Abstract
Full-field transmission X-ray microscopy has been used to determine the 3D structure of a whole individual fluid catalytic cracking (FCC) particle at high spatial resolution and in a fast, noninvasive manner, maintaining the full integrity of the particle. Using X-ray absorption mosaic imaging to combine multiple fields of view, computed tomography was performed to visualize the macropore structure of the catalyst and its availability for mass transport. We mapped the relative spatial distributions of Ni and Fe using multiple-energy tomography at the respective X-ray absorption K-edges and correlated these distributions with porosity and permeability of an equilibrated catalyst (E-cat) particle. Both metals were found to accumulate in outer layers of the particle, effectively decreasing porosity by clogging of pores and eventually restricting access into the FCC particle.
Highlights
In our study, we sought to provide elemental information at a high-spatial resolution and hereby present a study of 3D Fe and Ni relative distributions as well as porosity and permeability of a whole equilibrated catalyst (E-cat) fluid catalytic cracking (FCC) particle using full-field transmission hard Xray microscopy (TXM)
The reconstructed tomography data recorded for the total FCC particle (Figure 1) shows nodules and valleys on the surface, causing a mottled shape
The relative Fe and Ni distributions within the FCC particle are shown in Figure 1b− d, where the Fe distribution is indicated by a red to yellow color scale, and Ni is indicated by a blue to green color scale, where yellow and green represent larger relative elemental concentrations
Summary
Relative Fe and Ni distributions plotted as a function of distance from the FCC particle surface (a), and related porosity changes caused by the presence of these metals (b). (volume of voxels in the shell assigned to pore space) to the total volume of all voxels in the shell This allowed us to correlate changes in porosity with the presence or absence of Fe and/or Ni. The resulting plots (Figure 3) clearly show that Fe and Ni mainly accumulate at and near the surface of the particle, which indicates that both metals have been incorporated during the FCC process, entering the particle from the surface.
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