首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 140 毫秒
1.
以金属有机骨架(MOFs)UiO-66-NH2和吡啶-2-甲醛为原料,采用后合成修饰法制备一种UiO-66-NH2接枝吡啶亚胺配体,然后以UiO-66-NH2接枝吡啶亚胺配体和CoCl2·6H2O为原料,经配合反应,合成出一种UiO-66-NH2接枝吡啶亚胺钴系催化剂。采用傅里叶红外变换光谱(FT-IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、电感耦合等离子体质谱(ICP-MS)和氮气吸附-脱附等方法对合成产物的结构进行了表征,并考察了该催化剂在乙烯齐聚反应中的催化性能。研究结果表明,反应温度、n(Al)/n(Co)和乙烯压力对催化乙烯齐聚活性和产物选择性均有较大的影响,当以环己烷为溶剂,甲基铝氧烷(MAO)为助催化剂,在反应温度为25℃、n(Al)/n(Co)为1000、乙烯压力为1.0 MPa时,UiO-66-NH2接枝吡啶亚胺钴系催化剂催化乙烯齐聚的活性可达1.23×105g/(molCo·h),对丁烯的选择性为88.96%。  相似文献   

2.
合成了硅胶负载的聚(4-乙烯吡啶)或聚(2-乙烯吡啶)-聚(苯乙烯-顺丁烯二酸)-钯催化剂(P4VP-PSM-Pd/SiO_2和P2VP-PSM-Pd/SiO_2),研究了合成条件、组成等对其催化性能的影响及对丙烯酸甲酯的催化加氢性能。发现,同时含两种高分子的催化剂比只含一种高分子的催化剂具有较高的催化活性,催化剂在常温常压下对丙烯酸甲酯的氢化反应具有很高的催化活性和选择性,且能重复使用,表现出良好的稳定性。同时还研究了其它因素对催化剂性能的影响。  相似文献   

3.
采用分子模拟方法系统研究了杂质(水、O2和SO2)对5种金属-有机骨架材料(ZIF-8,NOTT-300,UiO-66(Zr),UiO-66-NH2和UiO-66-2COOH)的烟道气分离性能的影响,并探讨了其微观机理.结果表明,O2和SO2对这些材料的CO2/N2分离选择性影响不大;水对ZIF-8和UiO-66(Zr)的分离选择性影响不大,而对NOTT-300和UiO-66-NH2的分离选择性具有提升作用;UiO-66-2COOH对CO2的选择性有所降低.在干燥的环境下,UiO-66-2COOH的选择性最高,而在湿润的环境下,UiO-66-NH2的选择性最高.为捕获CO2的新型材料设计提供理论指导.  相似文献   

4.
 合成了硅胶负载的聚(4-乙烯吡啶)或聚(2-乙烯吡啶)-聚(苯乙烯-顺丁烯二酸)-钯催化剂(P4VP-PSM-Pd/SiO2和P2VP-PSM-Pd/SiO2),研究了合成条件、组成等对其催化性能的影响及对丙烯酸甲酯的催化加氢性能。发现,同时含两种高分子的催化剂比只含一种高分子的催化剂具有较高的催化活性,催化剂在常温常压下对丙烯酸甲酯的氢化反应具有很高的催化活性和选择性,且能重复使用,表现出良好的稳定性。同时还研究了其它因素对催化剂性能的影响。  相似文献   

5.
碳酸二甲酯(DMC)是一种重要的工业产品, 被广泛应用于制备锂离子电池溶剂和聚碳酸酯等化工产品. 一氧化碳(CO)酯化反应制DMC是一种新型的碳一技术路线, 具有成本低、反应效率高和安全等优势, 近年来引起了广泛的研究兴趣. 许多研究表明, Pd单位点催化剂(Pd SSCs)可以催化该反应高选择性合成DMC, 却易被反应物CO还原成Pd纳米颗粒, 从而导致DMC选择性快速下降. 因此, 设计合成稳定的Pd SSCs显得尤为重要. 通常, 研究人员通过增加Pd原子与载体之间的相互作用来稳定催化剂. 在各种载体中, 金属有机框架材料(MOFs)由于具有比表面积大、稳定性好、可修饰性强等特点, 是稳定单金属位点的理想载体. 选择自身较为稳定且易修饰的UiO-66-NH2作为载体, 采用后合成修饰的方法将吡啶-2-甲醛引入UiO-66-NH2的孔中. 吡啶-2-甲醛通过与氨基进行反应连接在UiO-66-NH2的框架上, 进而创造了相近的双氮原子位点共同鳌合Pd原子, 记为PdII-UiO-66-X%. 该催化剂在反应中, 展现出极高的DMC选择性, 同时也具备良好的催化稳定性, 在70 h的连续评价中, 依旧能够保持85%以上的DMC选择性. 该工作这一发现对构筑稳定Pd SSCs高选择性催化合成DMC提供了新思路.  相似文献   

6.
张艳梅  戴田霖  张帆  张静  储刚  权春善 《催化学报》2016,(12):2106-2113
金属有机骨架(MOF)材料是由过渡金属离子与有机配体通过配位键连接构成的高度有序的超分子化合物.这类材料比表面积大,孔隙率高,热稳定性好,而且具有规整可调控的孔结构、易于功能化的骨架金属离子和有机配体,在多相催化领域具有潜在应用前景.将纳米尺寸的MOF材料等多孔材料作为催化剂,可以提高反应传质效率,从而提高催化反应活性,但纳米MOF催化剂的分离和回收困难.将磁性纳米粒子和MOF材料组装成核壳结构的磁性MOF材料,不仅可简化催化剂的分离回收,而且通过控制壳层材料的厚度可以实现催化剂的高活性和高选择性.我们曾将磁核Fe3O4纳米粒子交替放入含有一种MOF材料前体的DMF溶液中,采用层层组装法制备了磁性Fe3O4@UiO-66-NH2纳米复合材料.经过十步组装后的材料的透射电镜(TEM)结果证实为核壳结构.但未出现明显的UiO-66-NH2的X射线衍射(XRD)特征峰,说明壳层材料UiO-66-NH2的结晶度较低;同时由于其孔结构的破坏或堵塞,在反应中出现明显失活.本文进一步改进自组装方法制备了核壳结构的磁性Fe3O4@UiO-66-NH2纳米复合材料,用XRD、傅里叶变换红外光谱(FT-IR)、TEM、扫描电镜(SEM)和氮气吸附等方法对材料的组成和结构进行了表征,并考察了其在Knoevenagel缩合反应中的催化性能.结果表明,所制材料是以Fe3O4为核,以UiO-66-NH2为壳的核-壳结构材料.经三次组装后出现了一系列UiO-66-NH2的XRD特征峰,说明采用新方法制备的复合材料中壳层材料UiO-66-NH2结晶度高,晶体结构规整.N2吸附-脱附结果表明,材料具有较高的比表面积和孔容.该复合材料在Knoevenagel缩合反应中表现出与纳米UiO-66-NH2相当或更好的催化活性和选择性,而且因壳层材料的孔道限阈效应而对底物表现出尺寸选择性.由于材料结晶度和晶体结构规整度的提高,催化剂稳定性更好,通过简单磁性分离即可分离和回收催化剂,循环使用4次而未出现明显失活.相对于本课题组之前报道的Fe3O4@CuBTC-NH2,Fe3O4@IRMOF-3和Fe3O4@UiO-66-NH2材料,本文所制的Fe3O4@UiO-66-NH2是一类结构更加稳定的高效固体碱催化剂.  相似文献   

7.
通过后合成修饰方法(PSM)构筑了空心纳米球(Void@UiO-66-Ⅰ)和实心块(UiO-66-Ⅰ) 2种形貌的季铵盐功能化UiO-66-NH2(Zr), 得到兼具酸碱活性位点和氢键给体的新型功能化金属-有机框架材料. 通过一系列表征证明2种催化剂的成功合成, 并将它们用于催化转化CO2和氧化苯乙烯的环加成反应. 由于Void@UiO-66-Ⅰ催化剂的季铵盐部分含有大量的羟基和卤素阴离子, 可以通过氢键和亲核攻击与环氧化合物连接, 诱导环氧化合物开环, 促使反应顺利进行, 且催化剂的中空结构有利于物质进出催化剂, 起到加快反应速率的作用, 使得该催化剂在CO2与氧化苯乙烯环加成反应中表现出比实心块UiO-66-Ⅰ催化剂更好的催化性能. Void@UiO-66-Ⅰ催化剂在120 ℃, CO2压力为1.2 MPa, 反应时间为6 h, 无溶剂和助催化剂的反应条件下, 碳酸苯乙烯酯的收率和选择性分别为85.5%和95%.  相似文献   

8.
 以 Ce(NO3)3•6H2O 为铈源, 采用不同沉淀剂制备了 CeO2 催化剂. 运用 N2 吸附-脱附、X 射线衍射、高分辨透射电镜和 H2程序升温还原等技术对催化剂进行了表征, 并评价了其对 1,4-丁二醇选择性脱水合成 3-丁烯-1-醇反应的催化性能. 结果表明, 以不同沉淀剂制得的 CeO2 样品形貌不同, 其中以 Na2CO3 为沉淀剂制备的 CeO2 呈边缘清晰的长方体形貌, 晶粒尺寸较大, 结晶较完整, 优先暴露的 (111) 晶面较多, 在 1,4-丁二醇选择性脱水反应中表现出较高的催化活性和选择性, 3-丁烯-1-醇收率可达 59.7%.  相似文献   

9.
半导体光催化剂作为一种可再生和可持续降解有机污染物的材料被广泛研究.K2Ti4O9由于无毒、低成本、稳定的物理化学性质和独特的光电性能被应用于光催化反应.但是,K2Ti4O9只能被紫外光所激发(因为其带隙能为3.2-3.4 eV),所以大量工作致力于研究如何降低其带隙能,从而使其可以被太阳光中的可见光激发,扩大其应用范围.其中N元素掺杂K2Ti4O9 (N-K2Ti4O9)是最常见的方法之一.单纯的N-K2Ti4O9虽然具有光催化能力,但其吸附容量太小,不能有效地将溶液中的有机物吸附至其表面,因而催化降解有机物效果不显著.UiO-66-NH2是一种Zr基金属-有机骨架化合物,它对阳离子染料具有良好的吸附性能,且具有一些常规无机半导体光催化材料所没有的性质.本文将UiO-66-NH2和N-K2Ti4O9经高温焙烧制备了N-K2Ti4O9/UiO-66-NH2复合材料,发现该复合材料不仅具有UiO-66-NH2优良的吸附性能,还因为复合提高了其光电性能,从而大大提高了光催化性能,当N-K2Ti4O9/ZrCl4质量比为3∶7时光催化性能最佳.为了考察N-K2Ti4O9/UiO-66-NH2复合材料的微观形貌、复合结构及光生电子-空穴分离效率,首先通过场发射透射电镜分析N-K2Ti4O9,UiO-66-NH2和N-K2Ti4O9/UiO-66-NH2(3∶7)复合材料的形貌,然后采用能量散射谱测定复合材料的元素分布,并利用N-K2Ti4O9和UiO-66-NH2中代表性元素K,Ti和Zr的分布判断复合材料的复合结构,最后运用高分辨电镜观察复合材料中N-K2Ti4O9和UiO-66-NH2的异质结界面,确定了两者是通过自组装复合在一起,而不是简单的物理混合.X射线衍射结果表明,复合材料具有N-K2Ti4O9和UiO-66-NH2两者的特征衍射峰,仅在强度和位置上略有变化.这可能是N-K2Ti4O9/UiO46-NH2异质结构所致.通过UiO-66-NH2和N-K2Ti4O9的紫外-可见吸收光谱,用公式计算出它们的带隙能分别是2.645和3.195 eV,与文献结果基本一致.由于光催化剂的光生载流子迁移速率同样影响光催化性能,因此我们在CHI-660D电化学工作站上控制光源反复开关数次,同时记录N-K2Ti4O9,UiO-66-NH2和N-K2Ti4O9/UiO-66-NH2(3∶7)的光响应电流,发现N-K2Ti4O9/UiO-66-NH2(3∶7)复合材料展现出最高的光响应电流强度,表明其具有最高的光生载流子迁移速率和最低的光生载流子复合速率.可见,N-K2Ti4O9和UiO-66-NH2复合有利于光生载流子迁移,这可能是由于N-K2Ti4O9/UiO-66-NH2异质结界面有利于光生载流子在两种材料之间迁移所致.测试了N-K2Ti4O9/UiO-66-NH2(3∶7)复合材料对不同染料的光催化降解性能.结果发现,该材料对阳离子型染料(罗丹明B和亚甲基蓝)的光催化性能远远高于对阴离子型染料(甲基橙和刚果红).这是由于它对阳离子型染料的吸附性能远高于对阴离子型染料,因此N-K2Ti4O9/UiO-66-NH2复合材料对阳离子型染料具有选择性光催化.  相似文献   

10.
赵振华 《合成化学》2003,11(5):427-430
研究了负载ZnCl2的固体催化剂在2,3-二甲基-2-丁烯与乙酐酰化合成3,3,4-三甲基-4-戊烯-2-酮反应中的催化活性。结果表明,K10粘土是最好的载体,但是HY沸石、Synclyst S13(一种无定型的酸性固体)、硅胶和氧化铝也都是制备负载ZnCl2的固体催化剂的有效载体。ZnCl2的负载量和改性方法都影响负载ZnCl2的固体催化剂的催化活性。  相似文献   

11.
In this study, bis(diphenylphosphinemethyl)dimethyl silane ( L1 ) and its palladium(II) halide complex, L1 /PdCl2 ( C1 ), were synthesized and characterized. Single‐crystal X‐ray analysis of the complex revealed bidentate coordination at the Pd center. In combination with methylaluminoxane (MAO) as co‐catalyst, C1 exhibited excellent catalytic activity and selectivity for ethylene dimerization toward butene. The maximum catalytic activity obtained from the C1 /MAO system for ethylene dimerization to yield butenes was 7.33 × 105 g/(molPd · h). The selectivity toward butene remained stable and high (> 96%) over the various conditions.  相似文献   

12.
Two new hyperbranched bispyridylamine ligands and multinuclear chromium complexes were synthesized with 1.0?G hyperbranched macromolecules, 2-chloropyridine, 2-chloro-4-methylpyridine and CrCl3(THF)3 as raw materials. The structures of hyperbranched ligands and chromium complexes were characterized by UV, FT-IR, 1H NMR, ESI-MS, and elemental analysis. These hyperbranched chromium complexes were evaluated as catalyst precursors by using MAO as activator in the oligomerization of ethylene. Effects of reaction temperature, reaction pressure, Al/Cr molar ratio, concentration of catalyst, solvent, and the structure of catalysts on the catalytic activity and product selectivity were investigated. The oligomerization results showed that with increase of reaction temperature, reaction pressure, and Al/Cr molar ratio, the catalytic activity increased and then decreased; the catalytic activity continuously decreased as the amount of catalyst increased. The products were mainly based on C6 and C8. Under optimized conditions, the catalytic system of hyperbranched NNN/Cr(III)/MAO led to activity of 1.26?×?105 g/(mol·Cr·h) and 63.34% selectivity for C6 and C8.  相似文献   

13.
A series of nickel(II) complexes have been synthesized and characterized. Molecular structure analysis exhibits that a square planar geometry around nickel is adopted. Upon activation with MAO, these nickel(II) complexes are efficient in catalyzing the ethylene dimerization, providing 1‐butene with an activity of up to 1.4×107 g/(mol·h·atm). The heteroatoms of the sidearm in the complexes were proved to have great impact on the activity and selectivity of 1‐butene.  相似文献   

14.
Two hyperbranched bisphosphinoamine (PNP) ligands and chromium complexes were synthesized in good yield with 1.0 generation (1.0 G) hyperbranched macromolecules, chlorodiphenylphosphine (Ph2PCl) and CrCl3(THF)3 as raw materials. The hyperbranched PNP ligands and chromium complexes were characterized by FT-IR, 1H NMR, 31P NMR, UV and ESI-MS. Comparing with the chromium complexes, the hyperbranched PNP ligands, in combination with Cr(III), and activation by methylaluminoxane (MAO) in situ generated species with better catalytic performance for ethylene oligomerization. The effect of solvent, chromium source, ligand/Cr molar ratio, reaction temperature, Al/Cr molar ratio and reaction pressure on the catalytic activity and product selectivity were studied. The results showed that with increase of ligand/Cr molar ratio, reaction temperature and Al/Cr molar ratio, the catalytic activity increased at first and then decreased. However, the catalytic activity continuously increased with increase of reaction pressure. Under the optimized conditions, the catalytic system of hyperbranched PNP/Cr(III)/MAO led to catalytic activity of 2.68 × 105 g/(mol Cr·h) and 37.71% selectivity for C6 and C8.  相似文献   

15.
A series of nickel (II) complexes bearing silicon bridged diphosphines ligands (PNSiP) have been synthesized and characterized. All nickel precatalysts, activated with ethylaluminum dichloride (EtAlCl2), exhibited moderate to high activities for ethylene dimerization to butylene. The in situ nickel precatalysts formed by mixing N-cyclopentyl-N-((diphenylphosphanyl)dimethylsilyl)-1,1-diphenylphosphanamine (L2) with NiBr2(DME) showed high catalytic activity (2.40 × 108 g/(molNi·h)) and high product selectivity (88.6%) towards butene using methylcyclohexane as solvent at 1.0 MPa ethylene pressure and 45°C temperature, no polyethylene(PE) was observed. Ligand backbone tuning of PNSiP-based catalytic systems help in precise understanding of steric bulk variation effects on catalytic performance.  相似文献   

16.
王俊 《分子催化》2019,33(6):429-437
以不同端基烷基链长度的1.0G超支化大分子为桥联基,通过对其端基氨基进行催化功能改性,合成了系列具有不同桥联基长度的超支化PNP铬系催化剂。采用红外光谱(IR)、核磁共振氢谱(1H-NMR)、核磁共振磷谱(31P-NMR)、紫外光谱(UV)和质谱(MS)等表征方法证明合成催化剂的结构与理论结构相符。详细考察了溶剂种类、反应温度、Al/Cr摩尔比、反应压力、催化剂用量和催化剂结构对催化剂乙烯齐聚性能的影响。实验结果表明,当以甲苯为溶剂,甲基铝氧烷(MAO)为助催化剂时,超支化PNP铬系催化剂表现出良好的催化乙烯齐聚性能,产物以低碳烯烃为主。最佳条件下,催化活性最高可达到1.69×105g/mol Cr·h,己烯和辛烯的选择性为43.3%以上。相同聚合条件下,其催化活性随着端基烷基链长度的增加而下降。  相似文献   

17.
A series of neutral nickel complexes featuring N‐fluorinated phenyl salicylaldiminato chelate ligands was synthesized, and the novel molecular structure of complex C14 was further confirmed by X‐ray crystallographic analysis. The neutral nickel complexes showed high activity up to 9.96×105 g oligomers/(mol Ni·h) and high selectivity of C6 in catalyzing ethylene oligomerization using methylaluminoxane (MAO) as cocatalyst. It was observed that the strong electron‐withdrawing effect of the fluorinated salicylaldiminato ligand was able to significantly increase the catalytic activity for oligomerization of ethylene. In addition, the influence of reaction parameters such as Al/Ni molar ratio, reaction temperature, a variety of cocatalyst and ethylene pressure on catalytic activity was investigated.  相似文献   

18.
Short straight-chain alkylamine based hyperbranched molecules and their corresponding salicylaldimine nickel complexes have been synthesized in high yield and characterized by FTIR, 1H-NMR and mass spectrometry. The optimal reaction parameters were determined under the catalytic system of methylaluminoxane (MAO) as co-catalyst and toluene as solvent. Under these conditions, the effect of catalyst structure, solvent and co-catalyst were determined. Upon activation of MAO in toluene, ethylene oligomerization products were homogeneous distribution of butene, hexene and octene with trace higher olefin. The same catalytic system under cyclohexane and methyl cyclohexane as solvent, however, produced majority of butene. Under the activation of EtAlCl2, Et2AlCl and EASC as co-catalyst in toluene, ethylene oligomerization reaction was tandem with Friedel-Crafts reaction in catalytic system.  相似文献   

19.
A number of manganese-based catalysts employing ligands whose structures incorporate pyridyl groups have been reported previously to achieve both high turnover numbers and selectivity in the oxidation of alkenes and alcohols, using H(2)O(2) as terminal oxidant. Here we report our recent finding that these ligands decompose in situ to pyridine-2-carboxylic acid and its derivatives, in the presence of a manganese source, H(2)O(2) and a base. Importantly, the decomposition occurs prior to the onset of catalysed oxidation of organic substrates. It is found that the pyridine-2-carboxylic acid formed, together with a manganese source, provides for the observed catalytic activity. The degradation of this series of pyridyl ligands to pyridine-2-carboxylic acid under reaction conditions is demonstrated by (1)H NMR spectroscopy. In all cases the activity and selectivity of the manganese/pyridyl containing ligand systems are identical to that observed with the corresponding number of equivalents of pyridine-2-carboxylic acid; except that, when pyridine-2-carboxylic acid is used directly, a lag phase is not observed and the efficiency in terms of the number of equivalents of H(2)O(2) required decreases from 6-8 equiv. with the pyridin-2-yl based ligands to 1-1.5 equiv. with pyridine-2-carboxylic acid.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号