Fe-Ceria catalyst for Volatile Organic Compounds oxidation

BALZAROTTI R.; CRISTIANI C.; GARBARINO G.; SPENNATI E.; BASBUS J.F.; LAGAZZO A.; FINOCCHIO E.

Congreso; XXIII National Catalysis Congress GIC 2023; 2023

A series of ceria-based catalysts have been prepared at Politecnico di Milano in the form of powders and also deposited onto open cell ceramic foam. Nickel, cobalt, iron and copper were selected as representative active phases, to be supported over commercial high surface area (HS) and low surface area (LS) cerium oxides1. Among the different formulations studied, 7% wt Fe-Ceria HS powdered catalyst, prepared by incipient wetness impregnation, has been fully characterized and tested in the oxidation of ethanol and methanol by using in situ IR spectroscopy and Temperature Programmed Surface Reactivity (TPSR), with and without oxygen in the gas phase. Indeed, in recent years, alcohols have been considered a promising alternative fuel, thus the application of catalytic combustion in controlling emission from their oxidation deserves further study2.Characterization data by FT IR spectroscopy, UV Vis.-NIR DR spectroscopy, XRD, and SEM techniques indicate the formation of mainly Fe2O3 particles interacting with cerium oxide component, and lowering the basicity of the surface, while new OH groups are formed, other than those of pure ceria. Moreover, the impregnation procedure from nitrate salt appears to slightly change support particle morphology that becomes more irregular than pure ceria. In situ IR spectroscopy shows reactive adsorption of both ethanol and methanol at the surface of Ceria and Fe-Ceria HS. As first step, alkoxide species are formed, strongly adsorbed at both surfaces already at room temperature, with an indication of alkoxide species interacting selectively with iron oxide particles and traces of carbonyl compounds. The evolution of adsorbed species at increasing temperatures, and without molecular oxygen, shows the formation of carboxylate and carbonate species, likely precursors of combustion products, together with partial oxidation products. Thus, the activity of lattice oxygen has been proven in these experiments. Preliminary IR studies on in situ oxidation of 2-chloropropane compound over Fe-Ceria HS catalyst indicate that a nucleophilic substitution readily occurs at the catalyst surface already at room temperature, and leads, once again, to the formation of strongly adsorbed alkoxy species, prone to further oxidation steps to CO2. In our conditions, TPSR experiments show that alcohols total oxidation is not greatly increased by Fe doping, at least at the metal loading of the tested catalyst. However, the addition of iron oxide seems to lower the selectivity to partial oxidation products, for instance CO, which formation is, indeed, a drawback in the combustion processes.