CO Total and preferential oxidation over stable Au/TiO2 catalysts derived from preformed au nanoparticles

CO preferential oxidation (PROX) is an effective method to clean reformate H2 streams to feed low-temperature fuel cells. In this work, the PROX and CO oxidation reactions were studied on preformed Au nanoparticles (NPs) supported on TiO2 anatase. Preformed Au NPs were obtained from gold cores stabilized by dodecanethiols or trimethylsilane-dendrons. A well-controlled size of ca. 2.6 nm and narrow size distributions were achieved by this procedure. The catalysts were characterized by high-resolution transmission electron microscopy and ex situ and in situ X-ray photoelectron spectroscopy (XPS). The XPS results showed that the preformed Au NPs exhibited high thermal stability. The different ligand-derived Au catalysts, as well as a conventional gold catalyst for comparison purposes, were loaded onto cordierite supports with 400 cells per square inch. The activity and selectivity of the samples were evaluated for various operation conditions. The catalyst prepared using dodecanethiol-capped Au NPs showed the best performance. In fact, CO conversions of up to 70% at 40% CO2 selectivity and 90% O2 conversion were observed operating at 363 K in H2-rich atmospheres. The performance of the best catalysts was subsequently tested on stainless steel microreactors. A 500-hour stability test was carried out under a real post-reformate stream, including 18 vol.% CO2 and 29 vol.% H2O. A mean CO conversion of ca. 24% was measured for the whole test operating at 453 K and a gas hourly space velocity (GHSV) of 1.3 × 104 h−1. These results reveal our dodecanethiol-and carbosilane-derived Au catalysts as extremely promising candidates to conduct a PROX reaction while avoiding deactivation, which is one of the major drawbacks of Au/TiO2 catalysts.Fil: Divins, Núria J.. Universidad Politécnica de Catalunya; EspañaFil: Lopez, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Angurell, Inmaculada. Universidad de Barcelona. Facultad de Química; EspañaFil: Neuberg, Stefan. Fraunhofer Institute of Microengineering and Microsystems; AlemaniaFil: Zapf, Ralf. Fraunhofer Institute of Microengineering and Microsystems; AlemaniaFil: Kolb, Gunther. Fraunhofer Institute of Microengineering and Microsystems; AlemaniaFil: Llorca Piqué, Jordi. Universidad Politécnica de Catalunya; Españ

In situ investigation of the mechanochemically promoted Pd–Ce interaction under stoichiometric methane oxidation conditions

The optimization of the supported Pd phase for CH4 activation on Pd/CeO2 catalysts has been a matter of great interest in the recent literature, aiming at the design of efficient methane abatement catalysts for Natural Gas fueled Vehicles (NGVs). Under lean conditions, a mixed Pd0 /PdO combination has been indicated as exhibiting the best performance, while controversial results have been reported under stoichiometric conditions depending on the support oxide, where either Al2O3 or zeolite-based supports are usually considered. Here, by means of synchrotron-based in situ NAP-XPS and XRD measurements, we follow the evolution of Pd species on Pd/CeO2 samples prepared by dry mechanochemical synthesis (M) under stoichiometric CH4 oxidation feed, unravelling a stable Pd0 /Pd2+ arrangement in a close to 1 : 1 ratio as the most active palladium state for CH4 activation when excess oxygen is not available, in contrast to what was reported for Pd/alumina materials, where metallic Pd0 nanoparticles showed the highest activity. The combination of NAP-XPS analysis and activity test results highlights the promotional effect of the Pd–Ce interaction, resulting in enhanced oxygen transfer and improved activity and stability of the Pd/CeO2 catalyst prepared by a novel mechanochemical approach even under low O2 content, large excess of water vapor (10 vol%) and high temperature exposure (4700 1C)

Modelling and simulation of catalytic ammonia decomposition over Ni-Ru deposited on 3D-printed CeO2

3D-printed ceria structures have been prepared by robocasting, without using any additive, and impregnated with different amounts of Ni and Ru, characterized and tested for the catalytic decomposition of ammonia in a fixed bed reactor. The best catalytic performance has been achieved with an active phase of 0.5Ni0.1Ru (w/w%). A kinetic expression has been obtained using a crushed catalytic structure, which has been employed in a 1D model to simulate the behaviour of the Ni-Ru impregnated 3D-printed ceria structures. The results have been compared with the experimental data to validate the proposed model. A series of simulations have been performed to determine the relationship between the geometric parameters of the 3D-printed structures and their catalytic performance in the ammonia decomposition, in order to optimize the catalytic structure with the aim of supplying the hydrogen produced to a PEM-type fuel cell.Fil: Lucentini, Ilaria. Universidad Politécnica de Catalunya; EspañaFil: Garcia Colli, Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Luzi, Carlos Daniel. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Serrano, Isabel. Universidad Politécnica de Catalunya; EspañaFil: Soler, Lluís. Universidad Politécnica de Catalunya; EspañaFil: Divins, Núria J.. Universidad Politécnica de Catalunya; EspañaFil: Martinez, Osvaldo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Llorca Piqué, Jordi. Universidad Politécnica de Catalunya; Españ