Catalytic Oxidation of Xylene in Air using TiO<Subscript>2 </Subscript>under Electron Beam Irradiation

The oxidation of xylene and its irradiation byproducts in air using TiO₂ was studied under electron beam (EB) irradiation for the purification of ventilation gases emitted from paint factories. EB irradiation experiments were mainly performed under two different conditions: a TiO₂ pellet layer was placed in an irradiation or a non-irradiation space. The results revealed that xylene was decomposed and CO was formed in the gas phase of the irradiation space irrespective of the presence of TiO₂ pellets, while CO₂ was produced in the gas phase of the irradiation space and on the surface of TiO₂ pellets. The total CO₂ concentration increased when the pellet layer was in the non-irradiation space. On the other hand, the concentration of CO₂ produced on the surface of the TiO₂ pellets in the irradiation space was higher than that in a non-irradiation space.     

A theoretical study of the interactions between N,N-dimethylformamide and xylenes

The ab initio and density functional (DFT) methods were performed on binary systems of N,N-dimethylformamide (DMF) with xylenes (o-, or m-, or p-xylene), and seven stable configurations were obtained with no imaginary frequencies. To obtain the interaction energies of these complexes, single-point energy calculations with basis set superposition error (BSSE) correction were carried out at B3LYP/6-31G* and MP2/6-31G* levels. The structures, Chelpg (charges from electrostatic potentials using a grid-based method) charge distribution and bond characteristics of the mentioned complexes were calculated. The results indicated the presence of double C–H···O hydrogen bonds between DMF and xylenes in these complexes and the interaction energies of hydrogen bonding between DMF and xylene systems decreased in the following sequence: DMF–o-xylene: a1 > DMF–m-xylene: b1 > DMF–p-xylene: c1.     

负载型La0.8Sr0.2CoO3燃烧催化剂的载体效应

负载型Ｌａ０．８Ｓｒ０．２ＣｏＯ３／β－Ａ）催化剂,由于钴离子在不太高的温度下易和载体γ－ＡＩ２Ｏ３作用形成ＣｏＡｌ２Ｏ４尖晶石或在尖晶石,因而不能有效地成为ＣＯ、ＨＣ化合物完全氧化的催化剂,采用ＸＲＤ、ＢＥＴ、ＤＴＡ、ＴＧ和二甲苯完全氧化催化活性测试等手段,研究了ＣｏＡｌ２Ｏ４的形成过程,可以认为这是一个放热、释氧而失重的过程,并伴有晶胞的稍微增大,若在γ－ＡＩ２Ｏ３表面涂数一层以ＭｇＡｌ２Ｏ４     

印刷废液中苯、甲苯和二甲苯的测定

以乙酸乙酯对印刷废液进行预处理,并用GC测定处理后样品溶液中苯、甲苯、和二甲苯.方法加标回收率为95.72%-102.66%,6次测定的RSD(n=6)小于3.29%.方法操作方便,分析速度快,结果准确.     

Selective vapor‐phase oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H3PW12O40@TiO2 using molecular oxygen as a green oxidant

The oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H₃PW₁₂O₄₀@TiO₂ was investigated. The experimental results demonstrated that the prepared catalyst effectively catalyzed the oxidation of o‐xylene to phthalic anhydride. Also, the synergistic effect between three metals plays vital roles in this reaction. From a green chemistry point of view, this method is environmentally friendly due to carrying out the oxidation in a fixed‐bed reactor under solvent‐free condition and using molecular oxygen as a green and cheap oxidizing agent. The resulting solid catalysts were characterized by FT‐IR, XRD, XPS, ICP‐OES, FESEM, TEM, EDX, DR‐UV spectroscopy, BET and thermogravimetric analysis. The oxidation of o‐xylene yields four products: o‐tolualdehyde, phthaldialdehyde, phthalide and finally phthalic anhydride as the main product. The reaction conditions for oxidation of o‐xylene were optimized by varying the temperature, weight hourly space velocity and oxygen flow rate (contact time). The optimum weight percentage of phosphotungstic acid (HPW) and Co/Mn for phthalic anhydride production were 15 wt % and 2 wt%, respectively. The best Co/Mn ratio was found to be 10/1. Oxygen flow rate was very important on the phthalic anhydride formation. The optimum conditions for oxidation of o‐xylene were T = 370 °C, WHSV = 0.5 h^?1 and oxygen flow rate = 10 mL min^?1. Under optimized conditions, a maximum of 88.2% conversion and 75.5% selectivity to phthalic anhydride was achieved with the fresh catalyst. Moreover, reusability of the catalyst was studied and catalytic activity remained unchanged after at least five cycles.     

二甲苯兰FF-溴化十六烷基三甲基铵-核酸共振光散射光谱研究及分析应用

在pH9.90的Tris-HCl缓冲溶液中,阴离子染料二甲苯兰FF(XCFF)对阳离子表面活性剂溴化十六烷基三甲基铵(CTMAB)与核酸(fsDNA、ctDNA、yRNA)的共振光散射光谱有协同增强作用。考察了影响因素,在优化条件下研究了共振光散射强度与核酸浓度之间的关系,对于fsDNA、ctDNA、yRNA的线性范围分别为0.05—3.0mg/L、0.05—6.0mg/L、0.5—2.0mg/L,检出限分别为24.1、18.4、57.0μg/L。据此建立了一种测定核酸的新方法。     

近红外差谱法选择信息区提高同分异构体预测模型准确度

以短波近红外光谱法定量检测了二甲苯三种同分异构体混合溶液中各自的体积相对含量。分别采用全光谱、截取具有高相关系数的波段和差谱法选择光谱差异大的波段三种不同的建模方式建立偏最小二乘回归 (Partial L east- Squares Regression)预测模型并对被预测样品进行了相互验证 (Cross Validation)。实验表明 ,采用差谱法选择光谱差异大的波段建立的预测模型显著地克服了同分异构体光谱之间的相似性 ,其预测准确度优于前两者。     

CF-2沸石的表面酸性及催化性能

CF-2是一种新型的高硅沸石。1981年我们实验室首先在二乙醇胺-甘油-Na₂O-SiO₂-Al₂O₃-H₂O体系中制备成功^[1],以后才见到关于Theta-1^[2],ISI-1^[3],KZ-2^[4],NO-10^[5]和ZSM-22^[6]沸石的报道。     

Ab initio quantum chemical study on the zeolite catalyzed transformations of para-xylene

Unimolecular 1,2-methyl shift reaction and disproportionation of para-xylene is investigated by means of ab initio quantum chemical calculations. Isolated gas-phase models are used to estimate the optimum volume of the reaction complex. Space filling of the computed models is examined in zeolite Y, Beta and ZSM-5. It is suggested that the shape selectivity effect of zeolite molecular sieves on the disporportionation reaction can be associated with the steric conditions of the intrinsic rearrangement of the reaction complex in the course of the chemical transformation.     

Headspace-mass spectrometry determination of benzene, toluene and the mixture of ethylbenzene and xylene isomers in soil samples using chemometrics

A simple and fast method has been developed for the determination of benzene, toluene and the mixture of ethylbenzene and xylene isomers (BTEX) in soils. Samples were introduced in 10 mL standard glass vials of a headspace (HS) autosampler together with 150 μL of 2,6,10,14-tetramethylpentadecane, heated at 90 °C for 10 min and introduced in the mass spectrometer by using a transfer line heated at 250 °C as interface. The volatile fraction of samples was directly introduced into the source of the mass spectrometer which was scanned from m/z 75 to 110. A partial least squares (PLS) multivariate calibration approach based on a classical 3³ calibration model was build with mixtures of benzene, toluene and o-xylene in 2,6,10,14-tetramethylpentadecane for BTEX determination. Results obtained for BTEX analysis by HS-MS in different types of soil samples were comparables to those obtained by the reference HS-GC-MS procedure. So, the developed procedure allowed a fast identification and prediction of BTEX present in the samples without a prior chromatographic separation.