Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-04-29
2004-02-17
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S619000, C568S680000
Reexamination Certificate
active
06693222
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a process for the splitting of water-soluble ethers. The invention also concerns a process for the production of 1,3-propanediol (PDO).
BACKGROUND OF THE INVENTION
Generally ethers can be split in the gas phase, such as the splitting of n-butylalkyl ethers or n-butylaryl ethers into butene and alcohols or phenols, or the splitting of esters, vinyl ethers and alkenes with beta-positioned chlorine in the pipe reactor of Vycor glass into unsaturated chlorine compounds such as vinyl chloride. Another example is gas phase pyrolysis with benzylphenyl ether in a glass container in the presence of tetraline.
Ether splitting in the liquid phase is also possible. For instance, the pyrolysis of dibutyl ether in a gold reactor into n-butane, butyraldehyde and also 1-butanol.
For the splitting of the ethers both subcritical and supercritical solvents can also be used. For instance, thermolysis of benzylphenyl ether in subcritical and supercritical water and supercritical methanol, results in, among others, phenol and toluene.
Ethers such as 1-phenoxynaphthalene and 9-phenoxyphenanthrene are capable of being split by so-called aquathermolysis in a pipe of V4A steel only in the presence of water into 1-napthene and 9-hydroxyphenathrene and phenol respectively.
U.S. Pat. No. 6,218,580 (counterpart to EP 0 915 075), which is incorporated herein by reference, teaches that the acid-catalyzed intermolecular etherification of mono- or polyhydric alcohols and acid-catalyzed ether cleavage in the presence of water can be improved if etherification or ether cleavage is carried out in the presence of an acid catalyst with a hydrogenation catalyst under a hydrogen atmosphere. Comparison Example 2 describes cleavage of dipentaerythritol with propionic acid in water wherein the reaction mixture is heated to 280° C.
As is known from U.S. Pat. No. 5,364,987 (counterpart to EP 0 577 972), which is incorporated herein by reference, processes for the production of 1,3-propanediol from acrolein are generally based on two reaction steps. The first step, step (a), comprises hydration of acrolein in the presence of an acid hydration catalyst. The second step, step (b), comprises catalytic hydrogenation of the reaction mixture containing 3-hydroxypropionaldehyde from step (a), which reaction mixture has been freed of unreacted acrolein. (Preferably, acrolein levels can be reduced to about 200 ppm or less.) The processes also comprises step (c), distillative refining of the reaction mixture. Pure 1,3-propanediol (which can contain as much as 99.9 weight % or more 1,3-propanediol) is obtained by distillative refining of the reaction mixture in step (c), i.e. evaporation of the water, the distillation of the residual water, intermediate boiler distillation (removing low boiling compounds) and distillation-purification.
The disadvantage of the known process for the production of 1,3-propanediol is the fact that due to various secondary reactions, especially during the hydration step, the total yield of 1,3-propanediol is reduced. During the refining of the reaction mixture from the catalytic hydrogenation, the high boiler fraction (boiling point above that of 1,3-propanediol) contains as primary products 4-oxa-1,7-heptanediol (DiPDO) (also known as 3,3′-oxybis-1-propanol or bis(3-hydroxypropyl)ether) and 4-hydroxy-3-hydroxymethyl tetrahydropyran (HMT, in the form of two isomers H-HMT1 and H-HMT2).
U.S. Pat. No. 5,364,987 teaches a process comprising (1) distilling the aqueous 1,3-propanediol mixture which contains by-products having boiling points higher than 1,3-propanediol; (2) separating DiPDO from the by-products having boiling points higher than 1,3-propanediol; and treating the DiPDO in aqueous solution at from 100-300° C. with an solid acid catalyst in order to cleave DiPDO to form 1,3-propanediol; and returning the resulting reaction mixture from which the solid acid catalyst has been removed to the distilling step. U.S. Pat. No. 5,364,987 teaches that separation of DiPDO is necessary, whereas it is desired that such a separation not be used, i.e., that the high boiler sump accumulating in the process can be utilized directly.
Other processes for the producing of 1,3-propanediol can also result in the production of DiPDO and conversion of DiPDO to 1,3-propanediol would also be beneficial to these processes.
One object of this invention is to provide a simple and effective method for splitting or cleaving oligomeric water-soluble ethers.
Another objective of the present invention is to provide a method for increasing the yield of 1,3-propanediol in the process for the production of 1,3-propanediol from acrolein in a simple way.
Other objectives will become evident from the following description of the invention.
SUMMARY OF THE INVENTION
The invention is directed to a process for production of 1,3-propanediol including the steps: (a) hydrating acrolein in the presence of an acid hydration catalyst; (b) catalytically hydrogenating the reaction mixture of step (a), which reaction mixture comprises 3-hydroxypropionaldehyde and is freed of unreacted acrolein; (c) refining the reaction mixture of step (b) containing water, 1,3-propanediol and the by-products boiling higher than 1,3-propanediol; and (d) treating 4-oxa-1,7-heptanediol to form 1,3-propanediol by (1) removing a boiler sump comprising 4-oxa-1,7-heptanediol from the refining step (c), (2) treating the boiler sump in an aqueous solution in the presence of an acid catalyst at about 200 to about 300° C. to form a solution comprising 1,3-propanediol, (3) neutralizing the solution obtained is step (2), and returning the neutralized solution from step (3) to the refining step (c).
The invention can be used to treat any such sump. According to a preferred process of making 1,3-propanediol, the sump preferably contains at least about 50 weight %, preferably at least about 55 weight %, 4-oxa-1,7-heptanediol. It preferably contains up to about 70 weight %, more preferably up to about 65 weight %, 4-oxa-1,7-heptanediol.
Preferably water is added to the boiler sump to form the aqueous solution. Preferably the water is added so that the ratio of organic compounds in the sump:water (organic:water ratio) is at least about 0.5:1, preferably at least about 1:1. Preferably, the organic:water ratio is up to about 1:20, more preferably up to about 1:8.
In one preferred embodiment, the boiler sump further comprises 4-hydroxy-3-hydroxymethyl tetrahydropyrane.
The invention is also directed to a process for splitting oligomeric water-soluble ether comprising: (a) treating an aqueous solution comprising oligomeric water-soluble ether in the presence of homogeneous acid catalyst at a temperature of from about 200 to about 300° C. to form the monomer of the oligomeric water-soluble ether; and (b) neutralizing the solution obtained in step (a). Preferably, the oligomeric water-soluble ether is selected from the group consisting of C
4
-C
7
ethers and mixtures thereof, more preferably the group consisting of 4-oxa-1,7-heptanediol, diethyleneglycol dimethyl ether, diglycol, dipropyleneglycol, dipropyleneglycol methyl ether, and propyleneglycol methyl ether. Preferably, the aqueous solution further comprises organic compounds having boiling points higher than the oligomeric water-soluble ether. In the most preferred embodiment, the oligomeric water-soluble ether is 4-oxa-1,7-heptanediol and the monomer is 1,3-propanediol. In that embodiment, the organic compounds having boiling points higher than the oligomeric water-soluble ether comprise 4-hydroxy-3-hydroxymethyl tetrahydropyran.
The acid catalyst is preferably a mineral acid, which is preferably selected from the group consisting of H
2
SO
4
, H
3
PO
4
or HNO
3
, and mixtures thereof.
Alternatively, the acid catalyst is preferably an organic acid, which is preferably selected from the group consisting of propionic acid, trifluoracetic acid or pyridine hydrochloride, and mixtures thereof.
The acid catalyst is used in an amount of at least 0.05 weight %, more preferably at least a
Haas Thomas
Hahn Torsten
Ronge Christian
Barts Samuel
E. I. du Pont de Nemours and Company
Kuller Mark D.
Witherspoon Sikarl A.
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