Development of Catalytic Processes for Production of Biodiesel and Renewable Aromatics

The current energy infrastructure is based on non-renewable petroleum resources. Finding a renewable source for producing energy and fuels that fit with our current infrastructure is of great importance. One such renewable source is biomass, which can be converted to biofuels and chemical. Two methods that can be used to convert biomass are transesterification of plant oils (to produce biodiesel) and catalytic fast pyrolysis (CFP) of lignocellulosic biomass (to produce aromatics and olefins). A three-step kinetic model was developed to describe the reaction kinetics for the transesterification of soybean oil using basic catalysts (homogeneous NaOH or heterogeneous SrO). There was an observed change between the rate constants for the third step of the transesterification reaction for the two catalysts, suggesting there may a difference in the reaction mechanism between the two catalysts. The heating method (conventional or microwave) was not found to have any effect on the reaction kinetics while using SrO as the catalyst. Various techniques (predominantly by modifying the ZSM-5 catalyst) for improving the yield of aromatics and olefins from CFP were investigated. Furan was a used a model biomass compound in a fixed bed reactor; pine wood was used as a real biomass feed in a fluidized bed reactor. It was determined that the presence of moisture promoted the hydrolysis of furan (a biomass model compound) over ZSM-5, increasing the yields of propylene and CO2. This is significant, since all biomass inherently contains moisture; this moisture may affect CFP of real biomass as well. The addition of metals (gallium or zinc) to ZSM-5 was found to increase the aromatic and olefin yield during the CFP of furan or pine wood. The addition of these metals adds new Lewis acid sites, which may be directly responsible for this observed increase in yield. The selectivity among xylenes towards the para isomer was increased by depositing a layer of silica on the external surface of the ZSM-5 catalyst to potentially poison external acid sites and constrict pore mouth openings, thereby modifying the catalyst to produce specific desired product species. Therefore there are several types of catalyst design that may be employed to improve yields of desired products from CFP.