Editing Xylene (section)

==Industrial production==
Xylenes are produced by the [[methylation]] of [[toluene]] and [[benzene]].<ref name="Ullmann" /><ref>Martindale, David C. and Kuchar, Paul J., [https://web.archive.org/web/20180717100321/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=5043502.PN.&OS=PN/5043502&RS=PN/5043502 Production of xylenes from light aliphatic hydrocarbons via dehydrocyclodimerization and methylation], United States Patent No. 5,043,502, 1991-8-27. Accessed 2012-4-28.</ref> Commercial or [[chemical purity|laboratory-grade]] xylene produced usually contains about 40–65% of [[m-Xylene|''m''-xylene]] and up to 20% each of [[o-Xylene|''o''-xylene]], [[p-Xylene|''p''-xylene]] and [[ethylbenzene]].<ref>{{cite web |title=Xylene (Mixed Isomers), Air Toxic Hazard Summary |url=http://www.epa.gov/airtoxics/hlthef/xylenes.html |publisher=United States Environmental Protection Agency |access-date=8 February 2015}}</ref><ref name="Kandyala">{{cite journal | last1 = Kandyala | first1 = Reena | last2 = Raghavendra | first2 = Sumanth Phani C. | last3 = Rajasekharan | first3 = Saraswathi T. | year = 2010 | title = Xylene: An overview of its health hazards and preventive measures | journal = J Oral Maxillofac Pathol | volume = 14 | issue = 1| pages = 1–5 | doi = 10.4103/0973-029X.64299 | pmid = 21180450 | pmc=2996004 | doi-access = free }}</ref><ref name="Sweden">[http://apps.kemi.se/flodessok/floden/kemamne_eng/xylen_eng.htm Xylene] ({{webarchive |url=https://web.archive.org/web/20110811152832/http://apps.kemi.se/flodessok/floden/kemamne_eng/xylen_eng.htm |date=August 11, 2011 }}), Swedish Chemicals Agency, apps.kemi.se, 2010. Accessed 2012-4-28.</ref> The ratio of isomers can be shifted to favor the highly valued ''p''-xylene via the patented UOP-''Isomar'' process<ref>{{cite web |title=Capturing Opportunities for ''Para''-xylene Production |url=http://www.uop.com/?document=uop-capturing-opportunities-for-para-xylene-production-tech-paper&download=1 |publisher=UOP, A Honeywell Company |access-date=8 February 2015}}</ref> or by [[transalkylation]] of xylene with itself or trimethylbenzene. These conversions are catalyzed by [[zeolite]]s.<ref name="Ullmann" />

[[ZSM-5]] is used to facilitate some isomerization reactions leading to mass production of modern plastics.