Hybrid Catalytic Systems for the Sustainable Reduction of Carbon Dioxide to Value-Added Oxygenates
Akash Biswas, Chemical Engineering, Chen Group
Abstract: Atmospheric carbon dioxide (CO2) concentrations have increased rapidly in recent decades due to the burning of fossil fuels, deforestation, and other industrial practices. One potential solution to closing the carbon cycle is utilizing CO2, rather than fossil fuels, as the carbon source for fuels and chemicals production. This lowers atmospheric CO2 levels while simultaneously providing an economic incentive for capturing and converting CO2 into more valuable products. This dissertation includes studies on three hybrid catalytic reactor systems coupling electrochemistry, thermochemistry, and plasma chemistry for the conversion of CO2 into value-added oxygenates, such as methanol and C3 oxygenates (propanal and 1-propanol). First, a tandem two-stage system is described where CO2 is electrochemically reduced into syngas followed by the thermochemical methanol synthesis reaction. The work here specifically focuses on the electrochemical CO2 reduction reaction to produce syngas with tunable H2/CO ratios. Second, another tandem two-stage system is demonstrated where CO2 is electrochemically reduced into ethylene and syngas followed by the thermochemical hydroformylation reaction to produce propanal and 1-propanol. Third, a hybrid plasma-catalytic system is investigated where CO2 and ethane are directly converted into multi-carbon oxygenates in a one-step process under ambient conditions. It is also critical to assess whether the proposed CO2 conversion strategies consume more CO2 than they emit. A comparative analysis of the energy costs and net CO2 emissions is conducted for various reaction schemes, including four hybrid pathways (thermocatalytic-thermocatalytic, plasma-thermocatalytic, electrocatalytic-thermocatalytic, and electrocatalytic-electrocatalytic) for converting CO2 into C3 oxygenates. Hybrid catalytic systems can potentially provide a more sustainable alternative to traditional processes, and these concepts can be extended to other chemical reactions and products, thereby opening new opportunities for innovative CO2 utilization technologies.