Biodiesel and Preparation Method Thereof

Abstract

A method for preparing biodiesel includes the steps of: by using larvae or pupae of complete metamorphosis insect as raw materials, extracting insect oil by solvent process, conducting transesterification or pre-esterification-transesterification respectively of the low-acid-value (acid value≦2) insect oil or the high-acid-value (acid value>2) insect oil to get crude biodiesel after stratification; and purifying and processing the crude biodiesel by using adsorption clarification technic, molecular distillation techinic, and freezing (low temperature) separation technic to get refined biodiesel. The advantages of the method include wide variety of raw materials, easy to breeding, and low cost of production. The present invention provides a new technical way of producing biodiesel, and on the other hand, it also provides a new way of exploiting insects.

1 . A method for preparing biodiesel, comprising the following steps:
 (a) an insect oil preparation step including   drying and crushing larvae and/or pupae of complete metamorphosis insect, adding a solvent of 1-10 times as heavy as the larvae and/or pupae, extracting at room temperature for 1-48 hours, filtering to obtain a filtrate, and then recovering the solvent from the filtrate to obtain a low-acid-value insect oil with an acid value less than or equal to 2, or a high-acid-value insect oil with an acid value greater than 2; when the high-acid-value insect oil is obtained, pre-esterifying the high-acid-value insect oil to get the low-acid-value insect oil with an acid value less than or equal to 2 with processing conditions of a molar ratio of 1:6-1:13 of the high-acid-value insect oil to methanol or ethanol, adding an acidic catalyst at a weight of 0.5% -5% as heavy as the insect oil, a reaction temperature of 40° C.-90° C., and a reaction time of 0.5-4 hours; wherein the solvent is a single lipophilic organic solvent, or a mixture of lipophilic organic solvent and hydrophilic organic solvent;   (b) a transesterification: step including   conducting transesterification of the low-acid-value insect oil with methanol or ethanol with reaction conditions of a molar ratio of 1:4-1:9 of the low-acid-value insect oil to methanol or ethanol, adding a basic catalyst at a weight of 0.5% -2.5% as heavy as the insect oil, a reaction temperature of 40° C.-90° C., and a reaction time of 10-60 minutes;   (c) a phase separation: step including   after the transesterification is completed, standing the reactant for stratification and then obtaining a supernatant liquid which is coarse ester; and   (4d) a refining process step including   washing the supernatant liquid obtained from the step (c) with hot water, adding an adsorbent at a weight of 1% -10% as heavy as the supernatant liquid, heating to 30° C.-100° C., stirring, and then suction filtering to get a filtrate which is the biodiesel; or   washing the supernatant liquid obtained from the step (c) with water, placing in 0° C.-10° C. for freezing for 24-120 hours, and then suction filtering to get a filtrate which is the biodiesel; or   refining processing the supernatant liquid obtained from the step (c) by using molecular distillation technology with processing conditions of a vacuum of 0.1-10 Pa and a distillation temperature of 100-200° C. to separate out the biodiesel.   
     
     
         2 . The method according to  claim 1 , wherein the complete metamorphosis insect is fly, yellow mealworm, superworm, silkworm, bee or moth. 
     
     
         3 . The method according to  claim 1 , wherein the lipophilic organic solvent is n-hexane, cyclohexane, petroleum ether, ethyl ether, ethyl acetate, chloroform or benzene; the hydrophilic organic solvent is methanol, ethanol, propanol or acetone. 
     
     
         4 . The method according to  claim 1 , wherein the extracting at room temperature is conducted under nitrogen atmosphere. 
     
     
         5 . The method according to  claim 1 , wherein the acidic catalyst is concentrated sulfuric acid or p-toluene sulfonic acid. 
     
     
         6 . The method according to  claim 1 , wherein the basic catalyst used in step (b) is alcohol sodium, alkali metal, NaOH, or KOH. 
     
     
         7 . The method according to  claim 1 , wherein the adsorbent used in step (4d) is selected from a group consisting of activated clay, diatomite, attapulgite, activated carbon, alumina and any combination thereof. 
     
     
         8 . The method according to  claim 1 , wherein in the step (c), the subnatant liquid after stratification mainly is a mixture of glycerol, water, catalyst and methanol or ethanol, the subnatant liquid is neutralized by dilute hydrochloric acid, centrifuged, and evaporated under reduced pressure to get a by-product glycerol. 
     
     
         9 . A method for preparing biodiesel, wherein the method mainly comprises the following steps:
 (a) an insect oil preparation: step including drying and crushing larvae or pupae of complete metamorphosis insect, adding a solvent of 1-10 times as heavy as the larvae or pupae, extracting at room temperature for 1-48 hours, filtering to obtain a filtrate, and then recovering the solvent from the filtrate to obtain a low-acid-value insect oil with an acid value less than or equal to 2, or high-acid-value insect oil with an acid value greater than 2; when the high-acid-value insect oil is obtained, pre-esterifying the high-acid-value insect oil to get the low-acid-value insect oil with an acid value less than or equal to 2 with processing conditions of a molar ratio of 1:6-1:13 of the high-acid-value insect oil to methanol or ethanol, adding an acidic catalyst at a weight of 0.5% -5% as heavy as the insect oil, a reaction temperature of 40° C.-90° C., and a reaction time of 0.5-4 hours; wherein the solvent is a single lipophilic organic solvent, or a mixture of lipophilic organic solvent and hydrophilic organic solvent;   (b) as transesterification step including conducting transesterification of the low-acid-value insect oil with methanol or ethanol with reaction conditions of a molar ratio of 1:4-1:9 of the low-acid-value insect oil to methanol or ethanol, adding a basic catalyst at a weight of 0.5% -2.5% as heavy as the insect oil, a reaction temperature of 40° C.-90° C., and a reaction time of 10-60 minutes; and   (c) refining the reactants from (b) with molecular distillation technology by the following two stages:   I. separating out glycerol and methanol or ethanol from the reactants by molecular distillation with processing conditions of a vacuum of 100-10 Pa and a distillation temperature of 80° C.-160° C., and   II. separating out biodiesel by molecular distillation with processing conditions of a vacuum of 10-0.1 Pa and a distillation temperature of 100° C.-200° C.;   or by the following three stages:   I. separating out methanol or ethanol by molecular distillation with processing conditions of a vacuum of 5000-100 Pa and a distillation temperature of 65° C.-150° C.,   II. separating out glycerol by molecular distillation with processing conditions of a vacuum of 100-10 Pa and a distillation temperature of 100° C.-200° C., and   III. separating out biodiesel by molecular distillation with processing conditions of a vacuum of 10-0.1 Pa and a distillation temperature of 100° C.-200° C.   
     
     
         10 . The method according to  claim 9 , wherein the complete metamorphosis insect is fly, yellow mealworm, superworm, silkworm, bee or moth. 
     
     
         11 . The method according to  claim 9 , wherein the lipophilic organic solvent is n-hexane, cyclohexane, petroleum ether, ethyl ether, ethyl acetate, chloroform or benzene; the hydrophilic organic solvent is methanol, ethanol, propanol or acetone. 
     
     
         12 . The method according to  claim 9 , wherein the extracting at room temperature is conducted under nitrogen atmosphere. 
     
     
         13 . The method according to  claim 9 , wherein the acidic catalyst is concentrated sulfuric acid or p-toluene sulfonic acid. 
     
     
         14 . The method according to  claim 9 , wherein the basic catalyst used in (b) is alcohol sodium, alkali metal, NaOH, or KOH; when using NaOH or KOH as catalyst, the catalyst in solid state is firstly dissolved in methanol or ethanol respectively to get an alcohol solution with a base concentration of 4-8 wt %. 
     
     
         15 . A biodiesel prepared by the method according to  claim 1 . 
     
     
         16 . A biodiesel prepared by the method according to  claim 9 .