Isobutylene: Difference between revisions

Polymer and chemical grade isobutylene is typically obtained by dehydrating [[tertiary butyl alcohol]] (TBA) or [[catalysis|catalytic]] [[dehydrogenation]] of [[isobutane]] (Catofin or similar processes).<ref>{{citation | title = Hydrocarbon Chemistry | first1 = George A. | last1 = Olah | authorlink1 = George Andrew Olah | first2 = Árpád | last2 = Molnár | publisher = Wiley-Interscience | isbn = 978-0-471-41782-8}}.</ref> Gasoline additives [[methyl tert-butyl ether]] (MTBE) and [[ethyl tert-butyl ether]] (ETBE), respectively, are produced by reacting [[methanol]] or [[ethanol]] with isobutylene contained in butene streams from olefin steam crackers or refineries, or with isobutylene from dehydrated TBA. Isobutylene is not isolated from the olefin or refinery butene stream before the reaction as separating the ethers from the remaining butenes is simpler. Isobutylene can also be produced in high purities by "back-cracking" MTBE or ETBE at high temperatures and then separating the isobutylene by distillation from methanol or ethanol.

Isobutylene is used in the production of a variety of products. It is alkylated with butane to produce [[isooctane]] or dimerized to diisobutylene (DIB) and then hydrogenated to make [[isooctane]], a fuel additive. Isobutylene is also used in the production of [[methacrolein]]. [[Polymerization]] of isobutylene produces [[butyl rubber]] (polyisobutylene or PIB). Antioxidants such as [[butylated hydroxytoluene]] (BHT) and [[butylated hydroxyanisole]] (BHA) are produced by [[Friedel-Crafts alkylation]] of [[phenol]]s with isobutylene.