Pretreatment, esterification, and transesterification of biodiesel feedstock

A method for producing biodiesel and glycerin comprising the steps in the order recited:

• (a) filtering a biodiesel feedstock, thereby separating from the feedstock solid particles having a diameter up to 2 microns, to provide a filtrate and a retentate;
• (b) separating water from the filtrate, to provide a dried filtrate;
• (c) distilling the dried filtrate, to provide a distillate and a residue;
• (d) distilling the distillate to provide a subsequent distillate and optionally a subsequent residue;
• (e) repeating at least one of steps (c) and (d), one or more times, by distilling the subsequent distillate, to obtain a final distillate;
• (f) passing the final distillate through an ion exchange resin;
• (g) contacting (i) methanol, (ii) a solid heterogeneous esterification catalyst immobilized on a solid support, and (iii) the final distillate, wherein the contacting is carried out under conditions suitable to provide an esterification reaction product comprising biodiesel, methanol, water, and optionally free fatty acids;
• (h) separating water and methanol from the esterification reaction product;
• (i) contacting the esterification reaction product with (i) methanol and (ii) a solid heterogeneous esterification catalyst immobilized on a solid support, 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;
• 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, transesterification, or combination thereof;
• (j) contacting at a temperature of less than 102° F. (38.89° C.) (i) methanol, (ii) a solid heterogeneous transesterification catalyst immobilized on a solid support, and (iii) the esterification reaction product, wherein the contacting is carried out under conditions suitable to provide a biodiesel, methanol, water, glycerin and optionally triglycerides;
• (k) separating water, glycerin and methanol from the transesterification reaction product;
• (l) contacting the transesterification reaction product with (i) methanol and (ii) a solid heterogeneous transesterification 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
• (m) separating, via distillation, the methanol and water from the transesterification reaction product, to provide the biodiesel and glycerin;
• 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 esterification, transesterification, or combination thereof.