Method for producing biodiesel material

Abstract

A method for producing biodiesel. The method involves providing a waste fat feedstock, pretreating the feedstock, a first glycerolysis fatty acid reduction reaction where the subsequent water vapor is removed by a vacuum, a second transesterification reaction wherein the fatty acid feedstock is reacted with methanol or suitable alcohol in very slight excess to form methyl or alkyl esters and glycerin, a separation recovery process to separate glycerol from methyl esters, a methanol recovery flash process, and a methyl ester flash process to yield pure methyl or alkyl ester biodiesel.

1 . A process for producing a biodiesel fuel, the process comprising:
 providing a feedstock;   pretreating the feedstock;   performing a glycerolysis reaction by adding glycerol and a caustic base to the pretreated feedstock and heating the resulting mixture, resulting in a mixture of mono-, di- and tri-glycerides and soap;   performing a transesterification reaction by combining the mixture of mono-, di-, and tri-glycerides and soap with a slight excess of alcohol and catalyst, resulting in an alkyl ester reaction product;   separating glycerol from the alkyl ester reaction product in a glycerol separation processing step, leaving behind 0.1 wt. % to 1.0 wt. % free glycerol in the alkyl ester reaction product from the transesterification reaction;   recovering alcohol in an alcohol recovery flash resulting in a stream of alkyl ester free from glycerol;   flashing the stream in an alkyl ester flash process resulting in a pure alkyl ether biodiesel, bottoms and partial glycerides that contain catalyst; and   recycling catalyst, bottoms and partial glycerides that contain catalyst back to the transesterification reaction.   
   
   
       2 . The process of  claim 1 , wherein the caustic base is selected from the group consisting of NaOH and KOH. 
   
   
       3 . The process of  claim 1 , wherein the glycerolysis reaction is conducted at a temperature T 2  within the range of 250° F.≦T 2 ≦420° F. at a pressure of 5 mm Hg to 15 mm Hg absolute pressure. 
   
   
       4 . The process of  claim 1 , wherein trace amounts of citric acid or phosphoric acid are added to the feedstock during pretreating. 
   
   
       5 . The process of  claim 1 , wherein the slight excess amount of alcohol required in the transesterification reaction is 1.1 to 1.5 moles of excess alcohol added for each mole of fatty acid present in the reaction mixture. 
   
   
       6 . The process of  claim 1 , wherein glycerol in the glycerolysis reaction is added in an amount between 1 wt. % to 10 wt. % of total reaction mixture. 
   
   
       7 . The process of  claim 1 , wherein caustic base in the glycerolysis reaction is added in an amount between 0.1 wt. % to 0.5 wt. % of total reaction mixture. 
   
   
       8 . The process of  claim 1 , wherein the transesterification reaction proceeds to 70-90% completion. 
   
   
       9 . The process of  claim 1 , wherein after the glycerol separation processing step, 0.1 wt. % to 1.0 wt. % of free glycerol remains in the alkyl ester, based on total weight of the alkyl ester. 
   
   
       10 . The process of  claim 1 , the pretreatment step further comprising adding a bleaching clay to the feedstock followed by a drying process and a filtering process, wherein clay is added to the feedstock in an amount of 0.3 wt. % to 0.5 wt. % based on a total weight of the reaction mixture, and the pretreating is conducted at a temperature T in the range of 150° F.≦T≦230° F. 
   
   
       11 . The process of  claim 10 , wherein the bleaching clay is selected from the group consisting of silica and traditional bentonite clays. 
   
   
       12 . The process of  claim 1 , wherein pretreating is selected from the group consisting of dewatering, degumming, and bleaching glycerolysis. 
   
   
       13 . The process of  claim 1 , wherein catalyst is added in the transesterification in an amount x in the range of 0.1 wt. %≦x≦0.35 wt. % based on total weight of reaction mixture. 
   
   
       14 . The process of  claim 1 , wherein the feedstock is selected from the group consisting of crude soy oil, refined soy oil, yellow grease, refined and crude vegetable oils, trap grease, edible animal tallow, inedible animal tallow, raw trap grease, brown grease, corn oil, olive oil, cottonseed oil, butter, lard, poultry fat, fish oils, linseed oil, raw trap grease, restaurant waste grease, animal fat, coconut oil, recycled greases, soy, rapeseed, jatropha, mahua, mustard, flax, sunflower, palm oil, hemp, field pennycress, pongamia pinnata, algae, and other microbial sources such as bacterial sources of lipids and waste streams such as acid oil from standard refining processes. 
   
   
       15 . The process of  claim 1 , wherein the transesterification reaction is conducted at a temperature T 3  within the range of 130° F.≦T 3 ≦200° F. 
   
   
       16 . The process of  claim 1 , wherein the alcohol recovery flash is conducted at a temperature T 4  within a range of 200° F.≦T 4 ≦300° F. and at a pressure of 2 to 25 mm Hg absolute pressure. 
   
   
       17 . The process of  claim 1 , wherein the alkyl ester flash is conducted at a temperature T 5  within a range of 170° F.≦T 5 ≦250° F. and at a pressure of 0.5 to 15 mm Hg. 
   
   
       18 . The process of  claim 1 , wherein the catalyst is selected from the group consisting of sodium or potassium alkylate of the formula R—ONa or R—OK, where the alkylate moiety corresponds to the R-moiety of the alcohol and R is a straight or branched hydrocarbon chain, NaOH and KOH. 
   
   
       19 . The process of  claim 1 , wherein the alcohol is selected from the group consisting of methanol, ethanol, isopropanol and butanol. 
   
   
       20 . A process for producing a biodiesel fuel, the process comprising:
 providing a feedstock;   pretreating the feedstock by adding a bleaching clay to the feedstock followed by a drying process and a filtering process, wherein clay is added to the feedstock in an amount of 0.3 wt. % to 0.5 wt. % based on a total weight of the reaction mixture, and the pretreating is conducted at a temperature T in the range of 150° F.≦T≦230° F., resulting in a pretreated feedstock;   performing a glycerolysis reaction by adding glycerol and a caustic base to the pretreated feedstock and heating the resulting mixture, resulting in a mixture of mono-, di- and tri-glycerides and soap;   performing a transesterification reaction by combining the mixture of mono-, di-, and tri-glycerides and soap with a slight excess of alcohol and catalyst, resulting in an alkyl ester reaction product;   recovering alcohol in an alcohol recovery flash resulting in a stream of alkyl ester substantially free from glycerol;   optionally water washing the stream of alkyl ester to remove traces of glycerin and reduce soap in the alkyl ester stream;   flashing the stream in an alkyl ester flash process resulting in a pure alkyl ether biodiesel, bottoms and partial glycerides that contain catalyst; and   recycling catalyst, bottoms and partial glycerides that contain catalyst back to the transesterification reaction.