Reduction of NO with methane over Fe/ZSM-5 catalysts

<正>The catalytic activity of Fe/ZSM-5 for the selective reduction of NO to N_2 with methane in the presence of excess O_2 was studied.Fe/ZSM-5 catalysts with various Fe loadings were prepared by impregnation method.It is well known that methane is inactive when Fe/ZSM-5 as the catalyst for the selective catalytic reduction(SCR) of NO with methane.However,this paper shows that when the content of Fe was about 0.5%,Fe/ZSM-5 showed higher catalytic activity and selectivity of methane,and put forward measurable activation for CH_4 is an important factor for the reaction of removal of NOx with CH_4.     

改性PAN纤维与Fe3+的配位反应及配合物的催化性能

采用盐酸羟胺和水合肼的混合物分别对PAN纤维进行改性制备了偕胺肟改性PAN纤维(AO-PAN)和混合改性PAN纤维(M-PAN), 并分别与Fe³⁺进行配位反应生成两种改性PAN纤维铁配合物(Fe-AO-PAN和Fe-M-PAN). 研究了配位反应的动力学特性及温度和Fe³⁺初始浓度的影响, 并采用DRS和ESR技术比较了两种不同改性PAN纤维铁配合物对偶氮染料活性红195氧化降解反应的催化性能. 结果表明, 在所设定的温度和浓度范围内, 两种改性PAN纤维与Fe³⁺之间的配位反应平衡符合Langmuir 和Freundlich 吸附等温模型以及Lagergren准二级动力学方程, 并且AO-PAN比M-PAN更容易与Fe³⁺发生配位反应. 在相同条件下AO-PAN与Fe³⁺反应的配合量和反应速率常数均比M-PAN与Fe³⁺反应的高. 两种配合物对染料的氧化降解反应具有催化作用, 暗态条件下Fe-M-PAN比Fe-AO-PAN表现出更高的催化活性, 而光辐射条件下Fe-AO-PAN的催化活性显著增强.     

Unprecedented Fe(IV) Species in a Diheme Protein MauG: A Quantum Chemical Investigation on the Unusual Mössbauer Spectroscopic Properties

Ferryl species are important catalytic intermediates in heme enzymes. A recent experimental investigation of a diheme protein MauG reported the first case of using two Fe(IV) species as an alternative to compound I in catalysis. Both Fe(IV) species have unusual M?ssbauer properties, which was found to originate from novel structural features based on a quantum chemical investigation. With comparison to the previously reported Fe(IV)=O and Fe(IV)-OH species, results here provide the first evidence of a couple of new mechanisms by which proteins influence the properties of ferryl species by directly providing the O via Tyr, or stabilizing exogenous O via hydrogen bonding interaction. These results expand our ability to identify and evaluate high-valent heme proteins and models.     

PEG1000-DIL/甲苯温控两相体系中硝基芳烃的还原反应

研究了PEG1000-DIL/甲苯温控体系中硝基芳烃的还原反应.考察了催化加氢、水合肼/FeCl3.6H2O和水合肼/Fe5HO8.4H2O等3种还原体系,发现水合肼/Fe5HO8.4H2O在PEG1000-DIL/甲苯温控体系中具有很高的催化活性,将其用于12种硝基芳烃的还原反应,产率最高可达99%.该催化体系重复使用3次后产率无明显变化,用于卤代硝基苯类化合物的还原可以有效防止脱卤副反应的发生.     

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.     

硅铁ZSM-48沸石的CO加氢催化性能

考察了硅铁ＺＳＭ－４８负载铁、钾催化剂在ＣＯ加氢制备低碳烯烃反应中的催化性能。结果表明,Ｆｅ（Ⅲ）离子同晶取代Ｓi（Ⅳ）后,不仅使沸石分子筛的表面能量分布更加趋 于均匀,而且明显促进了活性组分铁的还原和减弱了催化剂表面吸附氢的能力,从而大大提高了反应活性和选择性。硅铁ＺＳＭ－４８负载过量的铁、钾都不利于ＣＯ加氢合成低碳烯烃,其负载量的量侍值分别为８％和１．９％。另外,硅铁ＺＳＭ－４８的焙烧温度和焙烧     

Simultaneous determination of trace iron and aluminum by catalytic spectrophotometry based on a novel oxidation reaction of xylene cyanol FF.

A new, simple, sensitive and selective method for the simultaneous determination of trace iron and aluminum by catalytic spectrophotometry was presented, based on the catalytic effects of iron and aluminum on the discoloring reaction of xylene cyanol FF proceeded by hydrogen peroxide and potassium periodate in weak nitric acid medium. No catalytic effect was obtained in the presence of hydrogen peroxide or potassium periodate only. With the conditional rate constants determined in reaction systems catalyzed by Al or Fe only, the concentrations of Fe and Al in the samples can be calculated. The method was applied to the simultaneous determination of trace Fe and Al in tap water, lake water, river water and tea leaves without separation and preconcentration.     

新型铁锰复合氧化物催化低温脱除NOx

采用溶胶-凝胶法合成了一系列铁锰复合氧化物催化剂,利用X射线衍射(XRD)对催化剂的活性相态进行研究,并考察了铁锰摩尔比及焙烧温度对催化性能的影响.结果表明,该催化剂体系征低温(80-220℃)下选择性催化氨还原NOx反应中显示出优异的活性.其中Fe(0.4)-MnOx(500)(即摩尔比n(Fe)/(n(Fe)+n(Mn))=0.4,焙烧温度500℃)催化剂具有最佳低温催化活性,在空速30000 h-1,温度80℃的条件下,NOx转化效率达到90.6%,N2 选择性达100%.Fe-MnOx复合氧化物催化剂中形成的Fe3Mn3O8晶相有利于促进NO氧化成NO2,从而提高低温选择性催化还原的活性.     

A facile chemical reduction method for synthesis of platinum–iron catalysts on carbon fiber papers for methanol oxidation

To enhance catalytic activity and durability for methanol oxidation reaction (MOR), we have fabricated bimetallic Pt–Fe catalysts on carbon fiber papers (denoted as Pt–Fe@CFP) by a facile chemical reduction method using iron as the precursor, ascorbic acid and sodium hypophosphite as the reductants, respectively. When ascorbic acid is using as the reductant, the Pt–Fe@CFP catalysts are composed of platinum and disordered Pt–Fe phases. The atomic ratio between Pt and Fe can be adjusted by altering deposition conditions. The Pt–Fe@CFP catalysts with Pt/Fe ratio of 1.1, which deposited with surfactant CTAB in bath at room temperature, exhibit excellent catalytic activity and stability in MOR. However, when sodium hypophosphite is employed as the reductant, the co-deposition of phosphorus would lead to a decreased catalytic performance in MOR.     

H(M)ZSM-5杂原子分子筛的表面酸性和裂解催化行为

用IR和ITPD技术研究了H(Al)ZSM-5、H(Ga)ZSM-5和H(Fe)ZSM-5杂原子分子筛的表面酸性。结果表明,这些分子筛表面既存在B酸中心,也存在L酸中心,但是就两种酸的表面浓度比值C_L/C_B而言,H(Ga)ZSM-5和H(Fe)ZSM-5要比H(Al)ZSM-5高得多。在十五烷裂解时,L酸中心起的作用可能更大。     

新型铁锰复合氧化物催化低温脱除NOx

采用溶胶-凝胶法合成了一系列铁锰复合氧化物催化剂, 利用X射线衍射(XRD)对催化剂的活性相态进行研究, 并考察了铁锰摩尔比及焙烧温度对催化性能的影响. 结果表明, 该催化剂体系在低温(80-220 ℃)下选择性催化氨还原NOx反应中显示出优异的活性. 其中Fe(0.4)-MnOx(500)(即摩尔比n(Fe)/(n(Fe)+n(Mn))=0.4, 焙烧温度500 ℃)催化剂具有最佳低温催化活性, 在空速30000 h-1, 温度80 ℃的条件下, NOx转化效率达到90.6%, N2选择性达100%. Fe-MnOx复合氧化物催化剂中形成的Fe3Mn3O8晶相有利于促进NO氧化成NO2, 从而提高低温选择性催化还原的活性.     

MIL-100(Fe) Supported Pt−Co Nanoparticles as Active and Selective Heterogeneous Catalysts for Hydrogenation of 1,3-Butadiene

Superior catalytic performance for selective 1,3-butadiene (1,3-BD) hydrogenation can usually be achieved with supported bimetallic catalysts. In this work, Pt−Co nanoparticles and Pt nanoparticles supported on metal–organic framework MIL-100(Fe) catalysts (MIL=Materials of Institut Lavoisier, PtCo/MIL-100(Fe) and Pt/MIL-100(Fe)) were synthesized via a simple impregnation reduction method, and their catalytic performance was investigated for the hydrogenation of 1,3-BD. Pt1Co1/MIL-100(Fe) presented better catalytic performance than Pt/MIL-100(Fe), with significantly enhanced total butene selectivity. Moreover, the secondary hydrogenation of butenes was effectively inhibited after doping with Co. The Pt1Co1/MIL-100(Fe) catalyst displayed good stability in the 1,3-BD hydrogenation reaction. No significant catalyst deactivation was observed during 9 h of hydrogenation, but its catalytic activity gradually reduces for the next 17 h. Carbon deposition on Pt1Co1/MIL-100(Fe) is the reason for its deactivation in 1,3-BD hydrogenation reaction. The spent Pt1Co1/MIL-100(Fe) catalyst could be regenerated at 200 °C, and regenerated catalysts displayed the similar 1,3-BD conversion and butene selectivity with fresh catalysts. Moreover, the rate-determining step of this reaction was hydrogen dissociation. The outstanding activity and total butene selectivity of the Pt1Co1/MIL-100(Fe) catalyst illustrate that Pt−Co bimetallic catalysts are an ideal alternative for replacing mono-noble-metal-based catalysts in selective 1,3-BD hydrogenation reactions.     

Active sites for NO reduction over Fe-ZSM-5 catalysts

A study of Fe-ZSM-5 catalysts with variable amounts of isolated, oligomeric and heavily aggregated Fe3+ oxo sites (as evidenced by UV-Vis and EPR spectroscopic data) and their catalytic properties in the selective catalytic reduction of NO by isobutane or by NH3 is presented, which allows development of a unified concept of the active Fe sites in these reactions, according to which isolated Fe sites catalyse both SCR reactions while oligomeric sites, though also involved in the selective reduction path, limit the catalyst performance by causing the total oxidation of the reductant.     

Co/Fe催化剂乙醇裂解和部分氧化制氢研究

采用共沉淀法制备的Co/Fe催化剂催化乙醇裂解和部分氧化制氢反应，考察了反应温度对两种途径反应的影响。结果发现，Co/Fe催化剂对乙醇部分氧化制氢显示出较高的氢选择性，且稳定性较好；该催化剂对乙醇裂解制氢也具有较高的氢选择性，但其稳定性很很差。XRD表征结果表明，在催化乙醇部分氧化反应后，Co70Fe30催化剂中存在CoFe合金和CoO相；而催化乙醇裂解反应后，Co70Fe30催化剂中仅存在CoFe合金，即CoFe合金可能是裂解反应的活性组分。     

Catalytic Metallopolymers from [2Fe‐2S] Clusters: Artificial Metalloenzymes for Hydrogen Production

Reviewed herein is the development of novel polymer‐supported [2Fe‐2S] catalyst systems for electrocatalytic and photocatalytic hydrogen evolution reactions. [FeFe] hydrogenases are the best known naturally occurring metalloenzymes for hydrogen generation, and small‐molecule, [2Fe‐2S]‐containing mimetics of the active site (H‐cluster) of these metalloenzymes have been synthesized for years. These small [2Fe‐2S] complexes have not yet reached the same capacity as that of enzymes for hydrogen production. Recently, modern polymer chemistry has been utilized to construct an outer coordination sphere around the [2Fe‐2S] clusters to provide site isolation, water solubility, and improved catalytic activity. In this review, the various macromolecular motifs and the catalytic properties of these polymer‐supported [2Fe‐2S] materials are surveyed. The most recent catalysts that incorporate a single [2Fe‐2S] complex, termed single‐site [2Fe‐2S] metallopolymers, exhibit superior activity for H₂ production.     

Preparation of FePd‐RGO Bimetallic Composites with High Catalytic Activity for Formic Acid Electro‐Oxidation

FePd‐RGO composites through the growth of uniformly dispersed iron‐palladium bimetallic nanoparticles (NPs) on reduced graphene oxide (RGO) nanosheets were prepared by a two‐step method. The firstly formed Fe is used as the seed for the subsequent Pd growth. The formation of Fe NPs on RGO in the first step is performed by an in‐situ reduction reaction with the reducer ethylene glycol under oil bath at 180°C. NPs in the as‐prepared FePd‐RGO have an average particle size of 6.5 nm, and Pd is added to one side of Fe which leads to the formation of Fe‐Pd bimetallic interfaces. As compared with the commercial Pd black at the same loading, the composites have higher electro‐catalytic activity, better electrochemical stability and higher resistance to CO poisoning for formic acid electro‐oxidation.     

A Bimetallic Zn/Fe Polyphthalocyanine‐Derived Single‐Atom Fe‐N4 Catalytic Site:A Superior Trifunctional Catalyst for Overall Water Splitting and Zn–Air Batteries

Developing an efficient single‐atom material (SAM) synthesis and exploring the energy‐related catalytic reaction are important but still challenging. A polymerization–pyrolysis–evaporation (PPE) strategy was developed to synthesize N‐doped porous carbon (NPC) with anchored atomically dispersed Fe‐N₄ catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe‐N₄ site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn–air battery devices containing the Fe‐N₄ SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.     

Nitrogen fixation catalyzed by ferrocene-substituted dinitrogen-bridged dimolybdenum–dinitrogen complexes: unique behavior of ferrocene moiety as redox active site

A series of dinitrogen-bridged dimolybdenum–dinitrogen complexes bearing metallocene-substituted PNP-pincer ligands is synthesized by the reduction of the corresponding monomeric molybdenum–trichloride complexes under 1 atm of molecular dinitrogen. Introduction of ferrocene as a redox-active moiety to the pyridine ring of the PNP-pincer ligand increases the catalytic activity for the formation of ammonia from molecular dinitrogen, up to 45 equiv. of ammonia being formed based on the catalyst (22 equiv. of ammonia based on each molybdenum atom of the catalyst). The time profile for the catalytic reaction reveals that the presence of the ferrocene unit in the catalyst increases the rate of ammonia formation. Electrochemical measurement and theoretical studies indicate that an interaction between the Fe atom of the ferrocene moiety and the Mo atom in the catalyst may play an important role to achieve a high catalytic activity.     

Fe(II)-induced transformation from ferrihydrite to lepidocrocite and goethite

The transformation of Fe(II)-adsorbed ferrihydrite was studied. Data tracking the formation of products as a function of pH, temperature and time is presented. The results indicate that trace of Fe(II) adsorbed on ferrihydrite can accelerate its transformation obviously. The products are lepidocrocite and/or goethite and/or hematite, which is different from those without Fe(II). That is, Fe(II) not only accelerates the transformation of ferrihydrite but also leads to the formation of lepidocrocite by a new path. The behavior of Fe(II) is shown in two aspects—catalytic dissolution-reprecipitation and catalytic solid-state transformation. The results indicate that a high temperature and a high pH(in the range from 5 to 9) are favorable to solid-state transformation and the formation of hematite, while a low temperature and a low pH are favorable to dissolution-reprecipitation mechanism and the formation of lepidocrocite. Special attentions were given to the formation mechanism of lepidocrocite and goethite.