三维有序介孔铈钴铜催化剂的制备及其降解邻二甲苯的机制

以PMMA为模板,通过聚乙二醇(PEG400)和柠檬酸辅助的溶胶凝胶法制备三维有序介孔铈钴铜(3DOM 3C)催化剂,应用BET、SEM、XRD和XPS等对不同煅烧温度的3DOM 3C催化剂进行表征分析,研究了催化剂活性及其影响因素,并利用FT-IR和GC-MS对降解产物进行分析,推测出催化降解邻二甲苯的机理.结果表明,煅烧温度500℃时制备的3DOM 3C催化剂表面具有三维介孔结构,且分散均匀,表面的晶体氧化物最少,存在大量的Cu~(2+)、Ce~(3+)和表面氧,催化剂表面存在更多的固溶体、表面活性位点和氧空位,有利于提高催化活性.在邻二甲苯初始浓度600 ppm、空速16000 h~(-1)、50%O_2条件下,煅烧温度500℃时制备的3DOM 3C催化效果最佳,在260℃时,3DOM 3C催化剂对邻二甲苯的转化率达98%,T_(90)为250℃. 3DOM 3C对邻二甲苯的转化率随着初始浓度、空速和相对湿度的升高而呈下降趋势,随着O_2含量的增加而增加.气流中混入150 ppm的乙酸乙酯能够提高邻二甲苯的转化率,提高其低温催化性能.邻二甲苯催化反应后催化剂表面的O—H、■、C—H和金属—氧键都相应的减少,降解中间产物主要有邻甲基苯甲醛和邻甲基苯甲酸.邻二甲苯降解反应涉及Mars Van Krevelen机理(MVK),先被氧化成邻甲基苯甲醛,再进一步氧化成邻甲基苯甲酸,最终生成CO_2和H_2O.     

上海市文教区大气中苯系物冬季污染特征

2004年冬天对上海市文教区大气中的苯系物(BTEX-苯,甲苯,乙苯和二甲苯)浓度进行了监测.结果表明,上海市文教区冬季苯、甲苯、乙苯、对问二甲苯、邻二甲苯的平均浓度分别为13.23 μg/m3,43.66 μ g/m3,13.50μg/m3,16.49 μ g/m3,5.52μg/m3,高于国内外相似功能区的苯系物浓度,与国外大城市交通干道附近的浓度相近.所测苯系物中,甲苯的含量最高,达47.3%.白天苯系物浓度高于夜间.甲苯、乙苯、二甲苯相互间具有较好的相关性,但与苯的相关性不显著,说明苯的来源不同与其他苯系物.     

邻二甲苯汇露 火灾员工应急卡（九）

适用对象：当班操作员、控制室人员、相关职能部门 危险目标：原科罐区一、拱顶罐区一、苯酐氧化区 事故预测：储罐阀门泄露、储罐发生火灾爆炸 健康危害：有低毒危害、高温分解产生毒气 应急常识：掌握风向观察风向标（旗）,注意住上风向撤离。     

低温等离子体协同锰基催化剂降解甲苯、邻二甲苯的实验研究

VOCs的化学成分复杂,对于人体健康和生态环境产生潜在威胁。文章选取了甲苯和邻二甲苯两 种典型的苯系物VOCs,制备5种Cu-Mn/γ-Al2O3系列催化剂并进行XRD、BET和XPS表征。将催化剂置于DBD反应器的放电区域来降解苯系物,探寻其降解效果和副产物生成情况。实验结果表明,Cu掺杂的MnO2催化 剂的引入显著提高了VOCs去除率和CO2选择性。其中,等离子体催化系统中催化剂Cu0.15Mn的性能最佳,甲苯和邻二甲苯的去除率可达100％,CO2的选择性为92.73％,同时能抑制副产物O3和NO2的产生。催化剂的表征 结果表明,Cu-Mn固溶体中Cu和Mn的协同作用可以提高表面活性氧的量和还原性,从而提高催化性能。     

Effect of pretreatment on Pd/Al2O3 catalyst for catalytic oxidation of o-xylene at low temperature

The effect of pretreatment on Pd/Al₂O₃ catalysts for the catalytic oxidation of o-xylene at low temperature was studied by changing the pretreatment and testing conditions. The fresh and pretreated Pd/Al₂O₃ catalysts were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The results showed that the pretreatment dramatically changed the Pd/PdO ratio and then significantly affected the Pd/Al₂O₃ activity; while the pretreatment had not much influence on Pd particle size. The Pd/Al₂O₃ pre-reduced at 300℃/400℃, which has fully reduced Pd species, showed the highest activity; while the fresh Pd/Al₂O₃, which has fully oxidized Pd species, presented the worst performance, indicating the Pd chemical state plays an important role in the catalytic activity for the o-xylene oxidation. It is concluded that metallic Pd is the active species on the Pd/Al₂O₃ catalyst for the catalytic oxidation of o-xylene at low temperature.     

基于电磁场模拟微波对土壤苯系污染物的脱附研究

微波热脱附土壤中的有机污染物凭借高效、清洁等优点受到广泛关注。近年来,多数微波土壤热脱附研究装置均由家用微波炉改造而来,无法满足微波热脱附实际应用所需的高功率、高精度温度控制等条件。因此,选用苯系物中的邻二甲苯作为目标污染物,以自配污染土壤为样品,采用自制微波热脱附装置为平台进行实验,针对微波功率、微波加热时长、土壤含水率等工艺条件进行单因素影响实验。同时,构建微波加热土壤模型,设置相同条件,并得到相符的结果。并利用该模型推测其他单因素影响实验的假设。实验与模拟结果表明：微波对土壤热脱附的最佳功率为1600 W,热脱附时间为27 min,含水率为17%,推测样品放置于临近加热腔中心位置时对邻二甲苯去除率最佳。     

苯酐工程中的环境风险评价研究

以苯酐工程的环境风险评价为范例，探索通过工程风险特征分析，参照ＧＢ１３５４８－９２安全评价通则进行工程的安全评价，以确实工程的火灾，爆炸毒性危险等级。同时，通过车内外风险事故分析确定了风险事故的隐患源及事故污染源，并按世界银行的Ｐａｓｑｕｉｌｌ模式进行了风险事故的预测。在此基础上提出了相应的对策。     

In situ adsorption-catalysis system for the removal of o-xylene over an activated carbon supported Pd catalyst

An activated carbon (AC) supported Pd catalyst was used to develop a highly efficient in situ adsorption-catalysis system for the removal of low concentrations of o-xylene. In this study, three kinds of Pd/AC catalysts were prepared and tested to investigate the synergistic efficiency between adsorption and catalysis for o-xylene removal. The Pd/AC catalyst was first used as an adsorbent to concentrate dilute o-xylene at low temperature. After saturated adsorption, the adsorbed o-xylene was oxidized to CO2 and H2O by raising the temperature of the catalyst bed. The results showed that more than 99% of the adsorbed o-xylene was completely oxidized to CO2 over a 5% Pd/AC catalyst at 140℃. Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), temperature-programmed desorption (TPD), and temperature-programmed oxidation (TPO) were applied to investigate the physical properties of o-xylene adsorption-desorption and the in situ adsorption-catalysis activity of the AC support and Pd/AC catalyst. A synergistic relationship between the AC support and the active Pd species for the removal of low concentrations of o-xylene was established.     

Benzene, toluene and xylenes levels in new and used vehicles of the same model

The aim of this work was to determine the level of benzene, toluene, o-xylene and m, p-xylene （BTX） in air samples collected from the cabins of new and used vehicles of the same model. Ten new vehicles were examined in order to check interior emission from materials used to equip the passenger compartment. In order to compare and define the impact of exhaust gases, air samples were also collected from two used cars, at different mileages （up to 20,000 kin）. All vehicles tested were of the same type. Samples were collected onto Carbograph 1TD sorbent, thermally desorbed and examined with the use of gas chromatography with flame ionisation and mass spectrometry detectors. All results obtained were referred to Polish and German requirements for indoor air quality （both in public buildings and in workspace environments）. Average benzene, toluene, o-xylene and m, p-xylene concentrations in new cars were determined at the level of 11.8 μg/m^3, 82.7 μg/m^3, 21.2 μg/m^3 and 89.5 μg/m^3, respectively. In the used cars, BTX concentration increased with increasing vehicle mileage. The most significant increase of BTX concentration was observed above 11,000 km mileage.     

离子交换树脂法吸附分离水中的邻二甲苯-4-磺酸

采用阴离子交换树脂吸附分离水中的邻二甲苯-4-磺酸。实验结果表明:201×7型阴离子交换树脂(简称树脂)对邻二甲苯-4-磺酸有很强的吸附能力,即使在4 mol/L NH_4Cl存在的情况下,树脂对邻二甲苯-4-磺酸的静态吸附率仍超过90%;适宜的动态吸附—解吸条件为吸附液流速为0.50 L/h、吸附液体积2 L,用含60%(质量分数)乙醇和1 mol/L盐酸的解吸剂解吸、解吸剂流速1.0 L/h、解吸剂体积1.5 L;该方法可有效回收水中的邻二甲苯-4-磺酸。