过渡金属氧化物催化剂上NH3 分解Claus反应机理研究

运用浸渍法制备了七种过渡金属氧化物催化剂.对于NH3 分解反应均可获得很高的NH3转化率;对于NH3分解Claus反应则可以获得较高的SO2转化率和单质硫选择性.通过比较发现Co3O4-TiO2和Fe2O3-TiO2催化剂的低温活性比较高.经过XRD表征发现,在NH3分解Claus反应中,催化剂的活性相可能是过渡金属硫化物.结合活性评价和XRD表征结果提出了NH3分解Claus反应的机理.     

Epoxy-rich Fe Single Atom Sites Boost Oxygen Reduction Electrocatalysis

Electrocatalysts for highly efficient oxygen reduction reaction (ORR) are crucial for energy conversion and storage devices. Single-atom catalysts with maximized metal utilization and altered electronic structure are the most promising alternatives to replace current benchmark precious metals. However, the atomic level understanding of the functional role for each species at the anchoring sites is still unclear and poorly elucidated. Herein, we report Fe single atom catalysts with the sulfur and oxygen functional groups near the atomically dispersed metal centers (Fe1/NSOC) for highly efficient ORR. The Fe1/NSOC delivers a half-wave potential of 0.92 V vs. RHE, which is much better than those of commercial Pt/C (0.88 V), Fe single atoms on N-doped carbon (Fe1/NC, 0.89 V) and most reported nonprecious metal catalysts. The spectroscopic measurements reveal that the presence of sulfur group induces the formation of epoxy groups near the FeN4S2 centers, which not only modulate the electronic structure of Fe single atoms but also participate the catalytic process to improve the kinetics. The density functional theory calculations demonstrate the existence of sulfur and epoxy group engineer the charges of Fe reactive center and facilitate the reductive release of OH* (rate-limiting step), thus boosting the overall oxygen reduction efficiency.     

La0.7Sr0.3Co1-xFexO3催化剂氮氧化物储存及抗硫性能

采用溶胶-凝胶法通过在静态空气中700°C焙烧制备了不同Fe掺杂量的La0.7Sr0.3Co1-xFexO3(x=0,0.2,0.6,1.0)系列钙钛矿催化剂.考察了Fe掺杂量对催化剂的结构、氮氧化物储存、抗硫及再生性能的影响.研究结果表明:在La0.7Sr0.3CoO3钙钛矿B位用Fe部分取代Co,可有效提高SrCO3物相的分散,X射线衍射(XRD)结果显示样品中基本为钙钛矿物相.随着Fe掺杂量的增加,催化剂的NOx储存量(NSC)下降.对预硫化样品进行NOx储存测试,发现La0.7Sr0.3CoO3催化剂由于表面沉积了硫酸盐,同时钙钛矿结构也遭到了部分破坏,使得NOx储存量和NO氧化能力均大幅度下降,NOx储存量下降了64.2%,NO-to-NO2转化率从72.8%降至43.4%.掺杂Fe元素后,催化剂的抗硫性能都有不同程度的提高,特别是Fe掺杂量为60%的样品具有最佳的抗硫性能和可再生性能.与新鲜样品相比较,再生后样品的NOx储存量仅下降16.6%,而NO-to-NO2转化率为69.1%,几乎与新鲜样品相同.     

Synergistic Effects between Atomically Dispersed Fe−N−C and C−S−C for the Oxygen Reduction Reaction in Acidic Media

Various advanced catalysts based on sulfur‐doped Fe/N/C materials have recently been designed for the oxygen reduction reaction (ORR); however, the enhanced activity is still controversial and usually attributed to differences in the surface area, improved conductivity, or uncertain synergistic effects. Herein, a sulfur‐doped Fe/N/C catalyst (denoted as Fe/SNC) was obtained by a template‐sacrificing method. The incorporated sulfur gives a thiophene‐like structure (C−S−C), reduces the electron localization around the Fe centers, improves the interaction with oxygenated species, and therefore facilitates the complete 4 e⁻ ORR in acidic solution. Owing to these synergistic effects, the Fe/SNC catalyst exhibits much better ORR activity than the sulfur‐free variant (Fe/NC) in 0.5 m H₂SO₄.     

含磷阻垢剂对重油加氢催化剂失活的影响

收集了炼油厂添加含磷阻垢剂的固定床反应器中失活的三种加氢催化剂和粉尘,用Ｘ射线荧光、比表面孔容测定、扫描电子显微镜－Ｘ射线能量色散谱、Ｘ射线衍射和红外光谱等手段对样品的组成及结构进行了表征。结果表明,含磷阻垢剂的加氢催化剂失活是由于磷、铁和硫等元素在催化剂表面大量沉积所引起。对沉积物元素的分布分析分析,磷、铁和硫等元素主要沉积在催化剂的外层,磷沉积层较厚,且可进入催化剂孔道,在加氢脱金属催化剂、加     

添加金属氧化物的V2O5/AC在烟气脱SO2及脱SO2后H2再生制备硫磺的活性研究

干法脱除烟气SO2的多种催化剂均可在H2气氛中再生,直接制备硫磺。该过程的实现不仅要求再生尾气循环,而且要求催化剂具有双重功能,即在脱硫过程中催化氧化SO2为H2SO4以及在再生过程中将催化还原释放出的SO2进一步转化为硫磺。添加有金属氧化物的V2O5/AC催化剂具备双重功能。着重考察了添加Ce、W、Fe、Co 等氧化物的V2O5/AC催化剂烟气SO2脱除能力及脱除SO2后经H2再生制备硫磺的能力,并对添加Co的催化剂进行了优化。结果表明,在这类催化剂中,对烟气脱SO2起主要催化氧化作用的是V2O5,对H2再生硫磺制备起作用的是添加的金属氧化物。除Ce2O3外,WO3、Fe2O3和CoO都提高了再生中的硫磺收率,CoO的作用最为显著。较合适的催化剂组成是1%V2O5和0.5%CoO。这些金属氧化物在AC上的担载方法,对烟气脱SO2和H2再生结果的影响不明显。硫磺的生成需要CoO向CoS2的转变,再生后催化剂上残余有部分CoS2,且残余硫量还与V2O5量有关。     

钙钛矿型CO氧化催化剂耐SO2中毒性质的研究

钙钛矿型ＣＯ氧化催化剂耐ＳＯ２中毒性质的研究马春曦王宝辉（大庆石油学院石油化工系安达１５１４００）关键词钙钛矿型催化剂一氧化碳氧化硫中毒近年来，人们对钙钛矿型复合物ＣＯ氧化催化剂作了大量研究，证明其具有很高的ＣＯ氧化活性［１－３］，并开始尝试应用于汽...     

STUDY ON XPS OF IRON CATALYSTS

IntroduCtioniron-basedcatalystSareactiveinformingliquidfuelsfromthehydrogenationofCO[l~6].However,itiswellknownthatthepoisoningofironcatalystsespeciallythesulfurandoXygenisoneofthemostseriousdeactivationproblemsincommercialproduCtionofsubstitUtenatUralgas…     

金属Sr、Fe掺杂对LaCoO3催化氧化碳烟及抗硫性能影响

利用柠檬酸-EDTA(乙二胺四乙酸)配位法制备了La1-xSrxCo1-yFeyO3催化剂,展现出较好的催化氧化碳烟(soot)活性和抗硫性能。通过X射线衍射(XRD)、傅利叶红外光谱(FT-IR)、扫描电镜(SEM)、H2-程序升温还原(H2-TPR)、X射线光电子能谱(XPS)和SO2程序升温脱附(SO2-TPD)等研究了Sr、Fe掺杂对催化剂物理化学性质及抗硫能力影响。当Sr掺杂LaCoO3时有利于形成较多的表面吸附氧(O2^-、O^-)和氧空位,且低温氧化还原性能亦有较大改善,提高了催化氧化碳烟活性,其Ti(起燃温度)和Tm(最大碳烟燃烧速率温度)分别为284和347℃。当催化剂同时掺杂Sr、Fe时,其低温氧化还原性能进一步改善,并形成较多Fe^4+离子,有利于提高催化氧化碳烟活性。催化剂SO2中毒失活主要来源于Co^2+/Co^3+和表面吸附氧的硫酸化(SO3^2-、SO4^2-)。XPS和SO2-TPD结果表明,LaSrCoFeO3抗硫性主要来源于Fe^3+与SO2结合形成的硫酸盐物种,降低了SO2对活性组分表面吸附氧和Fe^4+毒化。TPO(程序升温氧化)结果表明,硫化后的LaSrCoFeO3-S仍具有较好的催化氧化碳烟活性,其Tm仅为361℃,表明Sr、Fe同时掺杂具有较好的低温催化氧化碳烟活性和良好的抗硫性能。     

F-T合成催化剂羰基硫中毒热力学分析

利用热力学基础数据和相关软件对F-T合成催化剂COS中毒的热力学进行了计算。在热力学上,Ru、Fe、Co的COS中毒在F-T合成反应可以发生的条件下均是自发过程。F-T合成反应体系中10^-9级的COS即可使Ru基催化剂中的金属Ru生成RuS₂而中毒。Fe和Co毒化后生成的硫化物种类较多,对反应的热力学计算结果表明,对于不同的反应,其平衡常数的差异很大,对应中毒反应发生时,所需COS的浓度也不同。由于Fe基F-T合成催化剂活性相的复杂性,利用对催化剂相关性质的修饰开发具有一定抗硫性的铁基F-T合成催化剂是可行的;对于Co催化剂,利用F-T合成的反应特点和催化剂改性开发具有一定抗硫性催化剂也是可能的。     

A DFT study of the adsorption and dissociation of CO on sulfur-precovered Fe100

Sulfur is known to be a poison to several catalytic reactions, e.g., the Fischer-Tropsch synthesis (FTS), in which it affects drastically the performance of both iron- and cobalt-based catalysts. However, despite the importance of this industrial process, little is known about what elementary steps are poisoned by sulfur. In the present article, we report, using density functional theory, the effect of sulfur on one of the most relevant reactions in the FTS: the dissociation of carbon monoxide over iron surfaces. We have studied the adsorption and dissociation of CO on Fe(100)-S-p(2 x 2) (theta(S) = 0.25 ML) and on Fe(100)-S-c(2 x 2) (theta(S) = 0.50 ML). We have found surface configurations that correlate well with the desorption features observed in temperature-programmed desorption mass spectroscopy. In addition, we have calculated the activation energy of CO dissociation on Fe(100)-S-p(2 x 2), which, interestingly, is very similar to the activation energy of CO dissociation on the sulfur-free Fe(100) surface. However, the sign of the reaction changes by the presence of sulfur; CO dissociation is highly exothermic on the sulfur-free Fe(100) surface, whereas on the Fe(100)-S-p(2 x 2) surface, it is slightly endothermic. Moreover, according to our results, the influence of sulfur in the CO dissociation seems to be short-ranged.     

Novel non-aqueous Fe(III)/Fe(II) redox couple for the catalytic oxidation of hydrogen sulfide to sulfur by air

A series of Fe(III) salts and organic solvents have been screened to develop novel non-aqueous catalysts for the conversion of H2S to sulfur. FeCl3/95% N-methylpyrrolidinone/5% H2O was found to be a most efficient non-aqueous system. The process chemistry, the proposed mechanism of catalytic oxidation of H2S, and the electrochemistry are discussed.     

CS2与大气颗粒物的多相催化反应研究

利用原位FTIR,XRD,XPS,BET,质谱和连续微量反应等手段研究了大气颗粒物及部分氧化物样品上CS₂多相催化反应,确认了反应产物,并对催化剂的晶化状况和比表面积等进行了考察.结果表明,CS₂在氧化物和大气颗粒物样品上发生氧化反应,生成COS及单质硫,部分样品上生成CO₂,活化状态下的[S]在大气颗粒物表面上能被进一步氧化为六价态硫.收集所得到的大气颗粒物样品成分主要是Ca(Al₂Si₂O₈)·4H₂O;CS₂在氧化物或大气颗粒物样品上催化生成COS是催化剂表面吸附氧的作用之故.     

Fe-V/TiO_2催化剂NH_3选择性催化还原柴油车尾气NO_x

采用浸渍法制备了一系列不同Fe/V比例的Fe-V/TiO2催化剂,考察了催化剂在模拟柴油车尾气中催化还原NOx的催化性能,采用TG、XRD、H2-TPR、NH3-TPD和Raman光谱对催化剂进行了表征。结果表明,当Fe引入后,能显著降低V2O5在高温下的挥发,减轻了钒系催化剂在移动源的生物毒性危害。其中,Fe/V比为1∶1(Fe1-V1/TiO2)的催化剂形成了FeVO4活性中心,表现出最好的催化活性,在220~420℃NOx转化率可达到90%以上。此外,Fe1-V1/TiO2催化剂高温热稳定性较好,并且具有较强的抗硫性能。     

CO气相合成草酸二乙酯催化剂性能评价

考察了Al2O3载体的类型和形状、活性组分Pd的负载量、活性组分Pd和助催化剂Fe之比对工业原料CO气相催化合成草酸二乙酯(DEO)反应的影响。结果表明,当Pd的负载量为1%～5%、Pd/Fe为0.2～2.0(mol比)、条状α-Al2O3为载体时,催化剂的性能优良,在此条件下,草酸二乙酯的最大收率可达60%, CO转化率可达63%,草酸二乙酯选择性可达98%。     

Catalytic oxidation of CS_2 over atmospheric particles and oxide catalysts

The catalytic oxidization of CS2 over atmospheric particles and some oxide catalysts was explored through FT-IR, MS and a fixed-bed stainless steel reactor. The results show that atmospheric particles and some oxide catalysts exhibited considerable oxidizing activities for CS2 at ambient temperature. The reaction products are mainly COS and elemental sulfur, even CO2 on some catalysts. Among the catalysts, CaO has the strongest catalytic activity for oxidizing CS2. Fe2O3 is weaker than CaO. The catalytic activity for AI2O3 reduces considerably compared with the former two catalysts, and SiO2 the weakest. Atmospheric particle samples' catalytic activity is between Fe2O3's and AI2O3's. The atmospheric particle sample collected mainly consists of Ca(AI2Si2O8) · 4H2O, which is also the main component of cement. COS, the main product, is formed by the catalytic oxidization of CS2 with adsorbed "molecular" oxygen over the catalysts' surfaces. The concentration of adsorbed oxygen over catalysts' surfaces may be th     

Synthesis, gas-phase photoelectron spectroscopic, and theoretical studies of stannylated dinuclear iron dithiolates

Stannylated dinuclear iron dithiolates (mu-SSnMe(2)CH(2)S)[Fe(CO)(3)](2), (mu-SCH(2)SnMe(2)CH(2)S) [Fe(CO)(3)](2), and (mu-SCH(2)SnMe(3))(2)[Fe(CO)(3)](2), which are structurally similar to the active site of iron-only hydrogenase, were synthesized and studied by gas-phase photoelectron spectroscopy. The orbital origins of ionizations were assigned by comparison of He I and He II photoelectron spectra and with the aid of hybrid density functional electronic structure calculations. Stannylation lowers the ionization energy of sulfur lone pair orbitals in these systems owing to a geometry-dependent interaction. The Fe-Fe sigma bond, which is the HOMO in all these systems, is also substantially destabilized by stannylation due to a previously unrecognized geometry-dependent interaction between axial sulfur lone pair orbitals and the Fe-Fe sigma bond. Since cleaving the Fe-Fe sigma bond is a key step in the mechanism of action of iron-only hydrogenase, these newly recognized geometry-dependent interactions may be utilized in designing biologically inspired hydrogenase catalysts.     

Hexacyanoferrate‐based ionic liquids as Fenton‐like catalysts for deep oxidative desulfurization of fuels

Two hexacyanoferrate‐based ionic liquids, [C₄Py]₃Fe(CN)₆ and [C₁₆Py]₃Fe(CN)₆, were synthesized and characterized using Fourier transform infrared and mass spectroscopies and CHN analysis. They were employed as Fenton‐like catalysts in extraction and catalytic oxidative desulfurization of model oil with dibenzothiophene (DBT), benzothiophene (BT), 4,6‐dimethyldibenzothiophene (4,6‐DMDBT), 4‐methyldibenzothiophene (4‐MDBT) and 3‐methylbenzothiophene (3‐MBT) as substrates. Various polar solvents, such as ionic liquids, water and organic solvents, were applied to choose a suitable extractant. The results showed the removal of DBT reached 97.1% with [C₄Py]₃Fe(CN)₆ as a catalyst and 1‐n‐octyl‐3‐methylimidazolium hexafluorophosphate ([C₈mim]PF₆) as an extractant under optimal conditions. The activity of sulfur removal followed the order DBT > 3‐MBT > BT > 4‐MDBT >4,6‐DMDBT. The effect of water content on sulfur removal was investigated by adding various concentrations of H₂O₂. It was found that excess water had a positive effect on sulfur removal but the catalysts were less sensitive than [FeCl₄^?]‐based catalysts to water. The mechanism was studied using electron spin‐resonance spectroscopy and gas chromatography–mass spectrometry. O₂^?? may be the active oxygen species in the catalytic oxidative desulfurization process and the oxidation products of various sulfur compounds were the corresponding sulfoxides and sulfones. Copyright © 2016 John Wiley & Sons, Ltd.     

乙酸调控MIL-53(Fe)的形貌演变及其高效选择性氧化H2S性能

硫化氢(H2S)广泛存在于以煤、石油和天然气等为原料的化工生产过程中,不仅腐蚀管道和设备,而且还会对健康和环境造成危害.因此,高效脱除H2S已成为工业废气减排的重点.在各种方法中,H2S选择性氧化技术(H2S+(1/2)O2→(1/n)Sn+H2O)由于具有设备需求低、反应不受热力学平衡限制、理论转化率可达100%等优点展现出了巨大的应用前景.实现这一过程的关键在于发展高效稳定的催化剂.作为一类新兴的多孔材料,金属-有机骨架材料(MOFs)由于其独特的结构和性质吸引了广泛的研究兴趣.与传统的脱硫材料相比,MOFs的优势主要体现在:1)高度分散的金属原子可作为催化活性中心;2)超高比表面积和规则的孔结构有利于反应物与活性位点之间的接触;3)结构可调变性高,通过在合成过程中有目的地引入配体或调控剂可产生额外的活性位点,满足特定催化的需求.基于以上特点可知,MOFs是一类有潜力的催化剂,但目前将其应用于H2S选择性氧化领域的研究尚处于起步阶段.本文以典型的铁基MOFs MIL-53(Fe)为研究对象,在制备MIL-53(Fe)过程中添加乙酸(HAc)作为调控剂,通过控制HAc的量,得到一系列具有不同形貌的MIL-53(Fe)-xH样品,并将其应用于H2S选择性氧化反应.SEM结果表明,在MIL-53(Fe)的合成过程中引入乙酸可以显著影响样品的形貌和尺寸.活化前后样品的XRD结果表明,HAc具有与对苯二甲酸(H2BDC)相似羧基基团,二者均可与Fe–O团簇配位.此外,TG-DSC结果证实,随着HAc加入量的提高,与Fe^3+形成配位的HAc/H2BDC比值随之增加.FT-IR和Raman结果进一步证明HAc成功地配位到MIL-53(Fe)的框架中,并且参与配位的HAc可通过真空活化移除从而暴露出Fe^3+不饱和位点.H2S选择性氧化测试表明,MIL-53(Fe)-xH的脱硫活性随着HAc含量的提高先增加然后降低,其中MIL-53(Fe)-5H活性最优.此外,MIL-53(Fe)-5H催化剂在连续运行55 h后仍能保持100%H2S转化率和86%硫选择性,性能远优于传统的Fe2O3催化剂.吡啶原位红外光谱结果表明,HAc的引入可以产生额外的Lewis酸性位点(LAS),LAS含量的不同是造成催化剂活性差异的主要原因.     

Preparation and characterization of Mn/MgAlFe as transfer catalyst for SOx abatement

A series of manganese-promoted MgAlFe mixed oxides, used as sulfur transfer catalysts, were prepared by acid-processed gelatin method and characterized by TGA-DTA, XRD, N2 adsorption-desorption and FT-IR techniques. It was found that the sulfur transfer catalysts with 0.5?3.0 wt% manganese showed its good dispersion in the precursor. The novel Mn/MgAlFe catalysts with 0.5?5.0 wt% manganese oxide showed a high oxidative adsorption rate and sulfur adsorption capacity, and 5.0 wt% Mn/MgAlFe sample was superior to the others for SO2 removal. Moreover, the presence of CO had no obvious effect on the adsorption activity of sulfur transfer catalysts for SO2 uptake.