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1.
Chao Guo Guo‐Xin Jin Fusong Wang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(19):4830-4837
2,6‐Diacetylpyridinebis (2,6‐diisopropylani) iron dichloride, a late‐transition metal catalyst for olefin polymerization, was supported on SBA‐15 successfully and the property of the supported catalyst was carefully studied. Ethylene polymerization was systematically investigated in the presence of MAO under various conditions employing this type of catalyst system. In general, after support, a decrease in the catalytic activity was observed and higher molecular weight and fibrous morphology of polyethylene were obtained. The “extrusion polymerization” phenomenon was observed in ethylene polymerization by using the supported catalyst system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4830–4837, 2004 相似文献
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Au‐dimercaprol functionalized cellulose aerogel: Synthesis,characterization and catalytic application
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A new derivative of cellulose aerogel was prepared via functionalization of cellulose with dimercaprol. Dimercaprol, as a chelating agent of Au(III), was applied for the loading of Au(III) on cellulose aerogel. The new organogold compound after characterization was used as an efficient heterogeneous catalyst in the oxidation reactions of aliphatic alcohols, benzyl alcohol, and ethylbenzene. Excellent selectivities and good conversions were obtained in the green oxidation reactions of alcohols and ethylbenzene. The high porosity of cellulose aerogel led to the good conversions with the low catalyst amounts. The significance of the presented work is the introducing of an environmentally benign process for the oxidation reactions based on a biocompatible catalyst. 相似文献
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SBA‐15‐Oxynitrides as a Solid‐Base Catalyst: Effect of Nitridation Temperature on Catalytic Activity
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Baljeet Singh Dr. Kaustubh R. Mote Dr. C. S. Gopinath Prof. Dr. P. K. Madhu Prof. Dr. Vivek Polshettiwar 《Angewandte Chemie (International ed. in English)》2015,54(20):5985-5989
Solid bases, such as SBA‐15‐oxynitrides, have attracted considerable interest for potential applications as catalysts in important industrial processes. Reported herein is that by simply tuning the temperature of nitridation (ammonolysis), the catalytic activity of these solid bases can be enhanced. Solid‐state NMR spectroscopy and XPS studies provided the reasoning behind this change in activity. 相似文献
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Kuwauchi Y Yoshida H Akita T Haruta M Takeda S 《Angewandte Chemie (International ed. in English)》2012,51(31):7729-7733
Despite the fragility of TiO(2) under electron irradiation, the intrinsic structure of Au/TiO(2) catalysts can be observed by environmental transmission electron microscopy. Under reaction conditions (CO/air 100?Pa), the major {111} and {100} facets of the gold nanoparticles are exposed and the particles display a polygonal interface with the TiO(2) support bounded by sharp edges parallel to the 〈110〉 directions. 相似文献
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《中国化学会会志》2018,65(7):875-882
Hollow Fe3O4@TiO2‐NH2/Pd as a light‐weight, magnetically heterogeneous catalyst was successfully prepared, and characterized by using different techniques including X‐ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX), vibrating sample magnetometer (VSM) measurements, and thermogravimetric analysis (TGA). Then this heterogeneous catalyst was tested in the Suzuki cross‐coupling reaction, and the results confirmed the success of this method. The catalyst could be separated easily using an external magnet and reused at least in five runs successfully without any appreciable loss in its catalytic activity. 相似文献
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Shao-Qing Shi Ya-Guang Chen Jian Gong Zhi-Ming Dai Lun-Yu Qu 《Transition Metal Chemistry》2005,30(2):136-140
Peroxo-tantalum and tantalum mono-substituted tungstosilicates with the Keggin structure, K5[-SiW11Ta(O2) O39]18H2O (1) and K5[-SiW11TaO40]14H2O (2) respectively, and peroxo-tantalum and tantalum mono-substituted tungstophosphates with the Wells–Dawson structure K7[2-P2W17Ta(O2)O61]16H2O (3) and K7[2-P2W17TaO62]14H2O (4), respectively, were prepared by stereoselective synthesis and characterized by elemental analysis, i.r. and u.v. spectroscopy, XPS, 31P and 183W n.m.r. spectroscopy, and polarography, as well as cyclic voltammetry. The presence of a peroxo group in the complexes (1) and (3) was supported by observation of an i.r. band due to the —O—O— bond at 881 cm–1, the charge transfer bands of (2—O2)Ta at ca. 316 and 389 nm, the O1s binding energy at 532.0 eV and a new irreversible reduction polarographic wave at E1/2 0.1 V, assigned to the reduction of peroxo group and which enhances the oxidant properties of the heteropoly anions. There are six lines for complex (1) and nine lines for complex (3) in the 183W n.m.r. spectra, showing that the complex (1) has a mono-substituted Keggin structure and complex (3) has a mono-substituted 2-Wells–Dawson structure. The catalytic activities of the complexes with respect to epoxidation of maleic acid with H2O2 as oxidant were examined and the best result, 83.5% yield, was obtained for [(C4H9)4N]5[-SiW11Ta(O)2O39]·18H2O. 相似文献
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Synthesis of insoluble polystyrene‐supported flavins and their catalysis in aerobic reduction of olefins
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Yukihiro Arakawa Risa Kawachi Yoshihiko Tezuka Keiji Minagawa Yasushi Imada 《Journal of polymer science. Part A, Polymer chemistry》2017,55(10):1706-1713
2′,4′‐p‐Vinylbenzylideneriboflavin ( 2′,4′‐PVBRFl ) was prepared as a flavin‐containing monomer and copolymerized with divinylbenzene and styrene or its p‐substituted derivatives such as 4‐acetoxystyrene, 4‐vinylbenzyl alcohol, and 4‐vinylbenzoic acid to give the corresponding non‐functionalized and functionalized PS‐DVB‐supported flavins PS(H)‐DVB‐Fl , PS(OAc)‐DVB‐Fl , PS(CH2OH)‐DVB‐Fl , and PS(COOH)‐DVB‐Fl , respectively. PS(OH)‐DVB‐Fl was also prepared by hydrolysis of PS(OAc)‐DVB‐Fl under basic conditions. These novel flavin‐containing insoluble polymers exhibited characteristic fluorescence in solid state, except PS(OH)‐DVB‐Fl , and different catalytic activities in aerobic reduction of olefins by in situ generated diimide from hydrazine depending on their pendant functional group. For example, PS(H)‐DVB‐Fl was found to be particularly effective for neutral hydrophobic substrates, which could be readily recovered by a simple filtration and reused more than 10 times without loss in catalytic activity. On the other hand, PS(OH)‐DVB‐Fl and PS(COOH)‐DVB‐Fl proved to be highly active for phenolic substrates known to be less reactive in the reaction with conventional non‐supported flavin catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1706–1713 相似文献
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Axial base‐controlled catalytic activity,oxidative stability and product selectivity of water‐insoluble manganese and iron porphyrins for oxidation of styrenes in water under green conditions
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A series of water‐insoluble iron(III) and manganese(III) porphyrins, FeT(2‐CH3)PPCl, FeT(4‐OCH3)PPCl, FeT(2‐Cl)PPCl, FeTPPCl, MnT(2‐CH3)PPOAc, MnT(4‐OCH3)PPOAc, MnT(2‐Cl)PPOAc and MnTPPOAc, in the presence of imidazole (ImH), F?, Cl?, Br? and acetate were used as catalysts for the aqueous‐phase heterogeneous oxidation of styrenes to the corresponding epoxides and aldehydes with sodium periodate. Also, the effect of various reaction parameters such as reaction time, molar ratio of catalyst to axial base, type of axial base, molar ratio of olefin to oxidant and nature of metal centre on the activity and oxidative stability of the catalysts and the product selectivity was investigated. Higher catalytic activities were found for the iron complexes. Interestingly, the selectivity towards the formation of epoxide and aldehyde (or acetophenone) was significantly influenced by the type of axial base. Furthermore, Br? and ImH were found to be the most efficient co‐catalysts for the oxidation of olefins performed in the presence of the manganese and iron porphyrins, respectively. The optimized molar ratio of catalyst to axial base was different for various axial bases. Also, the order of co‐catalyst activity of the axial bases obtained in aqueous medium was different from that reported for organic solvents. The use of a convenient axial base under optimum reaction catalyst to co‐catalyst molar ratio in the presence of the manganese porphyrin gave the oxidative products with a conversion of ca 100% in a reaction time of less than 3 h. However, the catalytic activity of the iron porphyrins could not be effectively improved by increasing the catalyst to co‐catalyst molar ratio. 相似文献
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S. Sugunan D. John N. K. Renuka M. Varghese K. Sreekumar C. G. Ramankutty 《Reaction Kinetics and Catalysis Letters》1999,66(1):39-45
The electron donating properties of manganese ferrospinels of various compositions (MnFe2O4, Mn1.2Fe1.8O4, Mn2FeO4 and Mn2.5Fe0.5O4) were studied from the adsorption of electron acceptors of various electron affinity values from acetonitrile as solvent.
The limit of electron transfer from the oxide surface is from 1.77 to 2.40 eV in terms of the electron affinity of the electron
acceptor. The data have been correlated with the catalytic activity of these oxides towards autoxidation of sulfites. Both
weak and strong electron donor sites catalyze the reaction. 相似文献
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Tetrakis[heptadecafluorononyl] substituted phthalocyanine complexes were prepared by template synthesis from 4‐(heptadecafluorononyloxy)phthalonitrile with Co(CH3COO)·2H2O or PdCl2 in 2‐N, N‐dimethylaminoethanol. The corresponding phthalonitrile was obtained from heptadecafluorononan‐1‐ol and 4‐nitrophthalonitrile with K2CO3 in DMF at 50 °C. The structures of the compounds were characterized by elemental analysis, FTIR, UV–vis and MALDI‐TOF MS spectroscopic methods. Metallophthalocyanines are soluble in fluoroalkanes such as perfluoromethylcyclohexane (PFMCH). The complexes were tested as catalysts for benzyl alcohol oxidation with tert‐butylhydroperoxide (TBHP) in an organic–fluorous biphasic system (n‐hexane–PFMCH). The oxidation of benzyl alcohol was also tested with different oxidants, such as hydrogen peroxide, m‐chloroperoxybenzoic acid, molecular oxygen and oxone in n‐hexane–PFMCH. TBHP was found to be the best oxidant for benzyl alcohol oxidation since higher conversion and selectivity were observed when this oxidant was used. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The catalytic activity of "naked" gold particles 总被引:2,自引:0,他引:2
Comotti M Della Pina C Matarrese R Rossi M 《Angewandte Chemie (International ed. in English)》2004,43(43):5812-5815
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A bipyridine‐based covalent organic polymer (COP) was successfully synthesized by condensation of trimesoyl chloride (TMC) and 2,2′‐bipyridine‐5,5′‐diamine (Bpy) under ambient conditions. This material was modified by coordination of PdCl2 to COP framework, affording a hybrid material, Pd@TMC‐Bpy COP, which was applied as a highly efficient heterogeneous catalyst for Suzuki‐Miyaura reaction under ligand‐free conditions in ethyl lactate. The catalyst could be reused for five times without obvious loss of its activity. 相似文献
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Dr. Ceri Hammond Dr. Robert L. Jenkins Dr. Nikolaos Dimitratos Dr. Jose Antonio Lopez‐Sanchez Dr. Mohd Hasbi ab Rahim Dr. Michael M. Forde Adam Thetford Dr. Damien M. Murphy Dr. Henk Hagen Dr. Eric E. Stangland Prof. Jacob M. Moulijn Dr. Stuart H. Taylor Dr. David J. Willock Prof. Graham J. Hutchings 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15735-15745
The partial oxidation of methane to methanol presents one of the most challenging targets in catalysis. Although this is the focus of much research, until recently, approaches had proceeded at low catalytic rates (<10 h?1), not resulted in a closed catalytic cycle, or were unable to produce methanol with a reasonable selectivity. Recent research has demonstrated, however, that a system composed of an iron‐ and copper‐containing zeolite is able to catalytically convert methane to methanol with turnover frequencies (TOFs) of over 14 000 h?1 by using H2O2 as terminal oxidant. However, the precise roles of the catalyst and the full mechanistic cycle remain unclear. We hereby report a systematic study of the kinetic parameters and mechanistic features of the process, and present a reaction network consisting of the activation of methane, the formation of an activated hydroperoxy species, and the by‐production of hydroxyl radicals. The catalytic system in question results in a low‐energy methane activation route, and allows selective C1‐oxidation to proceed under intrinsically mild reaction conditions. 相似文献
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Solvent‐free organic reactions were studied over periodic mesoporous silica (SBA‐15) containing a Cu(II) organometallic complex. This heterogeneous catalyst was achieved by coordination of Cu(II) ions with the diaminosarcophagine ligand and then its grafting onto the surface of SBA‐15. This catalyst displayed ordered mesoporous channels, which implies an extremely high dispersion of the Cu(II) complex and the convenient diffusion of reactant molecules into the pore channels. Therefore, this catalyst can offer high activity and also facile separation or recycling when compared with its homogeneous counterparts. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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A new approach was developed to fabricate nanowires of mixed oxides MoO3-V2O5 inside the channels of mesoporous silica SBA-15. The method involves functionalization of the channel surface of SBA-15 with aminosilane groups, immobilization of Keggin-type molybdovanadophosphoric acids through an acid-base interaction, and heat treatment. The immobilization of the heteropolyacid containing mixed addenda makes the molar ratio of the loaded components controllable. The formation of the MoO3-V2O5 nanowires inside the channels was monitored by variable temperature in situ XRD. The materials obtained by heat treatment at 400℃ for 5 h were characterized by TEM, N2-sorption measurements, laser Raman spectra and UV-Vis diffuse reflectance spectra. Further heat treatment of the MoO3-V2O5 nanowires inside the SBA-15 channels at higher temperature (700℃) destroys the framework integrity of SBA-15 by complete sublimation of MoO3 through the SBA-15 channel walls. 相似文献
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Carbon Monoxide Oxidation by Polyoxometalate‐Supported Gold Nanoparticulate Catalysts: Activity,Stability, and Temperature‐ Dependent Activation Properties
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Dr. Takuya Yoshida Prof. Dr. Toru Murayama Prof. Dr. Norihito Sakaguchi Prof. Dr. Mitsutaka Okumura Prof. Dr. Tamao Ishida Prof. Dr. Masatake Haruta 《Angewandte Chemie (International ed. in English)》2018,57(6):1523-1527
Nanoparticulate gold supported on a Keggin‐type polyoxometalate (POM), Cs4[α‐SiW12O40]?n H2O, was prepared by the sol immobilization method. The size of the gold nanoparticles (NPs) was approximately 2 nm, which was almost the same as the size of the gold colloid precursor. Deposition of gold NPs smaller than 2 nm onto POM (Au/POM) was essential for a high catalytic activity for CO oxidation. The temperature for 50 % CO conversion was ?67 °C. The catalyst showed extremely high stability for at least one month at 0 °C with full conversion. The catalytic activity and the reaction mechanism drastically changed at temperatures higher than 40 °C, showing a unique behavior called a U‐shaped curve. It was revealed by IR measurement that Auδ+ was a CO adsorption site and that adsorbed water promoted CO oxidation for the Au/POM catalyst. This is the first report on CO oxidation utilizing Au/POMs catalysts, and there is a potential for expansion to various gas‐phase reactions. 相似文献
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多酸-有机胺-氧化硅杂化催化剂的制备、表征及光催化性能研究 总被引:5,自引:5,他引:5
采用自组装技术制备了多酸-有机胺-氧化硅杂化催化剂K5Ni(H2O)PW11O39-APS-SiO2(APS=(C2H5O)3SiCH2CH2CH2NH2),通过XRD、UV/DSR,FT-IR,ICP-AES和元素分析等手段,对其组成和结构进行了表征,并考察了该杂化催化剂对可溶性染料罗丹明B的催化活性,实验结果表明,该杂化催化剂中Keggin阴离子的基本结构未发生变化,Keggin阴离子与有机胺修饰的氧化硅载体通过No-N配位键结合,光催化活性高于直接光解和均相体系中的K2[Ni(H2O)PW11O39](PW11Ni),并且耐水性好,反应过程中不易溶脱,可重复使用。 相似文献