Advanced Technology and Manufacturing Institute (ATAMI)

Microtechnology was used to study the chemical reduction of dissolved carbon dioxide into useful products. A novel TiO₂ photocatalyst was used to activate the reaction under ultraviolet irradiation. CO₂ was dissolved in aqueous and 50% BMIM-BF₄ (ionic liquid) solutions. The introduction of an ionic liquid increased the solubility of CO₂ by 60%. Both solutions were pumped through a continuous photochemical microreactor and analyzed for products. The aqueous photochemical microreactor process produced 5x10⁸-1x10⁶ moles of methane per liter of solution processed. These values vary with mean residence time within the 0.016 mL microreactor volume. Serial reduction intermediates are likely present in solution below the detection limits of our analytical instruments. The 50% ionic liquid process produced 4x10⁸-1x10⁷ moles of methane per liter of solution processed. Similarly, no intermediates were measured. Mathematical models for the kinetic mechanism, momentum transfer, and mass transfer within the reactor were developed. These models were added to a numerical simulation and compared to experimental values. An optimization scheme was executed to extract meaningful reaction rate constants from the simulation that best fit the experimental data. Reaction rate constants reflect the feasibility of operating these processes and the numerical models can be used as design tools.