ARS | Publication request: Biodiesel production using heterogenous catalyst

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 12, 2008
Publication Date: May 13, 2008
Citation: Tasaki, K., Moser, B.R., Doll, K.M., Hughes, S.R. 2008. Biodiesel production using heterogenous catalyst [abstract]. International Biofuels Development Summit. p. 2.

Technical Abstract: The current transesterification of triacylglycerides (TAG) to produce biodiesel is based on the homogenous catalyst method using strong base such as hydroxides or methoxides. However, this method results in a number of problems: (1) acid pre-treatment is required of feedstocks high in free fatty acids (FFA) to avoid saponification, (2) residual water de-activates the catalyst, (3) unwanted production of water as by-product in transesterification, (4) consumption of excessive water for water-washing during purification, requiring a waste-water treatment facility, (5) low quality crude glycerol, (6) the removal of FFA, alkali metals, water, and glycerol from the final product, which requires a costly and rigorous purification process. These issues keep the production cost high, often making it difficult to meet the ASTM D6751 standard, which is becoming increasingly stringent. Recently, producing biodiesel using corn oil extracted from DDG at an ethanol production site is receiving much attention. This approach allows the operator not only to increase the overall biofuel output, but also to switch between ethanol and biodiesel production, depending on the market conditions. Collocation of biodiesel production capacity at an ethanol plant saves the transportation cost. Further, the utilization of by-products improves the economics of ethanol production. Therefore, keeping production and plant site costs down are attractive benefits when considering biodiesel production near or at an existing ethanol plant. In our presentation, we will discuss a new biodiesel production process using a heterogenous catalyst for transesterification and ion exchange resins for pre-treatment of feedstock oil and dry purification of the fuel. The new solid catalyst, ether using an anion exchange resin or an enzyme-immobilized resin, eliminates: (1) the use of alkali catalyst, (2) a large amount of water for water-washing, and (3) the removal of alkali metals and water from the final product. Additionally, the glycerol co-product arising from biodiesel production is of higher quality when compared to the conventional homogeneous catalysis method. The resultant fuel is fundamentally cleaner in the absence of saponification and water, having inherently lower amount of K or Na. The physical space and cost for large water-washing and settling tanks can be saved, reducing the size of the operation site, and also eliminates the need for a waste-water treatment facility, which can be expensive. In pre-treatment of feedstock prior to transesterification, the new cation exchange resin can esterify FFA, thus not only reducing the amount of FFA in the raw oil feedstock, but also increasing the overall yield of the fuel. This reduces the acid number of the final product, which is specified in ASTM D6751. Since the cation exchange resin can remove a variety of impurities including FFA, a wide range of feedstock oil qualities can be accepted. In short, the new process will not only significantly simplify biodiesel production, thereby reducing production costs, but also yield a high quality fuel that meets relevant industry specifications.