共查询到20条相似文献,搜索用时 15 毫秒
1.
Frederick J. Karol Robert N. Johnson 《Journal of polymer science. Part A, Polymer chemistry》1975,13(7):1607-1617
Highly active catalysts for low pressure ethylene polymerization are formed when chromocene, bis (benzene)- or bis (cumene)-chromium or tris- or bis (allyl)-chromium compounds are deposited on high surface area silica-alumina or silica supports. Each catalyst type shows its own unique behavior in preparation, polymerization, activity, isomerization, and response to hydrogen as a chain transfer agent. The arene chromium compounds require an acidic support (silicaalumina) or thermal aging with silica to form a highly active catalyst. At 90°C polymerization temperature arene chromium catalysts produced high molecular weight polyethylene and showed, in contrast to supported chromocene catalysts, a much lower response to hydrogen as a chain transfer agent. An increase in polymerization temperature caused a significant decrease in polymer molecular weight. Addition of cyclopentadiene to supported bis (cumene)-chromium catalyst led to a new catalyst which showed a chain transfer response to hydrogen typical of a supported chromocene catalyst. Polymerization activity with tris- or bis (allyl)-chromium appears to depend on the divalent chromium content in the catalyst. Changes in the silica dehydration temperature of supported allyl chromium catalyst have a significant effect on the resulting polymer molecular weight. High molecular weight polymers were formed with catalysts that were prepared using silica dehydration temperatures below about 400°C. Dimers, trimers, and oligomers of ethylene were usually formed with catalysts that were prepared on silica dehydrated much above 400°C. The order of activity of the different types of catalysts was chromocene/silica > chromocene/silica-alumina > bis (arene)-chromium/silica-alumina ? allyl chromium/silica. 相似文献
2.
Min Hye Youn Jeong Gil Seo Ji Chul Jung Jin Suk Chung In Kyu Song 《Catalysis Surveys from Asia》2010,14(2):55-63
Recent progress on support modification of supported nickel catalysts for hydrogen production by auto-thermal reforming of
ethanol was reported in this review. Nickel catalysts supported on various materials, including metal oxides and metal oxide-stabilized
mesoporous zirconias, were prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal
reforming of ethanol. Various experimental measurements such as NH3-TPD (temperature-programmed desorption) and TPR (temperature-programmed reduction) were carried out to elucidate the different
catalytic performance of supported nickel catalysts. It was revealed that acid property of supporting materials served as
one of the important factors determining the catalytic performance. Hydrogen yield over nickel catalysts supported on metal
oxides showed a volcano-shaped curve with respect to acidity of the supports. Among the catalysts tested, Ni/ZrO2 catalyst with an intermediate acidity exhibited a superior catalytic performance. It was also observed that reducibility
of nickel catalysts supported on metal oxide-stabilized mesoporous zirconias played a key role in determining the catalytic
performance in the auto-thermal reforming of ethanol for hydrogen production. Hydrogen yield over nickel catalysts supported
on metal oxide-stabilized zirconias increased with increasing reducibility of the catalysts (with decreasing TPR peak temperature
of the catalysts). 相似文献
3.
Synergistic Interaction within Bifunctional Ruthenium Nanoparticle/SILP Catalysts for the Selective Hydrodeoxygenation of Phenols
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Dr. Kylie L. Luska Dr. Pedro Migowski Sami El Sayed Prof. Dr. Walter Leitner 《Angewandte Chemie (International ed. in English)》2015,54(52):15750-15755
Ruthenium nanoparticles immobilized on acid‐functionalized supported ionic liquid phases (Ru NPs@SILPs) act as efficient bifunctional catalysts in the hydrodeoxygenation of phenolic substrates under batch and continuous flow conditions. A synergistic interaction between the metal sites and acid groups within the bifunctional catalyst leads to enhanced catalytic activities for the overall transformation as compared to the individual steps catalyzed by the separate catalytic functionalities. 相似文献
4.
选用四种不同的分子筛(SAPO-34, ZSM-5, Y, MCM-41)与CuCoMn(高醇合成组元)构成双功能催化剂,利用N2吸脱附、H2-TPR、XRD、NH3-TPD等表征了催化剂的结构性质. 研究了催化剂在生物质基合成气一段法制取液态烃燃料的应用. 相比于CuCoMn催化剂,加入分子筛的双功能催化剂均不同程度地提高了液体烃燃料的选择性及收率,且收率按顺序递减呈CCM-ZSM-5〉CCM-SAPO-34〉CCM-Y〉CCM-MCM-41. 同时,共沉淀法制备的CuCoMn-ZSM-5 (20wt%, Si/Al=100) 具有最佳的CO转化率(76%)及液体产物收率(30%). 相比于CuCoMn氧化物,双功能催化剂的比表面及孔容均得到提高. CCM-ZSM-5具有适中的微孔尺寸和中等强度的酸性,增加CCM-ZSM-5中ZSM-5含量或降低ZSM-5中的Si/Al比,均有利于提高酸性位的数量,主要是较弱的酸性位. 而共沉淀法制备的CCM-ZSM-5具有更好的金属分散性及还原性能. 相似文献
5.
Recently, acid–base bifunctional catalysts have been considered due to their abilities, such as the simultaneous activation of electrophilic and nucleophilic species and their high importance in organic syntheses. However, the synthesis of acid–base catalysts is problematic due to the neutralization of acidic and basic groups. This work reports a facial approach to solve this problem via the synthesis of a novel bifunctional polymer using inexpensive materials and easy methods. In this way, at the first step, heterogeneous poly (styrene sulfonic acid‐n‐vinylimidazole) containing pentaerythritol tetra‐(3‐mercaptopropionate) (PETMP) and trimethylolpropane trimethacrylate (TMPTMA) cross‐linkers were synthesized in the pores of a mesoporous silica structure using click reaction as a novel bifunctional acid–base catalyst. After that, Ni‐Pd nanoparticles supported on poly (styrenesulfonic acid‐n‐vinylimidazole)/KIT‐6 as a novel trifunctional heterogeneous acid–base‐metal catalyst was prepared. The prepared catalysts were characterized by various techniques like FT‐IR, TGA, ICP‐AES, DRS‐UV, TEM, FE‐SEM, EDS‐Mapping, and XRD. The synthesized catalysts were efficiently used as bifunctional/trifunctional catalysts for one‐pot, deacetalization‐Knoevenagel condensation and one‐pot, three‐step and a sequential reaction containing deacetalization‐Knoevenagel condensation‐reduction reaction. It is important to note that the synthesized catalyst showing high chemo‐selectivity for the reduction of nitro group, alkenyl double bond and ester group in the presence of nitrile. Moreover, it was found that the different nanoparticles including Ni, Pd, and alloyed Ni‐Pd showing different chemo‐selectivity and catalytic activity in the reaction. 相似文献
6.
The capillary condensation is affected by micropore and nanopore of catalyst layer on fuel cell. Due to limitation of sluggish mass transport and electrocatalytic activity, to retain the pore skeleton of carbon and metal nanoparticles are very significant for enhanced utilizations of pore structure in electrochemical reaction. Besides, thickness of electrocatalyst layer is very crucial due to one of the factor affected by cell performance of direct methanol fuel cell. Highly loaded four Pt?Ru anode catalysts supported on resorcinol‐formaldehyde (RF) polymer based on meso‐porous carbons (80 wt.% Pt?Ru/carbon cryogel, 80 wt.% Pt?Ru/carbon xerogel and 80 wt.% Pt?Ru/carbon aerogel) and conventional carbon (80 wt.% Pt?Ru/Vulcan XC‐72) were prepared by colloidal method for direct methanol fuel cell. These catalysts were characterized by X‐Ray diffraction (XRD), High resolution transmission electron microscopy (HR‐TEM) and X‐ray photoemission (XPS). The results of CO stripping voltammetry, cyclic voltammetry (CV) and single cell test performed on DMFC show that Pt?Ru/carbon cryogel and Pt?Ru/carbon aerogel exhibits better performances in comparison to Pt?Ru/carbon xerogel and Pt?Ru/Vulcan XC‐72. It is thus considered that particle size, oxidation state of metal and electrochemical active surface area of these catalysts are important role in electrocatalytic activity in DMFC. 相似文献
7.
2-ethylhexanal is synthesized directly from crotonaldehyde over a bifunctional acidic resin-supported palladium catalyst via hydrogenation and aldol condensation in supercritical CO2. 相似文献
8.
V. I. Bogdan A. E. Koklin D. O. Kozak L. M. Kustov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(12):2352-2357
The reduction of carbon dioxide with hydrogen on metal–carbon (Ru, Rh, Ir) catalysts is investigated under supercritical conditions for the first time. High selectivity (close to 100%) toward methanation with good stability of catalytic activity is observed for Ru- and Rh-containing catalyst, while the preferred reduction to CO is observed for Ir/C catalyst. 相似文献
9.
碱木质素在超临界水中Ru/C纳米管催化气化的降解研究 《燃料化学学报》2015,43(10):1195-1201
针对碱木质素难降解的特点,在间歇式反应器中,以Ru/C纳米管为催化剂,对碱木质素在超临界水中的气化进行研究。分别探讨了碱木质素在不同温度、水密度、反应时间、反应浓度、催化剂量的影响,并且分析了Ru/C纳米管催化剂的催化效率。通过单因素实验分析,确定了Ru/C纳米管催化剂催化气化碱木质素的最佳反应条件为,反应温度600 ℃、水密度0.128 4 g/cm3、反应时间60 min、反应质量分数3.0%、催化剂量0.5 g/g(碱木质素)。结果表明,碱木质素在超临界水气化过程中,高温、高水密度(或压力)、长反应时间、低反应物浓度及适量的催化剂将更有利于碱木质素的气化。在最佳反应条件下碱木质素的气化率和碳气化率分别达到73.74%和56.34%,且制氢能力也得到明显提高。 相似文献
10.
Metal-support interaction(MSI) is an efficient way in heterogeneous catalysis and electrocatalysis to modulate the electronic structure of metal for enhanced catalytic activity. However, there are still great challenges in promoting the hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) simultaneously by this way. Herein, Fe-doped Co3O4 supported Ru(Ru/FeCo) catalysts are synthesized by MSI strategies to further improve the electrocatalytic activity and sta... 相似文献
11.
Mohamed Triki Doan Pham Minh Zouhaier Ksibi Abdelhamid Ghorbel Michèle Besson 《Journal of Sol-Gel Science and Technology》2008,48(3):344-349
The wet air oxidation of p-hydroxybenzoic acid, chosen as a model compound of olive mills wastewaters was carried out at 140 °C and 50 bar air over
Ru catalysts supported on TiO2 prepared by sol–gel method. These catalysts were characterized by means of N2 adsorption–desorption, XRD and TEM. Optimization of the catalytic performances was obtained by studying some parameters such
as the catalyst preparation method, the solvent evacuation way, the nature of the hydrolysis agent, the influence of the ruthenium
salt used as the metal precursor (Ru(NO)(NO3)3 or Ru(acac)3) and the catalyst pretreatment. The pre-calcination of the catalyst precursor at 300 °C under oxygen, before the reduction
step under hydrogen, was detrimental to the activity. The results showed that the use of nitric acid as hydrolysis agent,
drying under supercritical conditions and the use of Ru(NO)(NO3)3 leads to the more efficient catalyst with high TOC abatement. 相似文献
12.
金属载体结合方式对镍钨催化剂费托合成蜡加氢裂化性能的影响 总被引:1,自引:0,他引:1
以Ni/W为加氢金属组分, HY/Al2O3为载体, 采用浸渍法制备三种金属-载体不同结合方式的加氢裂化催化剂, 研究了结合方式对催化剂酸性、加氢性能及FT合成蜡加氢裂化性能的影响。调整金属-载体的结合方式可明显调节催化剂加氢性能与裂解性能之间的平衡, Ni/W预先浸渍在HY分子筛上提高了催化剂的加氢性能, 降低了载体的酸性。结果表明, 高加氢性能-弱酸性的匹配有利于抑制F-T蜡的二次裂解, 提高柴油选择性。而Ni/W均匀浸渍在HY/Al2O3载体上可获得相对均衡的加氢/裂解性能匹配, 催化剂具有较高的反应活性及灵活的反应调控性。 相似文献
13.
Supported Ru catalysts were prepared by wet impregnation to evaluate the role of different oxide supports(Al_2O_3,SiO_2,TiO_2,ZrO_2) in sorbitol hydrogenolysis to glycols.X-ray diffraction,transmission electron microscopy,hydrogen chemisorption,X-ray photoelectron spectroscopy,and NH3temperature-programmed desorption were used to characterize the catalysts,which were active in the hydrogenolysis of sorbitol.The support affected both the physicochemical properties and catalytic behavior of the supported Ru particles.The characterization results revealed that the Ru/Al_2O_3catalyst has a high surface acidity,partially oxidized Ru species on the surface,and a higher surface Ru/Al atomic ratio,which gave it the highest selectivity and yield to glycols. 相似文献
14.
Ni基催化剂上木质素模型化合物苯基苯乙醚C-O键的加氢裂解 总被引:2,自引:0,他引:2
研究了Ni基催化剂上木质素模型化合物苯基苯乙醚中C-O-C键加氢裂解性能.结果表明,Ni/C催化剂显示出优异的加氢裂解能力,苯基苯乙醚的转化率达到99%以上.Ni/C催化剂的还原方法对裂解选择性有重要影响;氢气还原制备的Ni/C-H催化剂上,C-O-C键裂解选择性为85%.Ru/C和Pd/C催化剂上裂解选择性分别为40%和69%.采用碳热还原方法制备的Ni/C-C催化剂,可以实现高选择性加氢和裂解,C-O-C键裂解选择性达到99%以上,其中芳烃化合物收率为44%.这可能与镍组分和载体碳之间的相互作用有关. 相似文献
15.
A series of 3 wt% Ru embedded on ordered mesoporous carbon (OMC) catalysts with different pore sizes were prepared by autoreduction between ruthenium precursors and carbon sources at 1123 K. Ru nanoparticles were embedded on the carbon walls of OMC. Characterization technologies including power X-ray diffraction (XRD), nitrogen adsorption-desorption, transmission electron microscopy (TEM), and hydrogen temperature-programmed reduction (H2-TPR) were used to scrutinize the catalysts. The catalyst activity for Fischer-Tropsch synthesis (FTS) was measured in a fixed bed reactor. It was revealed that 3 wt% Ru-OMC catalysts exhibited highly ordered mesoporous structure and large surface area. Compared with the catalysts with smaller pores, the catalysts with larger pores were inclined to form larger Ru particles. These 3 wt% Ru-OMC catalysts with different pore sizes were more stable than 3 wt% Ru/AC catalyst during the FTS reactions because Ru particles were embedded on the carbon walls, suppressing particles aggregation, movement and oxidation. The catalytic activity and C5+ selectivity were found to increase with the increasing pore size, however, CH4 selectivity showed the opposite trend. These changes may be explained in terms of the special environment of the active Ru sites and the diffusion of products in the pores of the catalysts, suggesting that the activity and hydrocarbon selectivity are more dependent on the pore size of OMC than on the Ru particle size. 相似文献
16.
The combination of supported rhodium metal catalysts and supercritical carbon dioxide solvent was effective for the stereoselective ring hydrogenations of aromatic compounds at low temperature. Higher solubility of hydrogen in supercritical carbon dioxide provides higher concentration of hydrogen on the rhodium surface, but lower that of the intermediate on rhodium surface, which suppresses the flipping of surface intermediate, leading to higher catalyst activities and cis selectivities to the corresponding ring‐hydrogenated products as compared with those in organic solvents. 相似文献
17.
负载型钌催化剂催化山梨醇氢解制乙二醇(英) 总被引:1,自引:0,他引:1
Inmaculada Murillo Leo Manuel Lopez Granados Jose Luis Garcia Fierro Rafael Mariscal 《催化学报》2014,35(5):614-621
Supported Ru catalysts were prepared by wet impregnation to evaluate the role of different oxide supports(Al2O3,SiO2,TiO2,ZrO2) in sorbitol hydrogenolysis to glycols.X-ray diffraction,transmission electron microscopy,hydrogen chemisorption,X-ray photoelectron spectroscopy,and NH3temperature-programmed desorption were used to characterize the catalysts,which were active in the hydrogenolysis of sorbitol.The support affected both the physicochemical properties and catalytic behavior of the supported Ru particles.The characterization results revealed that the Ru/Al2O3catalyst has a high surface acidity,partially oxidized Ru species on the surface,and a higher surface Ru/Al atomic ratio,which gave it the highest selectivity and yield to glycols. 相似文献
18.
Zhang X Guo X Chen Y Tang Y Lei M Fang W 《Physical chemistry chemical physics : PCCP》2012,14(17):6003-6012
In this paper, the mechanism of ketone hydrogenation catalyzed by five Ru bifunctional catalysts with different structural frameworks was studied in detail using density functional theory (DFT). This mechanism contains hydrogen transfer, dehydrogenation of alcohol, and dihydrogen activation fundamental reactions. The involvement of alcohol is also discussed and found with different activities in hydrogen transfer, dehydrogenation and dihydrogen activation steps in five systems. Our calculated results indicate that the weak Ru-H bond, stronger basicity of hydride and stronger X-H acidity will decrease the barrier of the HT step, and that the polar micro-environment of dihydrogen coordinating with Ru catalysts and short hydrogen transfer distance would be able to facilitate the heterolytic splitting of dihydrogen in the dihydrogen activation step. 相似文献
19.
分别采用超临界甲醇流体、浓硝酸氧化、浓硝酸结合超临界甲醇流体等不同手段对椰壳活性炭进行了表面处理,用N2物理吸附、Boehm滴定、X光电子能谱仪(XPS)、电感耦合等离子原子发射光谱分析(ICP)、透射电镜(TEM)等手段研究了处理方法对活性炭表面孔结构及表面基团的影响;并以活性炭为载体,三氯化钌为活性前驱体,采用等容水浸渍法制备了钌炭催化剂,以葡萄糖加氢生产山梨醇为模型反应对制备的钌基催化剂的催化活性进行了评价.结果表明:各种处理方法对活性炭的比表面、孔径等孔结构性能影响不大;但超临界甲醇处理活性炭可明显减少活性炭表面含氧酸性基团的含量,尤其是羧基等不稳定基团的含量;而硝酸处理活性炭则可大幅度提高活性炭表面含氧酸性基团的含量,尤其是羧基等不稳定基团的含量增加更大.ICP分析结果表明:超临界甲醇处理活性炭并不改变活性炭样品对钌的吸附量,但硝酸氧化处理活性炭却能明显提高样品对钌的吸附能力.活性炭表面的这些含氧基团虽然有利于钌离子的吸附,但却不利于钌在活性炭表面的分散.由于超临界甲醇流体处理活性炭时的表面反应及萃取作用,可有效清除活性炭表面的不稳定含氧酸性基团,避免还原过程中钌的迁移聚集,使负载钌的分散度提高,有利于增强钌与活性炭间的相互作用,使钌部分缺失电子,钌的结合能升高;可明显提高负载钌炭催化剂葡萄糖催化加氢的活性. 相似文献
20.
Anton V. Tokarev Elena V. Murzina Kari Eränen Heidi Markus Arie J. Plomp Johannes H. Bitter Päivi Mäki-Arvela Dmitry Yu. Murzin 《Research on Chemical Intermediates》2009,35(2):155-174
Liquid-phase lactose oxidation was investigated over supported Pd/C and Pd-carbon nanofibre catalysts, which were characterized
by several methods. A complex relationship between catalyst activity and catalyst acidity was established, i.e. optimum catalyst
acidity resulted in the highest activity in lactose oxidation. In-situ catalyst potential measurements during lactose oxidation
gave information about the extent of accumulation of oxygen on the metal surface. These results could be correlated with catalyst
deactivation, which was extensive over the most acidic catalysts at low reaction temperatures. Selectivity for the desired
product, lactobionic acid, was a maximum of approximately 83% at 93% conversion. The main side-product was lactulose formed
via isomerisation of lactose. Lower selectivity toward lactobionic acid was obtained when the rate of oxidation of lactose
was low. 相似文献