Transesterification of biodiesel feedstock with solid heterogeneous catalyst

1. A method for transesterifying, with methanol, triglycerides present in a biodiesel feedstock comprising the steps in the order recited:

(a) passing a filtered and dried biodiesel feedstock through a guard bed ion-exchange column, to remove undesired components;

(b) contacting at a temperature of less than 102° F. (38.89° C.) (i) methanol, (ii) a solid heterogeneous transesterification enzyme catalyst immobilized on a solid support, and (iii) a biodiesel feedstock comprising triglycerides, wherein the contacting is carried out under conditions suitable to provide a transesterification reaction product comprising biodiesel, methanol, water, glycerin and optionally triglycerides;

(c) separating water, glycerin and methanol from the transesterification reaction product;

(d) contacting the transesterification reaction product with (i) methanol and (ii) a solid heterogeneous transesterification enzyme catalyst immobilized on a solid support, wherein the contacting is carried out under conditions suitable to provide a subsequent transesterification reaction product comprising biodiesel, methanol, water, glycerin and optionally triglycerides; and

(e) separating water and methanol from the subsequent transesterification reaction product;

wherein the methanol that is separated from the one or more transesterification reaction products is purified to a purity of at least about 99.9 wt. %, and is employed in a subsequent transesterification.

2. The method of claim 1 , wherein the methanol is employed in at least a 5 molar or stoichiometric excess, relative to the triglycerides content of the biodiesel feedstock.

3. The method of claim 1 , wherein the contacting is carried out at a temperature of 95° F. (35° C.), ±6° F.

4. The method of claim 1 , wherein steps (a)-(e) are carried out in the absence of sodium methylate.

5. The method of claim 1 , which comprises a first stage reactor and a second stage reactor.

6. The method of claim 1 , wherein the methanol is employed in a stoichiometric excess, relative to the triglycerides content of the biodiesel feedstock.

7. The method of claim 1 , wherein the methanol, catalyst, and biodiesel feedstock are heated for a period of time of up to about 75 minutes.

8. The method of claim 1 , which provides for a crude reaction product comprising biodiesel, triglycerides, glycerin, methanol, and water;

the method further comprising separating at least one of methanol and water from the crude reaction product, purifying the methanol, and reusing the purified methanol in a subsequent transesterification.

9. The method of claim 1 , which provides for a crude reaction product comprising biodiesel, triglycerides, glycerin, methanol, and water;

the method further comprising separating triglycerides from the crude reaction product and transferring the triglycerides to a second stage reactor and contacting the triglycerides with methanol having a purity of at least about 98 wt. % pure.

10. The method of claim 1 , which provides for a crude reaction product comprising biodiesel, triglycerides, glycerin, methanol, and water;

the method further comprising separating biodiesel and triglycerides from the crude reaction product and transferring the biodiesel and triglycerides to a second stage reactor and contacting the biodiesel and triglycerides with methanol having a purity of at least about 98 wt. % pure.

11. The method of claim 1 , wherein the methanol is obtained from a previous transesterification.

12. The method of claim 1 , wherein at least about 90 wt. % of the triglycerides present in the biodiesel feedstock are converted to the biodiesel.

13. The method of claim 1 , carried out in a continuous fashion.

14. The method of claim 1 , wherein triglycerides, diglycerides, and monoglycerides present in the biodiesel feedstock are transesterified with methanol, to provide a reaction product comprising biodiesel, glycerin, water, and un-reacted methanol.

15. The method of claim 1 , wherein triglycerides, diglycerides, and monoglycerides present in the biodiesel feedstock are transesterified with methanol, to provide a reaction product comprising biodiesel, glycerin, water, un-reacted methanol, and optionally un-reacted triglycerides.

16. The method of claim 1 , wherein triglycerides, diglycerides, and monoglycerides present in the biodiesel feedstock are transesterified with methanol, to provide a reaction product comprising biodiesel, glycerin, water, un-reacted methanol, and optionally un-reacted triglycerides; and

at least one of methanol, water, and glycerin are separated from the reaction product.

17. The method of claim 1 , wherein triglycerides present in the biodiesel feedstock are transesterified with methanol, to provide a reaction product comprising biodiesel, glycerin, water, un-reacted methanol, and optionally un-reacted triglycerides, diglycerides, and monoglycerides;

at least one of methanol, water, and glycerin are separated from the reaction product; and

the reaction product comprising biodiesel and un-reacted triglycerides, diglycerides, and monoglycerides are subsequently transesterified to provide a subsequent reaction product comprising biodiesel, glycerin, water, and un-reacted methanol.

18. The method of claim 1 , wherein triglycerides present in the biodiesel feedstock are transesterified with methanol, to provide a reaction product comprising biodiesel, glycerin, water, un-reacted methanol, and optionally un-reacted triglycerides, diglycerides, and monoglycerides;

at least one of methanol, water, and glycerin are separated from the reaction product;

the reaction product comprising biodiesel and un-reacted triglycerides, diglycerides, and monoglycerides are subsequently transesterified to provide a subsequent reaction product comprising biodiesel, glycerin, water, and un-reacted methanol; and

the separation and transesterification are optionally repeated one or more times.

19. The method of claim 1 , wherein triglycerides present in the biodiesel feedstock are transesterified with methanol, to provide a reaction product comprising biodiesel, glycerin, water, un-reacted methanol, and optionally un-reacted triglycerides, diglycerides, and monoglycerides;

at least one of methanol, water, and glycerin are separated from the reaction product;

the reaction product comprising biodiesel and un-reacted triglycerides, diglycerides, and monoglycerides are subsequently transesterified to provide a subsequent reaction product comprising biodiesel, glycerin, water, and un-reacted methanol; and

the separation and transesterification are optionally repeated one or more times, until a further subsequent reaction product comprises no more than about 1 wt. % combined un-reacted triglycerides, diglycerides, and monoglycerides.

20. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel comprises less than about 2,000 ppmw of methanol.

21. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel comprises no more than about 0.12 wt. % of total glycerol.

22. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel comprises no more than about 200 ppmw of free glycerin.

23. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel comprises no more than about 0.2 acid number.

24. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel has a flash point of at least about 170° C.

25. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel has a moisture content of no more than about 50 ppmw.

26. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel has a sulfur content that is less than about 5 ppm.

27. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel has phosphorus content that is less than about 5 ppm.

28. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel has a content of polymerized triglycerides that is less than about 5 ppm.

29. The method of claim 1 , wherein the biodiesel is separated from the glycerin, and the purified biodiesel has a sterols content that is less than about 10 ppm.

30. The method of claim 1 , wherein steps (a)-(e) are carried out in the absence of a mineral acid.