Xylenes


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Xylenes

 

(dimethylbenzenes). Three isomers (ortho-xylene, meta-xylene, and para-xylene) are known. All are colorless liquids that are readily soluble in organic solvents and poorly soluble in water. (See Table 1 for some physical properties of xylenes.) Their structural formulas are

Xylenes form highly explosive vapor-air mixtures. They cause acute and chronic damage to the blood-forming organs, as well as dermatitis upon contact with skin. Oxidation of xylenes yields toluic and phthalic acids. Xylenes are obtained from the products formed as a result of the coking of coal or during petroleum aromatization. The isomers are separated by fractional

Table 1. Some properties of xylenes
Propertieso-xylenem-xylenep-xylene
*1 cp (centipoise) = 10−3 newtons • sec/m2
Melting point, °C ...........−25.18B47.8713.26
Boiling point, °C............144.41139.10138.35
Density at 20°C, g/cm3.........0.88020.86420.8611
Refractive index np20 .....1.50541.49721.4958
Viscosity at 20°C, cp* ........0.8090.6170.644

crystallization and rectification. Xylenes are used as solvents, high-octane additives to aviation gasoline, and the initial material in the preparation of xylidines. Of greatest importance is ρ-xylene, which is used in the manufacture of terephthalic acid.

References in periodicals archive ?
In this review, the results were divided into articles containing data on exposure to solvents and mixtures such as gasoline and those containing data on subsequent exposure to each of the hydrocarbons (benzene, toluene, ethylbenzene, and xylene isomers) separately, and in chronological order.
* Xylenes industry market dynamics in Russia from 2005 to 2019, consisting of market size, demand and production outlook, demand by end-use sector, and average prices
* Xylenes industry market dynamics in Korea from 2005 to 2019, consisting of market size, demand and production outlook, demand by end-use sector, and average prices
Global production of metaxylene is limited to few manufacturers and accounts for an only small share of global xylenes production.
The relative selectivity's for xylenes were not affected by lowering the molar ratio of toluene: methanol from 1:2 to 1:4 and 1:8.
The health effects of some fractions can be adequately characterized with respect to their components or representative compounds (e.g., light aromatic BTEX fraction (benzene, toluene, ethylbenzene, and xylenes) and naphthalene.
Therefore, the four chemicals of major concern (toluene, butanol, xylene and styrene) were used to develop the criteria for risk assessment model.
[USPRwire, Wed Mar 23 2016] GlobalData's new report, "Xylenes Industry Outlook in Brazil to 2019 - Market Size, Company Share, Price Trends, Capacity Forecasts of All Active and Planned Plants", provides in-depth coverage of Brazil's Xylenes industry and presents major market trends.
GlobalData's new report, "Xylenes Industry Outlook in Argentina to 2019 - Market Size, Company Share, Price Trends, Capacity Forecasts of All Active and Planned Plants", provides in-depth coverage of Argentina's Xylenes industry and presents major market trends.
The Polymer Char CRYSTEX QC instrument represents a step forward in technology for automation of the amorphous phase determination, previously measured as xylenes solubles.
Benzene, toluene, ethylbenzene, and xylenes (BTEX) are generally compounds associated with traffic emissions; toluene is also released with the use of solvents (painting, printing, dry cleaning, etc.) as discussed in many works [7-9].