What is Monsanto process?
The '''Monsanto process''' is a way of making [[acetic acid]]. It uses a [[catalyst]] to add a [[carbonyl]] group to [[methanol]]. This process operates at a [[pressure]] of 30&ndash;60 [[atmosphere (unit)|atm]] and a [[temperature]] of 150&ndash;200 °C. It gives a selectivity greater than 99%. It was developed 1960 by German chemists working at [[BASF]]. Chemists at [[Monsanto]] introduced a new catalyst system in 1966.<ref>{{cite web|url=http://www.greener-industry.org.uk/pages/ethanoicAcid/6ethanoicAcidPM2.htm|title=Greener Industry - Ethanoic Acid - Production Method: The Monsanto Process|website=www.greener-industry.org.uk|access-date=2011-12-09|archive-date=2017-03-30|archive-url=https://web.archive.org/web/20170330042810/http://www.greener-industry.org.uk/pages/ethanoicAcid/6ethanoicAcidPM2.htm|url-status=dead}}</ref> Today, chemists make acetic acid by the [[Cativa process]], a similar [[iridium]]-based process developed by [[BP|BP Chemicals Ltd]] which is more economical and environmentally friendly. So, the Monsanto process is not used very much in industry. ==Catalytic cycle== The process has several steps, which repeat to remake the catalyst: [[File:Monsanto-Prozess.svg|center|450px|The catalytic cycle of the Monsanto process]] The [[catalysis|catalytically]] active [[chemical species|species]] is the [[anion]] cis-[Rh(CO)<sub>2</sub>I<sub>2</sub>]<sup>−</sup> '''(1)'''. The [[catalytic cycle]] has been shown to involve six steps, two of which do not involve rhodium: conversion of [[methanol]] to [[methyl iodide]] and the hydrolysis of the [[acetyl iodide]] to [[acetic acid]]. (These steps are in the middle of the above diagram.) The first [[organometallic chemistry|organometallic]] step is the [[oxidative addition]] of [[methyl iodide]] to ''cis''-[Rh(CO)<sub>2</sub>I<sub>2</sub>]<sup>−</sup> to form the [[octahedral molecular geometry|hexacoordinate]] species [(CH<sub>3</sub>)Rh(CO)<sub>2</sub>I<sub>3</sub>]<sup>−</sup> '''(2)'''. This anion rapidly transforms, by the migration of a [[methyl]] gro