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Kim M.,National Biofuels Energy Laboratory | Kim M.,Wayne State University | DiMaggio C.,National Biofuels Energy Laboratory | DiMaggio C.,Wayne State University | And 4 more authors.
Bioresource Technology | Year: 2012

A new class of zirconia supported mixed metal oxides (ZnO-TiO 2-Nd 2O 3/ZrO 2 and ZnO-SiO 2-Yb 2O 3/ZrO 2) has demonstrated the ability to convert low quality, high free fatty acid (FFA) bio-oils into biodiesel. Pelletized catalysts of ZrO 2 supported metal oxides were prepared via a sol-gel process and tested in continuous flow packed bed reactors for up to 6months. In a single pass, while operating at mild to moderate reaction conditions, 195°C and 300psi, these catalysts can perform simultaneous esterification and transesterification reactions on feedstock of 33% FFA and 67% soybean oil to achieve FAME yields higher than 90%. Catalytic activity of the ZrO 2 supported metal oxide catalysts was highly dependent on the metal oxide composition. These heterogeneous catalysts will enable biodiesel manufacturers to avoid problems inherent in homogeneous processes, such as separation and washing, corrosive conditions, and excessive methanol usage. © 2012 Elsevier Ltd.

Kim M.,National Biofuels Energy Laboratory | Kim M.,Wayne State University | Yan S.,National Biofuels Energy Laboratory | Yan S.,Wayne State University | And 4 more authors.
Bioresource Technology | Year: 2010

Methylesters and ethylesters of fatty acids were synthesized using homogeneous CH3ONa and CH3CH2ONa, anion exchanged resin, and CaO-La2O3 catalysts. Methanol, ethanol, and methanol/ethanol mixtures were used as the alcohol feed for transesterification of soybean oil. With a homogeneous catalyst (CH3ONa) there was essentially no difference in conversion rates between methanolysis and ethanolysis in batch reactions. However, with a heterogeneous resin and CaO-La2O3 catalysts, significant differences in the conversion rates between the methanolysis and ethanolysis were observed. The formation rate of methylesters over a CaO-La2O3 catalyst was higher than that of ethylesters, which may be attributable to a steric hindrance effect. Conversely, with a heterogeneous resin catalyst, the conversion rate of ethylester was higher than that of methylesters which may be attributable to the surface hydrophobicity of the anion exchanged resin. When the transesterification of soybean oil was carried out with an equimolar methanol/ethanol mixture, the yield ratio of methylester to ethylester formed within the first 30 min was 2.6 for the homogeneous catalyst (0.3% CH3ONa), and 3.4 for the heterogeneous CaO-La2O3catalyst. These differences in selectivity are likely due to both the higher reactivity of methoxide and to a steric hindrance effect of ethoxide on the catalyst surface. In addition, the transformation of methylester to ethylester was observed when a methanol/ethanol mixture was used. Crown Copyright © 2010.

Kim M.,National Biofuels Energy Laboratory | Kim M.,Wayne State University | DiMaggio C.,National Biofuels Energy Laboratory | DiMaggio C.,Wayne State University | And 6 more authors.
Applied Catalysis A: General | Year: 2010

In an effort to enhance the transesterification reaction of soybean oil and thereby the lubricity properties of the resulting biodiesel as well, the alcohol component of the reaction blend was altered to include several different combinations of methanol, ethanol, and propanol, rather than a single alcohol. For this work, various concentrations of a homogeneous catalyst, such as CH3ONa or C2H5ONa, or a heterogeneous catalyst, CaO-La2O3 or an anion exchanged resin, were used in the reaction. Ethanolysis was found to be faster than methanolysis with highly basic homogeneous catalysts due to the higher nucleophilicity of ethoxide relative to methoxide. The ethyl-ester yield approached a maximum earlier than the methyl-ester yield, even though the methyl-ester yield continuously increased with reaction. Also, methanolysis became linked with ethanolysis when a methanol-ethanol equimolar mixture was used as an alcohol source. In addition, significant improvement in the transesterification activity was observed at very earlier reaction times when a methanol-ethanol mixture was used and a high basicity condition existed where ethoxide can be formed. To explain this effect, a combined structure of methoxide-ethanol or ethoxide-methanol has been proposed and tentatively supported by reaction measurements and FTIR. In this model, the formed alkoxide generates two reactive sites resulting in an accelerated transesterification rate. © 2010 Elsevier B.V. All rights reserved.

Kim M.,National Biofuels Energy Laboratory | Kim M.,Wayne State University | Dimaggio C.,National Biofuels Energy Laboratory | Dimaggio C.,Wayne State University | And 6 more authors.
Green Chemistry | Year: 2011

The effects of support materials - lanthanum oxide, cerium oxide, zirconium oxide, titanium oxide, γ-alumina, and ZSM-5 - on the transesterification activity of CaO-La2O3 and CaO-CeO2 catalysts were investigated. The metal composition and surface acidity (or basicity) of the supported catalysts played a significant role in determining the activity of the catalyst. Results showed that both catalytic activity and basicity of the supported catalysts decreased in the following order: CaO-La2O 3/La2O3 ≥ CaO-La2O 3/CeO2 > CaO-La2O3/ZrO 2 > CaO-La2O3/γ-Al2O 3 > CaO-La2O3/ZSM-5 > CaO-La 2O3/TiO2. In addition, leaching of Ca species from the catalyst was more pronounced with basic supports. However, Ca leaching could be minimized by coupling with La2O3 or CeO 2 on an appropriate support. This was verified in a flow reactor study of the CaO-CeO2/La2O3 catalyst, where, over 200 h of continuous operation, the transesterification yield held constant at 88∼90% while the initial Ca concentration in the product decreased from 194 ppm to below 5.0 ppm after 144 h. This further suggests that Ca leaching had little long-term effect on the overall FAME activity of the catalyst. © 2011 The Royal Society of Chemistry.

Kim M.,National Biofuels Energy Laboratory | Kim M.,Wayne State University | DiMaggio C.,National Biofuels Energy Laboratory | DiMaggio C.,Wayne State University | And 8 more authors.
Bioresource Technology | Year: 2011

In order to achieve a viable biodiesel industry, new catalyst technology is needed which can process a variety of less expensive waste oils, such as yellow grease and brown grease. However, for these catalysts to be effective for biodiesel production using these feedstocks, they must be able to tolerate higher concentrations of free fatty acids (FFA), water, and sulfur. We have developed a class of zirconia supported metaloxide catalysts that achieve high FAME yields through esterification of FFAs while simultaneously performing desulfurization and de-metallization functions. In fact, methanolysis, with the zirconia supported catalysts, was more effective for desulfurization than an acid washing process. In addition, using zirconia supported catalysts to convert waste grease, high in sulfur content, resulted in a FAME product that could meet the in-use ASTM diesel fuel sulfur specification (<500 ppm). Possible mechanisms of desulfurization and de-metallization by methanolysis were proposed to explain this activity. © 2010 Elsevier Ltd.

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