Imaging of alumina supports by laser-induced breakdown spectroscopy: A new tool to understand the diffusion of trace metal impurities

Abstract : Imaging the distribution of reactive molecules in an internal diffusion-limited catalyst is of primary importance in the comprehension and modeling of these systems. Mesoporous alumina supports were impregnated with asphaltenes in a self-pressurized autoclave at high pressure (5 MPa) and high temperature (523 K). Extrudates were then analyzed by laser-induced breakdown spectroscopy (LIBS). We showed that LIBS can provide quantitative concentration maps of sulfur , nickel and vanadium in the ppm range. Processing of these maps is proposed to obtain one-dimensional profiles of the penetration of these elements. These profiles show that the penetration of asphaltenes into the catalyst support is a very complex process. These findings contribute to improving the comprehension of internal diffusion-limited processes, particularly the hy-drodemetallization (HDM) process of oil residues. This report also indicates that LIBS-based 2 imaging represents a powerful tool for quickly providing two-dimensional elemental maps over a large dynamic range, i.e., typically from ppm to tens of %, thereby opening up opportunities for innumerable applications in the field of catalysis.