Xylene Isomer Mixtures Research Articles

Selective formation of 1,2,4 isomer among trimethyl benzenes in the methylation of xylenes over Al-, Ga-, and Fe-silicates with MEL structure

The methylation of m-xylene with methanol over Al-, Ga-, and Fe-silicate analogs of ZSM-11 (MEL topology) resulted in very high selectivities for the 1,2,4 isomer (98.5 ± 1%) among trimethylbenzenes (TMBs) at about 50–80 wt% TMB yield. The methanol selectivity for alkylation reaction, the yield of TMBs and alkylation versus isomerization selectivity (log ( A/ I) obtained over metallosilicate molecular sieves followed the order: H-(Fe)-ZSM-I1 > H-(Ga)-ZSM-I l > H-(AI)-ZSM-11. The acid strength of these molecular sieves follows the reverse order. The yield for TMBs in the product could be enhanced significantly when an equilibrium mixture of xylene isomers was methylated, thus suppressing the isomerization reaction.

Evaluation of new organoclay stationary phases for the separation of ethylbenzene and xylene isomers

Several kinds of Bentones which have structures similar to Bentone 34 have been tested and compared for the purpose of improving the resolution of ethylbenzene and xylene isomers by gas chromatography. Bentone SD-3 was found to have higher selectivity toward these close-boiling compounds than the well known stationary phase Bentone 34. Modification effects of some conventional stationary phases which represent the whole range of polarity on the chromatographic property of Bentone SD-3 have been investigated and discussed. A number of new organoclays which have different structures of the organic cation in complexes have been synthesized and their properties evaluated for the separation of positional isomers. A simultaneously high selective organoclay for each component in the aromatic mixture of ethylbenzene and xylene isomers, without assistance of conventional stationary phases, has been described.

Multivariate Calibration of Infrared Spectra for Quantitative Analysis Using Designed Experiments

The principal component regression (PCR) and partial least-squares (PLS) methods are used to calibrate and validate models for quantitative prediction of the composition of mixtures from FT-IR spectra. An experimental system of two- and three-component mixtures of xylene isomers was sampled with the use of statistical experimental designs. For two-component mixtures, the prediction error of independent validation samples decreased with increasing numbers of design points in the calibration. Four design points were needed to achieve a prediction accuracy of 0.0013 weight fraction. For three-component mixtures, a Scheffé {3,3} simplex lattice design, which has ten design points, achieved an equivalent accuracy of 0.002 weight fraction. There was little difference in performance between PLS and PCR computations. The results demonstrate the application of statistical methodology to the calibration of infrared spectra and show the importance of including an adequate number of samples in the calibration. The F test on the residual spectrum is shown to be a valuable tool for the identification of spurious data.

Inclusion Selectivity for Aromatic Guests in catena-[Bis-(dimethylamine)cadmium(II) tetra-μ-cyanonickelate(II)] Host Clathrate

Inclusion selectivity has been examined for xylene isomers and benzene in the Hofmann-dma-type Cd[NH- (CH3)2]2Ni(CN) 4 metal complex host. This has a layered structure of a two-dimensionally extended cyanometal complex network with the dimethylamine ligands protruding up and down from the network. The o-isomer is preferentially enclathrated in the metal complex host from the mixtures of xylene isomers, but the presence of benzene in the mixture makes the p-isomer more preferable. Benzene is enriched from the mixtures with xylene isomers at very low concentrations. The selectivity behavior is discussed based on the crystal structures of the relevant clathrates.

A comparative study of the effects of benzene, toluene, and xylenes on their in vitro metabolism and drug-metabolizing enzymes in rat liver

Male Sprague-Dawley rats were injected ip with benzene, toluene, or a mixture of xylene isomers at 20 mmol hydrocarbon/kg daily for 3 days. The effects of administration of these hydrocarbons upon their own in vitro metabolism, as well as upon cytochrome P-450, NADPH-cytochrome c reductase, aminopyrine N-demethylase, aniline hydroxylase, glutathione, glutathione S-transferase, and UDPglucuronyltransferase in liver were studied. Each hydrocarbon studied increased its own in vitro metabolism. Benzene had no effect on the metabolism of toluene or xylenes. Toluene and xylenes increased the metabolism of benzene, toluene, and xylenes. Cytochrome P-450 was elevated by toluene and xylenes, but was not affected by benzene. NADPH-cytochrome c reductase was induced by all three hydrocarbons. Aminopyrine N-demethylase and aniline hydroxylase were induced by toluene and xylenes and were not affected by benzene. Glutathione was elevated by benzene, decreased by xylenes, and not affected by toluene. Glutathione S-transferase was induced differentially by these hydrocarbons toward various substrates: toward 1-chloro-2,4-dinitrobenzene by benzene and toluene, toward 1,2-dichloro-4-nitrobenzene by benzene and xylenes, and no effect toward 1,2-epoxy-3-( p-nitrophenoxy)propane by any hydrocarbons. UDPglucuronyltransferase was induced by benzene and toluene when o-aminophenol and phenol were used as the substrate. Xylenes had no effect. Benzene was more effective at inducing conjugation enzymes. Xylenes were more effective at inducing cytochrome P-450 dependent enzymes. Toluene was equipotent at inducing both types of enzymes. The results indicate that the addition of methyl groups to the aromatic ring affects the inductive pattern of these monocyclic aromatic hydrocarbons.

Comparison of adsorption separation processes in the liquid and vapor phase. Application to the xylene isomer mixture

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComparison of adsorption separation processes in the liquid and vapor phase. Application to the xylene isomer mixtureMassimo Morbidelli, Giuseppe Storti, and Sergio CarraCite this: Ind. Eng. Chem. Fundamen. 1986, 25, 1, 89–95Publication Date (Print):February 1, 1986Publication History Published online1 May 2002Published inissue 1 February 1986https://doi.org/10.1021/i100021a013RIGHTS & PERMISSIONSArticle Views258Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (878 KB) Get e-Alerts

SEPARATION OF XYLENE ISOMERS BY PERVAPORATION THROUGH A HIGHLY PERMSELECTIVE POLYMER MEMBRANE HAVING DINITROPHENYL GROUP

Abstract The separation of xylene isomers was carried out by pervaporation through a polymer membrane having a dinitrophenyl group. The polymer membrane was effective for selective permeation of m-xylene from the mixture of xylene isomers. This selectivity can be attributed to the difference in the charge-transfer complexing ability between xylene isomers and the dinitrophenyl group.

Advanced Algorithm for Determining Component Spectra Based on Principal Component Analysis

A method is proposed for determining the component spectra from a set of unknown two-component mixture spectra. This method is considered as an advanced version of the Lawton-Sylvestre self-modeling curve resolution. The disadvantage of the weakness against noise is overcome by the introduction of the concept of filtering; the uncertainty of the solution is removed by the reduction of the band for each curve to a single curve with aid of the concept of entropy minimization. Experimental results with infrared absorption spectra of xylene isomer mixtures and visible absorption spectra of dye mixtures demonstrate the power of this method.

Constrained nonlinear method for estimating component spectra from multicomponent mixtures

A method is described for estimating the spectra of pure components from the spectra of unknown mixtures with various relative concentrations. This method is based on principal component analysis and a constrained nonlinear optimization technique and is applicable to qualitative analysis of mixtures of more than three components. The method gives two curves as the estimate of a component spectrum: one consists of the set of the maxima and the other consists of the set of the minima for all sampling points subject to a priori information. Experimental results of the estimation of the infrared absorption spectra of xylene-isomer mixtures are shown; the noise problem with this method is also discussed.

The Efficiency of the Dynamic Tests Used to Evaluate the Adsorbents Used for Separation of C8Isomers

Abstract Results of liquid chromatographic tests used to screen zeolitic adsorbents for resolving xylene isomer mixtures are presented. The performances of two tests (pulse test and breakthrough test) were studied. The selectivities and standard deviations obtained, showing that the pulse test is less sensitive, are presented.

New p-Xylene Recovery and Xylene Isomerization Processes

Toray has developed two new processes for p-xylene production. The one is the Aromax process, in which p-xylene is separated from a mixture of xylene isomers by adsorption and the other is the Isolene process, in which the residual xylene isomers are converted to p-xylene by means of isomerization.The first commercial Isolene and Aromax units have been successfully on stream in Toray's Kawasaki Plant since September, 1971 and March, 1973, respectively. Distinguished features of Aromax and Isolene processes proved in commercial operation are as follows:1. Aromax Process(1) p-Xylene yield per pass can be more than 90% against about 60% in crystallization process.(2) Higher one pass yield causes lower flow rate of xylene feedstock and smaller investment in downstream plant for isomerization.(3) In crystallization process, complicated mechanical separation of p-xylene crystal from slurry is required while Aromax is operated under milder conditions which make operation and maintenance much easier.(4) Material of construction can be carbon steel throughout the unit.2. Isolene Process(1) One-pass yields of C8 hydrocarbon are as high as 97∼98% including ethylbenzene conversion to xylenes.(2) Regeneration of the catalyst is required only once or twice a year under normal operating conditions.(3) Hydrogen consumption is low.(4) Operating conditions are mild.(5) No corrosive chemicals are needed, eliminating special alloys for the unit.