共查询到20条相似文献,搜索用时 140 毫秒
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根据层状四水硫酸锆和Hβ沸石各自的催化性能和结构特点,设计并制备得到Hβ负载锆(Zr/Hβ)催化剂。以异丙苯歧化反应为目标体系,研究了Zr/Hβ的催化性能。利用吡啶吸附程序升温脱附和低温氮吸附等方法研究了Zr/Hβ的表面酸性和孔结构,与反应性能进行关联。结果表明,Zr/Hβ较Hβ弱酸强度更弱、强酸强度更强,导致其歧化反应活性较Hβ大大提高,歧化选择性较Hβ略有提高,但其初始歧化选择性较Hβ降低;Zr/Hβ和Hβ的最可几孔径基本一致,因而Zr/Hβ催化异丙苯歧化反应产物中间位-/对位-二异丙苯的摩尔比与Hβ的基本一致。 相似文献
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采用气相色谱-质谱技术对松脂的催化歧化新工艺的反应产物进行分析,共分离出45个峰,鉴定出其中的38个化合物,并发现松脂歧化产物中歧化松节油的主要成分为对伞花烃,含量为16.26%;歧化松香的主要成分为脱氢枞酸和氢化树脂酸,其含量分别为41.58%和21.43%。在此基础上对松脂歧化反应过程进行了初步探讨,认为松脂原料中的酸性物质发生分子间氢转移反应,萜烯烃的存在促进了脱氢反应的进行;在树脂酸提供的酸性环境下松脂原料中中性油的主要成分双环单萜烯发生开环异构形成单环单萜烯,单环单萜烯再进行催化脱氢转化为对伞花烃。分析结果表明,直接以松脂为原料进行催化歧化反应可同时获得特级歧化松香和高含量的对伞花烃。 相似文献
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用离子共聚法合成了硅锆层柱蒙脱石(SiZrPILM)和铁锆层柱蒙脱石(FeZrPILM),考察了它们对1,2,4三甲基苯(1,2,4TrMB)歧化反应的催化性能.1,2,4TrMB在催化剂样品上可发生歧化反应和异构化反应,歧化反应选择性达80%以上.随着催化剂预处理温度的提高,1,2,4TrMB转化率下降,歧化反应选择性和四甲基苯(TeMB)中1,2,4,5TeMB含量则升高.催化剂对1,2,4TrMB歧化反应有择形催化作用,1,2,4,5TeMB和间二甲苯、邻二甲苯为主要产物,并且其含量偏离其热力学平衡组成,TeMB中1,2,4,5TeMB的含量在85%以上. 相似文献
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Wolstenholme DJ Prince PD McGrady GS Landry MJ Steed JW 《Inorganic chemistry》2011,50(21):11222-11227
Density functional theory (DFT) calculations of [K(18-crown-6)SiH(3)] (1) and KSiH(3) (2) have shown that both the classical tet and non-classical inv coordination modes of the [SiH(3)](-) anion to the K(+) ion are energetically accessible. Single-crystal X-ray structures of the tet and inv derivatives [K(18-crown-6)SiH(3)·THF] (1a) and [K(18-crown-6)SiH(3)·HSiPh(3)] (1b) confirm this conclusion, showing that small changes in the coordination sphere of the metal are sufficient to alter the orientation of the anion. A topological analysis of the calculated electron densities for 1 and 2 reveals that the K···Si interaction in the tet conformer of 2 possesses a significant amount of covalent character. In contrast, the inv form of 2 displays primarily electrostatic character for the K···Si and K···H interactions. Incorporation of the 18-crown-6 ligand in 1 reduces the polarizing power of the K(+) cation, hardening the cation-anion interaction in both conformers. The experimental structures of 1a and 1b bear out these conclusions, with the strongly bound tetrahydrofuran (THF) ligand softening the K(+) ion in 1a and favoring the tet conformer, while the weakly interacting HSiPh(3) ligand in 1b has minimal effect on the K(+) center, resulting in an inv orientation. 相似文献
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A Ring Enlargement Reaction with a Barbiturate The (6-membered) barbituric acid derivative 3 was synthesized and treated with KF/DMF/18-crown-6 to form the ring-enlarged 14-membered compound 8 in good yield. 相似文献
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A novel synergistic extraction system was investigated for the possible selective separation of light lanthanoids using an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, as an extraction solvent and 2-thenoyltrifluoroacetone and 18-crown-6 as extractants. Trivalent lanthanum was efficiently extracted as a cationic ternary complex by the cation-exchange process, whereas europium and lutetium showed relatively low extractability without forming respective ternary complexes. This result is thought to originate in a size-fitting effect of 18-crown-6 to lanthanum and the unique nature of the ionic liquid as a chelate extraction solvent. 相似文献
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Lingui Zhu 《Tetrahedron letters》2010,51(47):6150-6152
Nucleophilic (phenylsulfonyl)difluoromethylation of both alkyl iodides and bromides was successfully accomplished by using CsF/15-crown-5 as an initiating system in DME, and the amount of 15-crown-5 was found to be critical to the yield of the product. The prepared (phenylsulfonyl)difluoromethylated alkanes were converted into gem-difluoroalkenes by a base-mediated 1,2-elimination reaction, and the latter species could be further transformed into trifluoromethyl compounds in the presence of KF/18-crown-6 or TBAF. 相似文献
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Babailov S. P. Stabnikov P. A. Tkachev S. V. Kruppa A. I. 《Journal of Structural Chemistry》2021,62(8):1184-1190
Journal of Structural Chemistry - Complexes [(Pr(DPM)3)2], [Pr(DPM)3(18-crown-6)], [(Pr(DPM)3)2(18-crown-6)], [Pr(DPM)(PTA)(18-crown-6)]+ and the temperature sensitivity of paramagnetic... 相似文献
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The ligands 4,7-diaza-2,3,8,9-dibenzo-15-crown-5 (L1), 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L2), 4,10-diaza-2,3,11,12-di(4′-tert-butylbenzo)-18-crown-6 (L3) and N,N-di(methylenecarboxyethoxy) 4,10-diaza-2,3,11,12-dibenzo-18-crown-6 (L4) have been prepared. Partition coefficients and acid dissociation constants for these four diazadibenzocrown ether compounds were determined in water-chloroform. Their effectiveness was assessed in solvent extraction of Pb2+ from aqueous solutions into toluene. Ligands L3 and L4 provide high selectivity for Pb2+ over Cd2+ and Zn2+ in transport across plasticized cellulose triacetate membranes. 相似文献
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Alfredo Ricci Alessandro Deglinnocenti Mariella Fiorenza Maurizio Taddei Maria A. Spartera David R.M. Walton 《Tetrahedron letters》1982,23(5):577-578
Benzyl- 4-picolyl- and phenylallyl(trimethyl)silanes react with electrophiles in the presence of KF/18-crown-6 or silica-TBAF under mild conditions. 相似文献
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Chekin F Bordbar M Fathollahi Y Alizadeh N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(2):370-376
1H NMR spectroscopy was used to investigate the stoichiometry and stability of the drug ketamine cation complexes with some crown ethers, such as 15-crown-5 (15C5), aza-15-crown-5 (A15C5), 18-crown-6 (18C6), aza-18-crown-6 (A18C6), diaza-18-crown-6 (DA18C6), dibenzyl-diaza-18-crown-6 (DBzDA18C6) and cryptant [2,2,2] (C222) in acetonitrile (AN), dimethylsulfoxide (DMSO) and methanol (MeOH) at 27 degrees C. In order to evaluate the formation constants of the ketamine cation complexes, the CH3 protons chemical shift (on the nitrogen atom of ketamine) was measured as function of ligand/ketamine mole ratio. The formation constant of resulting complexes were calculated by the computer fitting of chemical shift versus mole ratio data to appropriate equations. A significant chemical shift variation was not observed for 15C5 and 18C6. The stoichiometry of the mono aza and diaza ligands are 1:1 and 1:2 (ligand/ketamine), respectively. In all of the solvents studied, DA18C6 formed more stable complexes than other ligands. The solvent effect on the stability of these complexes is discussed. 相似文献
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Sun QF Wong KM Liu LX Huang HP Yu SY Yam VW Li YZ Pan YJ Yu KC 《Inorganic chemistry》2008,47(6):2142-2154
By employing functional diimine ligands coordinated dipalladium(II,II) or diplatinum(II,II) clips as corners and the coplanar 4,4'-bipyrazolate dianion (L(2-)) ligand as linker, a series of bipyrazolate-bridged metallo-macrocycles, namely, [M8L4](NO3)8 (M = Pd(dmbpy), 1; Pd(bpy), 2; Pt(bpy), 3a; Pd(phen), 4; Pt(phen), 5; Pd(15-crown-5-phen), 6; Pd(18-crown-6-phen), 8; Pd(benzo-24-crown-8-phen), 10a; Pt(15-crown-5-phen), 7a, Pt(18-crown-6-phen), 9a; Pt(benzo-24-crown-8-phen), 11a) and [M6L3](NO3)6 (M = Pt(bpy), 3b; Pt(15-crown-5-phen), 7b; Pt(18-crown-6-phen), 9b; Pd(benzo-24-crown-8-phen), 10b; Pt(benzo-24-crown-8-phen), 11b), have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the 1H-bipyrazolyl ligands in aqueous solution. All these compounds have a crown-shaped cavity that can serve as host to solvent molecules and anions. The structures are characterized by elemental analysis, (1)H and (13)C NMR, ESI-MS, and in the cases of 1a (the BF4(-) salt of 1), 2a (the BF4(-) salt of 2), and 3b by single-crystal X-ray diffraction analysis. Photophysical properties for complexes 1 and 2 are discussed. 相似文献
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Summary The extraction behaviour of tetrafluoroborate with crown ethers was studied. A high distribution ratio of tetrafluoroborate is obtained by extraction with dicyclohexano-18-crown-6 (DC18C6) in an organic solvent of high dielectric constant from potassium fluoride solution. The molar ratios of crown ether to KBF4 in the extracted species are probably 1:1 for DC18C6, dibenzo-18-crown-6 and 18-crown-6, and 2:1 for benzo-15-crown-5 and 15-crown-5. The flow-injection extraction-spectrophotometric determination of tetrafluoroborate with Brilliant Green was worked out. Many rock reference samples were analyzed for boron (1–150 ppm). 相似文献