气相色谱法测定塑料食品包装袋中甲苯残留

提出一种食品塑料包装袋中残留甲苯的气相色谱分析方法。     

复合改性对分子筛性能的影响

对ZSM-5烷基选择性的研究已有较多报道,但在提高对位选择性的同时,往往导致活性的损失,产生"反向效应",本文试图用复合改性来探讨解决这种效应的可能性。     

Theoretical study on the molecular structures of toluene,para‐fluorotoluene,para‐chlorotoluene,and 4‐methylpyridine and their sixfold internal rotational barriers

Two kinds of sixfold internal rotational configurations of toluene, para‐fluorotoluene, para‐chlorotoluene, and 4‐methylpyridine were calculated using Hartree–Fock (HF), second‐order Møller–Plesset (MP2), and Beck's three parameter hybrid functional using the LYP correlation functional (B3LYP) theory methods with various high‐level basis sets. Structures and energies were compared for different configurations. Calculations indicate that the orthogonal configuration has a local minimum while the planar configuration is a transition structure. Furthermore, geometries of the orthogonal and the planar configurations are quite similar, except for a methyl CH bond. Sixfold internal rotational barriers were calculated from the energy difference of two different configurations. For the calculated results, HF methods underestimated the rotational barriers, but MP2 calculations overestimated them. However, the density functional theory (DFT) method is a reliable method since the calculated internal rotational barriers are similar to the experimental ones. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 772–778, 2000     

Manganese dioxide and N,N′,N″‐trihydroxyisocyanuric acid: a novel and recyclable catalytic system for aerobic oxidation of toluene derivatives in PEG‐1000‐based dicationic acidic ionic liquid

N,N′,N″‐trihydroxyisocyanuric acid (THICA) with MnO₂ promotes the aerobic oxidation of toluene derivatives to corresponding acids in PEG‐1000‐based dicationic acidic ionic liquid (PEG₁₀₀₀–DAIL). It is demonstrated that THICA/MnO₂ is very active and selective and several toluene derivatives are efficiently oxidized to corresponding acids under mild conditions. Both the catalyst and PEG₁₀₀₀–DAIL can be reused after simple separation. A plausible mechanism is also proposed based on the experimental observations. Copyright © 2015 John Wiley & Sons, Ltd.     

Transition metal‐catalyzed oxidative transformations of methylarenes

Oxidation is one of the fundamental transformations in organic synthesis. The selective oxidation of inert substrates is interesting and important. In this review, the transition metal‐catalyzed oxidation of methylarenes is discussed. Benzaldehyde, benzoic acid, benzyl alcohol, etc., were produced as the target products. Copyright © 2014 John Wiley & Sons, Ltd.     

Silica Monolith for the Removal of Pollutants from Gas and Aqueous Phases

This study focused on the application of mesoporous silica monoliths for the removal of organic pollutants. The physico-chemical textural and surface properties of the monoliths were investigated. The homogeneity of the textural properties along the entire length of the monoliths was assessed, as well as the reproducibility of the synthesis method. The adsorption properties of the monoliths for gaseous toluene, as a model of Volatile Organic Compounds (VOCs), were evaluated and compared to those of a reference meso-structured silica powder (MCM-41) of commercial origin. Silica monoliths adsorbed comparable amounts of toluene with respect to MCM-41, with better performances at low pressure. Finally, considering their potential application in water phase, the adsorption properties of monoliths toward Rhodamine B, selected as a model molecule of water soluble pollutants, were studied together with their stability in water. After 24 h of contact, the silica monoliths were able to adsorb up to the 70% of 1.5 × 10⁻² mM Rhodamine B in water solution.     

多孔超薄g-C3N4纳米片负载Pt复合材料的制备及其光催化性能

以三聚氰胺为前驱体,通过热氧化刻蚀法制备多孔超薄g-C₃N₄纳米片（CNHS）,将其与氯铂酸钾溶液混合后采用原位光化学还原法成功制备了CNHS负载Pt光催化剂（Pt-CNHS）。使用粉末X射线衍射、场发射扫描电子显微镜、X射线光电子能谱、透射电子显微镜、紫外可见漫反射光谱和N₂吸附-脱附测试等技术对所制备样品的结构、形貌、光吸收特性、光电化学性能和比表面积等进行系统分析。并以气相甲苯为目标降解物,研究其光催化性能。结果表明,相对于体相g-C₃N₄（CNB）和CNHS,Pt的引入可以有效增强催化剂对可见光的吸收能力、响应范围及载流子分离效率。与纯g-C₃N₄和CNHS相比,Pt-CNHS在紫外和可见光照射下均表现出更高的光催化降解气相甲苯的活性。此外,也对Pt-CNHS光催化剂在可见光照射下降解气相甲苯的反应历程做了初步研究。     

气相色谱测定海绵文胸中甲苯二异氰酸酯残留

建立了气相色谱-内标法测定海绵文胸中的甲苯二异氰酸酯(TDI)残留量。样品经均质处理后,用经脱水处理的乙酸乙酯超声萃取25 min,过滤净化后,采用Agilent DB-624色谱柱(30 m×0.32 mm×1.8μm)分析,柱温采用程序升温,检测器为氢火焰离子化检测器,检测器温度为250℃,进样口温度为180℃,载气为氮气。结果表明:甲苯二异氰酸酯在10~200 mg/L范围内峰面积与质量浓度线性关系良好,线性相关系数(R~2)为0.998 9,平均回收率为80.5%~91.6%,RSD不大于7.9%(n=6),方法的检出限和定量限分别为10 mg/kg和100 mg/kg。在优化条件下,对生产企业、实体店和电商平台采购的100批次样品进行了检测。该方法操作简单、耗时短、灵敏度高、稳定性好,应用于日常检测可大大降低检测成本,缩短检测周期,具有实际应用价值。     

硬模板法制备铈基复合氧化物及其对甲苯燃烧的催化性能

采用硬模板法制得CeM-HT(M=Cu、Mn、Fe和Co)复合氧化物催化剂,借助XRD、BET、O₂-TPD和H₂-TPR研究了催化剂的物理化学性质,通过甲苯催化燃烧探针反应评价了催化剂的催化性能。结果表明,CuO、MnO_x、FeO_x和Co₃O₄能溶入CeO₂晶格形成Ce-O-Cu、Ce-O-Mn、Ce-O-Fe和Ce-O-Co固溶体,Cu和Mn离子的溶入导致CeO₂晶格发生了较大程度的晶格畸变,Fe和Co离子对CeO₂晶格的影响较小,且在CeCo-HT氧化物催化剂中还存在微量晶相Co₃O₄。所制得的CeM-HT氧化物催化剂表现出了优越的甲苯催化燃烧性能,在反应温度为300、270、260和230 ℃时,CeFe-HT、CeCo-HT、CeMn-HT和CeCu-HT氧化物催化剂上甲苯的催化燃烧转化率分别达93.7%、95.0%、96.5%和95.0%以上。Ce基复合氧化物催化剂的甲苯催化燃烧活性顺序与其氧脱附性能、储氧性能和可还原性能具有正相关性,遵从顺序为CeCu-HT > CeMn-HT > CeCo-HT > CeFe-HT。     

Effect of ZSM-5 zeolite morphology on the catalytic performance of the alkylation of toluene with methanol

A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the addition of NaCl and crystal seed. X-ray diffraction(XRD),scanning electron microscope(SEM), X-ray fluorescence(XRF) and temperature-programmed desorption of ammonia(NH3-TPD) were used to characterize these samples. The samples were tested with toluene methylation reaction. The modified sample composed of spherical particles with 3 μm crystal particles on the surface had a para-xylene selectivity of 95% and maintained 79% of the initial conversion after running the reaction for 50 h. This modified sample showed the best stability among the tested three modified samples.