Predicting the contents of BTEX and MTBE for the three types of tollbooth at a highway toll station via the direct and indirect approaches

This study was set out to assess the contents of five volatile organic compounds (VOCs), including BTEX (the acronym for benzene, toluene, ethylbenzene, and xylene) and methyl tertiary-butyl ether (MTBE), in three types of tollbooth (including the car lane/ticket-collecting, car lane/cash-collecting, and bus/truck lane tollbooths) at a highway toll station via the direct and indirect approaches. For the direct approach, VOC samples were collected from the breathing zone of booth attendants at all selected tollbooths during the three workshifts. For samples collected during the dayshift, we found VOC contents of BTEX and MTBE in both the car lane/ticket-collecting (=6.23, 21.93, 3.24, 8.56, and 5.63 ppb, respectively) and car lane/cash-collecting tollbooths (=5.98, 21.71, 3.25, 8.59, and 6.04 ppb, respectively) were quite comparable, but both were significantly higher than that in the bus/truck lane tollbooth (=3.13, 13.91, 2.05, 4.52, and 2.70 ppb, respectively). The same pattern can also be found for the other two workshifts. For the indirect approach, we conducted multivariate regression analyses to predict VOC contents for any given type of tollbooth by using the four independent variables of the vehicle flowrate, wind speed, relative humidity, and air temperature. We found that, except the vehicle flowrate, the other three factors did not have a significant effect on VOC contents in the three types of tollbooth. In addition, the magnitudes of the effect of the vehicle flowrate on VOC contents for the three types of tollbooth were: car lane/cash-collecting>bus/truck lane>car lane/ticket-collecting. All regression results yielded R²-values in the range of 0.41−0.74 indicating that the developed indirect approach was able to predict VOC contents for three types of tollbooth.     

Cr/γ-Al_2O_3对乙酸乙酯的催化燃烧

使用浸渍法制备不同负载量的Cr/γ-Al_2O_3催化剂,研究乙酸乙酯的催化燃烧.BET,XRD结果表明,Cr在γ-Al_2O_3上负载存在分散阈值效应,负载量在阈值以下时呈单层分散形式,在超过阈值时Cr形成结晶,实验测得单层分散阈值与理论计算一致.Raman结果表明Cr在单层分散时为Cr~(6+),而在非单层分散时为Cr_2O_3.催化乙酸乙酯燃烧的活性研究显示,阈值效应对催化活性有显著影响:催化活性在单层分散阈值时最好,此时活化能最高,指前因子最大.     

尾气循环技术在国内顺酐装置的应用

顺酐生产过程排放的废气中含有大量未反应原料、副产物CO和挥发性有机物(VOC)等,对其进行处理使之达标排放,回收其中可利用的物质或能量有重要意义。吐哈石化厂顺酐装置采用CONSER公司工艺技术,新增部分尾气回收生产工艺路线,回收40%的尾气中的正丁烷,实现了蒸汽分阶利用,排放的废气中SO2、NOx、颗粒物等达到GB16297-1996《大气污染物综合排放标准》中二级标准。     

生物法净化废气中低浓度挥发性有机物的过程机理研究

 针对生物法净化低浓度挥发性有机废气的过程机理研究表明，生物膜填料塔净化低浓度甲苯气体是一个以气膜控制为主的传质过程，其中甲苯的生化降解属于瞬时快速化学反应，即甲苯的生化降解反应速率远远超过甲苯在液膜中的扩散速率，甲苯的生化降解在气液相界面处即可发生，其宏观表现即为甲苯气体直接吸附在润湿的生物膜上后迅速被微生物生化降解。因此，可以从气体吸附理论的新角度去解释生物法净化废气中低浓度挥发性有机物的动力学过程。对于低浓度挥发性有机废气的生物法净化装置的设计与操作而言，凡能改善传质条件、减少气膜阻力的措施均能强化这一生物吸收净化过程。     

Cyclohexane oxidation and carbon deposition over metal oxide catalysts

Catalytic activity of V, Mn, Ni, Cu, Zn, Mo, Zr and Ce oxides over an -alumina support was evaluated for cyclohexane oxidation under oxygen deficient conditions in order to understand the relation between carbon deposition and catalytic activity/selectivity. Carbon formation over the catalysts during the oxidation reaction was measured by means of Fourier transformed infrared spectroscopy (FTIR). Catalysts Mn/Al₂O₃ and Ce/Al₂O₃, which are selective for deep oxidation of cyclohexane, possessed relatively carbon free surfaces. The catalysts with relatively high carbon deposition (V, Ni, Cu, Zn, Mo and Zr) produced CO in addition to CO₂. Traces of formaldehyde were produced over the catalysts Mo and V.     

Use of thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) on identification of odorant emission focus by volatile organic compounds characterisation

Volatile organic compounds (VOCs) from several different municipal solid wastes’ treatment plants in Mallorca (Spain) have been analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Ambient (immission) air was collected during February and March 2011 by active sampling onto sorbents Tenax™ TA and Carboxen™ 1000. The study presents the chemical characterisation of 93 volatile organic compounds (VOCs) from an overall set of 84 immission air samples. 70 VOCs were positively identified.The linear fit for all 93 external standard calibration, from 10 mg L⁻¹ to 150 mg L⁻¹ (n = 4), was within the range 0.974 < r² < 0.998. Limits of detection of the method (LOD) for all the standards were within the range 1.1-4,213 pg, as the absolute standard amount spiked into sorbent tubes in 1 μL standard mixture (dissolved in methanol).Overall results stated systematic correlation between waste’s nature and VOCs’ air composition. Organic wastes show main contribution of terpenes, waste water sludge residues’ of reduced sulphured compounds (RSCs) and municipal solid wastes show contribution of a wide sort of VOCs. The use of a chemometric approach for variable’s reduction to 12 principal components enables evaluation of similarities and dissimilarities between facilities. PCA clearly related samples to its corresponding facility on the basis of their VOCs composition and the ambient temperature.     

地下水中VOC挥发因子模型的研究

建立了一个计算地下水中挥发性有机物（VOC）挥发因子的模型.选用半挥发性的1,2,4-三氯苯和挥发性的四氯乙烯为VOC的代表,分别计算了非饱和区土壤为砂土和粘土时的挥发因子.结果表明：蒸发使VOC的挥发因子增大,而下渗则使VOC的挥发因子减小;不论VOC的挥发性强弱,蒸发（下渗）对挥发因子的影响均比较明显;蒸发情况下,非饱和区土壤性质对挥发因子的影响不明显,而下渗情况下,非饱和区土壤性质对挥发因子的影响则趋于明显;此外,当非饱和区土壤为粘土时,VOC的挥发因子受蒸发（下渗）的影响更明显.     

Location and Characterization of Emission Sources for Airborne Volatile Organic Compounds Inside a Refinery in Taiwan

This study aimed to locate VOC emission sources and characterized their emitted VOCs. To avoid interferences from vehicle exhaust, all sampling sites were positioned inside the refinery. Samples, taken with canisters, were analyzed by GC–MS according to TO-14 method. The survey period extended from Febrary 2004 to December 2004, sampling twice per season. To interpret a large number of VOC data was a rather difficult task. This study featured using ordinary application software, Excel and Surfer, instead of expensive one like GIS, to overcome it. Consolidating data into a database on Excel facilitated retrieval, statistical analysis and presentation in the form of either table or graph. The cross analysis of the data suggested that the abundant VOCs were alkanes, alkenes, aromatics and cyclic HCs. Emission sources were located by mapping the concentration distribution of these four types of VOCs in terms of contour maps on Surfer. During eight surveys, five emission sources were located and their VOCs were characterized.     

广佛公路(盐步段)两侧挥发性有机物(VOC)污染研究

选取广佛公路盐步路段作机动车尾气污染研究 ,结果表明 :污染物主要由烷烃、苯系物和氯代烃组成 ,主要是毒害性 VOC;污染随着与公路距离的增加而降低 ;污染源除机动车以外 ,还有大量的工业企业