Direct synthesis of dimethyl ether from syngas in structured reactors.

267 p.Los catalizadores estructurados metálicos se presentan como una alternativa de interés para las reacciones de altamente exotérmicas como la síntesis directa de dimetil éter (DME), compuesto prometedor como sustituto del diésel. La elevada conductividad de los sustratos metálicos favorece el control de temperatura evitando puntos calientes en el sistema que pueden reducir la vida útil de los catalizadores. La preparación de la suspensión juega un papel relevante en la preparación de los catalizadores estructurados, dónde la baja adherencia comúnmente proporcionada por los sustratos metálicos requiere del empleo de aditivos para mejorar las propiedades de recubrimiento de la suspensión. El objetivo de este trabajo ha sido la búsqueda de las formulaciones adecuadas de la suspensión para los dos catalizadores involucrados en la síntesis directa de DME, tanto de forma separada como conjunta, intentando no alterar las propiedades catalíticas de los catalizadores de partida.De esta manera se ha podido estudiar la reacción en sistemas estructurados. Se han realizado estudios en sustratos metálicos de diferente geometría y aleación metálica, a la vez que se han variado las condiciones del sistema en la búsqueda del aumento de la productividad volumétrica de DME (intensificación). Además, el contacto de los dos catalizadores de la síntesis directa de DME es otro parámetro de interés. La versatilidad del método de recubrimiento por inmersión ha permitido estudiar también diferentes arquitecturas de los catalizadores en los monolitos (sistemas multicapa)

Structuring Cu/ZnO/Al2O3 catalyst for methanol synthesis: Slurry additive effect in the washcoating method

The best slurry formulation to prepare a structured catalyst for methanol synthesis reaction by washcoating method was investigated. The effect of different inorganic oxide colloids in the slurry preparation of Cu/ZnO/Al2O3 catalyst was studied: colloidal ZnO, SiO2, and Al2O3. The addition of all these colloids showed an improvement in adherence obtained on Fecralloy® monoliths, but Al2O3 exhibited the best performance. Adherence >80% was obtained with a lower amount of Al2O3 than with the other colloids. Nevertheless, the addition of these additives changes the catalytic properties of the parent catalyst. Adding a high amount of colloids decreases the copper metallic surface area which is the active phase of the methanol synthesis reaction. Moreover, the addition of Al2O3 gave rise to the dehydration of methanol to dimethyl ether (DME) due to the high acidity that Al2O3 presents. Something similar happens but to a less extent with SiO2, which present weak acidity. In contrast, the basic character of ZnO neutralizes the parent catalyst's low acidity reducing the selectivity to DME. Finally, the slurry formulation containing 10% Al2O3 exhibited the best methanol yield. Hence, a methanol synthesis structured catalyst was successfully prepared with similar activity to the powder catalyst.The authors acknowledge the Basque Government (IT1069-16), the Spanish MINECO/FEDER (RTI2018-096294-B-C32 and CTQ2015-73901-JIN) and The University of the Basque Country (GIU21/033) for the financial support. I. Pérez-Miqueo also acknowledges the Basque Government for the PhD scholarship (PRE_2014_1_141)

Design and Test of a Miniature Hydrogen Production Integrated Reactor

A detailed study of the experimental issues involved in the design and operation of a methanol steam microreformer is presented in this paper. Micromachining technology was utilized to fabricate a metallic microchannel block coupling the exothermic and endothermic process. The microchannel block was coated with a Pd/ZnO catalyst in the reforming channels and with Pd/Al2O3 in the combustion channels by washcoating. An experimental system had been designed and fine-tuned allowing estimation of the heat losses of the system and to compensate for them by means of electric heating cartridges. In this way, the heat necessary for the reforming reaction is provided by methanol combustion, thanks to the temperature and flow cascade controller we developed. Thus, the coupling of both reactions in a block of microchannels without the interference caused by significant heat loss due to the small size of the laboratory microreactor could be studied. Runs of this microreformer device were carried out, varying the deposited catalyst amount, methanol steam reforming temperature and space velocity. When the reforming reaction was compensated by the combustion reaction and the heat losses by the electric heating, an almost isothermal behavior of the microchannel reactor was observed. In the less favorable case, with a 460 mg catalyst load, ΔTMSR was about 8 K and ΔTCOMB was about 16 K. This confirmed good coupling of the methanol steam reforming and the methanol combustion.This research was funded by MICINN/FEDER grant numbers RTI2018-096294-B-C32 and CTQ2015-73901-JIN and by the Basque Government grant number IT1069-16

Intensification of hydrogen production by methanol steam reforming

This paper studies the methanol steam reforming intensification to enhance the hydrogen production in a multi-channel block type micro-reformer. The effects of operating parameters such as reforming temperature, space velocity and catalyst layer thickness on reforming performance are investigated. For optimized design and operating conditions, the 8 cm3 reformer unit produced 170 LH2/h containing on dry basis 75.0% H2, 23.5% CO2, 0.06% CH3OH and 1.44% CO at 648 K allowing the production of 218e255 W in a commercial PEMFC with 80% hydrogen utilization. This study shows that high methanol conversion can be achieved with high Pd/ZnO catalyst loading at 648 K with very low CO content (<1.5%) in the outlet stream.The authors acknowledge financial support from the Spanish Ministry of Science and Innovation, Ministry of Economy and Competitiveness, FEDER funding (ENE2012- 37431-C03 Grant) and UPV/EHU (GIU11/13)

A Green Synthesis of Nanocatalysts Based on Reduced Graphene Oxide/Magnetic Nanoparticles for the Degradation of Acid Red 1

The increasing amount of organic dye-polluted wastewater from the textile industry makes the development of techniques for the efficient purification and reuse of wastewater an urgent issue. Accordingly, solid adsorbents based on three-dimensional (3D) reduced graphene oxide (rGO) aerogels combined with magnetic nanoparticles (rGO@Fe3O4) appear to be potential materials, which offer fast and efficient discoloration of dye solutions by dye adsorption, simultaneously acting as Fenton reaction nanocatalysts, and thus may eliminate organic dyes. In this work, 3D rGO@Fe3O4 aerogel nanocatalysts were synthesized via a low-energy, simple, one-step in situ method, in which GO and FeSO4 center dot 7H(2)O were simultaneously reduced. Consequently, monolithic porous nanocatalyst 3D structures were obtained, with a specific surface area of 241 m(2) g(-1) and pore volume 0.39 cm(3) g(-1). The nanocatalysts were applied for the degradation of Acid Red 1 azo-dye in aqueous solution in the presence of hydrogen peroxide, without the need for external energy. The effect of the adsorbent dose, and concentration of dye and peroxide on the dye removal was studied. The degradation of the dye was monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. It was found that an increase in the amount of peroxide allowed complete degradation of the dye together with high molar mass side-products with a conjugated aromatic structure. The good nanocatalyst performance was explained based on the charge-transfer complex established between rGO and the magnetic nanoparticles, allowing the regeneration of ferrous ions during the Fenton process.The authors gratefully acknowledge the financial support by NATO (SfP project G4255), Spanish Government (CTQ2016-80886-R, RTI2018-096294-B-C32 and CTQ2015-73901-JIN), and Basque Government (GV IT999-16 and IT1069-16)