Cerium-copper oxides prepared by solution combustion synthesis for total oxidation reactions: From powder catalysts to structured reactors

Abstract

A set of cerium-copper oxide catalysts with various Ce/Cu contents was synthesized using the solution combustion synthesis (SCS) technique. Catalytic activities of the prepared materials were tested for the CO oxidation, total oxidation of ethene and soot combustion. As a whole, the best performances in terms of both CO oxidation and ethene total oxidation were achieved for the binary oxide catalysts having Ce/Cu ratio ranging from 0.67 to 1.5. It has been observed that catalysts with CuOx clusters interacting with CeO2 are particularly effective for both the oxidation reactions. This confirms that CeOx and CuOx domains may cooperate synergistically, leading to higher oxidation activity because of the easier surface reducibility and more abundant structural defects (oxygen vacancies). On the other hand, the soot combustion activity increases as a function of the Ce-content up to 95 at.%. Indeed, the best soot oxidation catalyst exhibits copper highly dispersed into the ceria framework (Ce-O-Cu species), along with an abundant population of Cu+ species and H-bonded hydroxyl groups. Finally, the best performing powder catalysts were deposited on Silicon Carbide (SiC)-type monoliths through a novel synthesis and their catalytic activity was confirmed in a laboratory-scale pilot plant reactor. All the prepared catalysts were characterized by physico-chemical techniques, including XRD, FESEM, TEM, N2 physisorption at −196°C, H2-TPR, XPS, FT-IR and micro-Raman spectroscopies.