Date on Master's Thesis/Doctoral Dissertation

5-2019

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemical Engineering

Degree Program

Chemical Engineering, PhD

Committee Chair

Sunkara, Mahendra

Committee Member

Sathitsuksanoh, Noppadon

Committee Member

Starr, Thomas

Committee Member

Satyavolu, Jagannadh

Committee Member

Grapperhaus, Craig

Committee Member

Vasireddy, Sivakumar

Author's Keywords

CO2; DMR; 2-methyl-furan; nanowire; catalysts; adsorbent

Abstract

Even today, the major energy source is fossil fuels, which release CO2, a greenhouse gas that contributes to global warming. CO2 capture, storage (CCS) and/or utilization (CCU) technologies are two routes to mitigate this problem. Sorbents are being investigated in either temperature swing or pressure swing absorption approaches for carbon capture from flue gases. Solid sorbent based technology is a promising one but suffers from slow kinetics, low capacity and need for high temperatures. Thus, new sorbent materials that can have good CO2 sorption capacity, recyclability are sought. Similarly, one of the utilization approaches for CO2 is dry methane reforming reaction for hydrogen production. However, current catalysts undergo sintering and produce coking at high reaction temperatures making this reaction a challenge. In this dissertation, nanowire based materials provide uniformity of active surfaces, great stability against sintering and improved diffusion processes for reactions are potentially interesting for fast kinetics with carbon capture sorbents and stable catalyst supports for dry methane reforming reaction. Lithium silicate (Li4SiO4) nanowires were successfully synthesized using a Solvo-PlasmaTM method. Li4SiO4 nanowires exhibited ultrafast CO2 sorption kinetics and capacities closer to their theoretical value. Regeneration tests have shown cyclability but have shown stability with performance at high temperatures over longer durations. The fast kinetics is attributed to shorter time scales needed for lithium to reach surface and react with CO2. Titania nanowires decorated with nickel nanoparticles are investigated for dry methane reforming reaction. Results showed almost 90% CO2 conversion and sustained the catalytic activity under harsh reaction conditions when compared to other nickel supported on spherical titania nanoparticles. The data indicates that the catalysts supported on nanowires exhibited formation of carbons that are reversibly etched in the process making them stable over long periods of time. Overall, in this dissertation, the use of nanowire morphology is investigated to enhance CO2 capture kinetics for improved sorption processes, and to design coke resistant catalyst materials for dry methane reforming by boosting and modifying metal-support interactions.

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