area led to a relatively high dispersion of cobalt nanoparticles. This hierarchically supported cobalt catalyst exhibited a high FTS activity along with an extremely high selectivity towards liquid hydrocarbons compared with the cobalt-based catalyst supported on pristine α-Al2O3 or on CNTs carriers. This improvement can attribute to the high accessibility of composite surface area comparing with the macroscopic host structure alone or to the bulk CNTs where the nanoscopic dimension induced a dense packing with low mass transfer which favoured the problem of reactants competitive diffusion towards the cobalt active site. In addition, intrinsic thermal conductivity of decorated CNTs could help the heat dissipating throughout the catalyst body, thus avoiding the formation of local hot spots which appeared in high CO conversion under pure syngas feed in FTS reaction. Cobalt supported on CNTs decorated α-Al2O3 catalyst also exhibited satisfied high stability during more than 200 h on stream under relatively severe conditions compared with other catalysts reported in the literature. Finally, the macroscopic shape of such composite easily rendered its usage as catalyst support in a fixed-bed configuration without facing problems of transport and pressure drop as encountered with the bulk CNTs.     

Role of support nature （γ-Al2O3 and SiO2-Al2O3） on the performances of rhenium oxide catalysts in the metathesis of ethylene and 2-pentene

The metathesis of ethylene and 2-pentene was studied as an alternative route for propylene production over Re2O7/γ-Al2O3 and Re2O7/SiO2-Al2O3 catalysts. Both NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) results showed that Re2O7/SiO2-Al2O3 exhibited stronger acidity and weaker metal-support interaction than Re2O7/γ-Al2O3. At 35 60℃, isomerization free metathesis was observed only over Re2O7/γ-Al2O3, suggesting that the formation of metal-carbene metathesis active sites required only weak acidity. Our results suggest that on the Re2O7/SiO2-Al2O3, hydrido-rhenium species ([Re]-H) were formed in addition to the metathesis active sites, resulting in the isomerization of the initial 1-butene product into 2-butenes. A subsequent secondary metathesis reaction between these 2-butenes and the excess ethylene could explain the enhanced yields of propylene observed. The results demonstrate the potential for high yield of propylene from alternative feedstocks.     

Acid-base properties of α-aminomethylphosphine oxides

Ionization constants of a series of aminomethylphosphine oxides and respective amino precursors, as well as their isostructural amino phosphonates in water-2-propanol or water medium were determined. The main regularities of the effect of the phosphoryl group on the protolytic equilibria involving mono- and bisphosphorylated amines and diamines were found. The environment effect on the ionization constants of hydrophilic aminophosphoryl compounds and amines was estimated quantitatively. The relationship between the dissociation constants of aminophosphoryl compounds and related constants of amino precursors in the framework of the principle of linearity of free energies was demonstrated.     

Effects of the support crystallite size and the reduction temperature on the properties of Pd/α-Al2O3 catalysts in selective acetylene hydrogenation

Pd catalysts supported on the solvothermal-derived nanocrystalline α-Al₂O₃ (45 nm) exhibited superior performances in the selective acetylene hydrogenation than those supported on micron-sized ones (44–149 μm). Reduction at 500°C led to an improvement of the ethylene yield for the Pd/nanocrystalline α-Al₂O₃, but not for the Pd/micron-sized α-Al₂O₃.     

Hydrogenation of Cinnamaldehyde on Ir/γ-Al2O3 Catalysts. Influence of the Surface Acidity

The oxidation of methane has been studied in a flow system as a function of the chemical composition of zeolite catalyst using nitrous oxide as oxidant. It is concluded that methanol is a primary oxidation product which may undergo further oxidation to formaldehyde and to carbon oxides. However, it may also undergo conversion over the acidic catalyst to higher hydrocarbons. Reaction with nitrous oxide resulted in the production of carbon oxides, methanol, formaldehyde, C₂ - C₄ , C₅ - C₇ nonaromatics, and aromatics. The effect of Fe₂ O₃ and Al₂ O₃ , with or without, over HZSM5 on products was studied.     

超声波辅助浸渍法制备Fe2O3/γ-Al2O3 吸附剂脱除气相As2O3的实验研究

使用超声波辅助浸渍法制备Fe₂O₃/γ-Al₂O₃吸附材料,在固定床反应器上研究了前驱液浸渍浓度、载体粒径、吸附温度、吸附气氛等因素对脱除气相As₂O₃的影响。结果表明,前驱液浸渍浓度、载体粒径等会对吸附剂表面结构产生影响从而影响其砷吸附性能;吸附温度升高增强了其化学吸附能力,然而,温度过高反而造成吸附性能的下降;吸附气氛中的SO₂促进了Fe₂O₃/γ-Al₂O₃对气相砷的吸附,气氛中的NO对气相砷的影响不大。     

On the reduction of Pd2+ forms in Pd/γ-Al2O3 catalysts

The influence of the preparation method (i.e., Pd precursor and heat treatments) on the reduction pattern of Pd/-Al₂O₃ catalysts has been investigated by TPR. The role of the Cl^– ions and the effect of metal dispersity on the stability of Pd catalysts reduced at different T_r (400T_r800°C) have been discussed. Reoxidation of Pd^o occurs during exposure to the atmosphere and the formation both of easily reducible PdO forms and Cl-containign Pd²⁺ oxo-complexes, strongly interacting with alumina surface, has been pointed out.     

La2O3对Ni-Mo/γ-Al2O3催化剂CO和CO2甲烷化的影响

采用浸渍法制备了一系列Ni-Mo-La/γ-Al     

Activity of γ-Al2O3 modified by NaOH in disproportionation of methanethiol

Na⁺/Al₂O₃ catalysts in disproportionation of methanethiol are highly selective towards dimethyl sulfide but less active compared to -Al₂O₃. Their activity falls with increasing Na⁺ in the sample. This decrease is due to the neutralization of Brönsted acid centers on the catalyst.

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Na⁺/Al₂O₃ , , -Al₂O₃. Na⁺ . .

     

Nanostructured ruthenium on γ-Al2O3 catalysts for the efficient hydrogenation of aromatic compounds

Free and trioctylamine (TOA)-stabilized ruthenium nanoparticles have been prepared by decomposition of the metal precursor Ru(η⁶-cycloocta-1,3,5-triene)(η⁴-cycloocta-1,5-diene) under mild conditions (room temperature, hydrogen atmospheric pressure). The nanoparticles have been deposited on γ-Al₂O₃ supports having different surface area. The resulting systems are active in the hydrogenation of methyl benzoate to methyl cyclohexanoate with a reaction rate decreasing in the order Ru(TOA)/γ-Al₂ O₃ (high surface area, catalyst D) > Ru(TOA)/γ-Al₂O₃ (catalyst C) > Ru/γ-Al₂O₃ (high surface area, catalyst B) > Ru/γ-Al₂O₃ (catalyst A). Catalysts A-D are long lived and can be reused without loss of activity; they are considerably more active than a commercial ruthenium on γ-Al₂O₃ sample. High Resolution Transmission Electron Microscopy analyses of such systems show that the nanoparticles are homogeneously dispersed on the support and that the size distribution decreases in the order catalyst A, 2.9 nm > catalyst B, 2.8 nm > catalyst C, 2.4 nm > catalyst D, 2.3 nm. Based on the easy hydrogenation of the aromatic ring to the cyclohexane derivative, an efficient synthesis of 4-carbomethoxyformylcyclohexane, important starting material in the preparation of pharmaceutical products, from the largely available methyl 4-formylbenzoate, has been set up in the presence of catalyst D.     

Hydrogenation of 2-ethylanthraquinone over Pd/Zro2-γ-Al2O3 catalyst

A ZrO₂-γ-Al₂O₃ supported Pd catalyst was prepared and characterized by XRD, XPS, H₂-TPR and TEM techniques. The catalytic activity was evaluated in the liquid-phase hydrogenation of 2-ethylanthraquinone. Comparing with Pd/γ-Al₂O₃, it showed high catalytic activity.     

沉淀法结合超临界CO2干燥制备纳米γ-Al2O3

纳米γ-Al2O3具备多孔性、高比表面积、良好的吸附性、热稳定性和表面酸性[1,2],用作吸附剂和催化剂(及其载体),是催化剂载体领域应用最为广泛的品种[3～6].制备纳米氧化铝的方法有很多,大致可分为固相法、液相法、气相法等.     

Deposition of NiO onto MoO3/γ-Al2O3 extrudates by slurry impregnation method

NiO-MoO₃/γ-Al₂O₃ catalysts were prepared by the reaction of γ-Al₂O₃ extrudates with an aqueous slurry of MoO₃, followed by the reaction of the MoO₃/γ-Al₂O₃ catalyst with an aqueous slurry of NiO, Ni(OH)₂, NiCO₃·2Ni(OH)₂·xH₂O, or 2NiCO₃·3Ni(OH)₂·4H₂O and by subsequent drying. The NiO deposition was examined with electron probe microanalysis. The deposited Ni efficiently increased the activity in benzothiophene hydrodesulfurization.