Person: Imizcoz Aramburu, Mikel
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Imizcoz Aramburu
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Mikel
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Ciencias
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InaMat2. Instituto de Investigación en Materiales Avanzados y Matemáticas
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0000-0001-6569-5083
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811612
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Publication Open Access Assessing thermal and nonthermal contributions during CO2 hydrogenation over ruthenium catalysts: effects of the illumination conditions and the nature of the support(Elsevier, 2024-12-05) Imizcoz Aramburu, Mikel; Pellejero, Ismael; Gandía Pascual, Luis; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako GobernuaPhotothermal catalysis offers a promising approach for the clean production of carbon-neutral chemicals from CO2 through reactions with hydrogen as a renewable energy carrier. While the combined action of photons and heat from solar radiation can drive catalytic reactions, the interactions involved are very complex, depend on the catalyst composition, and often remain uncertain. Herein, we assessed the thermal and nonthermal contributions to the overall activities of a series of Ru catalysts during the photothermal hydrogenation of CO2. TiO2 (anatase/rutile mixture), anatase, ZrO2, CeO2, and SiO2 were used as supports for Ru nanoparticles (2 wt%) that were deposited using an amino-acid-assisted method. Ru@TiO2 and Ru@ZrO2 presented the best catalytic performance at relatively low reaction temperatures (220-250 °C), whereas Ru@CeO2 was the most active catalyst above 300 °C. The catalysts were tested under direct and indirect illumination conditions to assess their thermal and nonthermal contributions to the overall production of methane, with a nonthermal contribution of 60-75 % observed at the highest applied irradiance (2.2 W·cm-²). Ru@ZrO2 registered the highest nonthermal CH4 production, which is tentatively ascribable to the participation of photo-generated electrons in the catalytic reaction and the light-induced formation of oxygen vacancies. The selected catalysts were also tested under concentrated-sunlight conditions in outdoor experiments, with a maximum methane production of 200 mmolCH4·gcat-¹·h-¹ achieved over Ru@ZrO2, which resulted in 31 % CO2 conversion and 92 % selectivity for methane in a continuous flow reactor at a space velocity of 1500 mLSTP·g-¹·min-¹.Publication Open Access The 3D-printing fabrication of multichannel silicone microreactors for catalytic applications(MDPI, 2023) Ibáñez de Garayo Quilchano, Alejandro; Imizcoz Aramburu, Mikel; Maisterra Udi, Maitane; Almazán, Fernando; Sanz Carrillo, Diego; Bimbela Serrano, Fernando; Cornejo Ibergallartu, Alfonso; Pellejero, Ismael; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaMicrostructured reactors (MSRs) are especially indicated for highly demanding heterogeneous catalysis due to the small channel dimensions that minimize diffusional limitations and enhance mass and heat transport between the fluid and the catalyst. Herein, we present the fabrication protocol of the fused filament 3D printing of silicone monolithic microreactors based on a multichannel design. Microchannels of 200 to 800 µm in width and up to 20 mm in length were developed following the scaffold-removal procedure using acrylonitrile butadiene styrene (ABS) as the material for the 3D-printed scaffold fabrication, polydimethylsiloxane (PDMS) as the building material, and acetone as the ABS removing agent. The main printing parameters such as temperature and printing velocity were optimized in order to minimize the bridging effect and filament collapsing and intercrossing. Heterogeneous catalysts were incorporated into the microchannel walls during fabrication, thus avoiding further post-processing steps. The nanoparticulated catalyst was deposited on ABS scaffolds through dip coating and transferred to the microchannel walls during the PDMS pouring step and subsequent scaffold removal. Two different designs of the silicone monolithic microreactors were tested for four catalytic applications, namely liquid-phase 2-nitrophenol photohydrogenation and methylene blue photodegradation in aqueous media, lignin depolymerization in ethanol, and gas-phase CO2 hydrogenation, in order to investigate the microreactor performance under different reaction conditions (temperature and solvent) and establish the possible range of applications.Publication Open Access UiO-66 MOF-Derived Ru@ZrO2 catalysts for photo-thermal CO2 hydrogenation(MDPI, 2023) Almazán, Fernando; Lafuente, Marta; Echarte Villeras, Amaya; Imizcoz Aramburu, Mikel; Pellejero, Ismael; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaThe use of metal–organic frameworks (MOFs) as templates or precursors in the manufacture of heterogeneous catalysts is highly attractive due to the transfer of MOFs’ inherent porosity and homogeneous metallic distribution to the derived structure. Herein, we report on the preparation of MOF-derived Ru@ZrO2 catalysts by controlled thermal treatment of zirconium-based MOF UiO66 with ruthenium moieties. Ru3+ (3 or 10 mol%) precursor was added to UiO-66 synthesis and, subsequently, the as-synthesized hybrid structure was calcined in flowing air at different temperatures (400–600 ◦C) to obtain ZrO2 -derived oxides doped with highly dispersed Ru metallic clusters. The materials were tested for the catalytic photo-thermal conversion of CO2 to CH4 . Methanation experiments were conducted in a continuous flow (feed flow rate of 5 sccm and 1:4 CO2 to H2 molar ratio) reactor at temperatures from 80 to 300 ◦C. Ru0.10@ZrO2 catalyst calcined at 600 ◦C was able to hydrogenate CO2 to CH4 with production rates up to 65 mmolCH4·gcat. –1 ·h –1, CH4 yield of 80% and nearly 100% selectivity at 300 ◦C. The effect of the illumination was investigated with this catalyst using a high-power visible LED. A CO2 conversion enhancement from 18% to 38% was measured when 24 sun of visible LED radiation was applied, mainly due to the increase in the temperature as a result of the efficient absorption of the radiation received. MOF-derived Ru@ZrO2 catalysts have resulted to be noticeably active materials for the photo-thermal hydrogenation of CO2 for the purpose of the production of carbon-neutral methane. A remarkable effect of the ZrO2 crystalline phase on the CH4 selectivity has been found, with monoclinic zirconia being much more selective to CH4 than its cubic allotrope.