Enhanced photocatalytic carbon dioxide reduction with taylor flow within mini-channel

The increase in greenhouse gas emissions accelerated after the industrial revolution. Total carbon dioxide emissions, which were close to 2 billion tons in 1900, increased 18.5 times in 2022 and reached 37.12 billion tons. In the face of the increasing world population, the demand for industrial products and therefore carbon dioxide emissions from fossil fuel consumption will inevitably increase. Turning carbon dioxide emissions into a win-win situation between industry and the sustainable world is possible through the chemical conversion of carbon dioxide. In this study, it was aimed to convert carbon dioxide into other organic compounds which are commercially valuable. However, the chemical conversion of carbon dioxide is thermodynamically very difficult and requires external energy. To overcome this challenge, photocatalytic reactions are a "green" technology as the required activation energy comes from the interaction of the catalyst with light rather than from sources such as high temperature/pressure. Fot this reason, photocatalytic processes are an effective method for converting carbon dioxide chemically. These reactions were carried out in a UVA permeable mini channel to receive more luminous flux per unit area and to enable mass transfer more effective with the flow. Micro and mini flow reactors have a large surface area per volume, if energy transfer methods from the surface are used, they are highly efficient reactors. In addition, these reactors have an advantage over conventional reactors in mass transfer as the diffusion distance is very short. Taylor flow with gas and liquid multi phase system is used. Thanks to the low- and high-pressure regions that form the loops called taylor vortex in the liquid phase, the carbon dioxide diffused from the gas phase to the liquid phase and mix in the liquid phase and start the chemical reaction by meeting with the catalyst. In this study, Flow is regulated by taylor flow in a 1 mm diameter mini channel and methanol was used as the liquid phase reductant agent to benefit from the methyl groups in the reaction environment. To imitate sunlight and work with low energy consumption, the reactions were carried out with a 40 W lamp which provides 365 nm UV-A radiation in the region. All experiments were carried out at room temperature with a residence time of approximately 30 seconds. Catalyst particles obtained by precipitation and sol-gel method. Also, dopped catalyst particals which produced wet impregnation and incipient wetness impregnation method were used as catalysts. The effect of zinc oxide, titanium dioxide, aluminum oxide and silica particles and cerium doped particles fed into the system in liquid phase methanol mixture as heterogeneous catalyst with a target of 0.50% by mass (Catalyst mass/Liquid phase mass) on total conversion and selectivity was investigated. As a result of experiments with different catalysts, formic acid, acetic acid and 1-hexanol products were obtained. Therefore, this study aims to explain the semiconductor catalysts in carbon dioxide conversion and is a pioneer for future reactor and reaction conditions optimization (temperature, residence time, catalyst concentration) studies.