PhD defense Roozbeh Valadian

This PhD thesis focuses mainly on the characterization of complex porous materials at the low micrometer and sub-micron length scale. The characterization techniques used in this PhD Thesis can be classified into two synchrotron-based X-ray microscopy (XRM) techniques: i) X-ray holotomography and ii) correlative ptychographic X-ray computed tomography (PXCT) and X-ray fluorescence (XRF) tomography.

X-ray holotomography combined with pore network (PN) modeling was used to study deactivation mechanisms caused by coke and metal deposition within a single fluid catalytic cracking (FCC) catalyst particle. Furthermore, the same combination was used for studying the heterogeneity in the fragmentation behavior of a set of metallocene-type catalyst particles at different stages of ethylene polymerization. Correlative PXCT and XRF tomography was used to perform statistical analysis and to quantify the degree of fragmentation of an ensemble of Ziegler-type ethylene polymerization catalyst particles by mapping support, polymer, and mixed phases at high spatial resolution.

Moreover, the pore structure as well as the element distribution within a single FCC catalyst particle was mapped using correlative PXCT and XRF tomography. The obtained morphological and elemental information allowed performing a mass transport simulation based on pore network modeling, which revealed invaluable insights into the diffusion behavior of reactant and product molecules as well as active site accessibility within a single FCC catalyst particle.

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Source: website Utrecht University