Methods for producing an ester of an alpha, beta-unsaturated carboxylic acid

1. A method for producing an ester of an alpha,beta-unsaturated carboxylic acid, comprising:

a) obtaining a beta-hydroxyalkanoate containing composition, selected from the group consisting of 3-carbon beta-hydroxyalkanoates, 4-carbon beta-hydroxyalkanoates, or mixtures thereof, the beta-hydroxyalkanoate containing composition comprising:

(i) at least 40 percent by weight beta-hydroxyalkanoate equivalents

(ii) at least 0.1 percent by weight free beta-hydroxyalkanoates;

(iii) at least 1 percent by weight saccharide equivalents; and

(iii) less than 15 percent by weight water;

b) mixing a mono-alcohol in a molar ratio of from about 1.1 to 1.0 to about 10.0 to 1.0 of mono-alcohol to beta-hydroxyalkanoate equivalents present in the beta-hydroxyalkanoate containing composition to obtain a first mixture;

c) heating the first mixture to form a reaction product;

d) distilling the reaction product and recovering an ester of the alpha,beta-unsaturated carboxylic acid fraction comprising:

(i) at least 50 percent by weight the ester of the alpha,beta-unsaturated carboxylic acid ;

(ii) less than 1 percent by weight beta-hydroxyalkanoic acid;

(iii) less than 1 percent by weight water; and

(iv) less than 0.5 percent by weight saccharide equivalents.

2. The method of claim 1 , wherein step (d) further comprises separating the reaction product into a first fraction enriched in the mono-alcohol and water, and a second fraction enriched in the ester of the alpha,beta-unsaturated carboxylic acid , wherein the ester of the alpha,beta-unsaturated carboxylic acid fraction is recovered from the second fraction.

3. The method of claim 2 , wherein step (d) comprises a fractional distillation.

4. The method of claim 1 , wherein step (d) comprises:

(1) a first step to provide a first fraction enriched in water and mono-alcohol and a second fraction enriched in alkyl beta-hydroxyalkanoate and saccharide; and

(2) a second step to dehydrate the alkyl beta-hydroxyalkanoate of the second fraction to form an ester of the alpha,beta-unsaturated carboxylic acid.

5. The method of claim 4 , wherein (d) further comprises: (3) recovering the ester of the alpha,beta-unsaturated carboxylic acid fraction overhead from the second fraction.

6. The method of claim 4 , wherein the temperature during the second step is higher than the temperature utilized for step (c).

7. The method of claim 5 , wherein the pressure during step (c) is higher than the pressure during the second step.

8. The method of claim 1 , wherein the first mixture is heated during step (c) to a temperature of from about 50° C. to about 300° C.

9. The method of claim 1 , wherein the first mixture is heated to a temperature from about the reflux temperature of the first mixture for the given reaction pressure to about 20° C. below the reflux temperature of the first mixture for the given reaction pressure during step (c).

10. The method of claim 1 , wherein the first mixture is heated to a temperature from about the reflux temperature of the first mixture for the given reaction pressure to about 10° C. below the reflux temperature of the first mixture for the given reaction pressure during step (c).

11. The method of claim 1 , wherein the first mixture is heated to a temperature from about the reflux temperature of the first mixture for the given reaction pressure to about 5° C. below the reflux temperature of the first mixture for the given reaction pressure during step (c).

12. The method of claim 1 , wherein the pressure of the first mixture during step (c) is from 1 atmosphere to 100 atmospheres.

13. The method of claim 1 , wherein the pressure of the first mixture during step (c) is from 1 atmosphere to 265 PSIA.

14. The method of claim 4 , further comprising step (e) after step (d) (2) and prior to step (d)(3), adjusting the pH to from about 4 to about 8.

15. The method of claim 14 , wherein the pH is adjusted to from about 4 to about 6.

16. The method of claim 14 , wherein the pH is adjusted to from about 6.5 to about 7.5.

17. The method of claim 1 , wherein the beta-hydroxyalkanoate containing composition comprises at least 50 percent by weight of beta-hydroxyalkanoate equivalents.

18. The method of claim 1 , wherein the beta-hydroxyalkanoate containing composition comprises at least 60 percent by weight of beta-hydroxyalkanoate equivalents.

19. The method of claim 1 , wherein the beta-hydroxyalkanoate containing composition comprises at least 70 percent by weight of beta-hydroxyalkanoate equivalents.

20. The method of claim 4 , wherein the weight percent water during step (d)(2) of the second fraction is 2 wt % or less.