Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
2001-08-16
2003-02-18
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
C560S177000
Reexamination Certificate
active
06521752
ABSTRACT:
The invention relates to a process to separate linear 5-formylvalerate compound from a crude mixture comprising 5-formylvalerate compound and 2-, 3- and/or 4-formylvalerate compound by vacuum distillation.
Such a process is described in WO-A-9706126. This patent application describes a process in which the distillation is performed at a low pressure and at a temperature at the bottom of the distillation unit less than 150° C. According to this publication, the presence of a certain amount of oxygen during the distillation is allowed.
A disadvantage of this process is that the ultimate yield of the 5-formylvalerate compound is lowered. This is because a certain amount of the formylvalerate compounds is converted to the corresponding oxidized compounds and because the oxidized compounds in turn initiate the formation of other undesired compounds, for example aldol condensation compounds.
Another disadvantage of this process is that, due to the presence of oxygen, the thus obtained 5-formylvalerate is less suitable to be used as an intermediate to &egr;-caprolactam. We have found that the presence of oxidized compounds in the 5-formylvalerate product is not acceptable at all. This is because the oxidized compounds will negatively influence the &egr;-caprolactam quality. Furthermore the oxidized compounds or their derivatives are difficult to remove from &egr;-caprolactam.
The object of the invention is to minimize the formation of oxidized compounds in the 5-formylvalerate product.
This object is achieved in that the distillation is performed in the presence of a phenolic compound with a boiling point which is at least 10° C. higher than the boiling point of the 5-formylvalerate compound at 0.1-100 kPa.
It has been found that with the process according to the invention the amount of oxidized compounds, for example valerate and/or monoadipate compounds, in the 5-formylvalerate product is considerably reduced compared to the process according to the state of the art. The obtained 5-formylvalerate can be advantageously used to prepare &egr;-caprolactam. The 5-formylvalerate thus obtained may also be advantageously used as starting compound to prepare other products, for example adipic acid and &egr;-caprolacton. Another advantage is that the phenolic compound remains in the 5-formylvalerate distillation product, thus reducing oxidation after the distillation as well. In the process according to the invention the phenolic compound is easily separated from the 5-formylvalerate by distillation. The phenolic compound can thus advantageously be reused in for example the process according to the invention.
It was not to be expected that the presence of oxygen during the vacuum distillation of a mixture of 5- and 2-, 3- and/or 4-formylvalerate compound would have such a disadvantageous effect on 5-formylvalerate yield. No mention of this fact is found in the earlier mentioned WO-A-9706126.
EP-A-590613 describes a process for the preparation of a mixture of linear and branched aldehydes by hydroformylating an unsaturated olefin compound in the presence of a rhodium/bidentate phosphite complex catalyst system and an aromatic phenol compound, whereby the catalyst system is separated from the crude aldehyde product by means of distillation. The phenolic compound will be separated from the crude aldehyde product during this separation.
Phenolic compounds, which are employable in the present invention, can be well known compounds which are in general readily commercially available. Any phenolic compound having a boiling point which is at least 10° C. higher than the boiling point of the 5-formylvalerate at 0.1-100 kPa can be used in the process of the invention. Preferably, the phenolic compound has a boiling point which is at least 20° C. higher than the boiling point of the 5-formylvalerate.
Examples of suitable phenolic compounds are 4-hydrophenol (hydroquinone), 3-hydroxyphenol (resorcinol), 1,2,3-trihydroxybenzeen (pyrogallol), 2,6-di-tert.-butyl-4-methylphenol, 6-tert.-butyl-2,4-dimethylphenol, 2,4-dimethyl-6-(tetramethylbutyl)phenol, 2,4-diisoamylphenol, 4,4′-thiodiphenol, the commercially available Irganox-1076, Irganox-1330, Irganox-1010, Irganox-1098, Irganox-1035, Ultranox 210 and Ultranox 276.
Examples of preferred phenolic compounds are the commercially available Irganox compounds.
The process according to the present invention is performed in a vacuum distillation unit comprising one or more distillation columns. In case the vacuum distillation unit contains more than one distillation column, the crude mixture is fed to the first column. The distillation residue of the first column is subsequently fed to a second distillation column. The distilland (vaporized fraction) of the second column is preferably recycled to the first column. The pressure of the vacuum distillation is between 0.1-100 kPa, preferably between 0.1 and 15 kPa. The temperature of the vacuum distallation is between 30 and 250° C., preferably between 30 and 150° C.
The phenolic compound is present in the crude mixture which is fed to the (first) vacuum distillation column or it is added directly to the (first) vacuum distillation column. The phenolic compound can be fed to the distillation column at any point thereof. The phenolic compound is preferably fed to the column above the feed point of the crude mixture of linear and branched formylvalerate compounds. More preferably, the phenolic compound is fed to the top of the column.
The amount of pheholic compound in the mixture is preferably an effective amount sufficient to avoid substantial formation of the undesired byproducts in the 5-formylvalerate stream. In particular, the amount of phenolic compound in the mixture is between 0.01 and 0.2 wt. %, preferably between 0.05 and 0.15 wt. %.
The 5-formylvalerate ester compound can be represented by the following general formula:
where R is preferably an organic group with 1 to 20 carbon atoms and more preferably with 1 to 6 carbon atoms. The organic group is an alkyl, cycloalkyl, aryl or aralkyl group. More preferably R is an alkyl group. Examples of R groups include methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, isobutyl, cyclohexyl, benzyl and phenyl. By preference R is methyl or ethyl.
In the process according to the invention, the 5-formylvalerate is separated from its branched by-products, 2-, 3- and/or 4-formylvalerate, by vacuum distillation. These branched products can be combusted or decarbonylated to the corresponding pentenoate compound or oxidized to acid compounds like monomethyladipate by well known processes.
The 5-formylvalerate, which is obtained with the process according to the invention, can for example advantageously be used as starting compound for the preparation of adipic acid as described in EP-A-295551. Adipic acid is a precursor for Nylon-6,6.
Another example of an interesting use of the 5-formylvalerate ester compound is the preparation of &egr;-caprolacton. By reduction of the 5-formylvalerate ester compound and subsequent cyclization of the intermediate compound.
Another example of a very interesting use is the reductive amination of the 5-formylvalerate to an amino intermediate compound and the subsequent cyclisation to &egr;-caprolactam as for example described in EP-A-729944 and EP-A-234295. &egr;-caprolactam is a precursor for Nylon-6. The reductive amination may be performed in any suitable solvent in which the 5-formylvalerate compound is soluble. Examples of these solvents are water, ammonia, C
1
-C
6
alkanols, for example methanol, ethanol, propanol or butanol, ethers, for example diethyl ether, methyl tert-butyl ether, dipropylether or diisopropylether.
With reductive amination is meant the reaction of the 5-formylvalerate compound with a molar excess of ammonia and hydrogen. The reductive amination is generally performed in the presence of a group 8-10 metal hydrogenation catalyst, for example Ni, Co, Ru, Pt or Pd. Examples of specific hydrogenation catalysts are Raney nickel, Raney cobalt and supported Ru catalysts for example Ru on carbon or Ru on alumina. A
Borman Peter C.
Gelling Onko J.
DSM N.V.
Killos Paul J.
Pillsbury & Winthrop LLP
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