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Model CuO/Ce 0.8 X 0.2 O δ catalysts (with X = Ce, Zr, La, Pr, or Nd) have been prepared in order to obtain CuO/ceria materials with different chemical features and have been characterized by X-ray diffraction, Raman spectroscopy, N 2 adsorption, and H 2 temperature-programmed reduction. CO-PROX experiments have been performed in a fixed-bed reactor and in an operando DRIFTS cell coupled to a mass spectrometer. The CO oxidation rate over CuO/ceria catalysts correlates with the formation of the Cu + −CO carbonyl above a critical temperature (90 °C for the experimental conditions in this study) because copper−carbonyl formation is the rate-limiting step. Above this temperature, CO oxidation capacity depends on the redox properties of the catalyst. However, decomposition of adsorbed intermediates is the slowest step below this threshold temperature. The hydroxyl groups on the catalyst surface play a key role in determining the nature of the carbon-based intermediates formed upon CO chemisorption and oxidation. Hydroxyls favor the formation of bicarbonates with respect to carbonates, and catalysts forming more bicarbonates produce faster CO oxidation rates than those which favor carbonates.

The preferential CO oxidation (CO-PROX) reaction is paramount for the 22 purification of reformate H 2 -rich streams, where CuO/CeO 2 catalysts show promising 23 opportunities. This work sheds light on the lattice oxygen recovery mechanism on 24 CuO/CeO 2 catalysts during CO-PROX reaction, which is critical to guarantee both good 25 activity and selectivity, but that is yet to be well understood. Particularly, in situ Raman 26 spectroscopy reveals that oxygen vacancies in the ceria lattice do not form in significant 27 amounts until advanced reaction degrees, whereas pulse O 2 isotopic tests confirm the

Highlights Increasing loading of Ni and Ru increases the surface basicity and forms new CO2 adsorption sites.  High calcination temperature leads to an increase of RuO2 particle size and formation of inert Ni species.  Ni/Al2O3 catalysts present high metal-support interaction, so that only a relative amount of metal is active for CO2 methanation.  Ru/Al2O3 catalysts are more efficient than Ni/Al2O3 in hydrogen dissociation; TOF of the former is about ten times than TOF of Ni catalysts.  Optimal behavior was found for 12% Ni and 4% Ru, which provide metal surfaces of 5.1 and 0.6 m 2 g -1 , respectively.

Vicente s/n. E03080, Alicante (Spain). HIGHLIGHTS  Ceria catalysts have been prepared with conventional (Ref) and three dimensionally order macroporous (3DOM) structures  3DOM ceria is more active for soot combustion than conventional Ref ceria  3DOM ceria produces more active oxygen than conventional Ref ceria  3DOM ceria catalysts transfer active oxygen to soot more efficiently than conventional Ref ceria  3DOM ceria catalysts utilizes NO2 more efficiently than conventional counterpart Ref ceria

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Three-dimensional (3D)-printed catalysts are being increasingly studied; however, most of these studies focus on the obtention of catalytically active monoliths, and thus traditional channeled monolithic catalysts are usually obtained and tested, losing sight of the advantages that 3D-printing could entail. This work goes one step further, and an advanced monolith with specifically designed geometry has been obtained, taking advantage of the versatility provided by 3D-printing. As a proof of concept, nonchanneled advanced monolithic (NCM) support, composed of several transversal discs containing deposits for active phase deposition and slits through which the gas circulates, was obtained and tested in the CO-PrOx reaction. The results evidenced that the NCM support showed superior catalytic performance compared to conventional channeled monoliths (CMs). The region of temperature in which the active phase can work under chemical control, and thus in a more efficient way, is increased by 31% in NCM compared to the powdered or the CM sample. Turbulence occurs inside the fluid path through the NCM, which enhances the mass transfer of reagents and products toward and from the active sites to the fluid bulk favoring the chemical reaction rate. The nonchanneled monolith also improved heat dispersion by the tortuous paths, reducing the local temperature at the active site. Thus, the way in which reactants and products are transported inside the monoliths plays a crucial role, and this is affected by the inner geometry of the monoliths.