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

摘要

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 hydrodemetallization (HDM) process of oil residues. This report also indicates that LIBS-based imaging represents a powerful tool for quickly providing twodimensional 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. (C) 2018 Elsevier Inc. All rights reserved.