Biomass Based Solid Acid Catalysts for Biodiesel Production |
Biodiesel is an alternative type of diesel fuel obtained from renewable resources. Vegetable oils (also called triglycerides) can be used directly in diesel engines, but raw oils cause a number of engine problems, many relating to the high viscosity and low volatility of the oils. To address this problem, the oils are treated with an alcohol, usually methanol, with a catalyst and thereby undergo transesterification. This process produces fatty acid methyl esters (FAMEs), which have fuel properties similar to those of petroleum based diesel fuel. The FAMEs are the actual biodiesel product.
Typically, the catalyst used is a hydroxide such as NaOH or KOH, and methanol is usually added in excess (6-30:1 mole ratio) to drive the reaction to completion. The glycerol separates into a distinct phase along with the catalyst, excess methanol, and any residual water, although the biodiesel is usually washed with water to remove residual catalyst and methanol. While the use of homogeneous base catalysts provides high conversion of the triglycerides to biodiesel, the reaction is sensitive to the presence of water and any free fatty acids present in the oil. This limits the production of biodiesel to high quality vegetable oil feedstocks and anhydrous alcohols.
In the Midwest United States, soybean oil is readily available and there is a considerable body of literature available discussing the production of biodiesel using soybean oil. Soybean oil is therefore an important reagent in any novel catalyst study.
In addition, biomass based ethanol (mostly from fermentation of corn) is widely available in the midwest, and production continues to increase as more plants are being built. Currently, methanol is produced from fossil sources. In principle, any alcohol can be used in transesterification, so it is logical to develop fully renewable biodiesel, using corn-based ethanol with regionally produced soybean oil. In this system the product is called fatty acid ethyl esters (FAEE).
In our work,
we are designing catalysts for the transesterification of soybean oil
and ethanol. In particular, we are interested in heterogeneous catalysts, which
can be separated, recovered, and reused. We have found that corn stover, the
stalks and leaves of corn, can be pyrolyzed to form charcoal, which when
sulfonated with concentration sulfuric acid, forms a solid acid catalyst with
potential for use in transesterification. We are developing methods of preparing
sulfonated charcoal catalysts, and then evaluating their viability for biodiesel synthesis.
Poster presentation at MWRM of ACS. |
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This project has been supported through the Northern Plains Undergraduate Research Center (NPURC), an NSF funded project.
