Esterification of biodiesel feedstock with solid heterogeneous catalyst

1. A method for esterifying, with methanol, free fatty acids present in a biodiesel feedstock, the method comprising:

(a) passing through a guard bed column reactor comprising an ion exchange resin, a biodiesel feedstock, such that after passing through the guard bed column reactor, the phosphorous level of the biodiesel feedstock is below about 10 ppm, and the sulfur level of the biodiesel feedstock is below about 10 ppm;

(b) contacting (i) methanol, (ii) a solid heterogeneous esterification catalyst, and (iii) the biodiesel feedstock comprising free fatty acids, wherein the contacting is carried out under conditions suitable to provide an esterification reaction product comprising biodiesel, methanol, water, and free fatty acids;

(c) separating water and methanol from the esterification reaction product, such that the esterification reaction product comprises less than about 1.5 wt. % water;

(d) contacting the esterification reaction product with (i) methanol and (iii) a solid heterogeneous esterification catalyst, wherein the contacting is carried out under conditions suitable to provide a subsequent esterification reaction product comprising biodiesel, methanol, water and optionally free fatty acids;

(e) optionally repeating step (d) one or more times, to provide an esterification reaction product comprising biodiesel; and

(f) separating water and methanol from the subsequent esterification reaction product, such that the esterification reaction product comprises less than about 1 wt. % water;

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

2. The method of claim 1 , wherein the guard bed column reactor comprises a straight, flow-through 2 stage guard bed column reactors in series.

3. The method of claim 1 , wherein the methanol, catalyst, and biodiesel feedstock are heated to a temperature of up to about 200° F. (93.33° C.).

4. The method of claim 1 , wherein the methanol, catalyst, and biodiesel feedstock are heated at a pressure of up to about 50 psi (3.40 atm).

5. 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.

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

7. The method of claim 1 , wherein step (b) is carried out comprising a first stage reactor wherein the conversion of free fatty acids and methanol to biodiesel and water is at least about 90 wt. %.

8. The method of claim 1 , wherein each of steps (b) and (d) is carried out comprising a first stage reactor, wherein upon conversion of free fatty acid present in the biodiesel feedstock to biodiesel, water and methanol are separated from the biodiesel, triglycerides, and un-reacted free fatty acids, and the methanol is purified and transferred to a second stage reactor.

9. The method of claim 1 , which provides for the one or more esterification reaction products comprising water, methanol, biodiesel, triglycerides and free fatty acid; and the method further comprising separating at least one of water and methanol from the one or more esterification reaction products at a temperature of at least about 170° F. (76.67° C.).

10. The method of claim 1 , which provides for the one or more esterification reaction products comprising water, methanol, biodiesel, triglycerides and free fatty acid, and wherein the biodiesel and triglycerides are not subsequently separated from one another.

11. The method of claim 1 , wherein at least about 100 gallons of biodiesel feedstock is employed in step (a).

12. The method of claim 1 , wherein at least about 100 gallons of the one or more esterification reaction products is obtained, within 24 hours.

13. The method of claim 1 , wherein the catalyst is immobilized on a solid support.

14. The method of claim 1 , wherein the methanol is obtained from a previous esterification.

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

16. The method of claim 1 , wherein the free fatty acids present in the biodiesel feedstock are esterified with methanol to provide a reaction product comprising biodiesel, water, triglycerides, and un-reacted methanol.

17. The method of claim 1 , wherein the free fatty acids present in the biodiesel feedstock are esterified with methanol to provide a reaction product comprising biodiesel, water, triglycerides, un-reacted methanol, and un-reacted free fatty acids.

18. The method of claim 1 , wherein the free fatty acids present in the biodiesel feedstock are esterified with methanol to provide a reaction product comprising biodiesel, water, triglycerides, un-reacted methanol, and un-reacted free fatty acids; and

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

19. The method of claim 18 , wherein both water and methanol are separated from the one or more esterification reaction products.

20. The method of claim 1 , wherein the free fatty acids present in the biodiesel feedstock are esterified with methanol to provide a reaction product comprising biodiesel, water, triglycerides, un-reacted methanol, and un-reacted free fatty acids;

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

the reaction product comprising biodiesel, triglycerides, and un-reacted free fatty acids is subsequently esterified to provide a subsequent reaction product comprising biodiesel, water, triglycerides, un-reacted methanol, and optionally un-reacted free fatty acids.

21. The method of claim 1 , wherein the free fatty acids present in the biodiesel feedstock are esterified with methanol to provide a reaction product comprising biodiesel, water, triglycerides, un-reacted methanol, and un-reacted free fatty acids;

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

the reaction product comprising biodiesel, triglycerides, and un-reacted free fatty acids is subsequently esterified to provide a subsequent reaction product comprising biodiesel, water, triglycerides, un-reacted methanol, and optionally un-reacted free fatty acids; and

the separation and esterification are optionally repeated one or more times until a further subsequent reaction product does not comprise a significant or appreciable amount of un-reacted free fatty acids.

22. The method of claim 1 , wherein the biodiesel feedstock comprises at least one of triglycerides, gums, soaps, detergents, unsaponifiables, phosphatides, metals, phosphorus, sulfur, sulfates, sulfonates, sulfides, polyaromatic hydrocarbons, polychlorinated hydrocarbons, polyethylene, plant based sterols, animal based sterols, moisture, and water.

23. The method of claim 1 , wherein the biodiesel feedstock comprises elevated levels of at least one of water, sulfur, phosphorus, gums/lipids, sterols, calcium, magnesium, iron, copper, cobalt, manganese, nickel, sodium, potassium, chlorophyll, carotenoids, xanthophylls, proteins and carbohydrates, aldehydes, ketones, carboxylic acids, perchloroethylene, polyaromatic hydrocarbons, polychlorinated hydrocarbons, polymerized triglycerides, pesticides, soaps, detergents, sulfonates, sulfates, phosphatides, phytosterols, sitosterols, cholesterol, and sterol glucosides.

24. The method of claim 1 , wherein the feedstock comprises up to about 20,000 ppm of sulfur, sulfates, sulfides, and sulfonates.

25. The method of claim 1 , wherein the feedstock comprises up to about 4000 ppmw phosphorus.

26. The method of claim 1 , wherein the feedstock comprises about 10-4000 ppm phosphorus.

27. The method of claim 1 , wherein the feedstock comprises about 5 ppm-13,500 ppm sulfur, sulfates, suflides, sulfonates, and sulfones.

28. The method of claim 1 , wherein step (d) is carried out employing a second stage reactor, which provides for the conversion of free fatty acids and methanol to biodiesel and water, with a conversion of at least about 90 wt. %.

29. The method of claim 1 , wherein step (d) is carried out employing a third stage reactor, which provides for the conversion of free fatty acids and methanol to biodiesel and water, with a conversion of at least about 90 wt. %.