Dioxygen Affinities and Catalytic Oxidation Performance of Cobalt （Ⅱ）Complexes with N—Aryl Hydroxamic Acid

The oxygenation of cobalt(Ⅱ) hydroxamates(CoL2) and its catalytic performance in oxidation of p-xylene to p-toluic acid (PTA) were examined.The effects of X and Y bonded to hydroxamate group on dioxygen affinities and catalytic oxidation performance were also investigated.     

Effect of diluent and reaction parameter on selective oxidation of propane over MoVTeNb catalyst using nanoflow catalytic reactor

The selective oxidation of propane to acrylic acid over an MoVTeNb mixed oxide catalyst, dried and calcined before reaction has been studied using high-throughput instrumentation, which is called nanoflow catalytic reactor. The effects of catalyst dilution on the catalytic performance of the MoVTeNb mixed oxide catalyst in selective oxidation of propane to acrylic acid were also investigated. The effects of some reaction parameters, such as gas hourly space velocity （GHSV） and reaction temperature, for selective oxidation of propane to acrylic acid over diluted MoVTeNb catalyst have also been studied. The configuration of the nanoflow is shown to be suitable for screen catalytic performance, and its operating conditions were mimicked closely to conventional laboratory as well as to industrial conditions. The results obtained provided very good reproducibility and it showed that preparation methods as well as reaction parameters can play significant roles in catalytic performance of these catalysts.     

Total oxidation of ethanol and toluene over ceria—zirconia supported platinum catalysts

The effect of platinum loading (0.09–1.00 mass %) on the performance of ceria-zirconia supported catalysts in the total oxidation of ethanol and toluene in air was investigated. The introduction of platinum promoted the reduction of surface cerium and decreased the acidity of the catalysts. In ethanol oxidation, the temperature of 50 % conversion decreased with increasing platinum content. This increase in catalytic performance was more pronounced for the catalysts with 0.59 mass % and 1.00 mass % Pt. On the other hand, higher amount of by-products (mainly acetaldehyde) was observed at increased platinum loadings. For all catalysts, a correlation between their H₂-TPR profiles and catalytic performance was revealed. In toluene oxidation, only the catalysts with 0.59 mass % and 1.00 mass % Pt exhibited a lower temperature of 50 % conversion than pristine ceria-zirconia. The effect of platinum loading was less pronounced than in ethanol oxidation and a correlation between reduction behaviour and catalytic performance was not observed. The superior catalytic performance of the catalysts with 0.59 mass % and 1.00 mass % of Pt in both ethanol and toluene oxidation was ascribed to the presence of large platinum nanoparticles, which were not observed at lower Pt loadings.     

载体对Pd-Cu/活性炭催化剂在消除卷烟主流烟气中CO活性的影响

采用等体积浸渍法制备了Pd-Cu/活性炭催化剂, 用脉冲反应考察了催化剂对模拟卷烟主流烟气(4.4 CO-4.2 H₂O-19.2 O₂-72.2 He)(体积分数, %)中CO的常温催化氧化性能, 系统研究了不同的活性炭载体对催化剂的CO常温氧化活性的影响. 研究表明, 在室温条件下, 催化剂对CO氧化反应的活性顺序为: 椰壳活性炭为载体的催化剂(CAC)<木质活性炭为载体的催化剂(WAC)<超级活性炭为载体的催化剂(SAC), 并且活性炭载体对催化剂的反应诱导期也存在显著的影响. 对催化剂的表征结果表明, 不同活性炭载体表面上含氧官能团含量不同, 影响催化剂表面Pd和Cu的存在状态, 使得SAC催化剂上的Pd只以Pd²⁺形式存在, 而CAC和WAC催化剂上的Pd以Pd²⁺和Pd⁰形式存在, 导致SAC催化剂比CAC和WAC两种催化剂具有更好的CO催化氧化活性. 使用催化剂接装的三段式复合滤嘴试验卷烟, 与对照卷烟相比, 卷烟主流烟气中CO的释放量都有所降低, 其中添加SAC催化剂的效果最为明显. 如果将Pd的负载量增加为3.4% (w), SAC催化剂对卷烟主流烟气中CO的去除率高达25.4%.     

Synthesis of Iron Chlorophyllins and Their Catalytic Performance for Aerobic Oxidation of Cyclohexene

A series of iron(Ⅲ) chlorophyllins was prepared from silkworm excrement crude chlorophyll extract as a raw material. Aerobic oxidation of cyclohexene by using the prepared iron(Ⅲ) chlorophyllins as biomimetic catalysts was studied under atmospheric pressure in the absence of reducing agent and solvent. The results indicate that chlorophyll iron porphyrins have better catalytic performance than the industrial-applied iron tetraphenylporphyrin and cobalt tetraphenylporphyrin, and possess a higher selectivity for 2-cyclohexen-1-one. The smaller the polarity of iron(Ⅲ) chlorophyllin's ligand is, the easier the catalytic oxidation of cyclohexene will be. Esterification products of iron(Ⅲ) chlorophyllins can catalyze the oxidation of cyclohexene better than non-esterified iron(Ⅲ) chlorophyllins, and therefore show a higher conversion of cyclohexene and a higher selectivity for 2-cyclohexen-1-one than the non-esterified ones. Among the six synthesized iron(Ⅲ) chlorophyllin catalysts, iron(Ⅲ) methyl-pyropheophorbide-a is the best biomimetic catalyst for the highest conversion of cyclohexene. The influences of catalyst's substituent, polarity and ring structure on the catalytic performance were discussed. The catalytic performance of iron(Ⅲ) chlorophyllins improves with decreasing polarity, increasing conjugated degree of porphyrin's ring or enhancing chlorophyllins' stability. Possible mechanism of cyclohexene aerobic oxidation catalyzed by iron(Ⅲ) chlorophyllins was also discussed.     

Synthesis,O_2-binding ability and catalytic oxidation performance of cobalt(Ⅱ) complexes with dihydroxamic acid functionalized N-pivot lariat ethers

Novel Co(Ⅱ) complexes with dihydroxamic acids functionalized N-pivot lariat ether CoL~1-CoL~4 were synthesized and characterized.Their oxygenation constants(ln K_(O2)) and thermodynamic parameters(△H°,△S°) were measured.And their catalytic performance in oxidation of p-xylene to p-toluic acid(PTA) was investigated.The enhancement of O_2-binding and catalytic oxidation activity by the oxa aza crown ether ring of the cobalt complexes were discussed.     

锰基氧化物与冷等离子体协同催化氧化VOCs研究进展

挥发性有机化合物(VOCs)对环境的严重污染和对人体的危害引起了人们的重视。冷等离子体与催化剂耦合形成的协同效应可显著提高VOCs低温转化速率,减少二次污染和降低能耗,具有较好的应用前景。协同催化效果主要取决于催化剂物化性能,可通过调控催化剂的组成、粒径和结构改善协同催化活性。锰基氧化物因其具有较高的储氧能力、稳定的晶体结构、较好的氧气活化性能和良好的抗中毒能力等优点而被广泛应用于冷等离子体协同催化净化VOCs的应用研究。通过金属离子掺杂调控锰基氧化物的离子价态、氧迁移率和氧气吸附量,是改善催化剂与等离子体协同催化性能主要方法。本文总结了近年来锰基氧化物与冷等离子体协同催化氧化VOCs的研究进展,主要包括氧化锰晶型、分散度和掺杂金属离子对协同催化氧化VOCs的活性影响趋势及反应机理。分析冷等离子体与锰基氧化物催化剂协同氧化VOCs中存在的问题并对其发展前景进行了展望。     

干胶法制备钛硅沸石及其催化性能

以四丙基溴化铵为模板剂,以乙二胺(EDA)为碱源,采用干胶法制备了TS-1,并在此基础上引入介孔/大孔模板剂蔗糖而制备出多级孔道TS-1.采用X射线衍射、紫外-可见光谱及N2物理吸附-脱附等手段对所得样品进行了表征,并考察了它们催化噻吩(Th)及苯并噻吩(BT)氧化反应的性能.结果表明,随着釜底部n(EDA)/n(H2O)比的降低,TS-1结晶度、骨架Ti含量及其在Th氧化反应中的催化活性均升高.而当以乙胺和正丁胺为碱源时,TS-1难以晶化.所制备的多级孔道TS-1样品具有介孔/大孔孔道,在Th氧化反应中的催化活性高于TS-1;对于BT的氧化,当n(sucrose)/n(SiO2)为0.35时,制备的多级孔道TS-1样品的催化活性最高,BT脱除率可达100%,而TS-1则无催化活性.     

铋改性的钒磷氧化物液相催化氧化环己烷的反应机理

 制备了铋改性的钒磷氧化物(Bi-VPO)催化剂,并将其用于液相催化氧化环己烷,研究了该反应的反应机理. 结果表明,铋改性可大大提高VPO催化剂在温和条件下对环己烷液相氧化的催化性能. 无溶剂实验和四氢呋喃作溶剂的实验证明反应过程中溶剂乙腈和H2O2之间存在相互作用; 自由基捕捉实验证明环己烷氧化过程中存在自由基反应历程; 环己醇氧化实验证明环己酮并不是来自环己醇的氧化,而是由环己烷直接氧化得到的.     

Dioxygen Affinities and Catalytic Oxidation Performance of Co (II) Complexes with Phenol Ether Bridged Dihydroxamic Acids

Synthetic oxygen carriers are of great interest as models to mimic oxygen-carrying metalloenzymes for oxygen storage and transport1,2. Moreover, they possess great significance to realize high efficiency and selectivity catalytic oxidation of organic subs…     

单双核金属配合物选择性催化氧化对甲氧基苦杏仁酸

制备了以铜、钴、锰为中心离子的三种单核金属配合物L¹Cu、L¹Co、L¹Mn (L¹=N,N'-(2-羟乙基)丙二酰胺)和三种双核金属配合物L²Cu、L²Co、L²Mn (L²=N,N'-{2-(2-羟乙基氨基)乙基}丙二酰胺). 研究发现在缓冲溶液中六种金属配合物能将对甲氧基苦杏仁酸(4-MMA)高选择性地氧化成对甲氧基苯甲醛(AAD)以及少量对甲氧基苯甲酸(4-MBA), AAD的选择性(S)大于96%. 然而不同的催化体系在反应速率上表现了很大的不同: 铜金属配合物的催化活性最好; 双核配合物表现出更高的催化效率. 研究了酒石酸(TA)、磷酸(H₃O₄)、醋酸(HAc)三种缓冲溶液体系对L¹Cu催化H₂O₂氧化4-MMA反应的影响, 结果表明缓冲溶液种类对反应速率和选择性影响很大.研究了35℃时弱酸性条件(pH值从2.5到4.5的范围内)在酒石酸缓冲溶液中六种金属配合物催化H₂O₂氧化4-MMA的动力学, 计算出不同pH值条件下催化反应的表观反应速率常数k_obs, 并且讨论了pH值对催化反应的影响.     

Dioxygen affinities and catalytic oxidation performance of cobalt (ii) hydroxamates

The dioxygen affinities and catalytic oxidation performance of cobalt (II) complexes with N-phenylhydroxamic acids were investigated. The effects of substituting groups in aromatic ring of ligands on these properties were examined, and some relativity between the dioxygen affinities and catalytic oxidation activity were also discussed in this paper. This revised version was published online in June 2006 with corrections to the Cover Date.     

On the Catalytic Performance of (ZrO)n (n=1–4) Clusters for CO Oxidation: A DFT Study

The unique characteristic of superatoms to show chemical properties like those of individual atoms opens a new avenue towards replacing noble metals as catalysts. Given the similar electronic structures of the ZrO superatom and the Pd atom, the CO oxidation mechanisms catalysed by (ZrO)_n (n=1–4) clusters were investigated in detail to evaluate their catalytic performance. Our results reveal that a single ZrO superatom exhibits superior catalytic ability in CO oxidation than both larger (ZrO)_n (n=2–4) clusters and a Pd atom, indicating the promising potential of ZrO as a “single-superatom catalyst”. Moreover, the mechanism of CO oxidation catalysed by ZrO^+/− suggests that depositing a ZrO superatom onto the electron-rich substrates is a better choice for practical catalysis application. Accordingly, a graphene nanosheet (coronene) was chosen as a representative substrate for ZrO and Pd to assess their catalytic performances in CO oxidation. Acting as an “electron sponge”, this carbon substrate can both donate and accept charges in different reaction steps, enabling the supported ZrO to achieve enhanced catalytic performance in this process with a low energy barrier of 19.63 kcal/mol. This paper presents a new realization on the catalytic performance of Pd-like superatom in CO oxidation, which could increase the interests in exploring noble metal-like superatoms as efficient catalysts for various reactions.     

Integrating bimetallic AuPd nanocatalysts with a 2D aza-fused π-conjugated microporous polymer for light-driven benzyl alcohol oxidation

Efficient catalytic system with low energy consumption exhibits increasing importance due to the upcoming energy crisis.Given this situation,it should be an admirable strategy for reducing energy input by effectively utilizing incident solar energy as a heat source during catalytic reactions.Herein,aza-fused7 r-conjugated microporous polymer(aza-CMP)with broad light absorption and high photothermal conversion efficiency was synthesized and utilized as a support for bimetallic AuPd nanocatalysts in light-driven benzyl alcohol oxidation.The AuPd nanoparticles anchored on aza-CMP(aza-CM P/Au_xPdy)exhibited excellent catalytic performance for benzyl alcohol oxidation under 50 mW/cm^2 light irradiation.The improved catalytic performance by the aza-CMP/Au_xPdy is attributed to the unique photothermal effect induced by aza-CMP,which can promote the catalytic benzyl alcohol oxidation occurring at Au Pd.This work presents a novel approach to effectively utilize solar energy for conventional catalytic reactions through photothermal effect.     

金属卟啉/MgAl水滑石催化醇选择性氧化制备羰基化合物

将MgAl水滑石引入到金属四苯基卟啉(MTPPs,M=Co,Fe,Mn,Ni)催化氧化体系中,实现了醇的选择性氧化。 结果表明,在分子氧/异丁醛体系中,CoTPP在苯甲醇氧化制苯甲醛反应中表现出优异的催化活性,MgAl水滑石添加剂可有效地提高醛的选择性。 在苯甲醇1 mmol、乙腈2 mL、CoTPP 5 mg、MgAl水滑石18 mg、异丁醛5 mmol、反应温度60 ℃、氧气气氛下反应2 h,苯甲醇的转化率和苯甲醛的选择性分别达到94%和92%。 另外,此催化体系在其它醇类化合物的氧化反应中也具有较好催化活性。     

Highly Ordered and Thermally Stable FeRh Cluster Superlattice on Graphene for Low-Temperature Catalytic CO Oxidation

We report on bimetallic FeRh clusters with a narrow size-distribution grown on graphene on Ir(111) as a carbon-supported model catalyst to promote low-temperature catalytic CO oxidation. By combining scanning tunneling microscopy with catalytic performance measurements, we reveal that Fe−Rh interfaces are active sites for oxygen activation and CO oxidation, especially at low temperatures. Rh core Fe shell clusters not only provide the active sites for the reaction, but also thermally stabilize surface Fe atoms towards coarsening compared with pure Fe clusters. Alternate isotope-labelled CO/O₂ pulse experiments show opposite trends on preferential oxidation (PROX) performance because of surface hydroxyl species formation and competitive adsorption between CO and O₂. The present results introduce a general strategy to stabilize metallic clusters and to reveal the reaction mechanisms on bimetallic structures for low-temperature catalytic CO oxidation as well as preferential oxidation.     

TPR AND CTPR STUDIES ON Ni/Al_2O_3 CATALYST FOR CATALYTIC PARTIAL OXIDATION OF METHANE TO SYNGAS

lntroductionTheconversi0nofnaturalgast0syngasviQtheCatalyticPartialOxidaion(CPO)ofCH4(Eq.l)lledlethibitsthepotentiaIt0replaceconventionalsteamreforming(Eq.2),withasubstalialreductioninplantsizc.Thisproccssisnotcncrg}intensivc.andalso}'ieldss}.nthesisgasx`.ithH2/COmolarratioof2.O.x`hichissuitabIcforman}'chcmicalproccsscs-suchasthcproductionofmethanoIovcrCu/Zn0catal}'st(Eq.3)andFischcr-Tropschs}nthcsisovcrCo'CucataI}'sts(Eq.4).CO 2H2-CH30H(3)nCO 2nH2-C,,H(2,, l) nH2O(4)Atprcscnt-…     

多孔铜基催化剂的制备及对苯甲醇的选择性催化氧化

采用去合金化法制备了多孔铜(PC), 并以此为还原剂和模板与含有贵金属离子的溶液进行置换反应, 简单有效地制备了多孔M/PC(M=Ag, Au, Pt, Pd)双金属催化剂, 并对样品的形貌\, 结构和化学组成进行了表征, 利用苯甲醇气相选择性催化氧化实验评价了其催化性能. 实验结果表明, 所制备的多孔铜基催化剂具有良好的双金属协同催化效应, 对苯甲醇气相选择性氧化具有很好的催化活性和选择性, 其中Ag/PC具有最优的催化性能.     

单原子催化剂M1/FeOx(M=Pt,Fe)的理论研究:CO氧化反应

负载型纳米贵金属催化剂是用于多相催化反应的重要的催化剂之一,也是各国催化科学与技术研发的重点,其工业应用也越来越广泛.理论和实验的研究结果均表明,当载体表面的金属粒子尺寸减小至亚纳米级乃至更小的低配位、不饱和的原子团簇时,它们常常成为诱发催化反应的活性中心,呈现更高的催化活性和选择性.将负载的金属尺寸由纳米量级减小至分散的金属团簇甚至单原子而使每个原子成为反应的活性位点已成为研究的重点.最近,由张涛等首次合成的单原子催化剂(SAC)Pt1/FeOx引起了国内外催化及表面科学工作者的极大关注.单原子催化剂作为连接均相催化剂和多相催化剂的桥梁,不仅具有非均相催化剂的稳定、易于与反应体系分离、易表征等优点,而且具有均相催化剂活性中心结构均一、活性中心原子利用率百分之百等优点.一方面,单原子催化剂给多相催化领域注入了新的活力,另一方面也更有利于运用量子与计算化学的研究方法建立与实验相匹配的理论模型并从原子水平上进一步理解多相催化反应的微观作用机理.实验和理论的研究结果表明,其它单原子催化剂如Ir1/FeOx,Au1/FeOx和Ni1/FeOx催化CO氧化反应表现出不同的活性.然而,底物FeOx中的Fe同样是第VIII族中的3d过渡金属,却在低温下对CO氧化反应没有催化活性.我们围绕这一问题,重点研究了底物FeOx在负载单原子Pt1前后催化CO氧化的反应机理和活性,解释了单原子催化剂Pt1/FeOx相比于底物FeOx为何具有如此高的催化活性的原因.我们采用Vienna Ab-initio Simulation Package(VASP)从头算模拟软件和密度泛函理论(DFT)的广义梯度近似(GGA)进行了理论计算.其中,选择PBE泛函描述体系的交换关联相互作用,用投影缀加波(PAW)赝势基组方法描述体系中的电子和离子实之间的相互作用,对Fe原子采用了DFT+U方法进行d电子强相关校正,并使用Dimer计算方法搜寻反应过渡态.研究结果表明,底物FeOx中氧空位的再生伴随第二个CO2分子从催化剂表面脱附的过程需要较高的活化势垒(1.09 eV),这一过程是整个CO氧化反应的决速步.与此相比较,Pt1/FeOx催化剂中,由于Pt原子代替了表面Fe原子,导致电子结构及性质的显著变化,有利于CO的活化、氧化和CO2的脱附.我们从电子能量态密度(DOS)和Bader电荷分析及模型分子团簇的轨道相互作用的角度进一步分析了两种催化剂存在差异的本质;揭示了单原子催化剂Pt1/FeOx中Pt1和底物FeOx之间的相互作用的机理及催化剂表面Pt单原子在催化反应过程中的关键作用.     

担载纳米金催化乙醇选择氧化制乙酸乙酯

采用溶胶-凝胶法制备了一系列担载纳米金催化剂，用以催化乙醇选择氧化反应，模板剂的引入改变了催化剂载体的结构，从而提高了其催化活性和对乙酸乙酯的选择性，同时考察了反应温度、时间、以及催化剂制备方法对乙醇选择氧化反应的影响，实验结果表明使用以焙烧处理除去模板剂十八胺的Au／SiO2-O(C)为催化剂时，乙醇选择氧化一步制取乙酸乙酯的效果最佳，其选择性最高可达88．1％。