Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1998-10-05
2000-01-25
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
568854, 568464, 568853, 560234, 560238, C07C 4500, C07C 3118
Patent
active
060180749
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of polyalcohols, ie. polymethylolalkanes and polymethylolcycloalkanes, by reacting alkanes or ketones (which include cyclic ketones) with formaldehyde in the presence of a tertiary amine.
It is known that alkanals can be reacted with excess amounts of formaldehyde with the addition of stoichiometric amounts of an inorganic base (eg. sodium hydroxide solution, calcium hydroxide solution, calcium oxide or barium hydroxide) in aqueous solution to give di-, tri- and in the case of acetaldehyde tetramethylolalkanes. The reaction takes place in a plurality of steps. After one or two, in the case of acetaldehyde three aldol reactions of formaldehyde and the alkanal to give the corresponding mono-, di- and in the case of acetaldehyde trimethylolalkanal, the polyalcohol and an alkali metal formate or alkaline earth metal formate are formed in a crossed Cannizzaro reaction with formaldehyde under the action of the inorganic base.
The amounts of inorganic formate obtained in this procedure interfere with the isolation of the polyalcohol and must be quantitatively separated off before the purification. A plurality of methods is available for the separation, among which the extraction of the polyalcohol, electrodialysis or precipitation of the inorganic salt by a change of solvent are the commonest. A disadvantage is the high cost of these processes; in addition, an aqueous residue of the inorganic salt, contaminated with the extracting agent, remains behind and leads to considerable environmental pollution.
Various other processes for solving this problem in the preparation of polyalcohols have been suggested.
German Laid-Open Application DOS 2,507,461 describes a process for the preparation of 2,2-dimethylolalkanals. These are obtained by reacting aldehydes of the formula ##STR2## where R.sup.1 is an aliphatic radical, with formaldehyde in the presence of tertiary branched alkylamines. The 2,2-dimethylolalkanals prepared by this process are useful intermediates for the preparation of trimethylolalkanes via hydrogenation.
A camizzaro reaction shall be a voided. For example, the reaction of n-butyraldehyde with formaldehyde under the catalytic action of a branched tertiary amine gives dimethylolbutanal. This is distilled and can then be hydrogenated to trimethylolpropane (TMP), although the yields obtained here are unsatisfactory.
German Laid-Open Application DOS 2,813,201 describes also a process for the preparation of 2,2-dimethylolalkanals, aldehydes being reacted with formaldehyde in a molar ratio of 1:5-1:30 in the presence of hydroxides and/or carbonates of the alkali metals and/or alkaline earth metals and/or tertiary amines. A hydrogenation to form trimethylolalkanes may follow. Before the reduction to the trimethylolalkane, any amine used, the formaldehyde used in excess and unconverted aldehyde should be separated off. A high excess of formaldehyde is required for obtaining high yields.
This process is not very suitable for an industrial preparation of trimethylolpropane, since the large excess of formaldehyde has to be separated off before the catalytic hydrogenation. In the reaction formic acid formed is fixed as a trialkyl ammonium formiate and removed by distillation. The distillation is difficult to carry out in industrial scale it very pure products are desired.
EP-A-0 142 090 discloses a process for the preparation of trimethylolalkanes by reaction of 1 mol of an n-alkanal with 2.2-4.5 mol of formaldehyde and 0.6-3 mol of a trialkylamine in aqueous solution and subsequent hydrogenation. Here, the reaction mixture is worked up by distillation before or after the hydrogenation.
EP-A-0 289 921 describes a process in which the synthesis mixture is hydrogenated in the same manner as in the process described in EP-A-0 142 090. In the embodiment (a) of the process described in EP-A-0 289 921, in the preparation of trimethylolalkanes by reaction of n-alkanals with 2.2-4.5 mol of formaldehyde in aqueous solution in the presence of 0.6-3 mol of a tri
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Brudermuller Martin
Kratz Detlef
Stammer Achim
Witzel Tom
BASF Aktiengesellshcaft
Killos Paul J.
Oh Taylor V.
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