xAu/α-MnO2催化剂的结构及催化氧化VOCs气体性能

以NaOH为沉淀剂,采用沉积-沉淀法制备了α-MnO2负载Au催化剂xAu/α-MnO2(x=1.0%～7.0%,质量分数),利用X射线衍射(XRD)、N2吸附-脱附、H2程序升温还原(H2-TPR)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等技术对所得样品进行了表征,并对其催化氧化挥发性有机化合物(VOCs,苯和甲苯)的性能进行了研究.XRD结果表明,负载Au对α-MnO2载体结构影响不大,但对其晶粒大小和比表面积略有影响.随着Au含量的增加,α-MnO2结晶度增强,颗粒增大,Au粒径明显增大.XPS结果表明,随着Au负载量的增加,xAu/α-MnO2的晶格氧(O2-),Mn4+和Au3+的浓度增加.H2-TPR结果表明,由于贵金属的溢氢作用,Au明显提升了xAu/α-MnO2的还原能力,其中3%Au/α-MnO2的还原能力最强.负载Au明显影响xAu/α-MnO2的催化性能,xAu/α-MnO2的催化性能与Au的颗粒分散性、低温还原性能及表面氧物种密切相关,其中3%Au/α-MnO2显示出最佳活性,其催化氧化苯和甲苯的T100分别为280和250℃.     

Extraction and Dispersion of Large Gold Nanoparticles in Nonpolar Solvents

Gold nanoparticles up to 70 nm in diameter could be extracted from aqueous solutions into nonpolar organic solvents by tetrathiolated resorcinarenes 1 and 2. The resorcinarene-coated nanoparticles formed stable dispersions in toluene and chloroform and could be passed through a crosslinked polystyrene column without significant degradation, but exhibited variable resistance to alkanethiol-induced flocculation. Gold nanoparticles encapsulated by resorcinarene 2 were found to be exceptionally stable even in the presence of propanethiol and dodecanethiol, with an approximate dispersion half-life of one month at room temperature.     

Mass Spectrometry Study of OH-initiated Photooxidation of Toluene

The composition of products formed from photooxidation of the aromatic hydrocarbon toluene was investigated. The OH-initiated photooxidation experiments were conducted by irradiating toluene/CH₃ONO/NO/air mixtures in a smog chamber, the gaseous products were detected under the supersonic beam conditions by utilizing vacuum ultraviolet pho-toionization mass spectrometer using synchrotron radiation in real-time. And an aerosol time-of-flight mass spectrometer was used to provide on-line measurements of the individ-ual secondary organic aerosol particle resulting from irradiating toluene. The experimen-tal results demonstrated that there were some differences between the gaseous products and that of particle-phase, the products of glyoxal, 2-hydroxyl-3-oxo-butanal, nitrotoluene, and methyl-nitrophenol only existed in the particle-phase. However, furane, methylglyoxal, 2-methylfurane, benzaldehyde, cresol, and benzoic acid were the predominant photooxidation products in both the gas phase and particle phase.     

Molecular Dynamics Simulation: Influence of External Electric Field on Bubble Interface in Air Flotation Process

Molecular dynamics(MD) simulation was performed to investigate the influence of external electric field on the vapour-liquid interface of the bubble during the process of toluene separation by air flotation. The physicochemical properties of vapour-liquid interface, surface tension, probability of a hydrogen bonding near the vapour-liquid interface and the viscosity of liquid phase caused by external electric field were analyzed. The results show that the angle between the water molecule dipole moment and the normal z axis in the vapour phase changes smaller when the external electric field is applied. The surface tension and the probability of hydrogen bonding near the vapour-liquid interface increase with the increase of electric field strength. And the viscosity also increases under an external electric field. The results confirm that the external electric field has a positive effect on the performance of bubbles in air flotation, which may provide useful guidance for the combination of electric field and air flotation technology.     

Preparation of 3D micro/nanostructured CeO2: Influence of organic/inorganic acids

CeO₂ is an important porous material with a wide range of applications in the abatement of volatile organic compounds (VOCs). In this paper, we prepared a series of novel three-dimensional (3D) micro/nanostructured CeO₂ materials via a solvothermal method. Organic acid-assisted synthesis and inorganic acid post-treatment were used to adjust the CeO₂ microstructures. The size of the 3D micro/nanostructures could be controlled in the range from 180 nm to 1.5 μm and the surface morphology changed from rough to smooth with the use of different organic acids. The CeO₂ synthesized with acetic acid featured a hierarchical porosity and showed good performance for toluene catalytic combustion: a T₅₀ of 187 °C and a T₉₀ of 195 °C. Moreover, the crystallite size, textural properties, and surface chemical states could be tuned by inorganic acid modification. After treatment with HNO₃, the modified CeO₂ materials exhibited improved catalytic activity, with a T₅₀ of ∼175 °C and a T₉₀ of ∼187 °C. We concluded that the toluene combustion activity is related to the porosity and the amount of surface active oxygen of the CeO₂. Both these features can be tuned by the co-work of organic and inorganic acids.     

Steam reforming of toluene as model of tar compound over Mo catalysts derived from hydrotalcites

This study evaluated the catalytic activity of Mo catalysts derived from hydrotalcite-like compounds for steam reforming of toluene as a model compound for tar. The catalysts with 1.5, 3 and 4.5 Mo loadings (wt%), denoted as Mo_1.5MgAl, Mo₃MgAl and Mo_4.5MgAl respectively, were prepared by coprecipitation and characterized by BET, XRD, SEM, TEM, FT-IR and UV–VIS. The results showed that toluene conversion increased with increasing molybdenum content. The hydrogen amount depended on two factors: the presence of molybdate species on the surface and the presence of aluminum cations in tetrahedral sites (Mo₃MgAl), with molybdenum influence being more pronounced. The H₂/CO ratio decreased at increasing temperature while, the H₂/CO₂ ratio increased proportionally with temperature. Mo_1.5MgAl catalyst was more selective for CO₂ and H₂, while, Mo₃MgAl and Mo_4.5MgAl were more selective for CO and H₂.     

Effect of phosphorus on the performance of IM-5 for the alkylation of toluene with methanol into p-xylene

IM-5 zeolite was modified with different amounts of phosphorus species. The effect of the introduction of phosphorus into IM-5 zeolite (P-IM-5) was evaluated on the alkylation of toluene with methanol. The samples were characterized by X-ray diffraction, scanning electron microscopy, N₂ physical adsorption, ³¹P magic angle spinning nuclear magnetic resonance, inductively coupled plasma optical emission spectroscopy, temperature-programmed desorption of ammonia, Fourier transform infrared spectra of pyridine, 2,6-di-tert-butyl-pyridine and 2,6-lutidine adsorption, and thermogravimetric analysis after reaction. The results showed that the zeolite structure was not changed, but the total amount of acid sites decreased with increasing phosphorus loading. The phosphorus-modified IM-5 samples exhibited much higher stability on the alkylation of toluene with methanol than the parent zeolite and the optimal phosphorus amount added was 0.5 wt %. The excellent catalytic performance could be ascribed to the low ratio of B/L acid sites upon phosphorus modification, which suppressed coke formation.     

Ru/氧化物催化剂在甲苯部分加氢反应中的载体效应

采用浸渍-化学还原法制备了一系列负载型Ru催化剂,考察了一些常见的氧化物载体（SiO₂、m-ZrO₂、t-ZrO₂、γ-Al₂O₃和P25）对甲苯部分加氢制甲基环己烯催化性能的影响。采用N₂物理吸附、X射线粉末衍射（XRD）、透射电子显微镜（TEM）和X射线光电子能谱（XPS）等手段对催化剂进行了系统的表征。研究表明,载体通过影响Ru的粒径,进而影响甲苯部分加氢催化性能。当Ru纳米粒子的粒径由2.6 nm增大到17.3 nm时,甲苯的转换频率（TOF）以及甲基环己烯初始选择性（S₀）先增加,然后降低,呈火山型变化趋势,二者的最大值均在Ru粒径为3.0 nm时出现。在催化性能最优的Ru/P25催化剂上,进一步考察了修饰剂的种类和浓度、反应温度、反应压力等条件的影响。当反应温度为423 K、H₂压力为5.0 MPa,以0.25 g七水合硫酸锌为修饰剂时,Ru/P25催化剂上的初始加氢速率（r₀）为26 mmol·g^-1·min^-1,S₀为57%,甲基环己烯得率可达36%。     

甲苯光电离解离理论研究

The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods.The geometries and frequencies of the reactants,transition states and products have been performed at B3LYP/6-311++G (d,p) level,and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level.The ionization energies of toluene and the appearance energies for major fragment ions,C₇H₇⁺,C₆H₅⁺,C₅H₆⁺,C₅H₅⁺,are determined to be 8.90,11.15 or 11.03,12.72,13.69,16.28 eV,respectively,which are all in good agreement with published experimental data.With the help of available published experimental data and theoretical results,four dissociative photoionization channels have been proposed:C₇H₇⁺+H,C₆H₅⁺+CH₃,C₅H₆⁺+C₂H₂,C₅H₅⁺+C₂H₂+H.Transition structures and intermediates for those isomerization processes are determined in this work.Especially,the structures of C₅H₆⁺ and C₅H₅⁺ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.     

甲苯异构体在石墨电极上的直接电氧化

通过循环伏安法、电化学原位红外光谱和恒电位电解法研究了甲苯异构体在0.05 mol/L硫酸体系中的直接电氧化行为. 结果表明, 对甲氧基甲苯、对甲基甲苯、对氯甲苯和对叔丁基甲苯4种含不同取代基的甲苯异构体具有相似的电氧化行为, 均在1710 cm^-1左右出现向下的羰基伸缩振动峰(υ_C=O), 在1130 cm^-1左右出现向上的甲基消耗峰. 通过气相色谱-质谱法(GC-MS)对恒电位电解产物进行检测, 进一步证实了在石墨电极、硫酸水溶液体系中甲苯异构体直接电氧化主要产物为相应的芳香醛, 40 ℃时, 对甲氧基苯甲醛的产率为70.9%.