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.

Toluene methylation with syngas to para‐xylene by bifunctional ZnZrO_(x)‐HZSM‐5 catalysts

Toluene methylation with methanol on H‐ZSM‐5(Z5)zeolite for the directional transformation of toluene to xylene has been industrialized.However,great challenges remain because of the high energy barrier of methanol deprotonation to the methoxy group,the side reaction of methanol to olefins,coke formation,and the deactivation of zeolites.Herein,we report the toluene methylation coupled with CO hydrogenation to showcase an enhancement in para‐xylene(PX)selectivity by employing a bifunctional catalyst composed of ZnZrO_(x)(ZZO)and modified Z5.The results showed that a PX selectivity of up to 81.8%in xylene and xylene selectivity of 64.8%in hydrocarbons at 10.3%toluene conversion can be realized over the bifunctional catalyst on a fixed‐bed reactor.The selectivity of gaseous hydrocarbons decreased to 10.9%,and approximately half of that was observed in methanol reagent route where the PX selectivity in xylene was 38.8%.We observed that the acid strength,the quantity ratio of Brönsted and Lewis acid sites,and the pore size of zeolites were essential for the PX selectivity.The investigation of the H_(2)/D_(2) kinetic isotope effect revealed that the newborn methyl group in xylene resulted from the hydrogenation of CO rather than toluene disproportionation.Furthermore,the catalyst showed no evident deactivation within the 100 h stability test.The findings offer a promising route for the production of value‐added PX with high selectivity via toluene methylation coupled with syngas conversion.

Ethylbenzene disproportionation and p-xylene selectivity enhancement in xylene isomerization using high crystallinity desilicated H-ZSM-5

Desilication accompanied with minimum loss of crystallinity effect of a high alumina ZSM-5 zeolite on the isomerization reaction of ethylbenzene/xylene mixtures has been considered.Desilication was assessed through XRF,XRD,FTIR,TEM,nitrogen adsorption/desorption,NH_3-TPD,^(29)Si and^(27)Al MAS NMR analytical techniques.Desilication was accompanied with the creation of super acid sites.There exists a limit(Si/Al molar ratio of9.67)for keeping high crystallinity and obtaining improved catalytic performance.Desilication promotes ethylbenzene conversion by disproportionation and trans-alkylation reactions while the same reactions are limited for the xylene isomers.The p-xylene approach to equilibrium improves by more than 7% at 400℃ and a WHSV of 2 h^(-1)for the optimum sample with respect to the parent zeolite.At the same conditions,the optimum sample exhibits the maximum ethylbenzene conversion of 89%,i.e.more than 40%w.r.t.of the parent zeolite.However,the xylene yield decreases only 3%.

Solid-Liquid Equilibria of Musk Ketone, Musk Xylene and 1,3-Dimethyl-2,4-Dinitro-5-Tert-Butyl Benzene

The solid-liquid equilibria of musk ketone + musk xylene, musk xylene +l,3-dimethyl-2,4-dinitro-5-tert-butyl benzene are measured by differential scanning calorimeter (DSC), these systems are proved to be simple eutectics. Moreover the melting points and the fusion enthalpies of musk ketone, musk xylene and 1,3-dimethyl-2,4-dinitro-5-tert-butyl benzene are also measured by the DSC. These solid-liquid equilibrium data and the heats of fusion are reported for the first time. Then UNIFAC model is used to correlate the sofid-liquid equilibrium data. It is shown that the solid-liquid equilibria of musk systems can be predicted by the UNIFAC model.

Synthesis of an IMF zeolite membrane for the separation of xylene isomer

The synthesis of a continuous IMF zeolite membrane was fabricated on tubular substrates by seeded growth for the first time. The straight channels of IMF zeolite with diameters of 0.53–0.59 nm are distinguishable for p-xylene from o-xylene molecules. Pure IMF-phase high-silica IM-5 zeolite seeds with uniform and fine crystal size were fabricated by a new sonication-assisted aging process. The seeds were coated on the support by dipcoating and induced the formation of continuous membrane. Separation performance in p-/o-xylene mixture was investigated at various temperature and pressure. The typical IM-5zeolite membrane had p-/o-xylene separation factor of 3.7. Our results suggest that IM-5 zeolite is a potentially good membrane material for the separation of xylene mixtures.

Determination of hemoglobin adduct of a musk xylene metabolite in trout as biomarker of exposure by gas chromatography mass spectrometry

Musk xylene（MX） is frequently used as fragrances in formulation of personal care products. Quantification of a bound 4-amino- MX（4-AMX） as cysteine adducts in trout hemoglobin（Hb） was made by gas chromatography-ion trap-mass spectrometry（GC/MS）. The Hb samples were collected from trout after 24 h exposure to MX at 10μg/g, and or menhaden oil（control）. The formation of cysteine-Hb adduct was observed from nitroso derivative of MX, released by alkaline hydrolysis. The released 4-AMX metabolite was extracted in n- hexane. The extract was then reduced by evaporation, and analyzed by GC/MS. When similar agreement of mass spectral features and retention time of 4-AMX were obtained in both standard and sample solutions, the presence of 4-AMX metabolite in the Hb was confirmed. The concentration of 4-AMX was found to be 3.1 × 10^-6 6.9 × 10^-6 mg/g in the Hb solution. Quantitation was made based on an internal standard, a calibration plot, and response factor. In the non-hydrolyzed and laboratory blank extracts, the 4-AMX metabolite was not detected. Additionally, coeluting and interfefing ions were observed in the biological samples.

Synthesis of high-crystallinity MIL-125 with outstanding xylene isomer separation performance

MIL-125 is a metal-organic framework with great potential for the adsorption and separation of xylene isomers.However,MIL-125 is usually synthesized under anhydrous and anaerobic conditions.In this study,homogeneously shaped and highly crystalline MIL-125 was synthesized by introducing water-resistant titanium-containing oligomers into the synthesis process.With the assistance of the novel oligomers,MIL-125 can be synthesized in the presence of water,which meets batch-production requirements.The adsorption separation performance of the obtained highly crystalline MIL-125 was also significantly enhanced.The para-xylene/meta-xylene selectivity can reach 13.5 in mesitylene,which is higher than the selectivity values of most previously reported para-selective adsorbents.The MIL-125 xylene separation performance was verified using both batch adsorption and breakthrough experiments in the liquid phase.In addition,the influence of the solvent effect was evaluated through microcalorimetric experiments,liquid-phase adsorption experiments,and theoretical calculations.

Study on Solution Crystallization of Musk Ketone and Musk Xylene

The ternary phase diagrams of musk ketone, musk xylene and various solvent were obtained by calcu- lations. Moreover, the double saturated lines were found to be curve for the first time. The methods to separate eutectic mixtures of musks by solution crystallization were suggested on the basis of these phase diagrams. A new process was proposed to get musk ketone and musk xylene from the eutectics by adding acetonitrile and heptane in turn, which was verified by experiments. Musk xylene with purity of 97.50% and musk ketone with purity of 98.10% were obtained.

Synthesis of highly active Cu(Ⅰ)-Y(Ⅲ)-Y zeolite and its selective adsorption desulfurization performance in presence of xylene isomers

A bimetal-exchanged NaY zeolite(Cu(Ⅰ)-Y(Ⅲ)-Y)with a desirable adsorptive desulfurization(ADS)performance was prepared and characterized by means of X-ray diffraction,specific surface area measurements,X-ray fluorescence spectrometer,X-ray photoelectron spectroscopy,thermal gravity analysis and Fourier transform infrared spectroscopy.The effect of Y(Ⅲ)ions on ADS in the presence of the xylenes was investigated.Results indicated that the ADS performance of Y(Ⅲ)-Y is higher than that of most reported CeY.The Y(Ⅲ)-based Cu(Ⅰ)-Y(Ⅲ)-Y demonstrated the higher breakthrough loading than those of reported Ce(Ⅲ)/Ce(Ⅳ)-based transition metal Y zeolites,showing that Y(Ⅲ)ions play a promoting role in improving the ADS selectivity.For Cu(Ⅰ)-Y(Ⅲ)-Y,a new strong S-M interaction(S stands for sulfur,while M stands for metal)active site was formed,which might be caused by the synergistic effect between Cu(Ⅰ)and Y(Ⅲ).The Cu(Ⅰ)-Y(Ⅲ)-Y,which combined the advantages of Cu(I)-Y and Y(Ⅲ)-Y,is a kind of promising adsorbent.The breakthrough loading decreased in the order of Cu(Ⅰ)-Y(Ⅲ)-Y>Y(Ⅲ)-Y>Cu(Ⅰ)-Y,and the effect of xylene isomers on the sulfur removal was in the order of ortho-xylene>meta-xylene>para-xylene,which exhibited the same trend with the bond order of xylenes.

Successful Commercial Tests on Catalyst for Oxidation of Para-xylene

The Dalian Institute of Chemical Physics of CAS has made great strides in selective oxidation studies after having performed successful commercial testing of the novel catalyst for oxidation ofparaxylene in the 100 kt/a scale.

Enhanced xylene sensing performance of hierarchical flower-like Co_(3)O_(4) via In doping

Metal ions doping is a typical approach for tuning sensing properties of metal oxide semiconductors based gas sensors.Herein,hierarchical flower-like pure and In-doped Co_(3)O_(4) nanostructures assembled by porous two-dimensional(2D)nanosheets are synthesized via a solvothermal method and annealing process.The sensing measurements display that the In@Co_(3)O_(4)-4 based sensor possesses high response value of 55.9 toward 100 ppm xylene at 150 ℃,which is nearly 3.8times larger than that of pure Co_(3)O_(4) sensor.Furthermore,it possesses good selectivity and anti-humidity properties.Combined with the results of DFT calculations,the mechanism of enhanced gas sensing performance is analyzed systematically.

Comparison of air-borne xylene biodegradation between immobilizedcell biofilter and biofilm attached biofilter

The Bacillus firmus was immobilized into Ca-alginate beads according to the different initial biomass concentration, calcification time and activation time. Three types of immobilized Bacillus firmus beads were packed respectively in trickling biofilter to purify xylene contained waste gases, and the performance of immobilized-cell biofilter was compared with traditional biofilm attached biofilter packed with two types of ceramic pellets. The results showed that three types of immobilized beads had different capabilities for removing xylene and life-spans. Higher initial biomass in immobilized beads resulted in better performance but shorter life-span. Activation process can remarkably enhance the activity of bacteria, and the removal efficiency of xylene can substantially be improved. Calcification time had influence on life-span of immobilized beads. Without acclimation, the cell-entrapped biofilter can obtain the maximum elimination capacity of 92.4 g/（m^3·h）. However, compared with biofilm attached biofilter, it has a poorer intrinsic drawback in volatile organic compounds （VOCs） removal due to the existence of excess mass transfer resistance.

A Good GC Stationary Phase for Separation of Xylene Isomers

An excellent separation of xylene isomers is reported using 2, 6-O-di-pentyl-3-O-acetyl-beta-CD as capillary stationary phase. The optimum conditions for the separation are also discussed.

Technology for Manufacture of Xylene from Toluene and Methanol with Coproduction of Low-Carbon Olefins Passed Appraisal

On November 30, 2018 “The technology for manufacture of xylene from toluene and methanol with coproduction of low-carbon olefins” jointly developed by the Yanchang Petroleum Group (YPG) and the CAS Dalian Institute of Chemical Physics (DICP) had passed the appraisal of research achievements. In order to open up a new In order to open up a new technical route for alkylation of toluene to p-xylene, the technical personnel of YPG and DICP have been jointly engaging in the activities for tackling key problems to set up a 10 kt/a commercial unit for producing xylene through reaction of methanol with toluene along with coproduction of low-carbon olefins.

Equilibrium Study for Reactive Extraction of Caproic Acid in Mibk and Xylene

The recovery of caproic acid from the aqueous stream is of practical relevance due to its market value and the stringent environmental standards. The profound success of reactive extraction has been noted in the recovery of carboxylic acids from dilute solutions. In present paper, equilibrium of caproic acid with aliquat-336, a quaternary amine compound, in xylene and Methyl Isobutyl Ketone (MIBK) has been studied. Equilibrium parameters such as distribution coefficients, loading ratio, degree of extraction and equilibrium complexation constants have been presented. The data obtained is useful in understanding the equilibrium characteristics and efficient design of the recovery process of caproic acid by reactive extraction.

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.

Synthesis, physicochemical characterizations and catalytic performance of Pd/carbon-zeolite and Pd/carbon-Ce02 nanocatalysts used for total oxidation of xylene at low temperatures

In this work, xylene removal from waste gas streams was investigated via catalytic oxidation over Pd/ carbon-zeolite and Pd/carbon-CeO2 nanocatalysts. Acti- vated carbon was obtained from pine cone chemically activated using ZnC12 and modified by HaPO4. Natural zeolite of clinoptilolite was with HC1, while nano-ceria modified by acid treatment was synthesized via redox method. Mixed supports of carbon-zeolite and carbon- ceria were prepared and palladium was dispersed over them via impregnation method. The prepared samples were characterized by X-ray emission scanning electron diffraction （XRD）, field microscopy （FESEM）, Brunauer-Emmett-Teller surface area （BET）, Fourier transform infrared spectroscopy （FTIR） and thermogravi- metric （TG） techniques. Characterization of nanocatalysts revealed a good morphology with an average particle size in a nano range, and confirmed the formation ofnano-ceria with an average crystallite size below 60 nm. BET analysis indicated a considerable surface area for catalysts （-1000 m^2·g^-1）. FTIR patterns demonstrated that the surface groups of synthesized catalysts are in good agreement with the patterns of materials applied in catalyst synthesis. The performance of catalysts was assessed in a low-pressure catalytic oxidation pilot in the temperature range of 100℃-250℃. According to the reaction data, the synthesized catalysts have been shown to be so advantageous in the removal of volatile organic compounds （VOCs）, represent- ing high catalytic performance of 98% for the abatement of xylene at 250℃. Furthermore, a reaction network is proposed for catalytic oxidation of xylene over nanocata- lysts.

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.