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.

     

Investigation of toluene formation on Pt/Al2O3 catalyst in n-hexane dehydrocyclization

Formation of toluene, a chain lengthening product, has been observed on Pt/Al₂O₃ catalyst in n-hexane dehydrocyclization. Toluene formation is influenced by the catalyst pretreatment processes and the reaction temperature. A correlation has been found between the ageing phenomena and toluene formation.

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- Pt/Al₂O₃ — . . .

     

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, .

     

纳米膜组装介孔Al2O3：合成及Pt/Al2O3的硝基苯催化加氢性能

以"乙酸乙酯(EA)-偏铝酸钠-水"体系在室温下合成了纳米膜组装介孔Al2O3。研究发现:合成反应时间、静置前搅拌时间、NaAlO2用量、EA用量及反应温度等对合成产物的形貌有影响;另外,与用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂相比,纳米膜组装介孔Al2O3制备的Pt/Al2O3催化剂含有部分易被还原的PtOx物种。在硝基苯催化加氢反应中,用合成Al2O3为载体制备的Pt/Al2O3催化剂,比用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂具有更好的催化活性。     

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, . . . .

     

Influence of the preparation method on the pore spectrum of Pt?Cr/Al2O3 and Pt?Sn/Al2O3 catalysts

It is shown that, in contrast to classical impregnation methods, in bimetallic catalyst production the texture of the carrier is stabilized by introducing the promoting ion on the surface of Pt/Al₂O₃ with vapors of CrO₂Cl₂ or SnCl₄. This is shown by a relatively slower decrease of the specific area and the volume of the pores upon calcination.

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, Pt/Al₂O₃- CrO₂Cl₂ SnCl₄ . .

     

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.     

Catalytic properties of metallic and electron-deficient platinum in reforming over Pt/Al2O3 catalysts

The activity of Pt/Al₂O₃ catalysts with various contents of metallic (Pt^o) and electron-deficient (Pt) platinum has been examined in dehydrocyclization of n-heptane and dehydrogenation of cyclohexane. In the former case it is proportional to the number of surface Pt atoms and in the latter case it is proportional to the BET surface of metallic platinum Pt^o.

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(Pt^o) (Pt) - . , Pt, — Pt^o.

     

Coke deposits on Pt/Al2O3 catalysts of varying dispersities

Coke deposition during cyclopentane reaction was investigated on Pt/Al₂O₃ catalysts of varying dispersity. For all working pressures the higher the metallic accessibility, the higher the amount of coke deposited on the catalyst. Nevertheless, coke deposited on the less dispersed catalysts is more toxic for the metallic function. An increasing metal accessibility improves the graphitization of coke on the support and so, prevent the deactivation of the metal of a bifunctional catalyst.

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Pt/Al₂O₃ . , , , . , , , . , .

     

Ni/Al2O3催化甲烷裂解

分别通过浸渍法和共沉淀法制备了不同Ni负载量的Ni/Al2O3催化剂。考察了Ni负载量、制备方法以及反应温度对Ni/Al2O3催化甲烷裂解性能的影响。结果表明,在550℃,浸渍法制备的Ni/Al2O3催化剂,当Ni负载量为20%(质量分数)、Ni金属平均粒径为11.25 nm时,具有最佳的甲烷催化裂解效果,其每摩尔Ni的氢气产量和每克Ni碳产量分别为164 mol和15.30 g。催化剂制备方法对Ni/Al2O3甲烷催化裂解反应有显著影响,相同Ni负载量共沉淀法制备的Ni/Al2O3甲烷催化裂解总体效果要好于浸渍法制备的Ni/Al2O3,而且反应过程中生成的碳纤维较长,管径也较均一。550℃时,共沉淀法制备的Ni负载量为41.2%(质量分数)的Ni/Al2O3催化剂在反应至350 min时,仍保持着30%以上的转化率。     

Structure sensitivity and coke formation on Pt/Al2O3 catalysts

The initial rate of carbon formation during cyclopentane reaction has been studied on different Pt/Al₂O₃ catalysts of varying metal dispersity. It has been shown that coke deposition on the metal is a structure sensitive reaction which is preferably produced on large metallic particles. On the other hand, coke deposition on the whole catalyst is relevant to cyclopentadiene formation and is a structure insensitive reaction since the initial rate of coke deposition on the whole catalyst is proportional to the metallic surface area.

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Pt/Al₂O₃ . , , . , , , .. .

     

铌改性的Pd/Al2O3催化剂催化苯燃烧反应简

采用浸渍法制备了Nb改性的Pd/Al2O3催化剂,考察了该催化剂催化苯燃烧反应性能,并研究了催化剂的稳定性. 结果表明,Nb的添加明显提高了Pd/Al2O3催化剂性能,在195 ℃时苯转化率达到90%,苯的完全燃烧温度降低了40 ℃. 采用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、H2 程序升温还原(H2-TPR)、NH3程序升温脱附(NH3-TPD)和氮气吸附等手段对催化剂进行了表征,结果表明,Nb的加入不仅提高了Pd物种的分散度,同时改变了部分Pd的价态,形成适宜反应的PdO-Pd物种,并促进了催化剂表面氧浓度的增加,使氧物种氧化能力增强,从而提高了催化性能. 1%Pd-5%Nb/Al2O3催化剂的催化活性高于2.0%Pd/Al2O3催化剂.     

Catalytic activity of the Al2O3?Cr2O3?Fe2O3 system, I. Physico-chemical properties

The physico-chemical properties of a catalyst containing 90% Al₂O₃, 9% Cr₂O₃ and 1% Fe₂O₃ have been studied. Coexistence of acidic and basic (ionic) sites as well as electron acceptor radical centers have been found.

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- : 90% Al₂O₃, 9% Cr₂O₃ 1% Fe₂O₃. , () , - .

     

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.     

Thermal Stability of Pt/Al2O3 Catalysts Prepared by Sol-Gel

A series of Pt/Al₂O₃ catalysts were prepared using a sol-gel method. The influence of several parameters used in the synthesis including: metal content, identity of the metal precursor, and the water/alkoxide ratio on the structural properties of the fresh (dried) and calcined samples were studied. It was found that the BET surface area decreased with an increase in the platinum content. A surface area of 500 m²/g was obtained following calcination at 773 K. The structure of fresh samples as determined by FTIR corresponded to that of a pseudoboehmite structure. Samples prepared using a water/alkoxide ratio (H₂O/ATB) of 9 showed a well-defined, uniform pore size distribution following calcination at 773 K. Metal dispersions comparable to those obtained using impregnation methods were obtained. Aging studies (calcination at 873 K for 24 h) performed on these catalysts, exhibited sintering behavior which were similar to Pt/Al₂O₃ catalysts prepared by other methods. The sample prepared using a H₂O/ATB ratio of 9 had the highest surface area and was more thermally resistant towards metal sintering. A bimodal metal particle size distribution was observed: some particles exhibited sintering while others of similar size showed a greater thermal stability to sintering. The sample having the largest surface area and the highest thermal stability following thermal treatment was a consequence of a more condensed structure and a higher pore roughness obtained after drying the gel. This enabled the formation of an alumina structure which was more amorphous and limited aggregation of platinum particles due to surface diffusion within the pore structure.     

Partial oxidation of methane on Cr2O3/Al2O3

The oxidation of methane on supported chromia was studied at temperatures varying between 423 and 743 K and CH₄/O₂ ratios between 1 and 9 in a differential reactor. The main reaction products observed were carbon monoxide and formaldehyde. The rates of reaction obey a power law expression.

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, 423 743 CH₄/O₂ 1 9, . . .

     

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。     

Selective Catalytic Reduction of NO with Propene over Au/Fe2O3/Al2O3 Catalysts

A series of Au/Fe₂O₃/Al₂O₃ catalysts were prepared by the homogeneous deposition-precipitation method. The catalytic activity of the catalyst samples for selective catalytic reduction of NO by propene under oxygen-rich atmosphere was evaluated. The results showed that 2%Au/10%Fe₂O₃/Al₂O₃ exhibited good low-temperature activity. The maximum of NO conversion reached 43% at 300 °C, while it was only 21% over the 2%Au/Al₂O₃ catalyst at the same temperature. The addition of 2% steam to the feed gas had little effect on the catalytic activity. X-ray diffraction results indicated that both Au and Fe₂O₃ particles were highly dispersed over Al₂O₃. H₂-temperature-programmed reduction results indicated that there was strong interaction between Au and Fe₂O₃, which made the reduction of Fe₂O₃ easy. The synergistic effect between Au and Fe₂O₃ was probably responsible for the good catalytic performance of the Au/Fe₂O₃/Al₂O₃ catalyst at low temperature.     

BaO对Pd／AI2O3催化性能的影响

以Ｐｃ（Ｃ２Ｈ２Ｏ２）２为前身,制备了系列ＢａＯ－ＡＩ２Ｏ３复合氧化物负载钯的催化剂,用质量滴定法,测定了复合载体的零电荷点（ｐｚｃ）。结果表明,体系的ｐｚｃ随ＢａＯ含量的增加而增大,在５％～１０％之间存在一拐点,并与ＸＲＤ所测ＢａＯ在ＡＩ２Ｏ３上的单发散阈值相对应。复合载体在制务中发生固相反应,所生成的ＢａＡＩ２Ｏ４可以阻止ＡＩ２Ｏ３的相变,并极大地提高载体的热稳定性,其中５％ＢａＯ的作用最为明