Oihane Sanz

Washcoating of metallic monoliths and microchannel reactors

Abstract The most important parameters controlling the washcoating of metallic structures from catalytic slurries are reviewed. The slurry must be stable with adequate rheological properties controlled by the solid content, particle size and additives. The metallic substrate must be pre-treated to obtain an adherent surface scale compatible with the coating and presenting appropriate surface roughness. The quality of the produced coating (homogeneity, specific load and adherence) depends essentially on slurry properties (viscosity and solid content) and on the technique used to remove slurry excess.

Fischer-tropsch catalyst deposition on metallic structured supports

Structured catalysts for Fischer-Tropsch synthesis (FTS) have been obtained by deposition of thin 20 wt.Co/γ-A12O3 catalyst layers washcoats onto the metallic surface of monolithic supports applying a preparation procedure involving: (a) preparation of metallic monoliths, (b) preparation of stable slurry of catalyst, (c) dip-coating of monolithic supports. The quality of catalyst coatings was evaluated in terms of loading, homogeneity and adhesion force. Through this procedure, Fecralloy® monoliths pretreated by thermal oxidation have been loaded with a ≈ 450 mg well-adhered catalyst coating layer and tested in FTS at 250 °C, 10 bar, under synthesis gas composition H2/CO = 2. Both the coated monoliths and catalyst powder tested in FTS under similar operating conditions revealed rather comparable results in terms of activity and selectivity as a consequence of using thin layers and small particle size of powder (below 250 µm). Diffusion distances obtained for the catalytic materials resulted to be appropriate for minimizing the mass transfer effects or diffusion limitations.

Au/CeO2 metallic monolith catalysts: influence of the metallic substrate

Ceria-based gold catalysts were successfully deposited on ferritic stainless steel (Fecralloy) and aluminium monoliths. The prepared monolithic and reference powder catalysts were characterized by means of SBET, X-ray diffraction, glow discharge optical emission spectroscopy and scanning electron microscopy–energy dispersive X-ray analysis techniques and tested in the CO oxidation reaction. Characterization results put in evidence the diffusion of cations from the catalytic layer on the surface of the monoliths to the metallic oxide scale and inversely, from the oxide scale to the catalysts, thus altering the catalytic formulation and affecting the CO oxidation properties of the catalytic device. The extension and nature of the modifications produced depend on the nature of the catalysts and the metallic substrate, as well as the reaction conditions applied. These facts must be considered when gold catalysts are supported on metallic-structured devices.

Advances in Structured and Microstructured Catalytic Reactors for Hydrogen Production

Structured and microstructured catalytic reactors allow one to overcome the limitations of fixed beds to solve the compromise between pressure drop and diffusional limitations. Additionally, microstructured systems offer excellent opportunities in compactness and mobility of fuel processors for hydrogen production. The first part of this chapter will present the main points of this type of reactors including the description of structured catalysts and microstructured reactors and their fabrication discussing the influence of substrate materials and the catalytic coating techniques with special emphasis on washcoating. The second part will review the recent advances in the use of these types of systems for hydrogen production from different biofuels: bio-oil, producer gas, dimethyl ether, biomethanol, biodiesel, biogas, bioglycerol and bioethanol. Finally, due to the endothermic character of most reactions involved in hydrogen production, coupled combustion reactions will be also reviewed in structured and microstructured systems.

Highly porous hydrotalcite-like film growth on anodised aluminium monoliths

Abstract Zinc-aluminum hydrotalcite-like thin films were prepared by direct precipitation on the surface of Al 2 O 3 /Al monoliths. The mesopores of anodic alumina provided channels and nano-sized wall-edges for supplying Al 3+ and highly active reaction sites. In this work, the influence of temperature, time and Zn:NH 3 molar ratio in the obtention of highly homogeneous and adherent hydrotalcite films is studied. We show that the amount loaded, integrity and textural properties of the Zn-Al hydrotalcite-like film are strongly influenced by the preparation conditions. The prepared monoliths were tested for VOC abatement (total oxidation of ethanol and ethyl acetate) showing good activity.

Ethyl acetate combustion catalyzed by oxidized brass micromonoliths

Abstract The thermal treatments of brass micromonoliths were studied in order to generate a highly homogeneous oxide scale strongly attached to the base alloy. In this work it has been shown that the morphology, integrity and homogeneity of the scale are strongly influenced by the temperature and time of treatment. The prepared Cu/ZnO micromonolith were characterized by XRD, GD-OES and SEM, and tested in ethyl acetate total oxidation reaction. The results show that brass oxidation conditions forms different scales being most active when large nano-sheets scale is formed.