Esterification process
View Patent ↗A process that can be used for direct esterification of a dicarboxylic acid such as terephthalic acid with a glycol such as 1,3-propanediol. The process comprises (1) contacting, at an elevated temperature, optionally in the presence of a preformed oligomer, the acid with the glycol to produce a product mixture comprising (i) a water-glycol vapor mixture, which or a portion of which exits the product mixture at the temperature to form a water-glycol vapor mixture and (ii) a liquid product mixture comprising an oligomer having a degree of polymerization of from about 1.9 to about 3.5 and comprising repeat units derived from the acid; (2) separating the glycol from the water-glycol mixture to produce a recovered glycol; and (3) returning the recovered glycol to the product mixture such that the liquid product mixture comprises an excess free glycol.
1. A process comprising contacting, at an elevated temperature, a dicarboxylic acid with a glycol to produce a product mixture comprising (i) a water vapor mixture comprising water and volatile glycol, said water vapor mixture or a portion thereof exits said product mixture to form a water-glycol vapor and (ii) liquid product mixture comprising free glycol and an oligomer having a degree of polymerization of from about 1.9 to about 3.5 and comprising repeat units derived from the acid.
2. A process according to claim 1 further comprising separating said glycol in said water-glycol vapor from said water-glycol vapor to produce a recovered glycol; and combining said recovered glycol and said liquid product mixture thereby maintaining the degree of polymerization of said oligomer in the range of from about 1.9 to about 3.5.
3. A process according to claim 2 wherein said acid is terephthalic acid and said glycol is 1,3-propanediol; said process further comprises recovering said liquid product mixture; and said contacting, said separating, said combining, and said recovering are continuously repeated.
4. A process according to claim 2 wherein said liquid product mixture comprises about 1 to about 20 weight % free glycol based on the weight of said liquid product mixture.
5. A process according to claim 3 wherein said liquid product mixture comprises 3 to 15 weight % free glycol based on the weight of said liquid product mixture.
6. A process according to claim 5 wherein said temperature is in the range of from about 235° C. to about 255° C.
7. A process according to claim 1 wherein said process is carried out under a pressure in the range of from about 100 to about 500 KPa.
8. A process according to claim 1 wherein said process is carried in one stage.
9. A process according to claim 7 wherein said process is carried in one stage.
10. A process according to claim 6 wherein said process is carried in one stage and said separating is carried out by passing said water-glycol vapor through a condenser.
11. A process according to claim 10 wherein said process is carried out in the presence of a preexisting oligomer comprising repeat units derived from said terephthalic acid and said 1,3-propanediol.
12. A process according to claim 3 further comprising polymerizing said liquid product mixture under a polycondensation condition to produce poly(trimethylene terephthalate).
13. A process according to claim 7 further comprising polymerizing said liquid product mixture under a polycondensation condition to produce poly(trimethylene terephthalate).
14. A process according to claim 11 further comprising polymerizing said liquid product mixture under a polycondensation condition to produce poly(trimethylene terephthalate).
15. A process comprising (1) continuously contacting, at about 220 to about 260° C. terephthalic acid with 1,3-propanediol to produce a product mixture comprising (i) a water vapor mixture comprising vapor of said 1,3-propanediol, said water vapor mixture or a portion thereof exits said product mixture to form an water-glycol vapor and (ii) a liquid product mixture comprising free 1,3-propanediol and an oligomer having a degree of polymerization of from 1.9 to 3.5 and comprising repeat units derived from said terephthalic acid and 1,3-propanediol; (2) separating said 1,3-propanediol in said water-glycol vapor from said water-glycol vapor to produce a recovered 1,3-propanediol; and (3) returning said recovered 1,3-propanediol to said liquid product mixture such that said liquid product mixture comprises 1 to 20 weight % free 1,3-propanediol based on the weight of said liquid product mixture.
16. A process according to claim 15 wherein said liquid product mixture comprises 3.5 to about 15 wieght % free 1,3-propanediol.
17. A process according to claim 16 wherein said process is carried in one stage.
18. A process according to claim 17 wherein said process further comprises polymerizing said liquid product mixture under a polycondensation condition to produce poly(trimethylene terephthalate).
19. A continuous process for esterifying terephthalic acid with 1,3-propanediol comprising (1) contacting, at a temperature of about 235° C. to about 255° C., said terephthalic acid, in a single stage esterifier, with 1,3-propanediol sufficient to convert at least 95% of said terephthalic acid to produce a product mixture comprising (i) a water vapor mixture comprising 1,3-propanediol vapor and (ii) a liquid product mixture comprising an oligomer comprising repeat units derived from said terephthalic acid and said 1,3-propanediol and has a degree of polymerization of from 1.9 to 3.5 ; (2) passing said water vapor mixture through a cooling means under a temperature that produces 1,3-propanediol condensate; (3) returning said 1,3-propanediol condensate to said liquid product mixture such that said liquid product mixture comprises 1 to 20 weight % free 1,3-propanediol based on said liquid product mixture; and optionally (3) recovering said liquid product mixture.
20. A process according to claim 19 wherein said liquid product mixture comprises 3 to 15 weight % free 1,3-propanediol and said oligomer.
21. A process according to claim 20 further comprising polymerizing said liquid product mixture under a polycondensation condition to produce poly(trimethylene terephthalate).
22. A continuous process for esterifying terephthalic acid with 1,3-propanediol comprising contacting, under a pressure in the range of from 100 to 400 KPa, said terephthalic acid, in a single stage esterifier, with 1,3-propanediol sufficient to convert at least 95% of said terephthalic acid to produce a product mixture comprising (i) a water vapor mixture comprising unreacted 1,3-propanediol mixture and (ii) a liquid product mixture comprising an oligomer comprising repeat units derived from said terephthalic acid and said 1,3-propanediol and has a degree of polymerization of from 1.9 to 3.5.
23. A process according to claim 22 further comprising recovering said liquid product mixture and polymerizing said liquid product mixture under a polycondensation condition effective to produce poly(trimethylene terephthalate).
24. A process according to claim 22 further comprising separating said 1,3-propanediol in said water-glycol vapor from said water-glycol vapor to produce a recovered 1,3-propanediol; returning said recovered 1,3-propanediol to said liquid product mixture such that said liquid product mixture comprises 1 to 20 weight % free 1,3-propanediol based on the weight of said liquid product mixture; recovering said liquid product mixture; and polymerizing said liquid product mixture under a polycondensation condition effective to produce poly(trimethylene terephthalate).