甲烷催化部分氧化制合成气的反应机理

借助脉冲反应、质谱-程序升温表面反应（MS-TPSR）等技术研究了Ni／α-Al2O3催化剂上甲烷催化部分氧化制合成气（POM）的反应机理．结果表明,NiO上CH4不能解离产生H2只有当NiO被CH4还原为Ni0后,CH4才能解高产生H2,Ni0是CH4活化和POM反应的活性相;POM反应机理遵循直接氧化机理,CH4和O2均在Ni0上活化,活化过程形成的Ni…C和Niδ…Oδ物种是反应历程中的关键物种,Niδ …Oδ物种高选择性地与CH4解离产生的碳物种Ni…C反应生成CO．     

Study on Effect and Catalytic Mechanism of the Catalysts for Coal Oxidation in Alkaline Medium

Coal electro‐oxidation in sodium hydroxide solution with catalysts, K₃Fe(CN)₆, sodium hypochlorite and supported FeS, were investigated, respectively. Gas produced from electro‐analysis of coal slurry was collected by drainage‐method and I‐t curves were recorded to testify the catalysis of each catalyst for coal oxidation. The results show that the three kinds of catalysts can obviously improve the coal oxidation current. Furthermore, K₃Fe(CN)₆ and sodium hypochlorite played an indirect oxidation role in the electrolysis process. Catalysts bridge the coal particles and the solid electrode surface, thus increase the coal oxidation rates. The changes of catalyst content during the electrolysis were further determined by quantitative titration to discuss the catalytic Mechanism. The dynamic transition of K₃Fe(CN)₆/K₄Fe(CN)₆ and ClO⁻/Cl⁻ are proposed by iodometric method.     

异相Fenton催化水污染控制

高级氧化技术(AOPs)是当前水处理研究领域的热点问题。异相Fenton催化氧化是一种极具代表性的高级氧化技术,其反应过程中产生的羟基自由基(·OH)等活性氧物种可以无选择性地攻击有机污染物,将有机大分子逐步分解为小分子物质,从而达到高效去除废水中有毒有害污染物的目的。相比均相Fenton反应,它具有pH响应范围广、不产生铁泥、催化剂可循环利用等优点。然而,由于固相催化剂的本征特性和局限性,当前所研究的异相Fenton催化剂仍存在中性条件下活性低、过氧化氢(H₂O₂)利用率低、Fe(Ⅲ)/Fe(Ⅱ)转化速率不高等问题,难以实现异相Fenton催化在环境修复领域的大规模应用。本文综述了不同活性氧物种参与的异相Fenton反应机理,总结了多种异相Fenton催化剂及其在有机污染物控制方面的应用,为继续开展异相Fenton催化水污染控制研究提供参考。     

Catalytic Asymmetric Synthesis of Phosphine Boronates

The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β‐unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds.     

New Mechanism for the Catalytic Oxidation of Lignin to Vanillin

The previously proposed mechanism for lignin oxidation to vanillin was supported experimentally. This process begins with the formation of a phenoxyl radical and ends with the step of retroaldol cleavage of substituted coniferaldehyde to vanillin. The oxidation of model compounds was studied, and experimental evidence for the proposed mechanism was obtained. The postulated intermediate coniferyl alcohol was detected in the oxidation of eugenol. The proposed mechanism was supported by kinetic data and the composition of the oxidation products of vanillideneacetone, lignosulfonates, eugenol, isoeugenol, guaiacylethanol, and guaiacylpropanol.     

甲醛氧化催化剂及反应机理

甲醛具有致畸和致癌性,是主要的室内污染物。催化氧化法甲醛转化效率高,没有二次污染,相关研究日益受到关注。本文详细介绍了贵金属和非贵金属两类主要的甲醛氧化催化剂,探讨了活性组分、载体、催化剂助剂等催化剂组成对于其理化性质和反应性能的影响规律,讨论了制备方法、反应物中的水含量等因素对于催化反应的影响,分析了催化剂失活的主要因素。研究表明,催化剂表面活性氧、表面羟基、氧空位数量以及对反应物的吸脱附和存储能力是影响催化活性的关键因素。贵金属催化剂,特别是Pt催化剂具有较好的催化性能,可在较低温度实现甲醛充分转化;非贵金属催化剂具有可变价态,通过催化剂的合理设计可以具有足够的催化活性,其原料资源丰富,价廉易得,应用前景广阔。     

纳米银对水中三价砷的催化氧化研究

纳米银由于具有优良的杀菌性能,越来越多地用到饮用水消毒等领域.其作为杀菌剂主要针对饮用水中细菌超标以及水处理膜组件中存在的膜污染（菌污染）等问题.然而,由于AgNPs具有良好的光催化活性,可能会影响水处理系统中共存无机砷[As（Ⅲ）和As（V）]的形态转化.本研究采用液相色谱-电感耦合等离子质谱联用技术（HPLC-ICP/MS）测定As（Ⅲ）和As（V）,系统考察了水相中AgNPs对As（Ⅲ）和As（V）的吸附性能,体系pH值、NOM及共存离子（以Ca²⁺为例）等环境因素以及AgNPs的粒径和包覆剂等对As（Ⅲ）形态变化的影响.结果表明,AgNPs对As（Ⅲ）不存在物理吸附,但对As（Ⅲ）的氧化具有明显的催化作用.体系pH大于7.0时,AgNPs开始呈现对As（Ⅲ）氧化的显著催化作用,NOM、Ca²⁺、光照等环境因素均在一定程度上促进As（Ⅲ）的形态转化.此外,该过程与AgNPs本身的性质密切相关,粒径越小其催化性越好,PVP/CTS包覆AgNPs对As（Ⅲ）的催化氧化反应速率常数（k＝15.82×10^－2 h^－1）为柠檬酸包覆AgNPs的2倍.最后,在实际环境水样中验证了AgNPs对As（Ⅲ）的催化氧化.以上研究结果表明,水处理系统中的AgNPs在杀菌抑菌的同时,还能够促使As（Ⅲ）向低毒As（V）的转化,为As污染的去除提供了新的思路.     

A Million Turnover Molecular Anode for Catalytic Water Oxidation

Molecular ruthenium‐based water oxidation catalyst precursors of general formula [Ru(tda)(Lⁱ)₂] (tda^2? is [2,2′:6′,2′′‐terpyridine]‐6,6′′‐dicarboxylato; L¹=4‐(pyren‐1‐yl)‐N‐(pyridin‐4‐ylmethyl)butanamide, 1 b ; L²=4‐(pyren‐1‐yl)pyridine), 1 c ), have been prepared and thoroughly characterized. Both complexes contain a pyrene group allowing ready and efficiently anchoring via π interactions on multi‐walled carbon nanotubes (MWCNT). These hybrid solid state materials are exceptionally stable molecular water‐oxidation anodes capable of carrying out more than a million turnover numbers (TNs) at pH 7 with an E_app=1.45 V vs. NHE without any sign of degradation. XAS spectroscopy analysis before, during, and after catalysis together with electrochemical techniques allow their unprecedented oxidative ruggedness to be monitored and verified.     

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.     

Cu催化水煤气的变换反应机理

采用密度泛函理论(DFT), 对Cu催化水煤气变换反应三种可能的微观机理进行了理论研究. 在GGA-PW91理论水平下优化了反应通道上各驻点(反应物、中间体、过渡态和产物)的几何构型, 并通过频率分析对过渡态进行了验证. 研究结果表明, 甲酸根机理的可能性最小, 羧基机理与氧化还原机理的可能性较大, 且与氧化还原机理相比, 羧基机理因在反应过程中有中间体COOH(s)生成, 且它与OH(s)发生歧化反应仅需越过3.8 kJ·mol-1的活化能垒, 所以反应更易遵循这条路径进行.     

异核金属簇合成及催化作用的研究——Ⅰ.铂-钴羰基金属簇的合成及其催化醛化性能

本文报道用相转移催化作用合成异核金属簇络合物的新方法。在研究Co_2(CO)_8与Pt[P(C_6H_5)_3]_2Cl_2的反应时,除了得到异核金属簇Pt_2Co_2(μ_2-CO)_3(CO)_5[P(C_6H_5)_3]_2外,还分离出一种新的异核金属簇Pt_3Co_2(μ_2-CO)_5(CO)_4[P(C_6H_5)_3]_3和五核铂簇Pt_5(μ_2-CO)_5(CO)[P(C_6H_5)_3]_4. 考察了Pt_2Co_2(μ_2-CO)_3(CO)_5[P(C_6H_5)_3]_2对1-己烯的催化醛化活性,发现它是一种在温和条件下,有较高活性的催化剂。     

Reactions of Bis(Trifluoromethyl)Phosphine and Tetrakis(Trifluoromethyl)Phosphine with Ruthenium Carbonyl Clusters

Abstract

The reaction of (CF₃)₂P-P(CF₃)₂ with [Ru₃(CO)₁₂] yielded compounds : [Ru₁₄(CO)₁₃{μ-P(CF₃)₂)₂] (1), [Ru₄(CO)₁₄{μ-P(CF₃)₂}₂] (2), and [Ru₄(CO)₁₁{μ-P(CF₃)₂}₄] (3); reaction with [μ-H)₄Ru₄(CO)₁₂] yielded (1) and [(μ-H)₃Ru₄(CO)₁₂{μ-P(CF₃)₂}] (4). The reaction of (CF₃)₂PH with [Ru₃(CO)₁₂] yielded compounds (1) and (4) and compounds (1) and (2) using cluster : ligand ratios of 1:1 and 1:2 respectively. All the compounds have been characterised by X-ray crystallography; a schematic diagram of their structures is shown in Figure 1. The fluxional behaviour of the hydrides in (4) was studied using variable temperature ¹H NMR spectroscopy (see Figure 2). The result of this study was used in the assignment of hydride positions of (4) in the solid state.     

Mechanism of the Oxidation of Lower Aliphatic Alcohols with Catalysis by Giant Pd-561 Clusters

The mechanism of oxidation of lower aliphatic alcohols by oxygen in solutions of giant Pd-561 clusters was examined. The mechanism involves the formation of two types of intermediate particles on the surface of the metal cluster. Their further transformations involve interaction with the external substrates.     

载体对负载型金催化剂上甲醛催化氧化的影响

采用沉积.沉淀法和氨水络合法制备了Al2O3,TiO2,CeO2和SiO2负载的纳米金催化剂,利用元素分析、x射线衍射、氮气物理吸附、程序升温还原、透射电镜和拉曼光谱等技术对催化剂进行了表征,并考察了其低温催化甲醛氧化活性.结果表明,Au/CeO2的催化性能最佳,在40℃时甲醛转化率仍能保持在80%以上.催化剂的活性同时受Au的化学状态和载体性质的影响.Au/CeO2催化剂较高的低温活性可能与离子态的Au物种有关,同时AuxCe1-xO2-δ固溶体的形成产生了大量的氧缺位,提高了氧的活化能力,也有助于提高催化剂的低温活性.     

Catalytic Water Oxidation by Iridium‐Modified Carbonic Anhydrase

Carbonic anhydrase (CA) is a ubiquitous metalloenzyme with a Zn cofactor coordinated to trigonal histidine imidazole moieties in a tetrahedral geometry. Removal of the Zn cofactor in CA and subsequent binding of Ir afforded CA[Ir]. Under mild and neutral conditions (30 °C, pH 7), CA[Ir] exhibited water‐oxidizing activity with a turnover frequency (TOF) of 39.8 min^?1, which is comparable to those of other Ir‐based molecular catalysts. Coordination of Ir to the apoprotein of CA is thermodynamically preferred and is associated with an exothermic energy change (ΔH) of ?10.8 kcal mol^?1, which implies that the CA apoprotein is stabilized by Ir binding. The catalytic oxygen‐evolving activity of CA[Ir] is displayed only if Ir is bound to CA, which functions as an effective biological scaffold that activates the Ir center for catalysis. The results of this study indicate that the histidine imidazoles at the CA active site could be exploited as beneficial biological ligands to provide unforeseen biochemical activity by coordination to a variety of transition‐metal ions.     

Developing Insoluble Polyoxometalate Clusters to Bridge Homogeneous and Heterogeneous Water Oxidation Photocatalysis

Cluster catalysts are attractive for their atomically precise structures, defined compositions, tunable coordination environments, uniform active sites, and their ability to transfer multiple electrons, but they suffer from poor stability and recyclability. Here, we report a general approach to the direct insolubilization of a water soluble polyoxometalate (POM) [{(B-α-PW₉O₃₄)Co₃(OH)(H₂O)₂(O₃PC(O)-(C₃H₆NH₃)PO₃)}₂Co]¹⁴⁻ ( Co₇ ) and formation of a series of POM-based solid catalysts with the counter-cations Ag⁺, Cs⁺, Sr²⁺, Ba²⁺, Pb²⁺, Y³⁺, and Ce³⁺. They exhibit improved catalytic activities for visible-light-driven water oxidation following the trend CsCo₇ > SrCo₇ > AgCo₇ > Ce^IIICo₇ > BaCo₇ > YCo₇ > PbCo₇ . While CsCo₇ exhibits mainly homogeneous catalysis, the others are predominantly heterogeneous catalysts. An optimal oxygen yield of 41.3 % and a high apparent quantum yield (AQY) of 30.6 % for SrCo₇ is obtained, which is comparable to that of the parent homogeneous POM. Band gap structures, UV/Vis spectra, and real-time laser flash photolysis experiments collectively suggest that easier electron transfer from the solid POM catalyst to the photosensitizer promotes photocatalytic water oxidation performance. These solid POM catalysts exhibit good stability, which is directly confirmed by a combination of Fourier-transform infrared spectroscopy, electron microscopy, X-ray diffraction patterns, Raman spectroscopy, X-ray photoelectron spectroscopy, five cycles of tests, and poisoning experiments.     

气相色谱-氮磷检测器分析痕量磷化氢

采用柱前两次冷阱富集和气相色谱 -氮磷检测器 (GC -NPD)法 ,测定了大气环境中存在的痕量磷化氢 ;在原有的冷阱富集装置中配置温度控制仪和夹套冷阱控温 ,可在线检测并控制磷化氢的富集温度 ,并可选择不同的温度范围将其与厌氧环境中普遍存在的甲烷气体分离 ;该法的检出限为1.25×10-2pg。