二氧化硅固载Ru基催化剂上二氧化碳加氢合成甲酸的研究(III): 配体对催化剂反应性能的影响

考察了不同配体对原位合成的固载Ru基催化剂上CO2加氢合成HCOOH反应活性的影响,对于以单齿三苯基类ZPh3分子为配体的催化剂,活性大小顺序为:PPh3>AsPh3>NPh3.以PPh3为配体时,其相应的原位合成催化剂上HCOOH的TOF值为656h-1.其次,双齿膦配体的使用能带来比单齿膦配体更高的活性.以dppe[1,2-双(二苯基膦基)乙烷]为配体时,其相应的原位合成催化剂上HCOOH的TOF值为1190h-1.量子化学的理论计算结果表明,具有适中的σ给予性和π接受性,较小的空间位阻,较好的电子离域作用的PPh3配体性能优于其它单齿三苯基类配体.而具有较好的电子离域作用,并且有螯合作用的双齿膦配体性能优于单齿膦配体.     

铑-双膦配合物的咬角效应对催化1-十二烯氢甲酰化反应的影响

研究了HRh(CO)(PPh₃)₃-双膦配体(BISBI，BDPX，BDNA和BINAP)体系在1-十二烯氢甲酰化反应中的催化性能。4种双膦配体具有不同的空间结构，因而有不同的咬角(bite angle)，它们与铑催化剂前体HRh(CO)(PPh₃)₃进行配体交换后，形成不同的催化活性物种。4种复合催化剂体系中，HRh(CO)(PPh₃)₃-BISBI(咬角为120°)对直链醛的形成具有很高的区域选择性，这可能是因为形成了有利于生成直链烷基-铑的ee构型催化活性物种，其它3种双膦配体与HRh(CO)(PPh₃)₃组成的复合催化剂体系区域选择性没有多少变化，是与它们具有较小的咬角有关(BINAP85°，BDPX90°，BDNA104°)。上述4种HRh(CO)(PPh₃)₃ -双膦体系与HRh(CO)(PPh₃)₃-PPh₃体系相比较，催化活性较低，这可能是因为双膦的螯合配位作用使催化活性物种较稳定 。     

整体式 Cu-ZSM-5 催化剂上 NH3 选择性催化还原 NO 活性

 采用浸渍法制备了一系列不同 Cu 含量的 Cu-ZSM-5 催化剂, 并用于 NH₃ 选择性催化还原 (SCR)NO 反应. 结果表明, 当 Cu 含量为 8%时, Cu-ZSM-5 催化剂的活性最高; 当空速为 30 000 h^–1. , 在 198~440 ^oC 反应时 NO 转化率均高于 80%, 最高可达 97%, 且空速的影响较小. 经快速水热老化后, 该催化剂活性明显优于商用 V 基催化剂. H₂O 和 SO₂ 对 Cu-ZSM-5 催化剂的 SCR 活性有所影响, 但可明显恢复. X 射线衍射和 NH3 程序升温脱附结果表明, 当 Cu-ZSM-5 中 Cu 含量为 8% 时, 进入 ZSM-5 中阳离子位的 Cu 较多, 催化剂的活性较高, 且其表面具有较多的酸中心和酸量, 从而有利于 SCR 反应.     

固载Ru基催化剂上二氧化碳加氢合成甲酸的研究(IV): 反应机理

探讨了在CO₂加H₂合成HCOOH过程中原位合成的固载Ru基催化剂的可能结构、CO₂的活化方式以及可能的反应机理. 在反应中, 固载Ru配合物中的一个P配体首先解离, 被质子型溶剂ROH取代而生成循环活性物质, 然后CO₂正插入Ru—H键生成甲酸酯配合物, 之后甲酸酯配合物中的Ru—O₂CH键被H₂氢解生成HCOOH, 而本身重新转化为活性物质, 完成催化循环.     

固载Ru基催化剂上二氧化碳加氢合成甲酸的研究(IV): 反应机理

探讨了在CO₂加H₂合成HCOOH过程中原位合成的固载Ru基催化剂的可能结构、CO₂的活化方式以及可能的反应机理. 在反应中, 固载Ru配合物中的一个P配体首先解离, 被质子型溶剂ROH取代而生成循环活性物质, 然后CO₂正插入Ru—H键生成甲酸酯配合物, 之后甲酸酯配合物中的Ru—O₂CH键被H₂氢解生成HCOOH, 而本身重新转化为活性物质, 完成催化循环.     

桥头碳上氮杂芳基功能化的双吡唑甲烷与羰基钨反应

研究了(氮甲基咪唑-2-基)双(3,5-二甲基吡唑)甲烷(L¹),2-吡啶基双(3,5-二甲基吡唑)甲烷(L²)及4-吡啶基双(3,5-二甲基吡唑)甲烷(L³)与羰基钨的反应,合成了一系列以单齿,双齿及三齿氮配位的羰基金属衍生物LW(CO)₅ (L=L¹或L³),LW(CO)₄ (L=L¹,L²或L³)和LW(CO)₃ (L=L¹或L²).核磁,红外及X-射线单晶衍射分析表明这3种配体表现出了可变的配位方式.在LW(CO)₅中,当配体为L¹时,其倾向于通过咪唑氮与金属配位,而为L³则倾向于利用吡啶氮与金属作用;在LW(CO)₄中,配体L¹表现为通过咪唑氮和吡唑氮原子配位的[N,N']双齿配体,而L²和L³表现为通过吡唑氮原子配位的[N,N]双齿配体;在LW(CO)₃中,L¹和L²起着[N,N,N']三齿螯合配体的作用.     

Ru/CNTs-Al2O3氨合成催化剂的制备与表征

采用H₂O₂、HNO₃和空气等氧化剂(ox)对碳纳米管-氧化铝(CNTs-alumina)复合材料进行纯化改性处理, 制备了Ru/CNTs-alumina-ox系列催化剂. 透射电镜(TEM), 热重(TG), X射线衍射(XRD)和傅里叶变换红外(FTIR)光谱分析结果表明, CNTs-alumina-H₂O₂复合载体中碳管结晶度最好, 且部分碳管被打断, 长度变短, 使其表面的羟基、羧基和羰基的含量明显提高. 电感偶合等离子体发射光谱(ICP)分析结果还表明, 经HNO₃处理时CNTs-alumina-HNO₃复合载体中有Al的溶出, 溶液中Al含量为49.98 mg·g^-1. 经三种氧化剂处理后所得到的催化剂, 其结构和表面化学性质存在明显的差别, 影响了氨合成催化剂的活性, 其中以CNTs-alumina-H₂O₂复合载体制备的催化剂氨合成活性最高, 在10 MPa、425 °C、10000 h^-1条件下, Ru/CNTs-alumina-H₂O₂催化剂氨合成反应速率达到39.8 mmol·g^-1·h^-1.     

组合型Pt3Sn/Al2O3催化剂用于芳香硝基化合物一锅法合成N-烷基芳胺

采用吸附法制备了组合型Pt₃Sn/Al₂O₃双金属催化剂, 将该催化剂用于芳香硝基化合物原位液相加氢一锅法合成N-烷基芳胺. 研究表明, 在503 K, 空速为7.5 h^-1, 水体积分数为5%时, 1%(质量分数)Pt₃Sn/Al₂O₃催化剂具有较高的催化性能, 硝基苯的转化率为100%, N-乙基苯胺和N,N-二乙基苯胺的总选择性为98.2%. 同时,该催化剂对原位液相加氢烷基化反应具有一定普适性, 本文研究的14 种芳香硝基化合物与低级脂肪醇反应,均具有较高的N-烷基化产率.     

两种基于硫醇配体的银(Ⅰ)配合物的合成、表征和晶体结构

通过AgCl、PPh₃和MBT以1:2:1的物质的量之比反应得到2种不同的配合物[AgCl(PPh₃)₂(BTZT)]·CH₃OH (1)和[AgCl(PPh₃)₂ (BTZT)]₂ (2)(PPh₃=三苯基膦;MBT=2-巯基苯并噻唑;BTZT=苯并噻唑-2-硫酮)(其中2已报道)。配合物[AgBr(PPh₃)₂(BTZT)]·CH₃OH (3)和[AgBr(PPh₃)₂(BTZT)]₂ (4)改用AgBr以相似的反应获得(其中2已报道)。通过红外光谱、元素分析、核磁共振氢谱、X射线单晶衍射、荧光光谱对配合物1和3进行了分析和表征。我们发现在不同的化学环境中,MBT配体可以转化为BTZT配体,原因是其具有化学活性基团。荧光光谱表明1和3的发射峰均源于配体中的π-π^*跃迁。     

碱性CeO2载体对Ru/CeO2催化剂氨合成活性的影响

钌基催化剂因其在低温低压下具有比常规的铁基催化剂更具活性的特点成为合成氨催化剂的理想选择.我们研究了CeO₂载体表面碱性对Ru基合成氨催化剂的影响.通过调节KOH沉淀剂的量来制备具有不同碱性位点的CeO₂载体（pH=10/11/12）,证明了催化剂适当碱性位点密度提高了合成氨催化活性.催化性能测试结果表明,1.25% Ru/CeO₂-11催化剂在3.8 MPa,450℃,H₂/N₂=3（60 mL·min^-1）下表现出优异的氨合成活性（7040 μmol·g^-1·h^-1）.CeO₂-11的碱性位点增强了载体的电子给予能力,这有利于电子向活性金属Ru转移,从而促进了N₂的活化.碱金属和碱土金属的引入提高了活性金属Ru的还原能力.4% Cs-1.25% Ru/CeO₂-11（12 000 μmol·g^-1·h^-1）催化剂具有更多的氧空位,这增加了Ru周围的电子密度并促进了N≡N的裂解.通过XRD,BET,SEM,CO₂-TPD,H₂-TPR和XPS分析了不同碱性CeO₂载体对合成氨催化反应的影响.     

P/Rh比对PPh3-Rh/SiO2催化剂上丙烯氢甲酰化反应的影响

研究了P/Kh比对PPh3-Rh/SiO2催化剂上丙烯氢甲酰化反应性能的影响.结果表明,当P/Rh比为15时,丙烯氢甲酰化反应性能最好,丙烯转化率为25.9%,产物丁醛正异比为14,转换频率为241 h-1.PPh3-Rh/SiO2催化剂的固体31P核磁共振结果表明,在合成气气氛下,物理吸附的PPh3能够溢流到Rh/S...     

固载Ru基催化剂上二氧化碳加氢合成甲酸Ⅱ反应条件对催化剂性能的影响

The synthesis of formic acid from carbon dioxide and hydrogen using a silica immobilized ruthenium catalyst as precursor has been studied in different reaction conditions. The results revealed that the TOF （turn over frequency） of HCOOH achieved 1481.5 h^-1 on immobilized ruthenium catalyst near the critical pressure point of CO2 with H2 pressure of 4.0 MPa, reaction temperature of 80℃ and PPh3/Ru molar ratio of 6：1. The reaction activity of immobilized catalyst was higher than that of homogeneous catalyst, and the immobilized catalyst also offered the practical advantages such as easy separation and reuse.     

Highly Active Carbene Ruthenium Catalyst for Metathesis of 1-Hexene

A new carbene ruthenium complex, 1,3-bis（2,6-dimethylphenyl）-4,5-dihydroimidazol-2-ylidene）（PPh3）Cl2-Ru=CHPh, was synthesized and used as catalyst for the metathesis of 1-hexene. The resulting complex exhibited very high catalytic activity whose TOF is up to 6680 h^-1. However, at the same time significant olefin isomerization was observed and could be surpressed by changing reaction conditions, such as temperature, time, alkene/Ru molar ratio and solvent.     

Propylene Dimerization by（η^5—C9H7）2 Nickel（Ⅱ）Catalytic System

The catalytic performance of Ni(η^5-Ind)2 complex in the dimerization of propylene was studied in combimation with an organoaluminum co-catalyst,eventually in the presence of a phosphine ligand.The effects of the type of aluminum co-catalyst and its relative amount,the nature of phosphine ligand and P/Ni ratio as well as the reaction temperature were examined.The results indicated that the nickel precatalyst exhibited high productivity for the propylene dimerization together with organoaluminum.It was likely to strongly modify the reactivity in the catalytic sytem when using phosphine ligand as additives,especially at the reaction temperature below 0℃.The catalytic system based on Ni(η^5-Ind)2 complex displaed an extremely high productivity(TOF up to 16900h^-1)and a good regioselectivity to 2,3-dimethylbutenes (2,3-DMB) in dimers(66.4%)under proper reaction parameters.     

Intramolecular hydroamination catalysed by Ag complexes stabilised in situ by bidentate ligands

A series of silver complexes generated in situ from AgOSO₂CF₃ (AgOTf) and a range of bidentate ligands were investigated as catalysts for the intramolecular hydroamination of 4-pentyn-1-amine. A variety of P- and N-donor ligands were tested including the novel pyrazole-phosphine ligand 1-(2-(diphenylphosphino)phenyl)pyrazole. The best catalyst was formed from equimolar amounts of the P,N-donor ligand 1-(2-(diphenylphosphino)ethyl)pyrazole and AgOTf, which achieved a turnover rate of 129 h⁻¹ for the cyclisation of 4-pentyn-1-amine.     

Regulation of Catalytic Activity by Phosphine Ligand Design

Abstract

Starting with the catalytic complex [Rh(PPh₃)₃Cl], the influence of variation of phosphine ligand properties on the activity of rhodium phosphine complexes as catalysts for the hydrogenation of olefins was systematically studied. The following catalyst modifications were examined (a) varying the basicity of the triarylphosphine ligands, (b) replacing Cl^? by a non-coordinating anion (BF₄ ^?) to make the catalyst cationic, (c) substituting a chelating diphosphine for the monophosphine ligands to ensure cis-coordination, and (d) varying the chain length of the diphosphine ligand to vary the chelate ring size and flexibility. By systematic manipulation of these parameters, enhancements of catalytic activity by factors in excess of 10⁴ were achieved.     

Ultralow-Loading and High-Performing Ionic Liquid-Immobilizing Rhodium Single-Atom Catalysts for Hydroformylation

We have developed a Keggin polyoxometalate (POM)-based ionic-liquid (IL)-immobilizing rhodium single-atom Rh catalyst (MTOA)₅[SiW₁₁O₃₉Rh] (MOTA=methyltrioctylammonium cation) that can afford exceptionally high catalytic activity for the hydroformylation of alkenes to produce aldehydes at an ultralow loading of Rh (ca. 3 ppm). For styrene hydroformylation, both the conversion and the yield of the aldehyde can reach almost 99 %, and a TOF as high as 9000 h⁻¹ was obtained without using any phosphine ligand in the reaction process. Further characterization by FTIR, ICP and ESI-MS analysis revealed that the single Rh atom was incorporated in the lacunary POM anions. In particular, the bulky IL cation can play an additional role in stabilizing Rh species and thus prevent aggregation and leaching of Rh species. The IL catalyst was miscible with n-hexane at temperatures; this contributed to exceptionally high activity for hydroformylation even at ultra-low loading of IL catalyst.     

Ruthenium-catalysed conversion of oxime ethers into nitriles

The conversion of oxime ethers into nitriles has been achieved under neutral conditions using Ru(CO)(PPh₃)₃H₂ and the bidentate ligand Xantphos as the catalyst.     

The Effect of Metal‐Ligand Affinity on Fe3O4_Supported Co–Rh Catalysts for Dicyclopentadiene Hydroformylation

The catalytic performances of Co‐Rh/Fe₃O₄ catalysts modified with phosphine ligands (PPh₃) and its analogues on dicyclopentadiene hydroformylation were evaluated. Among these catalysts, Co‐Rh/Fe₃O₄ modified with tris(p‐trifluoromethylphenyl)phosphine was determined to be effective for monoformyltricyclodecanes production, whereas Co‐Rh/Fe₃O₄ modified with PPh₃ or tri‐p‐tolylphosphine was effective for the diformyltricyclodecanes production. To investigate the ligand effects, the complex catalyst system (Co‐Rh/Fe₃O₄ and phosphine ligand) was subjected to pretreatment with syngas and then characterized by thermogravimetry and differential thermal analysis (TG‐DTA). It was determined that the threshold decomposition temperature reflected the corresponding Rh‐phosphine interaction strength, affecting the catalytic selectivity toward different products. A weak Rh‐phosphine interaction was desirable to produce monoformyltricyclodecanes with fast reaction kinetics, whereas a strong Rh‐phosphine complex was required for the synthesis of diformyltricyclodecanes. In addition to the selectivity rule shown in the PPh₃ series, experiments with other ligands also demonstrated similar selectivity trends.     

Ruthenium–Indenylidene Olefin Metathesis Catalyst with Enhanced Thermal Stability

Two new ruthenium complexes bearing a bidentate (κ²O,C)‐isopropoxy–indenylidene ligand and a PPh₃ ( 9 ) or PCy₃ ( 10 , Cy=cyclohexyl) ligand have been synthesized and fully characterized by ¹H and ¹³C NMR spectroscopy and X‐ray crystallography. Complex 10 displays a very high thermal stability with a half life of six days at 110 °C in [D₈]toluene. Complex 10 was evaluated in various ring‐closing metathesis reactions and ring‐opening metathesis polymerization of dicyclopentadiene, in which it showed a latent behavior with low activity at room temperature and high activity upon thermal activation.