Patent ID: 8629291

Claim:
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.