George Avgouropoulos

Selective CO oxidation over CuO-CeO2 catalysts prepared via the urea–nitrate combustion method

CuO-CeO2 catalysts have been proposed as a promising candidate catalytic system for CO removal from reformed fuels via selective oxidation. In this work, the performance of CuO-CeO2 catalysts, synthesized via the urea–nitrate combustion method, in the reaction of selective CO oxidation in the presence of H2 has been investigated. The combustion method was found to be a simple and fast route for the synthesis of ultrafine, nanocrystalline CuO-CeO2 catalysts. The influence of the fuel/oxidant (urea/nitrate) ratio and the Cu content on the catalytic properties of CuO-CeO2 catalysts has been studied and optimal values of these parameters have been determined. Compared to CuO-CeO2 catalysts prepared with other techniques, the catalysts prepared via the combustion method exhibited similar catalytic performance, remaining very active and stable, remarkably selective and with good tolerance towards CO2 and H2O.

A comparative study of Pt/γ-Al2O3, Au/α-Fe2O3 and CuO-CeO2 catalysts for the selective oxidation of carbon monoxide in excess hydrogen

Three different catalysts, namely Pt/γ-Al 2 O 3 , Au/α-Fe 2 O 3 and CuO-CeO 2 were prepared (by wet impregnation, coprecipitation and a sol-gel method, respectively) and their catalytic performance for the selective oxidation of carbon monoxide in the presence of excess hydrogen was evaluated and compared. The effects of the presence of CO 2 and H 2 O in the reactant feed on the activity and selectivity of these catalysts, as well as their stability under realistic reaction conditions were also investigated. Regardless of whether CO 2 or both CO 2 and H 2 O are present in the reactant feed, the Au/α-Fe 2 O 3 catalyst is superior to the other two for the selective CO oxidation at relatively low reaction temperatures (<80-120°C, depending on contact time and feed composition employed), while at higher reaction temperatures, best results are obtained with the CuO-CeO 2 catalyst, which proved to be more active and remarkably more selective than the Pt/γ-Al 2 O 3 catalyst. The Au/α-Fe 2 O 3 catalyst was the most sensitive, while the Pt/γ-Al 2 O 3 the most resistant towards deactivation caused by the presence of CO 2 and H 2 O in the feed. Finally, while the Au/α-Fe 2 O 3 catalyst lost a considerable portion of its activity during the first 80 h under reaction conditions, the CuO-CeO 2 and Pt/γ-Al 2 O 3 catalysts exhibited a stable catalytic performance, at least during the time period tested in this work (7-8 days).

CuO–CeO2 mixed oxide catalysts for the selective oxidation of carbon monoxide in excess hydrogen

A series of mixed oxide CuO–CeO2 catalysts were prepared by coprecipitation and tested for the selective oxidation of carbon monoxide in the presence of excess hydrogen. These catalysts were found to be very active and exceptionally selective for this reaction and exhibited a good resistance towards CO2 and H2O. The catalytic performance of these non-noble metal containing catalysts is compared with that of other selective CO oxidation catalysts reported in literature.

A Novel Post-Synthesis Modification of CuO-CeO2 Catalysts: Effect on Their Activity for Selective CO Oxidation

Copper oxide nanoparticles were dispersed onto the surface of ceria nanorods, while a post‐synthesis modification was applied to the reference sample using ammonia solutions. The modified catalysts were characterized with a variety of analytical techniques, providing useful information on the effect of the Cu:NH3 ratio, employed in the modification step, on the physicochemical properties. Re‐dispersion of the active copper species under extremely basic conditions promoted the reducibility and the oxygen mobility of the catalyst, thus resulting in a more active and selective catalyst for preferential CO oxidation.