This Small Business Innovation Research (SBIR) Phase I project offers a completely new and novel approach to convert biomass to a gasoline-replacing mixed alcohol biofuel. The new approach uses a unique reactor called a controlled cavitation reactor (CCR). Specifically, the CCR provides a uniform source of heat by use of small bubbles in a non-reactive liquid; thus, facilitating heat transfer and the interaction of the reactants with the suspended solid catalyst. These improvements will improve the productivity of the reaction while decreasing the energy inputs; thus, decreasing the operating costs. The intellectual merit of this project is the demonstration of the three-phase (gas-solid-liquid) catalytic reactions by CCR to produce more of the desired product with less energy and lower capital cost. The broader commercial impacts of this research are that Maverick Biofuels is commercializing a technology to convert biomass to a mixed alcohol bio-fuel that can be easily blended with gasoline. This process requires that the feedstocks such as timber, crop residues and municipal solid waste (garbage going to the landfill) be converted to synthesis gas. The synthesis gas is then reacted using the CCR to produce a mixed-alcohol biofuel. Overall, this method for converting biomass to biofuel results in high yields of gasoline-compatible alcohols. Since a major deterrent to the commercialization of biofuels is the high capital costs, success in this project can change that economic equation. In addition, this concept has broader commercial application in the production of surfactants and other high value chemicals.
Major Findings and Project Outcome: Hydrodynamic cavitation is the process of bubble generation, subsequent growth and collapse of those cavitation bubbles. This phenomenon results in very high energy densities, resulting in very high temperatures and pressures at the surface of the bubbles for a very short time. This study attempted to apply these principles using a cavitation reactor supplied by Hydro Dynamics Inc. to increase the diffusion of reactant molecules to a solid catalyst in a Fischer-Tropsch reaction. A reactor process system (Figure 1) was constructed to test this idea. The process continuously circulated catalyst and paraffin oil. The reactant gas (CO and H2) were added just before the reactor. Product gas and unreacted gas were removed after the reactor. All gases were analyzed using a Gas Chromatograph. ? ???The conclusions from this project are: Cavitation creates a very large gas volume in the reactor that displaces the catalyst and paraffin oil used to remove heat from the reaction. This resulted in low conversions compared to a conventional slurry reactor. At the reaction conditions used in this study, most of the products were paraffins. Unlike a convnetional reactor, very few light olefins were produced. Cavitation in this reactor is created using a rotating perforated disk inside a cylinderical reactor. This required a motor that consumed. Scaled to commercial size, the power requirement would be uneconomical. There was no degradation of catalyst particle size due to cavitation. Although very high localized pressures can be obtained, the catalyst used in this study was not affected. And this is a positive attribute when compared to the high catalyst attrition rate observed in slurry reactors. Cavitation reactors have excellent mixing capabilities coupled with low shear forces. The best application for the type of reactor used in this study is where all the reactants are in liquid phase or liquid-solid phase. Controlled cavitation reactors are a new and promising field of development for chemical reactions. The reactor creates the rapid formation of bubbles in a liquid media. When the bubbles collapse, they generate localized areas of high temperature and pressure that, when controlled, can potentially increase the rate of chemical reactions and alter product selectivity compared to conventional systems. This concept was tested for a three phase Fischer-Tropsch reaction. It is our conclusion that cavitation in a liquid media, with gas present, creates very small stable bubbles. While we did not observe foaming, there was a sufficient volume of bubbles to displace a large amount catalyst from the reactor. This limited conversion of the reactant gases to products. It is our conclusion that cavitation reactors of the design used in this study are not appropriate when gas is present in the process stream.
