p-Xylenep-xylene, p-xylene structure
p-Xylene para-xylene is an aromatic hydrocarbon It is one of the three isomers of dimethylbenzene known collectively as xylenes The p- stands for para-, indicating that the two methyl groups in p-xylene occupy the diametrically opposite substituent positions 1 and 4 It is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and m-xylene All have the same chemical formula C6H4CH32 All xylene isomers are colorless and highly flammable The odor threshold of p-xylene is 062 parts per million ppm6
- 1 Production
- 2 Industrial applications
- 3 Toxicity and exposure
- 31 Inhalation
- 32 Skin
- 33 Eyes
- 34 Ingestion
- 35 Short-term exposure
- 36 Long-term exposure
- 4 References
- 5 External links
The production of p-xylene is industrially significant, with annual demand estimated at 37 million tons in 2014, and still on the increase78 p-Xylene is produced by catalytic reforming of petroleum naphtha as part of the BTX aromatics benzene, toluene and the xylene isomers extracted from the catalytic reformate The p-xylene is then separated out in a series of distillation, adsorption or crystallization and reaction processes from the m-xylene, o-xylene, and ethylbenzene Its melting point is the highest among this series of isomers, but simple crystallization does not allow easy purification due to the formation of eutectic mixtures
Such separation procedures are major cost factors in the production of p-xylene, and the search for alternative methods continues For example, a reverse-osmosis technique has been proposed to improve various aspects of the processes9
p-Xylene is an important chemical feedstock Among other industrial applications, it is a raw material in the large scale synthesis of various polymers In particular it is a component in the production of terephthalic acid for polyesters such as polyethylene terephthalate It also may be polymerised directly to produce parylene
Toxicity and exposureedit
Xylenes are not acutely toxic, for example the LD50 rat, oral is 4300 mg/kg Effects vary with animal and xylene isomer
Concerns with xylenes focus on narcotic efffects Overexposure of p-xylene in humans can cause headache, fatigue, dizziness, listlessness, confusion, irritability, gastrointestinal disturbances including nausea and loss of appetite, flushing of the face, and a feeling of increased body heat p-Xylene vapor exposure over the recommended exposure limit of 100 parts per million ppm can cause irritation to eye, nose, and throat and possible chest tightening and an abnormal gait10
p-Xylene occurs naturally in petroleum and coal tar It is emitted by most combustion sources, including automobile exhaust and tobacco smoke11
Inhaling p-xylene can cause dizziness, headache, drowsiness, and nausea If exposure through inhalation occurs, first aid includes fresh air, rest and possible medical attention Through the use of ventilation or breathing protection, exposure to p-xylene through inhalation can be prevented12
Exposure of p-xylene through the skin can cause dry skin and redness If skin exposure occurs, first aid includes rinsing and then washing the affected area with soap and water as well as removing any contaminated clothing and thoroughly cleaning and drying before reuse Exposure can be prevented through the use of protective gloves12
Exposure of p-xylene to eyes can cause redness and pain If eyes are exposed, first aid includes rinsing of the eyes with water for several minutes, removal of contact lenses if applicable, and medical attention Eye exposure can be prevented through the use of safety glasses or safety goggles12
Ingestion of p-xylene can result in a burning sensation, abdominal pain, dizziness, drowsiness, headache, and nausea If p-xylene is ingested one's mouth should be rinsed and vomiting should not be induced Further medical attention should be sought Ingestion can be prevented by not eating, drinking, or smoking when working with p-xylene12
p-Xylene can cause issues with the central nervous system and if swallowed could cause chemical pneumonitis when breathed into the lungs12
Liquid p-xylene exposure to the skin over long periods of time can remove the fat from the skin The substance may also have effects on the central nervous system Exposure can enhance hearing loss caused by noise exposure Animal tests suggest that this substance could cause damage to human development and reproductive systems12
- ^ "p-xylene" NIST Retrieved 21 February 2013
- ^ a b c d e f "NIOSH Pocket Guide to Chemical Hazards #0670" National Institute for Occupational Safety and Health NIOSH
- ^ Perry's Handbook of Chemical Engineers
- ^ a b c d "p-Xylene" International Chemical Safety Cards ICSC/NIOSH July 1, 2014
- ^ a b "Xylenes" Immediately Dangerous to Life and Health National Institute for Occupational Safety and Health NIOSH
- ^ "p-Xylene MSDS" ScienceLabcom Missing or empty |url= help; |access-date= requires |url= help
- ^ Fabri, Jörg; Graeser, Ulrich, and Simo, Thomas A, Xylenes, Ullmann's Encyclopedia of Industrial Chemistry, 2000, Wiley-VCH, Weinheim Accessed 2015-2-8 doi:101002/14356007a28_433
- ^ Nature 532,435–437 28 April 2016 doi:101038/532435a
- ^ Koh, D Y; McCool, B A; Deckman, H W; Lively, R P 2016 "Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membrane" Science 353: 804–7 doi:101126/scienceaaf1343
- ^ "MATERIAL SAFETY DATA SHEET PARA-XYLENE" Amoco Retrieved 13 February 2013
- ^ EPA-454/R-93-048 Locating and estimating air emissions from sources of xylene Emission Inventory Branch Technical Support Division Office of Air Quality Planning and Standards US Environmental Protection Agency March 1994
- ^ a b c d e f "para-Xylene" National Institute of Occupational Safety and Health Retrieved 12 February 2013
p-xylene, p-xylene density, p-xylene flash point, p-xylene infrared spectroscopy, p-xylene ir spectrum, p-xylene mass spectra, p-xylene molecular weight, p-xylene msds, p-xylene nmr, p-xylene structure
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