Co/MCM41 catalyst in the COProx reaction prepared by supercritical CO2 reactive deposition

Abstract

Co/MCM41 catalyst with 4.3 wt % Co (Co/sc) has been prepared by supercritical CO2 reactive deposition (‘scfrd’) and characterized by different physicochemical techniques. This synthesized method was compared with others conventional methodologies such as template-ion exchanged (Co/tie) and incipient wet impregnation (Co/iwi) with similar cobalt content. All the samples were studied as catalysts on the CO total oxidation (COTox) and preferential oxidation of CO on H2-rich streams (COProx). Incorporating cobalt with supercritical CO2 leads to a catalyst which produces values of CO conversion similar to those obtained by conventional methods such as incipient wetness impregnation (Co/iwi) or template-ion exchanged (Co/tie). It has been possible to identify different cobalt species present in catalysts depending on their synthesis methods by Temperature-Programmed Reduction (TPR), X-ray Photoelectronic (XPS), Laser Raman (LRS) and X-ray Absorption (XANES/EXAFS) spectroscopic studies. All samples containing a main cobalt species of cobalt (II) coordinated with Si tetrahedral sites form part of mesoporous structure and lesser extent, cobalt orthosilicate on the surface. In addition, Co3O4 species dispersed over the MCM41 support were detected for the Co/iwi and Co/sc catalysts. Thus, the combination of Co3O4 nanoparticles and Co(II) sites interacting with the siliceous structure, highly dispersed on the surface and inside the mesoporous support obtained by the ‘scfrd’ method resulted in a more active and selective catalyst for the COProx reaction.