Revealing the unexpected promotion effect of EuOx on Pt/CeO2 catalysts for catalytic combustion of toluene

Pt/Eu₂O₃-CeO₂ materials with different Eu concentrations were prepared and applied to toluene destruction, and the remarkable promotion impact of EuO_x on Pt/CeO₂ can be observed. The characterization results reveal that the presence of EuO_x significantly enhances the redox property, lattice O concentration, and Ce³⁺ ratio of the Pt/CeO₂ material, which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene. Among all catalysts, a sample with an Eu content of 2.5 at.% (Pt/EC-2.5) possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 °C under a relatively high GHSV of 50000 h^?1. The possible reaction pathway and mechanism of toluene combustion over Pt/Eu₂O₃-CeO₂ samples are presented according to in-situ DRIFTS, which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.     

Hydrothermal synthesis of MoS2 with controllable morphologies and its adsorption properties for bisphenol A

The effect of preparation conditions (molar ratio of S/Mo, hydrothermal temperature and time) on the morphologies of MoS₂ was investigated. The as-synthesized materials were characterized by X-ray diffraction (XRD), field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectra and Brunauer–Emmett–Teller’s (BET) surface area measurement. Results showed that the three kinds of morphologies of MoS₂ were obtained. Morphologies varied gradually from the coral-like aggregated particles to flower-like spheres to wrapped nano-sheet structure with increasing hydrothermal temperature and time. It is meaningful for specific morphology demand in different fields. Moreover, the prepared materials were used as tentative adsorbents for the removal of bisphenol A (BPA) as a representative of endocrine disruptors. The results showed that the prepared MoS₂ materials with wrapped nano-sheet structure had good adsorption capacity (39.03 mg/g) and fast adsorption rate (0.0053 g/(mg/min). The adsorption process was thermodynamically exothermic and spontaneous. The study indicated that electrostatic interaction is strong and π-π interaction between BPA and the MoS₂ materials play an important role for BPA adsorption.     

Carbon dots/Bi_2WO_6 composite with compensatory photo-electronic effect for overall water photo-splitting at normal pressure

Overall water photo-splitting is a prospective ideal pathway to produce ultra-clean H_2 energy by semiconductors.However,the band structure of many semiconductors cannot satisfy the requirement of H_2 and O_2 production at the same time.Herein,we illustrate that carbon dots(CDs)/Bi_2 WO_6 photocatalyst with compensatory photo-electronic effect has enhanced activity for overall water photo-splitting without any sacrificial agent.In this complex photocatalytic system,the photo-potential provided by CDs makes the CDs/Bi_2 WO6(C-BWO) composite could satisfy the band structure conditions for overall water photo-splitting.The C-BWO composite(3 wt% CDs content) exhibits optimized hydrogen evolution(oxygen evolution) of 0.28 μmol/h(0.12 μmol/h) with an approximate 2:1(H_2:O_2) stoichiometry at normal pressure.We further employed the in-situ transient photovoltage(TPV) technique to study the photoelectron extraction and the interface charge transfer kinetics of this composite catalyst.     

球形表面富锰MnxCo3−xO4−ƞ尖晶石型催化剂选择性催化还原NOx研究

采用共沉淀法制备了高比表面积的Mn_xCo_3−xO₄球形催化剂,研究了NH₃选择性催化还原NO_x性能。Mn-Co金属氧化物具有尖晶石结构,随着Co含量的增加,晶体结构由四方相转变为立方相。高浓度的表面活性氧物种和变价元素的强有效电子转移(Co³⁺ + Mn³⁺ ↔ Co²⁺ + Mn⁴⁺)有利于提高Mn_xCo_3−xO₄ (x = 1.0、1.5、2.0)尖晶型石催化剂的氧化还原能力,催化剂表面的Mn富集作用形成了氧缺陷结构和丰富的表面活性位点,进一步促进SCR脱硝反应,呈现出优异的催化性能。Co_tet(CoMn)_octO₄晶体结构中,Mn离子(Mn³⁺和Mn⁴⁺,以三价锰为主)和部分Co离子被配置到八面体中心,这些物种作为活性位点存在着较强的电子转移交互作用,该构型对促进低温脱硝活性和保护活性位点耐受SO₂毒害具有重要的意义。Mn-Co尖晶石表面的NH₃-SCR脱硝反应过程主要遵循Eley-Rideal反应机理,即吸附态NH₃与气态NO (或NO₂)的反应路径。随着反应温度的增加,反应生成的NH₄NO₃中间体很可能转化为NH₄NO₂物种,进而分解为N₂,提高了催化剂的氮气选择性。     

用以分解氟里昂-12的新型催化剂WO_3/Al_2O_3

氟里昂(CFCs)是破坏大气臭氧层的元凶,是仅次于CO2的第二大类温室气体;此外,它作为一类含氯挥发性有机物,对人体有一定潜在危害.为了禁止氟里昂的生产和使用,1987年签署了“蒙特利尔协定”,至今已有包括中国在内的163个缔约方.然而各国还存有几百万吨氟里昂,为此,探索分解氟里昂的技术已成当务之急.氟里昂能通过多种技术销毁,如:等离子体分解法、UV射线分解法、高能射线分解法、焚烧法、电化学分解法、超临界水法、超声辐照法等,而催化分解是最被看好的方法之一.所谓催化分解,即在催化剂的作用下,氟里昂与水蒸气反应生成CO2、HF和HCl,…     

Copper methanesulfonate-acetic acid as a novel catalytic system for tetrahydropyranylation of alcohols and phenols

A synergistic catalytic effect between copper methanesulfonate and acetic acid in tetrahydropyranylation of alcohols and phenol at room temperature under solvent free condition has been described. Both alcohols (primary, secondary and tertiary) and phenols reacted with 3,4-dihydro-2H-pyran smoothly to afford the corresponding tetrahydropyranyl ethers in good yields.     

停流FIA─协同系数补偿动力学方法双组份的同时测定

用停流光度法研究了Ｈｇ（Ⅱ）和Ａｇ（Ⅰ）对以硫脲为活化剂的Ｆｅ（ＣＮ）－α，α’－联吡啶配体交换反应的协同催化效应，提出了协同系数的概念。在协同系数补偿动力学体系中由于双组份的协同催化效应而引起的对吸光度加合性的偏离，建立了一种新的双组份同时测定方法，此法使双组份同时测定的线性范围显著扩大，且降低了检测限。测定了环境样品中汞和银含量，获得满意结果。     

Mechanism of the Selective Catalytic Reduction of NOx with NH3 over W-Doped Fe/TiO2 Catalyst

The W-doped Fe/TiO2 catalyst prepared by an impregnation method exhibited a good NH3-selective cata- lytic reduction（SCR） activity and N2 selectivity with broad operation temperature window. The interaction between Fe and W could increase the amount of surface chemisorbed oxygen, and thus enhances the low temperature SCR activity by facilitating the fast SCR of 2NH3＋NO＋NO2 →2N2＋3H2O. The NH3-SCR reaction mechanism over the W-Fe/TiO2 was fully investigated via in situ diffuse reflectance infrared Fourier transform spectroscopy（in situ DRIFTS）. In the low temperature range（〈250 ℃）, the reactive surface species were mainly coordinated NH3, ionic NH~ and adsorbed NO2 species, and the SCR mainly followed the Langmuir-Hinshelwood mechanism, during which the adsorbed NO2 species became the important active sites. In the high temperature range（〉250 ℃）, the reactive surface species were mainly NH2, and the SCR mainly followed the Eley-Rideal mechanism, during which the for- mation of NH2NO intermediate species after H-abstraction of NH3 was the rate-determining step.     

松散接触下 Au-Ce强相互作用对 Au/CeO2/3DOM Al2O3催化剂催化柴油炭烟燃烧活性的影响

与汽油发动机相比,柴油发动机具有热效率高、CO2排放低、寿命长、续航距离远和经济性好等优点,可大大缓解能源短缺,降低 CO2排放量.因此,机动车柴油化是当前发展趋势.然而,柴油发动机在使用过程中会排放大量炭烟颗粒物,对人体危害极大.因此,控制炭烟颗粒排放成为环境催化研究的重点之一.
　　炭烟颗粒物催化燃烧反应是典型的固(炭烟颗粒)-固(催化剂)-气(O2)多相催化反应.三维有序大孔氧化物(3DOM)具有大孔径和内部贯通的孔道结构,能有效提高炭烟颗粒与催化活性中心的接触性能.同时,纳米 Au颗粒在大孔氧化物表面的负载可有效提高催化剂本征活性,但纳米 Au颗粒催化剂热稳定性较差. CeO2具有较好的储放氧性能,可与贵金属活性组分发生相互作用,从而提高贵金属纳米颗粒的分散度和稳定性.因此,本文从柴油炭烟颗粒物催化燃烧反应本质出发,设计制备了高炭烟燃烧催化活性的3DOM氧化物担载 Au基催化剂,研究了 Au与 CeO2强相互作用对炭烟燃烧活性的影响.
　　采用胶体晶体模板法制备3DOM Al2O3载体,由微孔膜氨沉淀法制备 CeO2/3DOM Al2O3催化剂,以还原-沉积法制备 Au/3DOM Al2O3和 Au/CeO2/3DOM Al2O3催化剂,并利用扫描电镜、N2物理吸附-脱附、X射线衍射、透射电镜、紫外漫反射光谱、H2程序升温还原和 X射线光电子能谱等手段对催化剂形貌、比表面积、物理化学性质和氧化还原性进行了表征.结果表明,在 CeO2/3DOM Al2O3中, Al3+可进入到氧化铈晶格内,形成 Al-Ce-O固溶体,产生氧空位,这有利于氧物种转移.此外, Au/CeO2/3DOM Al2O3催化剂中 Au和 CeO2之间的强相互作用能增加 Au纳米颗粒表面活性氧物种数量,从而促进柴油炭烟燃烧反应.纳米颗粒 Au的担载使得催化柴油炭烟燃烧的起燃温度明显降低,其中 Au/CeO2/3DOM Al2O3催化剂表现出最高的催化活性,T10,T50和T90分别为273,364和412oC.     

Fabrication of S-scheme hollow TiO2@Bi2MoO6 composite for efficiently photocatalytic CO2 reduction

Herein, an S-scheme hollow TiO₂@Bi₂MoO₆ heterojunction was synthesized for photocatalytic reduction of CO₂ under simulated sunlight. Among all prepared composites, the TiO₂@Bi₂MoO₆ with 20% of TiO₂ exhibited the highest CO yield (183.97 μmol/g within 6 h), which was 4.0 and 2.4 times higher than pristine TiO₂ and Bi₂MoO₆, respectively. The improved photocatalytic activity may be due to the formation of S-scheme heterojunction to promote the separation and transfer of photogenerated charge carriers. Additionally, this hollow structure provided abundant sites in terms of CO₂ adsorption and activation. Meanwhile, the photogenerated charge transfer mechanism of the S-scheme was verified by work function calculations, Electron paramagnetic resonance (EPR) measurements as well as X-ray photoelectron spectroscopy (XPS). This research presents a novel approach to improve photocatalytic reduction of CO₂ via morphology modulation and the fabrication of S-scheme heterojunction.     

柠檬酸辅助水热法制备可见光高效去除甲基橙的Bi2WO6纳米片

以Bi(NO3)3·5H2O和Na2WO3 ·2H2O为原料,以柠檬酸为络合剂,采用辅助水热法制备了Bi2WO6纳米片,运用X射线衍射、扫描电镜、场发射高分辨透射电镜、拉曼光谱、红外光谱和紫外-可见漫反射光谱等手段对样品进行了表征,并考察了该催化剂光催化去除甲基橙反应性能.结果表明,通过调节体系的pH值可制得结晶度良好...     

Cl–改性对Ag/Al2O3催化剂结构及其催化C3H6-SCR和H2/C3H6-SCR反应性能的影响

以烯烃为还原剂的NOx选择性催化还原(HC-SCR)是重要的环境催化反应之一.Ag/Al2O3催化剂(SA)因在HC-SCR反应中表现高活性、高N2选择性及中等H2O和SO2耐受性等优点,而被广泛研究.SA催化剂中存在不同的Ag物种,包括孤立Ag+离子,带部分正电荷Agnδ+团簇和金属态Agn0团簇.文献研究结果表明,SA催化剂中Agnδ+团簇是催化HC-SCR反应的活性Ag物种,而Ag物种类型与Ag的负载量密切相关.因此文献中研究SA催化HC-SCR反应的结构-性能关系主要是通过改变Ag负载量来开展的,最优Ag负载量约为1％～2％.本文以Cl–改性的γ-Al2O3作为载体,采用传统的浸渍法制备了Ag/Al2O3-Cl催化剂(SA-Cl),通过XRD、TEM、H2-TPR、UV-Vis DRS以及XPS对催化剂进行了结构表征,并结合C3H6-SCR和H2/C3H6-SCR活性测试,建立催化剂结构-催化性能关系;同时利用原位傅里叶变换红外光谱(DRIFTS)和在线同步辐射单光子电离质谱(SVUV-PIMS)研究了SA催化HC-SCR的反应机理.结构表征结果表明,在SA催化剂中,Ag负载量的提高主要是增加了Agn0物种,而在SA-Cl催化剂中,Ag负载量的提高主要是增加了Agnδ+物种,因此Cl?改性能促进SA催化剂中Agnδ+物种的形成.活性测试结果表明,在相同Ag负载量下,SA-Cl催化剂表现出比SA催化剂更好的HC-SCR催化性能.Cl?改性对SA催化剂中Ag物种的调控作用和HC-SCR催化性能的促进作用随Ag负载量的增加变得更为明显.原位DRIFTS结果表明,γ-Al2O3载体(Al位点)是NO氧化形成硝酸盐物种的主要活性位点;Agnδ+物种催化丙烯适度氧化主要生成乙酸盐类物种,可以还原表面硝酸盐物种;而Agn0催化丙烯过度氧化主要生成羧酸盐类物种,进而生成CO2,不能还原表面硝酸盐物种.由此可见,Agnδ+是催化HC-SCR反应的活性Ag物种,而Agn0是催化烃类完全氧化反应的活性Ag物种;Cl–改性能有效促进Agnδ+的形成,进而提高HC-SCR催化反应活性.在线SVUV-PIMS结果检测到H2/C3H6-SCR反应中存在气态中间物种丙烯腈(CH2=CHCN).–CN和–NCO物种被认为是HC-SCR反应的关键中间物种,能够直接与气相NO+O2反应生成N2.因此,CH2=CHCN的存在说明HC-SCR反应涉及到气相反应机理.基于SA和SA-Cl催化剂,进一步研究了H2对C3H6-SCR低温活性的促进作用.结果表明,H2的促进作用是通过作用于Agnδ+物种,而不是通过Agn0物种来实现的;H2的引入有利于低温下强吸附硝酸盐物种的脱附或分解以及中间体向–NCO和–CN物种的转化,从而提高HC-SCR低温催化活性.综上,基于Cl–改性的Ag/Al2O3-Cl催化剂,本文成功证实了Agnδ+物种是催化HC-SCR反应的活性Ag物种,并结合原位DRIFTS在线SVUV-PIMS谱分别鉴定了催化反应表面中间物种和气相中间物种.这些结果加深了对SA催化HC-SCR反应构-效关系和反应机理的基础理解.     

Promotional effect of acidic oxide on catalytic activity and N2 selectivity over CeO2 for selective catalytic reduction of NOx by NH3

The CeO₂, CeO₂‐ZrO₂ and CeO₂‐WO₃ catalysts were prepared by hydrothermal method and used to the selective catalytic reduction of NO_x by NH₃. The addition of ZrO₂ or WO₃ into CeO₂ was favorable for pore structure, and then improved the number of active sites. Besides, the introduction of ZrO₂ into CeO₂ could improve the Lewis acid sites while WO₃ could contribute to the generation of Brønsted and Lewis acid sites, which could improve the catalytic performance and N₂ selectivity. The CeO₂‐WO₃ catalyst exhibited optimal catalytic activity with above 90% NO_x conversion performance at 220–425 °C and approximately 100% N₂ selectivity at 150–425 °C.     

Theoretical investigation on the reaction of N2O and CO catalyzed by Fe(C6H6)

The reaction of N₂O with CO, catalyzed by Fe⁺(C₆H₆) and producing N₂ and CO₂, has been investigated at the UB3LYP/6-311+G(d) level. The computation results revealed that the reaction of Fe⁺(C₆H₆), N₂O and CO, is an O-atom abstraction mechanism. For the reaction channels, the geometries and the vibrational frequencies of all species have been calculated and the frequency modes analysis also have been given to elucidate the reaction mechanism. On the basis for geometry optimizations, the thermodynamic data of these reactions channels have been calculated using the statistical theory at 295.15 K and pressure of 0.35 Torr. Using Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant and frequency factors for the these reaction channels also have been given. The results showed that CO and N₂O do not react without catalyst and Fe⁺(C₆H₆) can excellently mediate the reaction of N₂O and CO.     

La2-xSrxFeNiO6催化剂的制备及其催化甲烷燃烧性能研究

以柠檬酸为络合剂,通过溶胶-凝胶法制备La_(2-x)Sr_xFeNiO_6(x=0、0.5、1、1.5、2)系列催化剂,考察A位离子Sr掺杂对La_2FeNiO_6催化甲烷燃烧性能的影响。通过X射线衍射、程序升温还原、比表面积测定和热重分析等技术进行物理性能表征。结果表明,Sr的掺杂可以改变双钙钛矿晶体结构,提高了晶格氧的数量,改善催化活性。当x=1时,LaSrFeNiO_6催化甲烷燃烧活性最好,其比表面积为7.9m~2·g~(-1),T10%(起燃温度)为370℃,T90%(完全转化温度)为535℃;同时,反应活化能最小,为78.8k J·mol~(-1)。     

过渡金属对选择性催化还原脱硝CeO_2@TiO_2催化剂低温活性的促进作用

采用过渡金属M(M=Mn、Co、Fe和Cu)掺杂改性自发沉积策略制备的非晶态CeO_2@TiO_2催化剂,考察M-CeO_2@TiO_2选择性催化还原NO_x的低温活性,并通过XRD、TEM、N2吸附-脱附、H2-TPR、NH3-TPD及in-situ FT-IR等表征手段研究M-CeO_2@TiO_2的结构、表面性质以及低温NH3-SCR反应过程。结果表明,M-CeO_2@TiO_2具有更优异的低温氧化还原能力以及更多的表面酸量,且Cu掺杂对CeO_2@TiO_2选择性催化还原NO_x低温活性具有最为显著的促进作用。Cu-CeO_2@TiO_2催化剂在低温NH3-SCR反应过程中同时存在E-R机理和L-H机理,但是由于"快速SCR"使得L-H机理反应起关键作用。     

Preparation of magnetic separable CoFe2O4/PAC composite and the adsorption of bisphenol A from aqueous solution

CoFe₂O₄/PAC composite adsorbent has been prepared via an immersing-calcination process, using ethylene diamine tetraacetic acid (EDTA) and citric acid (CIT) ligands containing sol as the CoFe₂O₄ precursor. The microstructure characterization and magnetic property of as-prepared sample were performed by means of XRD and VSM measurements. The adsorption kinetics, isotherms and thermodynamic process toward Bisphenol A molecules (BPA, which is considered as one of the typical endocrine disrupting chemicals) occurred on as-prepared magnetic adsorbent which were investigated by the pseudo-second order kinetic/intraparticle models, the Langmuir/Freundlich adsorption isothermal models and basic chemical thermodynamics principles, respectively.     

A simple PdCl2/O2/DMF catalytic system for highly regioselective cyclotrimerization of olefins with electron-withdrawing groups

A highly regioselective cyclotrimerization of olefins with electron-withdrawing groups in a PdCl₂/O₂/DMF catalytic system is disclosed, and a possible mechanism has also been proposed, which reveals the PdCl₂-catalyzed cyclotrimerization of olefins with electron-withdrawing groups goes through a quite different pathway from that of alkynes.     

Fabrication and Characterization of Tailored TiO_2 and WO_3/MWCNT Composites for Methylene Blue Decomposition

A sol-gel method was used to prepare WO3/MWCNT-TiO2 composites.Their photocatalytic activities were evaluated by the degradation of methylene blue (MB) solution under UV light.The catalysts were characterized by X-ray diffraction,specific surface area measurement,energy-dispersive X-ray analysis,transmission and scanning electron microscopy.Aqueous MB solutions of 100 ml were photodegraded by a small amount of the WO3/MWCNT-TiO2 composite under UV light irradiation.The photocatalytic data showed that the WO...     

Copper nitrate/acetic acid as an efficient synergistic catalytic system for the chemoselective tetrahydropyranylation of alcohols and phenols

Abstract  Tetrahydropyranylation of alcohols and phenols was accomplished successfully using copper nitrate and acetic acid as a synergistic catalyst at room temperature under solvent-free condition. Compared with other synergistic catalytic systems, copper nitrate/acetic acid proved to be the most efficient. Both alcohols (primary, secondary, tertiary, benzylic, cyclic, allyl, cinnamyl, and furyl) and phenols reacted smoothly in high yields. Graphical abstract