(21b) Photocatalyst Development and Reactor Design for the Conversion of Carbon Dioxide and Water to Syngas

Photocatalytic conversion of CO₂ into valuable products has attracted much attention in recent years and is developing as a promising technology for reduction of exogenous CO2 contributions in the atmosphere. The energy consumption in modern life depends on the carbonaceous fuel consumption such as coal, petroleum, and natural gas. CO₂ is the main gas emission of the complete combustion of these fuel. According to the International Energy Agency (IEA), the total worldwide CO₂ produced in 2007 was approximately 29 x 10⁹ metric tons. Electricity and heat generation are the largest contributors of CO₂, about 41% of total CO₂. Transportation and industry contribute 23% and 20%, respectively. Therefore, it becomes vital for humanity to develop efficient and economic methods to capture, convert, and/or sequestrate CO₂.

In the photocatalytic reaction, the photoreactor geometry has a significant effect 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 and visible 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 a suitable 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.