Bio-removal of mixture of benzene,toluene,ethylbenzene,and xylenes/total petroleum hydrocarbons/trichloroethylene from contaminated water

Four pure cultures were isolated from soil samples potentially contaminated with gasoline compounds either at a construction site near a gas station in Fai Chi Kei,Macao SAR or in the northern parts of China（Beijing,and Hebei and Shandong）.The effects of different concentrations of benzene,toluene,ethylbenzene,and three isomers（ortho-,meta-,and para-） of xylene（BTEX）,total petroleum hydrocarbons（TPH）,and trichloroethylene（TCE）,when they were present in mixtures,on the bio-removal effciencies of microbial isolates were investigated,together with their interactions during the bio-removal process.When the isolates were tested for the BTEX（50-350 mg/L）/TPH（2000 mg/L） mixture,BTEoX in BTEoX/TPH mixture was shown with higher bio-removal effciencies,while BTEmX in BTEmX/TPH mixture was shown with the lowest,regardless of isolates.The TPH in BTEmX/TPH mixture,on the other hand,were generally shown with higher bio-removal effciencies compared to when TPH mixed with BTEoX and BTEpX.When these BTEX mixtures（at 350 mg/L） were present with TCE（5-50 mg/L）,the stimulatory effect of TCE toward BTEoX bio-removal was observed for BTEoX/TCE mixture,while the inhibitory effect of TCE toward BTEmX for BTEmX/TCE mixture.The bio-removal effciency for TPH was shown lower in TPH（2000 mg/L）/TCE（5-50 mg/L） mixtures compared to TPH present alone,implying the inhibitory effect of TCE toward TPH bio-removal.For the mixture of BTEX（417 mg/L）,TPH（2000 mg/L） along with TCE（5- 50 mg/L）,TCE was shown co-metabolically removed more effciently at 15 mg/L,probably utilizing BTEX and/or TPH as primary substrates.

Occupational Health Risk Assessment of Benzene,Toluene,and Xylene in Shanghai

Objective This study was designed to conduct a retrospective and systematic occupational health risk assessment(OHRA)of enterprises that used benzene,toluene,and xylene(BTX)in Shanghai,China.Methods All data for the study were obtained from 1,705 occupational health examination and evaluation reports from 2013 to 2017,and a semiquantitative model following Chinese OHRA guidelines(GBZ/T 298-2017)was applied for the assessment.Results The selected enterprises using BTX were mainly involved in manufacturing of products.Using the exposure level method,health risk levels associated with exposure to BTX were classified as medium,negligible,or low.However,the risk levels associated with benzene and toluene were significantly different according to job types,with gluers and inkers exhibiting greater health risks.For the same job type,the health risk levels assessed using the comprehensive index method were higher than those using the exposure level method.Conclusion Our OHRA reveals that workers who are exposed to BTX still face excessive health risk.Additionally,the risk level varied depending on job categories and exposure to specific chemicals.Therefore,additional control measures recommended by OHRA guidelines are essential to reduce worker exposure levels.

VAPOR-LIQUID EQUILIBRIUM FOR TERNARY MIXTURES OF BENZENE,TOLUENE,AND p-XYLENE

Vapor-liquid equilibrium composition and temperature were measured for binary andternary mixtures of benzene,toluene and p-xylene at 101.33 kPa The equilibrium cell of Boubliketal.was modified for the present study.The experimental vapor-liquid equilibrium data were corre-lated with the Wilson equation.

Optimizing support acidity of NiMo catalysts for increasing the yield of benzene, toluene and xylene in tetralin hydrocracking

To enhance the yields of benzene,toluene,and xylene in tetralin hydrocracking,the effect of the support acid properties of NiMo catalysts on hydrocracking performance of tetralin were investigated in this study.NaY zeolites were modified by hydrothermal treatment to form USY zeolites at different temperatures and adjust the type and amount of acid.In addition,H-Beta was loaded into the USY to further adjust the acidic properties of the catalysts.The result shows that when the total B acid content of the catalyst is maintained between 150 and 200μmol·g^(-1),the total acid amount is maintained between 1.7 and 1.9 mmol·g^(-1),and the L/B(L and B acids)ratio is maintained between 1.5 and 2,the catalysts have favorable performances on tetralin hydrocracking.Under this condition,the catalysts have a yield of benzene,toluene,and xylene higher than 30 wt%and a selectivity for benzene,toluene,and xylene higher than 35%.The tetralin conversion is greater than 85 wt%.The AB6 catalyst obtains the best hydrocracking effect with the conversion of tetralin reaching 90.24 wt%,the yields of benzene,toluene,and xylene reaching 33.58 wt%,and the selectivity of benzene,toluene,and xylene reaching 37.21%,respectively.

Anaerobic biodegradation of benzene series compounds by mixed cultures based on optional electronic acceptors

A series of batch experiments were performed using mixed bacterial consortia to investigate biodegradation performance of benzene, toluene, ethylbenzene and three xylene isomers （BTEX） under nitrate, sulfate and ferric iron reducing conditions. The results showed that toluene, ethylbenzene, m-xylene and o-xylene could be degraded independently by the mixed cultures coupled to nitrate, sulfate and ferric iron reduction. Under ferric iron reducing conditions the biodegradation of benzene and p-xylene could be occurred only in the presence of other alkylbenzenes. Alkylbenzenes can serve as the primary subs＇rates to stimulate the transformation of benzene and p-xylene under anaerobic conditions. Benzene and p-xylene are more toxic than toluene and ethylbenzene, under the three terminal electron acceptors conditions, the degradation rates decreased with toluene 〉 ethylbenzene 〉 m-xylene 〉 o-xylene〉 benzene 〉 p- xylene. Nitrate was a more favorable electron acceptor compared to sulfate and ferric iron. The ratio between sulfate consumed and the loss of benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene was 4.44, 4.51, 4.42, 4.32, 4.37 and 4.23, respectively; the ratio between nitrate consumed and the loss of these substrates was 7.53, 6.24, 6.49, 7.28, 7.81, 7.61, respectively; the ratio between the consumption of ferric iron and the loss of toluene, ethylbenzene, o-xylene, m-xylene was 17.99, 18.04, 18.07, 17.97, respectively.

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.

Photocatalytic oxidation of gaseous benzene,toluene and xylene under UV and visible irradiation over Mn-doped TiO_(2)nanoparticles

The photocatalytic oxidation of gaseous benzene,toluene and xylene(BTX)over un-doped,0.1 and 1 wt%Mn-TiO_(2)nanoparticles under ultraviolet and visible irradiation was studied in atmosphere of synthetic air or inert gas.The photocatalytic decomposition efficiency and the oxidation products were determined using a Static Photochemical Reactor coupled with FTIR spectroscopy.BTX underwent efficient decomposition over Mn-TiO_(2)photocatalysts under UV irradiation,more with oxygen presence and less without oxygen.More important toluene and xylene went substantial decomposition over 0.1 mol%Mn-TiO_(2)under visible irradiation with oxygen presence.The main final oxidation products in the UV photocatalysis of BTX were CO_(2),CO and H2O,with CO_(2) and CO yields 4 and 2 respectively.The conversion percentage of benzene,toluene,and xylene to CO_(2) were 63.6%,56.4%,51.8%,and to CO 29%,26.5%,23.2%,respectively.In the visible photocatalysis of toluene and xylene the yields of CO were insignificant.Formation of carbon containing deposits on TiO_(2)surfaces was observed after extensive UV photocatalysis of toluene and xylene,and such by-products surface coverage may reduce the photocatalytic activity of TiO_(2)samples.Some aspects of the photocatalytic mechanism were examined.

Effect of benzene,toluene,xylene on the semen quality of exposed workers

Objective To examine the effects on semen and sperm quality of workers after a short and long term exposure to benzene, toluene, and xylene Methods The semen and blood of 24 married workers exposed to benzene, toluene, and xylene from shoemaking, spray painting, or paint manufacturing factories were collected The concentration of benzene, toluene, and xylene in the blood and semen was determined by using headspace chromatographic method Routine sperm test was carried out and acrosin activity detected Results The results showed that benzene, toluene, and xylene were found in the blood and semen of some ex workers in a working environment where the air concentration of benzene, toluene, and xylene exceeded the maximum allowable concentration (MAC) This result was not found in workers of the control group There were also some effects on the quality of semen in the exposed workers For example, the percentage of semen with liquefaction time exceeding 30 minutes increased The sperm vitality, motility and acrosin activity decreased At the same time, there were a positive correlation between liquefaction time and the level of toluene in semen, and a negative correlation between sperm vitality, sperm activity or acrosin activity and working history Conclusions The results suggested that the mixture could affect the quality of semen and sperm, which might be the main reason of the abnormal pregnancy outcome among the wives of workers exposed to benzene, toluene, and xylene Further studies are, however, required to confirm these findings

Seasonal and Spatial Variation of BTEX in Ambient Air of Delhi

The present study aims to provide an indication of ambient levels of BTEX in the immediate vicinity of petrol filling stations in Delhi & other road side corridors of Delhi. In this study spatial and seasonal variation of BTEX has been measured at different locations in Delhi. For the measurement of VOCs, passive based diffusion methodology was adopted for the adsorption of BTEX over the activated charcoal. Four categories of sampling sites were chosen (residential, traffic junctions, road side corridors and petrol pumps). The result confirms that the aromatic concentrations in the ambient air of gas stations are appreciably higher than the average values in locations with high vehicular flux. The mean concentration of BTEX at all the locations was 0.622μg/m3, 0.361 μg/m3, 1.037 μg/m3 and 0.122 μg/m3. The average concentration of benzene was highest at petrol pump 3.5 μg/m3 however at all other sampling sites it was in the range of 0.294 to 0.712 μg/m3. The mean concentration value shows that the xylene concentration dominates more in Delhi as compared to benzene. The total average BTEX concentration at road side corridors was 0.594 μg.m-3, at residential corridors was 0.262 μg.m-3, at intersections it was 0.649 μg.m-3 and at petrol filling stations it was 1.457 μg.m-3. The concentration was in the order of petrol filling stations > intersections > road side corridors > residence. These data show the predominance of diesel driven vehicles in Delhi since xylene mainly comes from diesel exhausts. The influential VOC species in case of diesel engine exhaust are benzene, ethylbenzene, xylenes, propane, n-decane and undecane and in case of gasoline vehicle exhaust influential species are benzene, ethylbenzene, 1,2,4-methylbenzene, 1,3,5-methylbenzene, n-hexane and 2-methylhexane. So xylene is mainly coming from diesel exhaust since gasoline vehicle exhaust doesn’t show this species.

基于气质联用法的鞋用胶粘剂中6种苯系物的测定

建立了气质联用法测定鞋用胶粘剂中6种苯系物的分析方法。以乙酸乙酯为萃取溶剂,提取胶粘剂中的6种苯系物,优化了仪器分析条件。结果表明,本方法6种苯系物的检出限为35~65 mg/kg,加标回收率为91.9%~98.0%,相对标准偏差为3.8%~7.8%。本方法仪器分析时间短,回收率高,重复性好,结果可靠,适用于胶粘剂中6种苯系物的检测。

Indoor and outdoor BTX levels in Barcelona City metropolitan area and Catalan rural areas

Five aromatic hydrocarbons (benzene, toluene, and three isomeric xylenes) were monitored in indoor and outdoor air of 7 public buildings and 54 private homes, located in Barcelona City metropolitan area and in several rural areas of Catalonia. The sampling was carried out over four periods: spring-summer and winter of 2000, and summer and winter of 2001. Passive ORSA 5 Dra¨ger samplers were used for benzene, toluene, and xylenes (BTX) adsorption. BTX were extracted with carbon disulphide and analysed using ...

对二甲苯结晶相关三元和四元体系固液相平衡数据预测

针对对二甲苯结晶相关的由C_(8)芳烃、甲苯和苯组成的三元和四元固液相平衡体系,选取固液相平衡计算模型—Van′t Hoff方程简式,预测了对二甲苯-乙苯-苯、邻二甲苯-乙苯-苯和间二甲苯-乙苯-苯三元体系,以及对二甲苯-间二甲苯-乙苯-甲苯、对二甲苯-邻二甲苯-乙苯-甲苯、对二甲苯-间二甲苯-乙苯-苯、对二甲苯-邻二甲苯-乙苯-苯和间二甲苯-邻二甲苯-乙苯-苯四元体系固液相平衡数据。结果表明:Van′t Hoff方程简式适用于对二甲苯装置对二甲苯结晶相关体系中由C_(8)芳烃、甲苯和苯组分组成的三元和四元固液相平衡体系计算;利用三元和四元体系固液相平衡数据可绘制各体系的固液相平衡相图,为对二甲苯结晶相关的由C_(8)芳烃、甲苯和苯组分组成的体系固液相平衡数据测量和有关研究、设计、模拟优化提供理论指导和依据。

拉曼光谱分析技术在化工生产中的应用探析

利用拉曼光谱对间二甲苯和对二甲苯的特征波段进行了测定,并对该波段进行了拉曼定量测定。以991、785、1052、536、827 cm-1为定量峰,并绘制了其工作曲线。经t检验,结果表明,本方法的准确度达到了95%。经测定,该方法的回收率在94.60%~104.15%之间。

甲苯与C_(8)芳烃及苯多元体系固液相平衡数据预测

在对二甲苯结晶相关体系中,针对正常熔点非常接近的甲苯和乙苯两种组分同时存在的多元体系,利用固液相平衡计算模型——Van′t Hoff方程简式预测了乙苯-甲苯-苯三元体系,对二甲苯-乙苯-甲苯-苯、间二甲苯-乙苯-甲苯-苯、邻二甲苯-乙苯-甲苯-苯和间二甲苯-邻二甲苯-乙苯-甲苯等四元体系,及对二甲苯-邻二甲苯-乙苯-甲苯-苯、对二甲苯-间二甲苯-乙苯-甲苯-苯和间二甲苯-邻二甲苯-乙苯-甲苯-苯等五元体系的固液相平衡数据。这些新的相平衡数据未见文献报道,可为对二甲苯结晶相关体系的固液相平衡研究提供理论依据和指导。

环境空气中苯、甲苯、二甲苯气相色谱法检测实战分析

气相色谱法作为测定环境空气中苯、甲苯、二甲苯的标准检验方法,方法本身已经十分成熟和完善,但在样品处理和色谱仪使用过程中不同的操作手法可能会影响分析质量,导致检测结果不准确。本文针对样品的前处理、气体源、进样、分离和检测器几个方面进行研究分析,提出实战性观点,希望对相关检测人员有所帮助。

聊城市宾馆客房气态污染物暴露特征及对客房从业人员健康风险评估

目的分析聊城市宾馆客房空气中甲醛、苯、甲苯、二甲苯质量浓度的年度动态变化特征,识别其对客房从业人员潜在健康风险,为加强宾馆的卫生管理提供科学依据。方法2016—2021年每年在聊城市选取18家宾馆进行客房空气中甲醛、苯、甲苯、二甲苯质量浓度的检测,并对客房从业人员工作模式等基本情况进行问卷调查;依据《公共场所卫生检验方法第2部分:化学污染物》(GB/T 18204.2-2014)对收集的样品进行实验室检测,参照美国国家环境保护署(United States Environmental Protection Agency,USEPA)推荐的健康风险评价模型和我国《化学物质环境健康风险评估技术指南》(WS/T 777-2021)的方法,基于客房从业人员实际暴露时间评估宾馆室内空气中上述4种污染物吸入途径的致癌风险和慢性非致癌风险。结果2016—2021年该市宾馆客房室内空气样品中甲醛、苯、甲苯、二甲苯质量浓度总超标率分别为15.4%、0.3%、1.1%和1.2%,且质量浓度中位数均小于国家标准限值;按年度分别计算,4种污染物的浓度水平呈现出总体下降的趋势,且具有统计学意义;甲醛的致癌风险(carcinogenic risks,CR)和非致癌风险(hazard quotient,HQ)均最大,分别有2.5%(17/663)和60.0%(398/663)的潜在风险值超过10-4和1的水平,且最大值分别达到9.16×10-4和16.72;苯存在一定的致癌和非致癌风险,最大值分别为5.49×10-4和3.29;甲苯的HQ<1;二甲苯HQ最大值为2.30,可能存在一定的非致癌风险。结论聊城市宾馆客房空气中甲醛及苯系物均存在超标现象,少数场所点位两种气态污染物对客房从业人员存在不同程度的潜在健康风险。

One-pot synthesis of toluene from methane and methanol catalyzed by GaN nanowire

The generation of aromatic benzene,toluene,xylene(BTX)compounds from non-petroleum feedstocks is of particular interest for chemists in the eyes of sustainability.Herein,a novel synthesis of toluene catalyzed by GaN semiconductor nanowire arrays is reported.Using methane and methanol as starting materials,the GaN nanowire arrays can synergistically facilitate the facile generation of toluene under either photo-irradiation or thermal-conditions.The detailed computational studies unveiled different mechanisms involved for the photo-and thermal-toluene synthesis.

硫化物双功能催化剂上四氢萘加氢裂化制备BTX反应动力学和选择性研究

在反应温度400℃和反应压力6 MPa条件下,在Beta分子筛负载不同加氢活性中心(Co、Mo、Ni和W)的硫化物双功能催化剂上对四氢萘选择性加氢裂化(HDC)制备苯、甲苯和二甲苯(BTX)反应行为进行研究。通过建立四氢萘加氢裂化反应的九集总反应动力学模型,结合各反应速率常数,探讨不同双功能催化剂的反应性能。研究表明:NiW(Ni(5)W(20)/Beta-40)和NiMo(Ni(5)Mo(20)/Beta-40)催化剂中,Beta分子筛载体上活性金属和酸中心含量高,在四氢萘转化率分别为98%和96%时,表现出较高的BTX选择性(63%和56%,摩尔分数)。结合反应结果和反应速率常数数据可以发现:虽然Ni(5)W(20)/Beta-40和Ni(5)Mo(20)/Beta-40催化剂上积炭速率高,但是BTX生成速率与BTX过度加氢裂化反应速率的比值、BTX生成速率与催化剂积炭速率的比值也都高于其他催化剂,表现出优异的BTX选择性。

ZnW/β中ZnO含量对其催化四氢萘加氢裂化反应性能的影响

Zn的引入不仅可以调控β分子筛的酸性质,而且还会影响催化剂的加氢活性。为了研究Zn的引入对催化剂加氢裂化反应性能的影响,利用浸渍法合成了一系列不同ZnO含量的ZnW/β加氢裂化催化剂,并对其物理化学性能进行了分析表征。研究了ZnO含量对其催化四氢萘加氢裂化制备BTX(苯/甲苯/二甲苯)催化性能的影响。结果表明,最高BTX收率随着ZnO含量的增加先升高(质量分数<1%时)后降低(质量分数>1%时),这是由于随着ZnO含量的增加,ZnW/β催化剂的强酸量和总酸量明显减小,抑制了四氢萘的过度裂化。而当ZnO的负载量达到1%(质量分数)后,ZnO与WO_(3)反应会生成非活性组分ZnWO4晶体,非活性组分ZnWO4晶体的生成量随着ZnO的含量增大而增大,降低了催化剂中加氢活性组分WO_(3)的含量,导致ZnW/β催化剂的加氢中心与酸中心匹配不佳。ZnO负载量为1%的ZnW/β催化剂在反应空时为0.36 h时达到最高的BTX收率(41.57%,质量分数),说明该催化剂的酸量适中且加氢中心与酸中心匹配最佳。因此,催化剂金属中心与酸中心合适的匹配及适中的酸强度是提高BTX收率的关键。

基于高温裂解仪的氢化芳烃热裂解研究

以顺式十氢萘、反式十氢萘、四氢萘、茚满等为氢化芳烃模型化合物,利用高温裂解仪与气相色谱串联装置快速评价了不同结构氢化芳烃的热裂解性能,研究了其热裂解行为。结果表明:热裂解时,十氢萘以开环裂解反应为主,反应温度升高时,其开环裂解反应选择性降低,脱氢反应和氢转移反应增强,反应物原子利用变得不合理;受苯环大π键影响,四氢萘和茚满环烷环上C—H键的键能较低,其脱氢能力与氢转移能力较强,产物以芳烃为主;氢饱和度高的氢化芳烃是生产低碳烯烃的优质原料,含苯环的芳香基氢化芳烃是生产苯、甲苯、二甲苯(BTX)的优质原料。