Method of producing biodiesel fuel

Abstract

A method of producing a biodiesel fuel oil, in which all fats or oils having an acid value of 20 or less can be used as a raw material, and in which no wastewater treatment is needed to thereby attain reduction of environmental load, and in which a biodiesel fuel oil conformable to quality standard levels can be obtained. The process for producing a biodiesel fuel comprises the steps of providing a fat or oil having an acid value of 20 or less as a raw material and heating the raw material oil in vacuum to thereby distill off any moistures, odorous substances and free fatty acids; bringing the raw material oil into contact with a hydrophilic adsorbent to thereby adsorb off any remaining free fatty acids and acidic substances; carrying out an ester exchange reaction in the presence of a potassium based alkali catalyst; and purifying light liquid components as a product of ester exchange reaction in accordance with a nonaqueous method.

1 . A method of producing a biodiesel fuel from a raw material oil having an acid value of 20 or less, comprising:
 a step of heating the raw material oil under reduced pressure to distill and remove moisture, odorous substances and free fatty acids;   a step of causing the raw material oil to come in contact with a hydrophilic adsorbent to adsorb and remove residual free fatty acids and acidic substances;   a step of subjecting the raw material oil and alcohol to an ester exchange reaction in the presence of an alkali catalyst of at least one type selected from a group including potassium hydroxide, potassium carbonate, and potassium alcoholate;   a step of separating light liquid components from a reaction product resulting from the ester exchange reaction; and   a step of performing, to the light liquid components, processing of causing the light liquid components to come in contact with a basic substance adsorptive solid adsorbent, processing of removing solid impurities and the like by way of centrifugation, processing of heating the light liquid components under reduced pressure to remove low-boiling substances, and processing of removing solid impurities and the like through a filter.   
     
     
         2 . The method of producing a biodiesel fuel according to  claim 1 ,
 wherein the hydrophilic adsorbent is at least one type selected from a group including activated alumina, basic-treated activated carbon, and silica gel.   
     
     
         3 . The method of producing a biodiesel fuel according to  claim 1 ,
 wherein the ester exchange reaction step includes:   a step of preparing a catalyst-containing alcohol solution by dissolving the alkali catalyst which is 0.5 wt % in relation the raw material oil, in alcohol which is 1.05 to 1.25 molar equivalent in relation to a fatty acid moiety of the raw material oil; and   a step of mixing and agitating the raw material oil and the catalyst-containing alcohol solution.   
     
     
         4 . The method of producing a biodiesel fuel according to  claim 1 ,
 wherein the step of separating the light liquid components is performed by subjecting the reaction product to centrifugation.   
     
     
         5 . The method of producing a biodiesel fuel according to  claim 1 ,
 wherein the basic substance adsorptive solid adsorbent is at least one type selected from a group including activated clay, acid clay, activated carbon, bentonite, silica gel, activated alumina, and molecular sieves.   
     
     
         6 . The method of producing a biodiesel fuel according to  claim 1 ,
 wherein a pour point depressant and an oxidation stabilizer are added to the light liquid before performing the processing of heating the light liquid components under reduced pressure to remove low-boiling substances.   
     
     
         7 . The method of producing a biodiesel fuel according to  claim 1 ,
 wherein, prior to performing the distillation and removal step, performed are:   a step of gravity-separating water or an aqueous solution from the raw material oil; and   a step of removing solid substances from the gravity-separated raw material oil with a filter.   
     
     
         8 . The method of producing a biodiesel fuel according to  claim 1 ,
 wherein the alcohol used in the ester exchange reaction is at least one type selected from a group including methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol.   
     
     
         9 . The method of producing a biodiesel fuel according to  claim 1 , further comprising:
 a step of diluting sulfuric acid or phosphoric acid corresponding to protons of an equivalent mole in relation to an alkali catalyst with water having a molar equivalent of 0.3 to 5 in relation to potassium atoms in the alkali catalyst and adding the product to and neutralizing heavy liquid components after the light liquid components are separated from the reaction product; and   a step of distilling under reduced pressure a filtrate remaining after filtrating and removing the obtained clathrate hydrate, or a hydrated potassium sulphate crystal or a hydrated tripotassium phosphate crystal, and obtaining glycerin as a by-product.