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.

Para-Xylene分子结构和光谱的外场效应研究

对二甲苯(PX)是一种重要的化工原料,广泛地用于合成聚脂纤维树脂,是医药和农药用聚合单体,因此了解对二甲苯分子结构和光谱的外场效应具有十分重要的意义。为研究外电场对PX分子结构和红外(IR)光谱产生的影响,本文采用密度泛函理论(DFT)B3LYP方法在6-311++G(d,p)基组水平上优化了不同外电场(0～0. 030 a. u.,0～1. 542×1010V·m^(-1))作用下PX分子的基态几何结构,在此基础上利用同样的方法计算了PX分子在不同电场下的振动频率,得到了分子的IR光谱,最后对PX的分子结构和IR光谱受外电场作用的的影响规律进行了研究。结果表明:频率497 cm^(-1)的吸收峰为苯环上的C1-H7和C2-H8的面外摇摆振动,812 cm^(-1)的吸收峰是苯环上的C4-H9和C5-H10的面外摇摆振动,1 547 cm^(-1)为苯环上的C1-H7和C2-H8的面内弯曲振动,3 017 cm^(-1)为甲基上的C11-H14和C15-H17的伸缩振动所产生,3 164 cm^(-1)为苯环上的C4-H9和C5-H10的伸缩振动所产生;外电场与分子内电场的叠加效应使得R(4,9),R(5,10),R(11,14)和R(15,17)等的键长随着外电场的增强急剧增长,而R(1,7),R(2,8),R(11,12)和R(15,16)等随着外电场的增强变化不明显;随着R(4,9)和R(5,10)的增加,吸收峰Ⅱ和Ⅴ出现了明显的红移,它们的频率分别减少了133和140 cm^(-1),峰Ⅳ在外电场较弱时频率增加,而当外电场较强时频率又开始减小,峰Ⅰ和Ⅲ的频率变化不明显。总之,在外电场的作用下,分子结构变化剧烈,红外光谱吸收峰出现了红移或蓝移,伴随着吸收峰的移动,分子的摩尔收系数ε也进行了重新分配,分子的振动斯塔克效应(VSE)明显。

Isobaric vapor–liquid equilibrium for ternary system of ethanol, ethyl propionate and para-xylene at 101.3 kPa

Isobaric vapor–liquid equilibrium(VLE) data for the binary system ethyl propionate(2) + para-xylene(3) and ternary system ethanol(1) + ethyl propionate(2) + para-xylene(2) at atmospheric pressure(101.3 k Pa)were obtained by a VLE modified othmer still. All the experimental data passed a point to point consistency test of Van Ness method, which verified the data reliability. The Wilson and UNIQUAC activity coefficient models were employed to correlate the binary VLE data to obtain binary interaction parameters. Based on binary interaction parameters, ternary VLE data of ethanol(1) + ethyl propionate(2) + para-xylene(3) were predicted by Wilson and UNIQUAC models, which proved that predicted values are consistent with the experimental data.Furthermore, azeotropic phenomenon between ethanol and ethyl propionate disappears when the mole ratio of para-xylene and binary system of ethanol and ethyl propionate is 1:1. Therefore, this paper convinced that para-xylene is a proper extractive additive that could be used in extractive distillation to separate the binary azeotropic system of ethanol and ethyl propionate.

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.

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.

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.

Parex工艺中Para-Xylene纯度的调节

通过对Parex工艺物料组成、控制方案、产品在线监测等进行分析,解决Parex工艺中PX纯度调节问题。

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 Alkylation with Methanol to p-Xylene over Heteropoly Acids Supported by Clay

The alkylation of toluene with methanol for the selective formation of p-xylene was systematically studied. Very few studies have been reported on the use of superacids such as heteropolyacids on cheap supports, such as clay. This article deals with the use of different heteropoly acids （HPAs）, viz, Dodeca-Tungstophosphoric acid [H3PO4.12WO3.xH2O] （TPA）, Dodeca-Molyhdo phosphoric acid ammonium salt hydrate [H12Mo12N3O40P＋aq] （DMAA）, Dodeca-Molyhdo Phosphoric acid （PMA） on clay （MontmoriUonite, K-10） and as such plain clay. This comparative study reveals that 20%PMA/Clay shows 62% toluene conversion and 100% selectivity toward p-xylene.

Kinetics of Burning Side Reaction in the Liquid-phase Oxidation of p-Xylene

During the liquid-phase oxidation of p-xylene,over-oxidation of reactant,intermediates and solvent to carbon dioxide and carbon monoxide is generally known as the burning side reaction.Batch and semi-continuous experiments were carried out,and the experimental data of the burning side reaction were analyzed and reported in this paper.The results showed that the rates of burning side reactions were proportional to the rates of the main reaction,but decreased with the increasing concentrations of reactant and intermediates.The inter-stimulative and competitive relationship between the burning side reaction and the main reaction was confirmed,and the rates of the burning side reaction could be described with some key indexes of the main reaction.According to the mechanism of the side reactions and the kinetics model of main reaction which were proposed and tested in the previous papers,a kinetic model of the burning side reactions involving some key indexes of the main reaction was developed,and the parameters were determined by data fitting of the COx rate curves.The obtained kinetic model could describe the burning side reactions adequately.

Toluene Alkylation to Selective Formation of p-Xylene over Co-Crystalline ZSM-12/ZSM-5 Catalyst

The alkylation of toluene with methanol to selective formation of p-xylene has been systematically studied. ZSM-12 （MTW）/ZSM-5 co-crystalline zeolite in 40：60 proportions have been synthesized by the same molar gel composition, but at different temperatures and periods than that of ZSM-12 and ZSM-5, separately. All the prepared samples are characterized by XRD, SEM, BET, and XRF. The activity of toluene alkylation was investigated with a mixture of toluene and methanol as a feed over the ZSM-12, ZSM-12/ZSM-5 co-crystalline, ZSM-5, and physical mixture of ZSM-12/ZSM-5. From characterization, it is observed that the ZSM-12/ZSM-5 co-crystalline material is different from that of ZSM-12, ZSM-5, and their physical mixture. Further, the ZSM-12/ZSM-5 co-crystalline zeolite produces the highest content of xylene and has better selectivity for p-xylene than ZSM-12, ZSM-5, and their physical mixture.

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%.

A Molecular Mechanism of Fenton Oxidation Degradation of m-Xylene

Density functional theory（DFT） quantum chemical method was used to study the process of meta-xylene Fenton oxidation. The EHOMO energies of meta-xylene molecules are higher, so they have better ability to provide electron and prone to the nucleophilic reaction. M-xylene mainly reacts with OH free radical in addition reactions. And the position of C（6） is most likely to react with the OH free radical, rather than the C（3）, which is the most difficult to occur. According to all the above results, the most likely reaction mechanism of advanced oxidation degradation of meta-xylene is determined.

Viscosities of Pure Water, Acetic Acid ＋ Water, and p-Xylene ＋ Acetic Acid ＋ Water at Different Temperature and Pressure

The viscosities of pure water,the acetic acid+water binary system,and the p-xylene+acetic acid+ water ternary system at different concentrations were determined with a rolling-ball viscometer at temperatures from 313.15 to 473.15 K and pressures from 0.10 to 3.20 MPa.The viscosity data were fitted by a correlation equation for the estimation of the mixture viscosities.The average absolute deviations(AAD)of the correlation for binary and ternary systems are 2.48%and 1.77%,respectively.

Isobaric Vapor-Liquid Equilibrium of Binary Systems： p-Xylene ＋ （Acetic Acid, Methyl Acetate and n-Propyl Acetate） and Methyl Acetate ＋ n-Propyl Acetate in an Acetic Acid Dehydration Process

The vapor-liquid equilibrium data of four binary systems (acetic acid +p-xylene, methyl acetate +n-propyl acetate, n-propyl acetate +p-xylene and methyl acetate +p-xylene) are measured at 101.33 kPa with Ellis equilibrium still, and then both the NRTL and UNIQUAC models are used in combination with the HOC model for correlating and estimating the vapor-liquid equilibrium of these four binary systems. The estimated binary VLE results using correlated parameters agree well with the measured data except the methyl acetate +p-xylene system which easily causes bumping and liquid rushing out of the sampling tap due to their dramatically different boiling points. The correlation results by NRTL and UNIQUAC models have little difference on the average absolute deviations of temperature and composition of vapor phase, and the results by NRTL model are slightly better than those by UNIQUAC model except for the methyl acetate +n-propyl acetate system, for which the latter gives more accurate correlations.

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.

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.

Multi-objective optimization of p-xylene oxidation process using an improved self-adaptive differential evolution algorithm

The rise in the use of global polyester fiber contributed to strong demand of the Terephthalic acid(TPA).The liquid-phase catalytic oxidation of p-xylene(PX)to TPA is regarded as a critical and efficient chemical process in industry[1].PX oxidation reaction involves many complex side reactions,among which acetic acid combustion and PX combustion are the most important.As the target product of this oxidation process,the quality and yield of TPA are of great concern.However,the improvement of the qualified product yield can bring about the high energy consumption,which means that the economic objectives of this process cannot be achieved simultaneously because the two objectives are in conflict with each other.In this paper,an improved self-adaptive multi-objective differential evolution algorithm was proposed to handle the multi-objective optimization problems.The immune concept is introduced to the self-adaptive multi-objective differential evolution algorithm(SADE)to strengthen the local search ability and optimization accuracy.The proposed algorithm is successfully tested on several benchmark test problems,and the performance measures such as convergence and divergence metrics are calculated.Subsequently,the multi-objective optimization of an industrial PX oxidation process is carried out using the proposed immune self-adaptive multi-objective differential evolution algorithm(ISADE).Optimization results indicate that application of ISADE can greatly improve the yield of TPA with low combustion loss without degenerating TA quality.

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.