Method for preparing high purity biodiesel

摘要

Disclosed is a method for preparing high purity biodiesel from crude oils. The method comprises the steps of: pre-treating the crude oil raw material to remove impurities; pre-esterifying the pre-treated crude oil raw material under the effect of a catalyst of concentrated sulfuric acid; and then carrying out an ester exchange reaction in the presence of an alkali catalyst; recycling methanol, and separating glycerol, so as to obtain a crude fatty acid methyl ester; and subjecting the obtained fatty acid methyl ester to purification, distillation and segmentation to obtain a high-purity fatty acid methyl ester.

主权项

1. A method for preparing biodiesel from crude oils, comprising:
1) providing crude oil raw material, and pre-treating the crude oil raw material to remove impurities; 2) adding the pre-treated raw material into a reaction kettle; 3) pre-esterification step: adding methanol and 0.1-2 wt % concentrated sulfuric acid by the weight of the pre-treated raw material into the reaction kettle, and maintaining at 70-100° C., for 30 min-2 h, wherein the weight ratio of methanol to the pre-treated raw material is (1:11)-(1:6) to provide pretreated material; 4) esterification step of vapor phase: heating the pretreated material to 110-130° C., supplementing vapor phase methanol from the bottom of the reaction kettle under atmospheric pressure, reacting under the temperature until an acid value of liquid phase system is ≦2, and stopping supplementing methanol; 5) ester exchange step: cooling the reaction material obtained in the step 4) to below 70° C., adding mixture of potassium hydroxide and sodium hydroxide with equal weight ratio in the same reaction kettle to maintain pH of the reaction material in the reaction kettle at 8-9, and then reacting at 70-90° C., for 2-3 h; 6) recycling methanol, and separating glycerol via gravity settling, so as to obtain a crude fatty acid methyl ester; and 7) subjecting the crude fatty acid methyl ester obtained in the step 6) to purification and distillation to obtain biodiesel.