Characterization and Catalytic Performance of PtSn Catalysts Supported on Al2O3 and Na-doped Al2O3 in n-butane Dehydrogenation

PtSn/Al₂O₃ and PtSn/Al₂O₃–Na catalysts display important modifications of the metallic phase with respect to Pt/Al₂O₃ one. In this sense, TPR and XPS results show the presence of strong interactions between Pt and Sn, with probable alloy formation, which would be responsible for the decrease of the reaction rate and the increase of the activation energy in cyclohexane dehydrogenation. Besides the experiments of cyclopentane hydrogenolysis show that the alkali metal addition to bimetallic PtSn/Al₂O₃ catalysts completely eliminates the hydrogenolytic ensembles, which could be due to a geometric modification of the metallic phase. These important modifications in the nature of the metallic function due to the simultaneous addition of Na and Sn to Pt/Al₂O₃ are responsible for the excellent catalytic performance in the n-butane dehydrogenation, thus giving high conversions, selectivities to butenes higher than 95%, and lower deactivation capacity than those corresponding to bimetallic PtSn catalysts (with different Sn contents) supported on undoped alumina. The excellent stability of PtSn/Al₂O₃–Na catalysts would be due to a low carbon formation during the reaction, such as it was observed from pulse experiments.     

Change of catalyst texture upon the partial filling of its voids with active components,coke, sulfur,etc.

The changes in the main texture characteristics of catalysts, adsorbents, supports and other porous bodies are analyzed, upon the partial filling of their voids with the added components: coke, sulfur, active components of supported catalysts, etc. Equations are derived, that relate the changes of texture with the content and distribution of the introduced component.     

负载金属催化剂的结构性能表征

综述了H2-TPR,TEM,XRD等物化方法在负载型金属催化剂的结构性能（包括金属分散度、表面结构、电子状态）方面的应用,为更好地认识和使用负载型金属催化剂提供了可靠的依据。     

茂金属聚乙烯催化剂工业应用研究

北京化工研究院合成了50余种新型茂金属化合物,在茂金属催化剂均相乙烯聚合的系统研究基础上,深入研究了载体茂金属催化剂的制备方法和制备条件等因素与载体催化剂性能的关系,研制出性能优异的载体茂金属催化剂。采用载体茂金属催化剂进行了浆液法和气相法乙烯聚合中试研究,还进行了茂金属聚乙烯树脂的加工应用研究,树脂性能与国外同类产品相当。     

丙烯齐聚过程催化剂进展

综述了丙烯齐聚过程用催化剂的进展, 对反应机理和工业生产状况亦做了简介。最后对本领域的研究方向提出了建议。     

Reduction of supported cobalt catalysts by hydrogen

The reduction of cobalt catalysts supported on Al₂O₃, SiO₂, and TiO₂ was investigated using a closed system filled with hydrogen gas. Effects of support and metal loading on the rate of reduction were also discussed. The activation energy of reduction increased in the following order: Co/TiO₂2O₃2. For different metal loadings, it was found that the catalyst with the higher loading was more readily reducible than that with the lower metal loading. This was confirmed using the results from measurements of particle size, amount of CO adsorbed and activity.     

负载型固体酸催化制备生物柴油研究进展

负载型固体酸催化剂具有无腐蚀、分离容易、对环境不产生污染、原料适应性广等优点,已成为制备生物柴油首选的绿色催化剂。本文综述了负载型固体酸催化剂制备原理、生产工艺、研究方法及其结构表征,分析了负载型固体酸自身结构与油脂酯交换反应催化活性的关系,预测了负载型催化剂在生物柴油制造业的应用前景。     

Recent advances in the production of γ‐valerolactone from biomass‐derived feedstocks via heterogeneous catalytic transfer hydrogenation

γ‐valerolactone (GVL) is an important intermediate chemical with a wide range of applications as fuel, fuel additive and as a green solvent which has received a great deal of attentions from both academia and industry. This review aims to summarise the advances in conversion of renewable feedstocks into GVL through heterogeneous catalytic transfer hydrogenation (CTH) with a strong emphasis on discussing preparation, characterisation and performance of the catalysts in order to provide a better understanding of various catalytic systems and also to compare them in terms of catalytic performance. © 2017 Society of Chemical Industry     

甲烷—二氧化碳重整反应制取合成气的新进展

综述了９０年代以来ＣＨ４－ＣＯ２重整反应在改性镍基催化剂、贵金属负载型催化剂和分子筛催化材料研究方面的最新发展。     

反式聚异戊二烯聚合催化剂及合成胶的考评

介绍了反式聚异戊二烯(TPI)聚合催化剂及合成TPI产品的考评方法.对载体水含量、催化剂载钛量、催化效率、催化剂表观密度以及合成TPI产品的反式含量、结晶度、分子量及分布、物理力学性能、灰分等参数的测定做了详细研究.通过提出的考评方法对催化剂及合成胶产品进行质量控制,为优化生产工艺打下基础.     

Layered double hydroxides: precursors for multifunctional catalysts

One-pot cascade reactions which involve multifunctional catalysts possessing different functions on the surface attract a growing interest. Relevant examples of the use of this type of catalysts in one-pot syntheses involving hydrogenation/dehydrogenation and aldol condensation reactions which give rise to valuable organic compounds are reported in this paper. It is shown that the layered double hydroxides (LDH) are precursors materials particularly adapted for the preparation of catalysts exhibiting acido/basic and redox sites. The paramount importance of the nature (Lewis or Bronsted) and the strength of the basic sites, as well as the nature of the metallic function of the supported metal catalysts obtained from LDH is discussed. It is emphasized on the equilibrium between the basic and metallic functions required to reach high activities and selectivities.     

Ring opening of epoxides catalysed by poly(amidoamine) dendrimer supported on crosslinked polystyrene

Three generations of polystyrene supported poly(amidoamine) dendrimer were synthesized and characterized. The supported dendrimers were found to be efficient organocatalysts in the nucleophilic ring opening of epoxides by anilines under mild conditions. Higher generation dendrimer showed increased catalytic activity. The polymer supported catalyst was reusable. The catalytic activity of supported dendrimer was compared with the unsupported one and found that the supported dendrimer was a much more active catalyst. The higher activity of the supported dendrimer is assumed to be due to the better hydrophobic/hydrophilic interaction existing between the polystyrene matrix and the polar dendritic chains.     

Study on the properties of iron–cobalt alumina supported catalyst for ammonia

The addition of Co to Fe/Al₂O₃ increases the catalytic activity in NH₃ synthesis. The maximum effect is observed for 20% by weight of Co in the metallic phase. Bivalent cobalt atoms replace bivalent iron atoms (a similar ionic radius) in the crystal lattice. This process changes the reducibility of the samples. The Fe-Co compound and its formation results in the fairly high temperature of reduction (873 K) which is needed to prepare the most active catalyst. Changing the reactor atmosphere from reducing to inert causes the disappearance of free iron (escape of Fe to the crystal lattice of support with formation of a new compound with a spinel character). This is the effect of the iron-hydrogen interaction. The formation of an intermetallic iron-cobalt compound is crucial to the catalyst activity. This might be due to the surface restructuring by exposing the most active iron surface, Fe(111). The potassium addition in the form of KOH causes an increase in the catalytic activity. The increase is not as high as for a ‘super basic’ Fe-Co magnesium hydroxide carbonate supported catalyst studied earlier. A part of the potassium hydroxide is used to neutralize the acid sites on the surface of alumina.     

Polyaniline–rhodium composites: Preparation,physicochemical characterization,and catalytic properties

In this work, polyaniline (PANI)–rhodium composites have been obtained for the first time. Their preparation procedure has involved reduction of Rh³⁺ ions in RhCl₃ aqueous solutions with NaBH₄ in the presence of PANI. Using UV–vis spectroscopy, it has been found that the reduction process is fast. X‐ray diffraction and Rh3d XPS studies have confirmed that metallic rhodium is incorporated into PANI matrix. SEM and TEM investigations allowed to establish that the sizes of Rh crystallites formed depend on the amount of metal in the composite as well as on the preparation conditions. It has been demonstrated that the composites containing Rh nanoparticles whose size is predominantly below 10 nm can be obtained. IR spectroscopy has proved that PANI chain is protonated in the Rh³⁺ reduction process. Catalytic properties of PANI–Rh composites have been investigated using isopropyl alcohol conversion as the test reaction. It has been found that the composites containing Rh nanoparticles show high redox activity. Catalytic activity of the composites in which larger, agglomerated metal particles have been present is about three times lower. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of supported vanadium catalyst on ethylene polymerization reactions

BACKGROUND: In the research area of homogeneous Ziegler–Natta olefin polymerization, classic vanadium catalyst systems have shown a number of favourable performances. These catalysts are useful for (i) the preparation of high molecular weight polymers with narrow molecular weight distributions, (ii) the preparation of ethylene/R‐olefin copolymers with high R‐olefin incorporation and (iii) the preparation of syndiotactic polypropylenes. In view of the above merits of vanadium‐based catalysts for polymerization reactions, the development of well‐defined single‐site vanadium catalysts for polymerization reactions is presently an extremely important industrial goal. The main aim of this work was the synthesis and characterization of a heterogeneous low‐coordinate non‐metallocene (phenyl)imido vanadium catalyst, V(NAr)Cl₃, and its utility for ethylene polymerization. RESULTS: Imido vanadium complex V(NAr)Cl₃ was synthesized and immobilized onto a series of inorganic supports: SiO₂, methylaluminoxane (MAO)‐modified SiO₂ (4.5 and 23 wt% Al/SiO₂), SiO₂? Al₂O₃, MgCl₂, MCM‐41 and MgO. Metal contents on the supported catalysts determined by X‐ray fluorescence spectroscopy remained between 0.050 and 0.100 mmol V g^?1 support. Thermal stability of the catalysts was determined by differential scanning calorimetry (DSC). Characterization of polyethylene was done by gel permeation chromatography and DSC. All catalyst systems were found to be active in ethylene polymerization in the presence of MAO or triisobutylaluminium/MAO mixture (Al/V = 1000). Catalyst activity was found to depend on the support nature, being between 7.5 and 80.0 kg PE (mol V)^?1 h^?1. Finally, all catalyst systems were found to be reusable for up to three cycles. CONCLUSION: Best results were observed in the case of silica as support. Acid or basic supports afforded less active systems. In situ immobilization led to higher catalyst activity. The resulting polyethylenes in all experiments had ultrahigh molecular weight. Finally, this work explains the synthesis and characterization of reusable supported novel vanadium catalysts, which are useful in the synthesis of very high molecular weight ethylene polymers. Copyright © 2007 Society of Chemical Industry     

反式聚异戍二烯聚合催化剂及合成胶的考评

介绍了反式聚异戊二烯（TPI）聚合催化剂及合成TPI产品的考评方法。对载体水含量、催化剂载钛量、催化效率、催化剂表观密度以及合成TPI产品的反式含量、结晶度、分子量及分布、物理力学性能、灰分等参数的测定做了详细研究。通过提出的考评方法对催化剂及合成胶产品进行质量控制，为优化生产工艺打下基础。     

甲醇在Fe/MgO、Co/MgO和Ni/MgO催化剂上裂解制备氢气

采用浸渍法制备出3种MgO负载型过渡金属催化剂Fe/MgO、Co/MgO和Ni/MgO,系统研究了甲醇在3种催化剂上于600℃下的裂解产物。结果表明,3种催化剂均能催化甲醇裂解产生富氢气体,同时产生碳纳米管。其中,Ni/MgO具有最佳的催化效果。     

Selective hydrogenation of citral over gold nanoparticles on alumina

Gold nanoparticles have been supported on alumina by wet impregnation in the presence of sodium citrate and polyvinyl alcohol. The catalytic performance of these catalysts for the selective hydrogenation of 3,7-dimethyl-2,6-octadienal (citral) in the liquid phase has been evaluated. The presence of polyvinyl alcohol significantly improved the selectivity to cis-3,7-dimethyl-2,6-octadien-1-ol (nerol).     

Gaseous infiltration method for preparation of three-dimensionally ordered macroporous polyethylene

Three-dimensionally ordered macroporous polyethylenes (3DOM PE) with pore size ranging from 135 nm to 410 nm were prepared using supported catalysts on the surface of silica microsphere as template, followed infiltration of gaseous ethylene and polymerization. The morphology of 3DOM PE was characterized by SEM and the reflectance spectrum was recorded by UV-vis. It is shown that the pores are uniform, flexible and arranged in a highly ordered fashion. Reflectance spectrum of 3DOM PE also provided verification of the uniform nature of the sample. Moreover, the effect of confined space on polymerization was investigated by GPC and DSC. The results indicate that the porous PE possesses higher M_w compared with bulk PE, and exhibits lower melting temperature and crystallinity than those of bulk PE.