ARF05 - Biodiesel: Processes for Converting Agriculturally-Derived Ethanol, Soybean Oil and Waste Animal Fats to Biodiesel Fuel

| Alternative Renewable Fuels - Project Summaries 2004 |

Researcher:

Dr. David Boocock, Dept. of Chemical Engineering and Applied Chemistry, University of Toronto

Objectives:

Overall

To incorporate ethanol into new continuous processes for making ASTM biodiesel ethyl ester fuel.

Major

1. To provide industrial fuel uses in the form of biodiesel for agriculturally-derived ethanol.
   
2. To promote the incorporation of vegetable oils and refurbished waste vegetable oils and animal fats into biodiesel fuel.
   
3. To develop a continuous co-solvent-free process to convert vegetable oils to ASTM biodiesel ethyl/methyl ester mixtures.
   
4. To develop a continuous co-solvent-free two-step process to convert refurbished waste vegetable oils and animal fats to ASTM biodiesel ethyl and methyl esters.
   

Laboratory

1. To define laboratory conditions (ethanol/methanol/oil molar ratios, catalyst concentration, temperature and reaction time) to convert vegetable oils to ASTM biodiesel mixtures of ethyl and methyl esters.
   
2. To define laboratory conditions (ethanol/fatty acid/triglyceride molar ratios, catalyst concentration, residence time and temperature) to form ethyl esters from the fatty acid content of waste fats and oils.
   
3. To determine the distillation characteristics of methanol/ethanol mixtures containing small amounts of water. This information is required to dry recycled methanol/ethanol streams.

Expected Benefits:

A continuous one step co-solvent free process to convert vegetable oils to methyl/ethyl ester biodiesel, and a continuous two-step process to convert waste fats and oils to the same product.

Summary of Research Results:

Biodiesel is a renewable fuel which is normally made by the chemical reaction of methanol and vegetable oil triglycerides (TG) as well as in some cases, waste fats and oils. The methanol, a non-renewable alcohol, contributes approximately 10% to the biodiesel molecule. It would be advantageous from an environmental and agricultural standpoint if the methanol could be replaced, by a renewable alcohol, such as ethanol. This is easily made from the starches in corn, and less easily made from the cellulose in all plant materials. Unfortunately, there are some problems with using ethanol to make biodiesel. First, it forms emulsions during the reaction with the oils, which makes it difficult to isolate the biodiesel product. Secondly, the reaction of ethanol with oils does not proceed to the same extent as that for methanol. As a consequence, chemical intermediates in the reaction remain in the biodiesel, which then does not meet the legislated quality standards. These residuals are monoglycerides (MG) which contribute to the "glycerol content" of the biodiesel and fatty acids (FA) which contribute to the "acid number". Both of these are limited by the quality standards.

Researchers at the University of Toronto have discovered a non-reactive co-solvent which eliminates any emulsions and makes the reactions a single phase. The same co-solvent also promotes the formation of the biodiesel over a side reaction which actually forms FA. The co-solvent, along with excess methanol, is recovered and recycled to the front end of end of a continuous process.

The Biox Corporation located in Hamilton, Ontario, already uses the co-solvent as well as waste fats and oils to make biodiesel. These cheaper feedstocks already contain FAs, which must be converted first to biodiesel, before the normal TG's are reacted. The co-solvent also accelerates this conversion as well as the TG's in a second step. The Biox Process, which currently uses methanol, can remove residual MG's as well as some FA, to the extent that the researchers at the University of Toronto believe that ethanol could be used in the Biox Process to make ethyl ester biodiesel which would meet the North American and European standards. However, significant additions and modifications would have to be made to the Biox Process to adjust for the physical properties of ethanol.

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