Craig DiMaggio

Performance of heterogeneous ZrO2 supported metaloxide catalysts for brown grease esterification and sulfur removal

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.

The effect of support material on the transesterification activity of CaO–La2O3 and CaO–CeO2 supported catalysts

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–La2O3/La2O3 ≥ CaO–La2O3/CeO2 > CaO–La2O3/ZrO2 > CaO–La2O3/γ-Al2O3 > CaO–La2O3/ZSM-5 > CaO–La2O3/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 CeO2 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.