(138g) Optimized Annular Reactor Modeling and Performance for Photocatalytic Carbon Dioxide Conversion

Optimized Annular Reactor Modeling and Performance for Photocatalytic Carbon Dioxide Conversion

Mohammad E. Raihan, Daniel Chen, and Tracy J Benson

Long-term sustainability of modern chemical industry must include minimization of climate change practices, notably the release of exogenous CO₂ as it comprises 82 % of known greenhouse gases.

Day by day modern life demands more energy consumption, most of them by carbonaceous fuel such as coal, petroleum, gas etc, where CO₂ is the main emission of the complete combustion of these fuels. . According to the International Energy Agency (IEA), the total worldwide CO₂ produced was approximately 29 x 10⁹ metric tons in 2007. The largest contributors of CO₂, about 41% of total, are electricity and heat generation, where transportation and industry contributes 23% and 20%, respectively. Therefore, it becomes vital for humanity to develop efficient and economic methods to capture, convert, and/or sequestrate CO₂. Either must be economically attractive for industrial implementation and cannot bring about further harm to the environment.  Conversion of CO₂ using thermochemical methods (i.e. dry reforming) shows little profit potential due to very high reaction temperatures (~900 °C).  Therefore, photocatalytic methods would be promising since conversion could be achieved at much lower temperatures simply by harnessing photon energy to excite a catalyst surface.

In the photocatalytic reaction, the photoreactor geometry plays a significant role on the reactor performance, which depends on the photon collecting efficiency. This work presents an annular reactor design that converts CO₂ and H₂O to CO, H₂, CH₄ and C₂H₆ in a continuous flow heterogeneous reactor.  Owing to the uniqueness of the reactor (i.e. annular and photocatalytic), a special catalyst support technique was developed to maximize the catalyst surface area inside the reactor while also delivering UV light to the catalyst surface. Experimental work was performed for designing the reactor, choosing a suitable light source, developing a gauze for catalyst support, and determining an efficient catalyst coating procedure. The goal of the project was to design an annular photoreactor for CO₂ photoreduction with H₂O over TiO₂ and under UV light with optimal production rates and to serve as an enhancement to other common photoreactors. This work seeks to advance photoreduction applications of continuous, two-phase (solid-gas) systems. The new design has many advantages, including small reactor size relative to conversion, low light output, high surface area, and high light utilization.  Experiments using the reactor have lead to response surface models that can be used for scale-up and optimized performance.