MXPA01001772A

MXPA01001772A - Process for the purification of 1,3-propanediol

Info

Publication number: MXPA01001772A
Application number: MXPA/A/2001/001772A
Authority: MX
Inventors: Hari Babu Sunkara; Robert John Ii Umile
Original assignee: Ei Du Pont De Nemours And Company
Priority date: 1998-08-18
Filing date: 2001-02-16
Publication date: 2001-12-04

Abstract

Disclosed is a process for the removal of impurities, especially color forming impurities, from 1, 3-propanediol.

Description

PROCESS FOR THE PURIFICATION OF 1, 3-PRO ANODIOL FIELD OF THE INVENTION This invention concerns a process for the removal of impurities, especially color-forming impurities, of 1,3-propanediol.

Technical Background of the Invention 1,3-propanediol is a precursor of polyether glycols, homopolymers and copolymers of polyester, and thermoplastic elastomers. The quality of these products in general depends on the quality of the raw material. For some applications, such as in fibers, color quality is a primary concern. It is known that these 1,3-propanediol derivatives have suffered from discoloration. Samples of the commercially available 1, 3-propanediol raw material have resulted in brown polyether glycols. The attempts described to eliminate the color of the products made from the available 1,3-propanediol have been laborious and expensive. Ref: 127179 Even after extensive purification processes, many products retain a yellow color. The Patent of E. U. A. No. ' No. 2,520,733 describes a process for the purification of polyols which are prepared from 1,3-propanediol in the presence of an acid catalyst (2.5 to 6% by weight) and at a temperature ranging from about 175 ° C to 200 ° C. This purification process involves the filtration of the polymer through Fuller's earth after hydrogenation. Even after this extensive purification process, the final product remains light yellow in color. U.S. Patent No. 3,326,985 describes a process for the preparation of poly (1,3-propanediol) of molecular weights in the range of 1200-1400 which have an improved color by vacuum separation, under nitrogen, to poly (1). , 3-propanediol) of lower molecular weights. US Patent No. 5,659,089 describes a process for the preparation of poly (2-methyl-1,3-propanediol) by the etherification of 2-methyl-1,3-propanediol. No process is given for the purification of the diol. Any available diol grade can be used for the etherification process.

US Patent No. 5,527,973 describes a process for providing a purified 1,3-propanediol which can be used as a raw material for a low color polyester. This process has several disadvantages that include the use of a large equipment and the need for dilution with large amounts of water that is difficult to remove from the product. The process of the present invention alleviates the problem of the production of the bleached polymer in a relatively simple and economical process. The process of the present invention involves the purification of, and removal of, the color precursors from the initial 1,3-propanediol reagent rather than subjecting the resulting products to treatment. The diol purified from this process is useful for preparing a variety of polymers including polyether glycols, polyesters and thermoplastic elastomers having excellent color characteristics.

Brief Description of the Invention A process for the purification of 1,3-propanediol comprising the steps of a) contacting 1,3-propanediol with an acid catalyst at a temperature above that required for the impurities is described. react and below that required for extensive ether formation; and b) removing the purified 1, 3-propanediol from the impurities, impurities that have reacted and the acid catalyst.

Detailed Description of the Invention In the preparation of the low molecular weight polyether glycols by means of the dehydration of 1,3-propanediol, the quality of the polyol is an important detail. For some applications, such as fiber production, color is a primary concern. In the past, attempts to prepare polytrimethylene glycols that have good color properties have been a failure. This invention describes a process for the preparation of 1, 3-propanediol purified so that the products that are made of this, polyols, homopolymers and polyester copolymers, and thermoplastic elastomers, have excellent color characteristics. Color-free polyether glycols, ie free of chromophores, have been prepared from 1,3-propanediol which has been purified from its chromophore precursors by a two-step process. The first step in the treatment of the diol to liberate it from the color forming particles (referred to herein as "color forming precursors") involves the contact of the 1,3-propanediol with an acid catalyst at elevated temperatures. While not wishing to be limited by any mechanism, the Applicant believes that this step converts color-forming precursors and other impurities into colored and non-colored derivatives which, due to their changed chemical nature, are easily separable from 1,3-propanediol. . The second step of the purification process involves the separation of the desirable, 1, 3-propanediol purified from the colored and uncolored derivatives that are formed, from the acid catalyst that is used to effect the conversion and, potentially, from the residual impurities. An acid catalyst is used in the treatment process. This acid catalyst promotes the conversion of chromophore precursors to chromophores. The type of acid, (homogeneous or heterogeneous), its nature (strong or weak) and the amount of acid catalyst can vary widely. Although soluble acid catalysts, including inorganic acids and organic sulfonic acids, can be used, normal heterogeneous acid catalysts are preferred because they can be more easily removed and easily recycled. Soluble catalysts, if used, can be removed by extraction or neutralization. The solid and heterogeneous acid catalysts can be removed by filtration. The heterogeneous fixed catalyst can also be used, that is, in a continuous process, with the proviso that the contact time is sufficient. Suitable heterogeneous catalysts are perfluorinated ion exchange polymers (PFIEP) containing pendant sulfonic acid groups or pendant carboxylic acid groups, including the Nafion® catalyst, which can be obtained from the DuPont company, which is an example of perfluorinated ion exchange polymers containing pendent sulfonic acid groups, Nafion catalyst supported by silica or alumina, Nafion® Super acid catalyst, a porous nanocomposite of silica and resin, acid zeolites, or acid Naphion clays. The amount of acid catalyst that is used herein is not critical, as long as a sufficient amount of the catalyst is present. Small amounts of the catalyst may need prolonged treatment times. In the case of the commercial catalyst Nafion® NR50, 1% by weight of the catalyst against the weight of 1,3-propanediol is convenient in a batch process. The amount of the catalyst that is employed, in a batch process, is generally within the range of about 0.1 to 5% weight based on the amount of 1,3-propanediol that is used. The step temperature for the acid treatment is selected such that the reaction that converts the chromophore precursors can easily occur, but the dehydration reaction of 1,3-propanediol is essentially avoided. The process of the invention is carried out by heating the 1,3-propanediol and the acid catalyst at a temperature within the range of about 100-160 ° C for 0.1-3 hours under a nitrogen atmosphere. At a temperature above 170 ° C, the acid can function as a dehydrating catalyst that could lead to the formation of polyether glycols from 1,3-propanediol. Preferably, the reaction temperature is maintained within the range of 130 ° C-150 ° C so that the reaction of the chromophore precursors occurs, but essentially no dimers or trimers of 1,3-propanediol are formed. The acid treatment is carried out more conveniently at atmospheric or above atmospheric pressures. In a preferred mode of operation, after the color forming precursors are transformed, the mixture is cooled to room temperature, and the solid catalyst is removed either by filtration or by decanting. The filtered mixture is then distilled under reduced pressure, and 1,3-propanediol is collected. Impurities with color and other impurities are left in the distillation flask. The absence of an acid catalyst during the vacuum distillation process limits the occurrence of the 1,3-propanediol dehydration reactions. The purification of 1,3-propanediol, as described above, can be carried out either in a batch process or in a continuous process. The treatment can be carried out in an agitated system or, if the acid catalyst is in solid form or adhered / attached to the solid support, the treatment can be carried out by passing the diol over or through a solid acid catalyst bed. The process can be carried out as an autonomous process, carried out with the 1,3-propanediol available. Alternatively, it can be integrated into a process for the manufacture of 1, 3-propanediol carried out in the manner of one of the steps of a manufacturing process of 1,3-propanediol. The 1,3-propanediol can be prepared by a variety of manufacturing processes including the hydration of acrolein followed by a hydrogenation of the resulting hydroxypropanal, or the hydroformylation of the ethylene oxide followed by a reduction of the resulting hydroxypropanal. The purification process can be integrated with some of these or other manufacturing processes. The purified 1,3-propanediol is isolated by means known in the art, more preferably by vacuum distillation of the diol outside the converted color-forming precursors of the colored and uncolored derivatives. In a subsequent processing, the purified diol can be polymerized in the presence of either a soluble or insoluble acid catalyst to obtain a colorless polyether polyol of low molecular weight. In alternative end uses, the purified diol can be used to prepare polyesters, for example, poly (1,3-propylene terephthalate) by methods known in the art. Depending on the intensity of the color of the samples to be quantified, two different coloriometric scales are used. For products with light colors, the Platinum-Cobalt Standard (APHA) is used and for products with dark colors the Gardner Standard is used.

EXAMPLES EXAMPLE 1 Purification process of 1,3-propanediol using the acid catalyst Nafion® A three-neck flask of 5 L with a distillation column, a mechanical stirrer and a nitrogen inlet is charged with 1,3-propanediol (3714.2 g ) (commercial grade, Degussa) and catalyst Nafion® NR50 (37,147 g) (DuPont). The mixture is mechanically stirred and heated to 130 ° C under a nitrogen atmosphere. At this temperature, the liquid turns yellow. Then the liquid turns brown while heating at 150 ° C. The temperature is kept constant at 150 ° C for a period of about 2 hours and then it is allowed to cool to room temperature. No distillate is collected in the receiving flask, which indicates that essentially no dehydration reaction occurred under these conditions. The solid acid catalyst is removed by decanting the colored solution. The diol is then isolated from the colored impurities on distillation at 100 ° C under reduced pressure. The APHA color values as quantified in a HunterLab ColorQuest (Hunter Associates Laboratory, Inc., Reston, VA) for the purified diol and for the original diol are 3 and 7, respectively, indicating an improvement in color characteristics of the purified diol. Heating the 1,3-propanediol which is purified in this way until reflux under a nitrogen atmosphere for 3 hours causes the APHA color to increase from 3 to 20. A similar treatment of 1,3-propanediol initial produces a colored product that has an APHA color of 60 (that is, a change from 7 to 60 of APHA color). Example 2, below, and Comparative Example 1, wherein these two samples of 1,3-propanediol are converted to poly (1,3-propanediol) further illustrate the effectiveness of the process of the present invention in removing impurities color formers EXAMPLE 2 Synthesis of Poly (1,3-propanediol) from purified 1,3-propanediol To a 250 mL three-necked flask, 152.2 g (2.0 mol) of purified 1,3-propanediol, as prepared in the Example 1, and 1903 g (10 mmol) of p-toluenesulfonic acid (Aldrich Chemical Co., Milwaukee, Wl) are added at room temperature. The mixture is stirred and heated to 180-200 ° C under a nitrogen atmosphere. The distillate (33.1 mL), mostly water, is collected as the progress of the dehydration reaction. The reaction is terminated after 5.5 hours and the mixture is cooled to room temperature. The colorless poly (1,3-propanediol) is obtained from this process. The color APHA value for the polyol is quantified and had a value of 48.

COMPARATIVE EXAMPLE 1 Synthesis of poly (1,3-propanediol) from 1,3-propanediol without purification To an amount of 152.2 g (2.0 mol) of 1,3-propanediol (commercial grade, Degussa), 1903 g are added (10 mmol) of p-toluenesulfonic acid. The mixture is stirred and heated under a nitrogen atmosphere. While the temperature of the reaction mixture increases, the formation of color at a temperature of 130 ° C is observed and then the dehydration reaction occurs at 180-200 ° C. Approximately 32.5 mL of the distillate is collected during the dehydration reaction that continues for a period of 5.5 hours. The color properties of the polyol are quantified and have an APHA color value of > 300, that is, outside the APHA color scale. The color is quantified in Gardner units using a Hellige Daylite Comparison Illuminator (Hellige, Inc., Garden City, NY) which gives a Gardner value of.

EXAMPLE 3 Purification of Diol on a Larger Scale The purification process of the 1,3-propanediol described in Example 1 is proportionally increased. A 113.5 L (30 gallon) glass-lined autoclave is charged with polymer grade 1, 3-propanediol (80 kg) and Nafion® NR50 catalyst (0.80 kg (1.76 lb)). The mixture is mechanically stirred and heated to 150 ° C under a nitrogen atmosphere. The temperature is kept constant at 150 ° C for about 2 hours and then it is allowed to cool to room temperature. After cooling, the autoclave is discharged through a filter to recover the acid catalyst in solid state. The decolorized diol solution, having an APHA color value greater than 300, is distilled in batches by using a 22 L three neck flask equipped with a distillation column, a mechanical stirrer and a nitrogen inlet at 120 ° C under reduced pressure. After the distillation is finished the purified diol (65.3 kg (144 lb)) has a color APHA value of 3. When heating the 1,3-propanediol which is thus purified to a reflux, under an atmosphere of nitrogen for 3 hours, causes the color APHA value to increase from 3 to 12. As described in Example 2, the poly (1,3-propanediol) is made with the purified diol and the color APHA value of the polymer It is 30.

It is noted that in relation to this date, the best known method for the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A process for the purification of 1,3-propanediol comprising the steps of a) contacting the 1,3-propanediol with an acid catalyst at a temperature above that required for the impurities to have reacted, and below of that required for extensive ether formation; and b) isolating the purified 1,3-propanediol from the impurities, reacted impurities and the acid catalyst.

2. The process according to claim 1, characterized in that the purified 1,3-propanediol is isolated by 1) separating the acid catalyst and 2) distilling the 1,3-propanedione from the impurities and impurities that have reacted.

3. The process according to claim 1, characterized in that the temperature in step (a) is between 100 ° C and 160 ° C.

4. The process according to claim 3, characterized in that the temperature in step (a) is between 130 ° C and 150 ° C.

5. The process according to claim 1, characterized in that the acid catalyst is insoluble in 1,3-propanediol acid.

6. The process according to claim 5, characterized in that the acid catalyst is a solid.

7. The process according to claim 6, characterized in that the solid acid catalyst is selected from the group consisting of perfluorinated ion exchange polymers (PFIEP) containing pendant groups of sulfonic acid or pendent carboxylic acid groups, acid zeolites. , acid clays.

8. The process according to claim 7, characterized in that the solid acid catalyst is selected from the group consisting of perfluorinated ion exchange polymers containing pendant groups of sulfonic acid, perfluorinated ion exchange polymers supported by silica or alumina containing pendant groups of sulfonic acid and porous nanocomposites of perfluorinated ion exchange polymers containing pendent groups of sulfonic acid and silica.