An innovative way to reduce CO2: combination of ionic liquid and microtechnology

Reduction of carbon dioxide emission is a global concern owing to its significant contribution to the greenhouse effect. Processes that contribute to the sequestration of carbon dioxide have thus been under development and research worldwide. The efficient reduction of carbon dioxide in ionic liquids has over time been proven to be a resourceful sequestration technique, since ionic liquids have relatively high solubility of CO₂ allows more interactions with protons and electrons generating various chemical compounds that contain atomsone or multiple carbon atoms. From the wide variety of ionic liquids available for utilization in such a process, wet BMIM-BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) has been adopted in this study owing to the fact that it can form complex hydrogen bonds that lower the activation energy required for CO₂ reduction. Advantages of this technique can be viewed in the form of reduced carbon taxes for carbon dioxide emitting industries, or generation of fuels, such as methane and methanol, from renewable energy resources.

Dr. Yu Miao (currently a post-doctoral fellow at Baylor University), Professor Goran Jovanovic at Oregon State University, and Professor Alexandre Yokochi (currently at StateBaylor University) in collaboration with Nuchanart Siri-Nguan and Dr. Thana Sornchamni from PTT Public Company Limited in Thailand developed an electrochemical microscale-based reaction system that could convert CO₂ into more valuable chemicals such as methane and methanol. Generally, they are working on the updevelopment and design of systems that could sequester carbon dioxide gas from various sources such as combustion exhausts, landfill biogas and emission gas from natural gas reforming processes. Their work is currently published in the research journal, Chemical Engineering Journal.

The team commenced their studies by designing and fabricating an electrochemical microscale-based reaction system (see Figure 1). Next, the developed system was utilized for the reduction of CO₂ in the presence of wet ionic liquid BMIM-BF4 and studied under various experimental conditions controlled by factors such as micro-reactor height, solvent concentration and mean residence time of fluids in the micro-reactor. They then developed a mathematical model that reflected the geometry and flow conditions within the micro-reactor so as to simulate the chemical reaction process. Eventually, they determined the parameters of the mathematical model using an optimization process in which the best fit between the experimental data and the model prediction was achieved.

The authors observed that the ionic liquid solution used as the solvent increased the net consumption of CO₂ and current efficiency. A comparison between the primary reaction rate constants in de-ionized water and wet BMIM-BF4 solution revealed that in both solvents, the reaction rate constants were almost in the same order of magnitude with slight differences on the value. Furthermore, an improved understanding of the reactor system was achieved by comparing predictions from numerical simulations with experimental observations.

The significance of Yu Miao and colleagues’ study is in incorporating of such micro-based technology at an industrial level can be highly rewarding in terms of reduced carbon taxes and future reuse of carbon captured following combustion to produce useful products.