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Wacker process
The Wacker process or the Hoechst-Wacker process (named after the chemical companies of the same name) originally referred to the oxidation of ethylene to acetaldehyde by oxygen in water in the presence of tetrachloropalladate(II) as the catalyst.〔Translated in part from :de:Wacker-Verfahren.〕 The same basic reaction is used to produce aldehydes and ketones from a number of alkenes with the Monsanto process for producing acetic acid. This chemical reaction was the first organometallic and organopalladium reaction applied on an industrial scale. The Wacker process is similar to hydroformylation, which is also an industrial process and also leads to aldehyde compounds. The differences are that hydroformylation promotes chain extension, and uses a rhodium-based catalyst system. The Wacker process is an example of homogeneous catalysis. The palladium complex with ethylene is reminiscent of Zeise's salt, K() which is a heterogeneous catalyst.
==History==
The development of the chemical process now known as the Wacker process began in 1956 at Wacker Chemie.〔''Acetaldehyde from Ethylene — A Retrospective on the Discovery of the Wacker Process'' Reinhard Jira Angew. Chem. Int. Ed. 2009, ''48'', 9034–9037 〕 At the time, many simple aliphatic compounds were produced from acetylene (as calcium carbide) but the construction of a new oil refinery in Cologne by Esso close to a Wacker site, combined with the realization that ethylene would be a cheaper raw-material prompted Wacker to investigate its potential uses. As part of the ensuing research effort, a reaction of ethylene and oxygen over palladium on carbon in a quest for ethylene oxide unexpectedly gave evidence for the formation of acetaldehyde (simply based on smell). More research into this ethylene to acetaldehyde conversion resulted in a 1957 patent describing a gas-phase reaction using a heterogeneous catalyst.〔J. Smidt, W. Hafner, J. Sedlmeier, R. Jira, R. Rottinger (Cons. f.elektrochem.Ind.), DE 1 049 845, 1959, Anm. 04.01.1957.〕 In the meanwhile Hoechst AG joined the race and after a patent filing forced Wacker into a partnership called Aldehyd GmbH. The heterogeneous process ultimately failed due to catalyst inactivation and was replaced by the water-based homogeneous system for which a pilot plant was operational in 1958. Problems with the aggressive catalyst solution were solved by adopting titanium (newly available for industrial use) as construction material for reactors and pumps. Production plants went into operation in 1960.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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