The structure of Co species in novel active and selective Co/MCM41 catalyst in the COProx reaction prepared by supercritical CO2 reactive deposition

JOSE MARTIN RAMALLO LOPEZ; MARTÍN DANIEL MIZRAHI; ASPROMONTE, SOLEDAD; ALONSO, ESTHER; ALICIA BOIX

Campinas

Congreso; LNLS 27th Annual Users? Meeting; 2017

CNPEM

Thedeposition of catalytically active sites on supports with high dispersion is animportant and effective strategy for the design of catalysts. Conventionalmethods such as impregnation techniques often generate agglomerations or largeparticles with broad size distribution in the mesoporesand/or on the external surface of the porous catalyst. The incipient wetnessimpregnation (IWI) method allows a good control on metal loading but a poorcontrol on metallic dispersion.1, 2Thus, it is important to study and analyze different ways to introduce theactive phase in the mesoporoussupport. Aninteresting method for incorporating active phases on catalyst supports is thereactive deposition using supercritical fluids (SCFRD). It is a promisingmethod to deposit nanoparticles andfilms on inorganic porous supports, polymer substrates and carbon nanotubes.3, 4 Thisprocess involves the dissolution of an organometallicprecursor in a supercritical fluid (SCF), the impregnation of the substrate byexposure to this solution, and the subsequent decomposition of the precursor.CO2 isthe most commonly used supercritical fluid (scCO2) formaterial synthesis because it is non-toxic, non-reactive, nonflammable andinexpensive. Under supercritical conditions, CO2 as asolvent has intermediate properties between gases and liquids. The gas-likediffusivity and viscosity of scCO2 arefavorable for rapid diffusion and permeation into mesoporoussubstrates, whereas the liquid-like density allows the dissolution of a widerange of organometallicprecursors. The zero surface tension of scCO2allows a better penetration and wetting of pores than liquid solvents andavoids the pore collapse which can occur on certain structures. The simpleremoval from the substrate by controlled decompression is performed withoutleaving any residue on the support.5, 6 Thegoal of the present study is to investigate and compare the catalyticproperties of the cobalt-MCM41 catalysts prepared by methods (i)template-ionic exchange (TIE), (ii) incipient wet impregnation (IWI) and (iii)supercritical CO2reactive deposition (SCFRD) in the total and preferential CO oxidation inreductive atmosphere to purify H2streams.