Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1988-11-21
1991-10-01
Lone, Werren B.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568451, 568492, C07C 4550
Patent
active
050535510
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a continuous process for the production of aldehydes by hydroformylation of olefins.
Hydroformylation is a well known process in which an olefin, often a terminal olefin of the formula: group, is reacted under elevated temperature and pressure conditions in the presence of a suitable catalyst with carbon monoxide and hydrogen to yield an aldehyde, according to the following equation:
The catalysts initially suggested were based on cobalt but these require use of high operating pressures and usually result in production of significantly high quantities of the corresponding alcohol of formula R.CH.sub.2.CH.sub.2.CH.sub.2 OH, as well as by-products such as acetals, esters, and the like. In addition, product recovery is complicated by the fact that the cobalt carbonyl catalysts are volatile and toxic, which means that the product stream from the hydroformylation zone has to be subjected to a decobalting step, a procedure which generally destroys the cobalt catalyst, before the decobalted product stream can be subjected to distillation or further treatment for recovery of aldehyde product. Hence, for economic operation, provision has to be made for recovering cobalt and for regenerating the cobalt catalyst therefrom. Ethylene gives rise to a single aldehyde hydroformylation product, i.e. propionaldehyde, but when propylene or a higher olefin is hydroformylated, the product stream always contains, besides the desired n-aldehyde, a proportion of the corresponding iso-aldehyde, which is formed according to the equation: olefins, when using a cobalt hydroformylation catalyst, is of the order 4:1 or so.
A major advance in hydroformylation came with the advent of rhodium complex hydroformylation catalysts. These afforded great advantages, notably a non-volatile catalyst, a lower operating pressure, much reduced yields of alcohols and other by-products, and usually a significantly higher n-/iso- product aldehyde ratio. For further details of rhodium complex hydroformylation catalysts and conditions of operation therewith, the attention of the reader is drawn, for example, to U.S. Pat. No. 3,527,809. A description of a typical commercial plant employing such a catalyst will be found in the article: "Low-pressure OXO process yields a better product mix", Chemical Engineering, Dec. 5, 1977, pages 110 to 115.
The rhodium catalyst employed commercially in such a process generally comprises rhodium in complex combination with carbon monoxide and with a ligand, such as triphenylphosphine.
Usually the desired product of a hydroformylation reaction is the n-aldehyde, rather than the iso-aldehyde, for which there may be a limited commercial market; hence in many commercially operating hydroformylation plants the iso-aldehyde is burnt as a fuel since there is no ready market therefor. The use of a phosphine ligand, such as triphenylphosphine, has the advantage that high n-aldehyde/iso-aldehyde molar ratios can be obtained from terminal olefins. In some cases, however, the iso-aldehyde is the preferred product; for example, it has been proposed to produce isoprene from but-2-ene by hydroformylation to yield the iso-aldehyde, 2-methylbutanal, followed by dehydration by passage at elevated temperature over a suitable catalyst. When the desired product is the iso-aldehyde it has been proposed in EP-A-0096987 to use a rhodium complex hydroformylation catalyst and a phosphite ligand, such as triphenylphosphite. Alternatively it has been proposed in EP-A-0096988 to produce iso-aldehydes by hydroformylation of internal olefins using a rhodium complex hydroformylation catalyst and a cyclic phosphite ligand. Hydroformylation of alpha-olefins using a similar catalyst system to produce aldehyde mixtures whose n-/iso-aldehyde molar ratios approximate those obtained by using cobalt catalysts is described in EP-A-0096986.
Although the use of added solvents has been proposed on many occasions in the prior art, including U.S. Pat. No. 3,527,809, most commercially operating hydroformylation plants operate in so-called "n
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Dennis Alan J.
Harrison George E.
Davy McKee (London) Limited
Lone Werren B.
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