https://hdl.handle.net/10481/40908 2026-04-11T15:48:28Z 2026-04-11T15:48:28Z Vivo Vílches, José Francisco Bailón García, Esther Pérez Cadenas, Agustín Francisco Carrasco Marín, Francisco Maldonado Hodar, Francisco José https://hdl.handle.net/10481/101308 2025-01-30T11:21:20Z

Tailoring activated carbons for the development of specific adsorbents of gasoline vapors Vivo Vílches, José Francisco; Bailón García, Esther; Pérez Cadenas, Agustín Francisco; Carrasco Marín, Francisco; Maldonado Hodar, Francisco José The specific adsorption of oxygenated and aliphatic gasoline components onto activated carbons (ACs) was studied under static and dynamic conditions. Ethanol and n-octane were selected as target molecules. A highly porous activated carbon (CA) was prepared by means of two processes: carbonization and chemical activation of olive stone residues. Different types of oxygenated groups, identified and quantified by TPD and XPS, were generated on the CA surface using an oxidation treatment with ammonium peroxydisulfate and then selectively removed by thermal treatments, as confirmed by TPD results. Chemical and porous transformations were carefully analyzed throughout these processes and related to their VOC removal performance. The analysis of the adsorption process under static conditions and the thermal desorption of VOCs enabled us to determine the total adsorption capacity and regeneration possibilities. Breakthrough curves obtained for the adsorption process carried out under dynamic conditions provided information about the mass transfer zone in each adsorption bed. While n-octane adsorption is mainly determined by the porosity of activated carbons, ethanol adsorption is related to their surface chemistry, and in particular is enhanced by the presence of carboxylic acid groups.

Bailón García, Esther Carrasco Marín, Francisco Pérez Cadenas, Agustín Francisco Maldonado Hodar, Francisco José https://hdl.handle.net/10481/101304 2025-01-30T11:17:20Z

Microspheres of carbon xerogel: an alternative Pt-support for the selective hydrogenation of citral Bailón García, Esther; Carrasco Marín, Francisco; Pérez Cadenas, Agustín Francisco; Maldonado Hodar, Francisco José A new carbon xerogel (A8) was obtained in powder by polymerization of resorcinol-formaldehyde using a stirred batch reactor, microwave drying and carbonization in inert atmosphere. The ability of this material as Pt-support regarding SiO2, TiO2 and Al2O3 to develop selective catalysts for the citral hydrogenation was analyzed on the basis of their morphologic, textural and acid characteristics. Inorganic supports are crystalline and mesoporous materials while the carbon xerogel is exclusively microporous and is formed by spherical nanoparticles of around 250 nm in diameter of amorphous carbon. The supports acidity (pHpzc) vary in the sense Al2O3 > TiO2> SiO2 > A8. The Pt-dispersion depends on the support nature and pretreatment conditions used; in general, an increase of Pt-particle size favors the selectivity to unsaturated alcohols but the catalytic activity decrease. The conversion also strongly depends on the acidity of supports, but selectivity is more specifically influenced by the strength of the acid sites and pore size distribution. Cracking reactions are favored by Brönsted acid sites present in Al2O3 and the high mesopore volume of SiO2 induces mainly secondary cyclization and hydrogenation reactions. Pt-supported on carbon xerogel (Pt/A8) provided selectivity values to unsaturated alcohols of around 80%, a very high value for monometallic Pt-catalyst and only comparable with those obtained with Pt/TiO2 pretreated in H2-flow.

Davó Quiñonero, Arantxa Bailón García, Esther López Rodríguez, Sergio Juan Juan, Jerónimo Lozano Castelló, Dolores García Melchor, Max Herrera, Facundo C Pellegrin, Eric Escudero, Carlos Bueno López, Agustín https://hdl.handle.net/10481/101222 2025-01-30T10:24:06Z

Insights into the Oxygen Vacancy Filling Mechanism in CuO/CeO2 Catalysts: A Key Step Toward High Selectivity in Preferential CO Oxidation Davó Quiñonero, Arantxa; Bailón García, Esther; López Rodríguez, Sergio; Juan Juan, Jerónimo; Lozano Castelló, Dolores; García Melchor, Max; Herrera, Facundo C; Pellegrin, Eric; Escudero, Carlos; Bueno López, Agustín The preferential CO oxidation (CO-PROX) reaction is paramount for the purification of reformate H2-rich streams, where CuO/CeO2 catalysts show promising opportunities. This work sheds light on the lattice oxygen recovery mechanism on CuO/CeO2 catalysts during CO-PROX reaction, which is critical to guarantee both good activity and selectivity, but that is yet to be well understood. Particularly, in situ Raman spectroscopy reveals that oxygen vacancies in the ceria lattice do not form in significant amounts until advanced reaction degrees, whereas pulse O2 isotopic tests confirm the involvement of catalyst oxygen in the CO and H2 oxidation processes occurring at all stages of the CO-PROX reaction (Mars–van Krevelen). Further mechanistic insights are provided by operando near-ambient pressure X-ray photoelectron spectroscopy (NAP–XPS) and near edge X-ray absorption fine structure (NEXAFS) experiments, which prove the gradual CuO reduction and steady oxidized state of Ce ions until the very surface reduction of CeO2 at the point of selectivity loss. Experiments are complemented by density functional theory (DFT) calculations, which reveal a more facile oxygen refill according to the trend CuO > CeO2 > Cu2O. Overall, this work concludes that the oxygen recovery mechanism in CO-PROX switches from a direct mechanism, wherein oxygen restores vacancy sites in the partially reduced CuO particles, to a synergistic mechanism with the participation of ceria once CuxO particles reach a critical reduction state. This mechanistic switch ultimately results in a decrease in CO conversion in favor of the undesired H2 oxidation, which opens-up future research on potential strategies to improve oxygen recovery.

Cárdenas Arenas, Andrea Bailón García, Esther Lozano Castelló, Dolores Da Costa, Patrick Bueno López, Agustín https://hdl.handle.net/10481/101113 2025-01-30T09:12:15Z

Stable NiO–CeO2 nanoparticles with improved carbon resistance for methane dry reforming Cárdenas Arenas, Andrea; Bailón García, Esther; Lozano Castelló, Dolores; Da Costa, Patrick; Bueno López, Agustín High surface area mixed oxide 8.7% NiO-CeO2 nanoparticles (122 m2/g; 6–7 nm) were prepared using a reversed microemulsion method, and were tested for dry methane reforming (DRM). The catalytic activity of these nanoparticles remains stable under the severe conditions of DRM (700 °C), and they show better carbon resistance than conventional NiO-CeO2 catalysts prepared without control of the size. The activity and selectivity of nanoparticles and reference catalyst are similar, but nanoparticles reduce the accumulation of carbon by 63% during the DRM tests, which is a key feature for this reaction. XPS and H2-TPR suggest that the improved carbon resistance of the nanoparticles is due to the better interaction and cooperation between NiO and CeO2 mixed phases. In nanoparticles, the participation of cerium cations in the redox processes taking place during DRM stabilizes cationic species of nickel. On the contrary, the catalyst prepared without control of the size suffers segregation of Ni during DRM reaction, and segregated Ni explains the higher catalytic formation of carbon.

Chaparro Garnica, Cristian Bailón García, Esther Davó Quiñonero, Arantxa Lozano Castelló, Dolores Bueno López, Agustín https://hdl.handle.net/10481/101084 2025-01-30T08:51:55Z

Sponge-like carbon monoliths: porosity control of 3D-printed carbon supports and its influence on the catalytic performance Chaparro Garnica, Cristian; Bailón García, Esther; Davó Quiñonero, Arantxa; Lozano Castelló, Dolores; Bueno López, Agustín Sponge-like carbon monoliths with tailored channel architecture and porosity were prepared by combining sol–gel polymerization and 3D printing technology. The pore size distribution (PSD) and macropore volume were controlled by varying the water concentration used in the synthesis. The size and interconnection degree of primary particles, and consequently the pore width and macropores volume, increases by increasing the water concentration. However, a more heterogeneous PSD was detected at high water concentration, due to the better-defined spheres-like morphology of primary particles which leaves voids and corners between fused spheres together with bigger macropores leaves by the coral-like structure. The role of this porosity control on the CuO/CeO2 catalytic performance was pointed out in the CO-PrOx reaction. The CuO/CeO2 dispersion and distribution along the carbon network increases by increasing the water concentration, i.e. the pore width and macropore volume, enhancing the catalytic activity. However, this improvement is not observed at high water concentration in which preferential flow pathways are created favored by the heterogeneous PSD. This manifest that the porosity control plays an important role in the catalytic performance of monolithic catalysts and thus, the monolithic support must be specifically designed to optimize the catalytic performance of active phases for each application.