Innovative Microchannel-Structured Ceramic Beads for Intensifying Advanced Oxidation Processes

Abstract

Diffusional mass transfer is vital in heterogeneous catalysis, influencing reactants reach catalytic active sites and product removal. The interplay between diffusion and reaction rates significantly impacts overall reaction performance, particularly in catalyst pellets, which are key in determining reactor pressure drops. Most academic research, laboratory experiments, simulations, and engineering innovations on diffusional mass transfer in catalyst pellets rely on porous structures of randomly packed fine particles, which possess fixed parameters (e.g., porosity and tortuosity), limiting advancements in enhancing internal diffusional mass transfer. This thesis introduces a novel approach to overcoming these limitations by creating a new microchannel structure within spherical beads, a geometry widely used in industrial catalytic processes. The research explores the modification and optimisation of this unique structure, material synergies and related topics such as reusability. The findings provide a comprehensive overview of this innovation by intensifying advanced oxidation processes (AOPs) and its potential benefits for other diffusion-limited reactions. Chapter 4 introduces alumina beads with oriented finger-like microstructures to revolutionise diffusional resistance within spherical beads. Two types of mesoporous materials (γ-Al2O3 in Chapter 5 and carbon xerogel in Chapter 6) were incorporated into these innovative alumina beads to further enhance their specific surface area, facilitating the uniform catalyst dispersion. Furthermore, alternative inorganic material, silica, was applied in Chapter 7 to prepare the microchannel-structured silica beads. Most importantly, all samples after being used and regenerated exhibited significantly higher catalytic performance than the fresh ones due to the enhanced accessibility of open pores on the bead surface during regeneration, highlighting the significance of intensifying the diffusional transfer process to benefit catalytic reactions. Such benefits are highly transferable to a broader spectrum of heterogeneous catalysis applications. Notably, the ceramic beads in this research are easily separable from the bulk solution, addressing scalability issues common with conventional nano- or micro-scale catalysts.