乙醇辅助的化学沉积法制备硫化型Mo/γ-Al2O3加氢脱硫催化剂

以硫代乙酰胺为硫源,钼酸钠为钼源,乙醇为分散剂,采用化学沉积法制备了MoS₃/Al₂O₃催化剂前驱体,再用H₂高温处理得到高分散硫化型MoS₂/γ-Al₂O₃催化剂,运用N₂吸附-脱附、X射线光电子能谱以及高分辨透射电子显微镜等技术对MoS₂/γ-Al₂O₃催化剂进行了表征,并以二苯并噻吩作为模型化合物评价了催化剂的加氢脱硫(HDS)活性.结果表明,与浸渍法相比,所制催化剂具有更大的比表面积和孔体积、更高的活性金属分散度、更佳的Mo物种硫化度以及更短的MoS₂片层长度和更高的堆积度,因而在二苯并噻吩HDS反应中表现出远优于浸渍法所制催化剂的活性.乙醇可通过S?H-O氢键吸附至MoS₃纳米粒子表面,可有效防止其生长和团聚,起到分散剂的作用.     

Pt/Al2O3 and Pt/Ba?Al2O3 catalysts studied by temperature programmed desorption of oxygen: Evidence for a low temperature desorbing species

For fresh and aged Pt/Al₂O₃ catalysts, TPD of oxygen is fairly well related to the noble metal surface areas and to the catalytic activity in butane combustion, whereas for aged Pt/Ba−Al₂O₃ solids, the catalytic activity is still preserved despite a tremendous sintering of the metallic phase and seems to be connected to a surface barium superoxide.     

Temperature programmed reduction and oxidation of Ir/Al2O3 catalysts

3 % Ir/Al₂O₃ catalysts have been studied by means of temperature programmed reduction and oxidation. With growing degree of metal oxidation (higher T_ox) reducibility of the catalysts at low temperatures decreases.

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3% Ir/Al₂O₃ . ( ) .

     

The support and characterization of C60 and MoO3 on Al2O3

A new type of catalyst from supporting C₆₀ on MoO₃ and Al₂O₃ has been prepared. The effect of different order of impregnation and calcination atmosphere on catalyst are investigated by the solution test in toluene, UV-VIS spectroscopy and temperature programmed reduction (TPR). The results show that when the catalyst was prepared by supporting MoO₃ on C₆₀/Al₂O₃ and calcined in N₂, there is a stronger interaction between C₆₀, MoO₃ and Al₂O₃, but when supporting C₆₀ on MoO₃/Al₂O₃, the interaction is relatively weak. We consider that in the former method a new complex, Mo–C₆₀–O–Al, is formed.     

Influence of the activation temperature on structural and textural properties of NiMo/Al2O3 hydrodesulfurization catalysts

Investigations of a commercial NiMo/Al₂O₃ hydrodesulfurization (HDS) catalyst are directed towards optimization of the activation procedure of HDS catalyst concerning active phase formation and thermal stability. Structural and textural data obtained with XRD, IR-FTIR, XPS and LTNA reveal that the optimal temperature for the formation of active species on the catalyst surface and an appropriate pore structure is 300°C.     

螯合剂对Co-Mo/Al_2O_3成型加氢脱硫催化剂性能的影响

以拟薄水铝石为原料,添加有机溶剂,经挤条成型、干煅、焙烧制备了比表面积大、孔分布宽的柱状γ-Al2O3载体;采用共浸渍法制备了系列Co-Mo/Al2O3催化剂(CoO和MoO3质量分数分别为2%和8%)。利用低温氮吸附、XRD和H2-TPR技术对催化剂进行了表征,考察了螯合剂柠檬酸(CA)、草酸(OA)和乙二胺四乙酸(EDTA)对成型催化剂粗苯加氢脱硫活性的影响。结果表明,添加螯合剂后,催化剂的前驱体主要沉积在载体的3~10 nm中孔内,活性组分以无定形态高度分散在载体上。添加CA可提高催化剂的还原性,显著降低Mo6+的还原温度。在300℃、3.0 MPa、液体空速(LHSV)为2 h-1和氢油体积比为600的条件下,噻吩硫的脱除率可达到99.9%以上。     

Sulfuration of Pt/Al2O3, Pt?Re/Al2O3 and Pt?Ir/Al2O3 catalysts

Three reforming catalysts Pt/Al₂O₃, Pt–Ir/Al₂O₃ and Pt–Re/Al₂O₃ have been sulfurated by H₂S and tested by their activities in benzene hydrogenation. By treatment at 500°C under hydrogen flow only a part of the initial activity of the non-sulfurated catalyst is retained. So only a part of the adsorbed sulfur is easily removed in these conditions. The remaining sulfur for each of the catalysts (Pt/Al₂O₃, Pt–Ir/Al₂O₃ and Pt–Re/Al₂O₃) gives the same atomic ratio of 0.5 sulfur atom per accessible metallic atom.

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Pt/Al₂O₃, Pt–Ir/Al₂O₃ Pt–Pe/Al₂O₃ . 500°C H₂ . . ., . (Pt/Al₂O₃, Pt–Ir/Al₂O₃ Pt–Pe/Al₂O₃) 0,5.

     

Thiophene hydrodesulfurization activity of MoS2/Al2O3 catalysts prepared via exfoliation. The effect of cobalt

In contrast to the bulk MoS₂, the structure of the active phase of the catalyst prepared via exfoliation is shown to exhibit a number of distortions, which form a superstructure of the type of the charge density waves with a quasi-period of 30 ?. Due to such distortions, the ions of cobalt firmly chemisorb on the basal plane of MoS₂ occupying, along the perimeter of the MoS₂ clusters, the regions with a lower energy of the Mo-S interaction. A synergetic increase in the catalyst activity due to the introduction of cobalt was observed up to the atomic ratios of Co/(Co+Mo) = 0.33, which is possible for the nanoparticles of MoS₂ with a diameter 200 ?, only if cobalt adsorbs on the basal plane. This revised version was published online in June 2006 with corrections to the Cover Date.     

Catalytic activity of NiMo/TiO2?Al2O3 systems in thiophene hydrodesulfurization

A correlation exists between the number of surface acid sites and the catalytic activity of NiMo/TiO₂–Al₂O₃ systems in thiophene hydrodesulfurization. The catalytic activity for thiophene hydrodesulfurization and surface concentration of Brönsted acid sites increase with the titania content in the TiO₂–Al₂O₃ support.     

乙烷氧化脱氢用Ni/Al2O3催化剂中活性镍物种前驱体（英文）

Ni/Al2O3 catalysts for oxidative dehydrogenation(ODH) of ethane were prepared by impregnation of Al2O3 with nickel acetate or nickel nitrate,and by mechanical mixing of NiO and Al2O3.The Ni-based catalysts were characterized by N2 adsorption-desorption,X-ray diffraction,diffuse reflectance UV-visible diffuse reflectance spectroscopy,and temperature-programmed reduction of hydrogen.The results showed that formation of crystalline NiO particles with a size of < 8 nm and/or non-stoichiometric NiO species in the Ni/Al2O3 catalysts led to more active species in ODH of ethane under the investigated reaction conditions.In contrast,tetrahedral Ni species present in the catalysts led to higher selectivity for ethene.Formation of large crystalline NiO particles(22-32 nm) over Ni/Al2O3 catalysts decreased the selectivity for ethene.     

低温下Pt/Al_2O_3和Pd/Al_2O_3光辅助乙二醇水相重整制氢研究

采用浸渍还原法制备了氧化铝负载的Pt和Pd纳米颗粒催化剂,用于光辅助乙二醇水相重整制氢反应。结果表明,光照能够有效降低乙二醇水相重整制氢的活化能,Pt/Al_2O_3比Pd/Al_2O_3具有更高的H_2转换频率(TOF)和更低的CO选择性。采用XRD、TEM、UV-vis等技术对催化剂的结构和形貌进行了表征,原位漫反射红外光谱(DRIFTS)表明,光照能促进乙二醇分子O-H键的断裂。理论计算表明,Pt/Al_2O_3催化乙二醇重整制氢反应产物中较低的CO选择性主要归因于CO在Pt表面较小的反应能垒,能够较快与H_2O解离的O反应生成CO_2。     

Sulfurization of Pt/Al2O3?Cl catalysts. IV. Adsorption sites of H2S on Al2O3, Al2O3?Cl and Pt/Al2O3?Cl

Chemisorption of H₂S on Al₂O₃, Al₂O₃–Cl and Pt/Al₂O₃–Cl has been studied by gravimetry and IR spectroscopy. The influence of the amount of Cl on the H₂S adsorption equilibrium value and the nature of the adsorption sites at low and high coverages are discussed.

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H₂S Al₂O₃, Al₂O₃–Cl Pt/Al₂O₃–Cl . Cl H₂S, .

     

TPR studies on steam reforming of 2-propanol on Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3

Reaction pathways for steam reforming of 2-propanol (isopropyl alcohol, IPA) on Rh/Al₂O₃, Ru/Al₂O₃ and Pd/Al₂O₃ have been studied by temperature-programmed reactions (TPRs) of IPA and acetone in the presence of steam. The results of TPRs suggest that that of IPA on Rh/Al₂O₃ and Ru/Al₂O₃ proceeds via acetone, while the steam reforming of IPA on Pd/Al₂O₃ takes place via propene from acetone. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oxidized platinum surface in Pt/Al2O3 reforming catalysts: IR studies

The influence of halide ions on the state of dispersed Pt in oxidized catalysts has been investigated, adsorbed CO being used as a probe. Charged platinum complexes form upon catalyst oxygenation, with CO bands at 2130, 2150, 2165, 2170 and 2180 cm^–1. Composition of the complexes depends on the oxidation temperature and the nature of the halide ion.     

Investigation of the acidity of Ni/Al2O3 and Ni/SiO2?Al2O3 catalysts

Acidity of Ni-modified alumina and silica-alumina catalysts was determined using n-butylamine titration and pyridine adsorption methods. Strong influence of Ni²⁺ ions on the Brönsted acidity of silicaalumina was observed. Improved Brönsted acidity of such system was confirmed by the results of the test reaction.     

Fischer-Tropsch synthesis over Ru/Al2O3 catalysts

Fischer-Tropsch syntheses (FTS) were carried out in a slurry phase over Ru/Al₂O₃ catalysts using hexadecane as a solvent. The outcome of the FTS was dependent on the oxide support, calcination temperature, synthesis gas composition and sulfur content. The addition of Mn/Na to Ru/Al₂O₃ was effective in raising the initial activity and C5+ selectivity, but after 20 hours, the performance of the modified catalyst was similar to that of the unmodified catalyst. An additional investigation involving the use of fresh vs used catalysts demonstrated that an agglomeration of the metallic Ru, at least in part, does occur during the reaction.     

HIO4/Al2O3 as a new system for iodination of activated aromatics and 1,3-dicarbonyl compounds

The use of a periodic acid/alumina system for the iodination of activated aromatics and 1,3-dicarbonyl compounds is described.     

Kinetic studies of hydrogen and carbon monoxide adsorption on Re2O7/Al2O3 catalysts

Kinetic studies of hydrogen and carbon monoxide adsorption on reduced Re₂O₇/Al₂O₃ catalysts have revealed that its activation energy decreases with increasing reduction degree of rhenium oxide. Adsorption of gases is suggested to take place on metallic rhenium atoms.

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Hydrodechlorination of dichlorodifluoromethane (CFC-12) over Pd/Al2O3 and Pd-Au/Al2O3 catalysts

During an initial stage of the reaction of CCl₂F₂ with hydrogen on alumina-supported Pd and Pd-Au catalysts, an extensive defluorination occurs. However, at steady state, this undesired defluorination is greatly reduced; CH₄ and CH₂F₂ constitute the only major reaction products. A temperature programmed hydrogen treatment study shows retention of fluorine (and carbon) in used catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

X-ray study of Re/Al2O3 and Re+Pt/Al2O3 catalysts using synchrotron radiation

Uning synchrotron radiation, L_III rhenium absorption spectra have been studied for Re/Al₂O₃ and Re+Pt/Al₂O₃ catalysts obtained by impregnation. For individual rhenium compounds a linear dependence between the shift of absorption edge and the state of rhenium oxidation has been found. The absorption spectra of reduced catalysts are significantly broadened as compared with those of individual compounds of the same valency. This points to the presence of rhenium compounds in different oxidation states.

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L_III- , Re/Al₂O₃ Re+Pt/Al₂O₃, . . . .