Palladium and platinum catalysts supported on carbon nanofiber coated monoliths for low-temperature combustion of BTX
ABSTRACT In this work carbon nanofiber (CNF)-coated monoliths with a very thin, homogeneous, consistent and good adhered CNF layer were obtained by means of catalytic decomposition of ethylene on Ni particles.The catalytic behaviour of Pt and Pd supported on the CNF-coated monoliths was studied in the low-temperature catalytic combustion of benzene, toluene and m-xylene (BTX) and compared with the performance of Pt and Pd supported on γ-Al2O3 coated monoliths.The catalysts supported on CNF-coated monoliths were the most active, independent of the metal catalyst or the type of the tested aromatic compound. TPD experiments showed that the γ-Al2O3 phase retained important amounts of the water molecules produced during the reaction. When water vapour was supplied to the reactant flow, the activity of Pd catalysts decreased much stronger than the Pt ones, and the activity of the Pt catalysts supported on the γ-Al2O3 was more affected than that of the catalysts supported on CNF.BTX combustion reactions seem to be catalyzed by Pt and Pd through different kinetic mechanisms, explaining why Pt catalysts always were more active than the Pd ones deposited on the same type of support. Pd catalyzed combustion of benzene is strongly inhibited by oxygen and by water.Catalysts supported on CNF-coated monoliths showed a selectivity to burn benzene better than toluene or m-xylene, attributed to a better aromatic-CNF surface interaction.
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ABSTRACT: Direct vapor-phase upgrading of biomass pyrolysis products requires a catalytic reactor able to treat high reactant flow rates without generating a large pressure drop, because conventional pyrolysis reactors operate near atmospheric pressure. Monolithic catalysts exhibit important advantages that make them good candidates for this purpose. In this paper, low-surface-area Inconel monoliths were coated with in-situ-grown carbon nanofibers (CNFs), which were subsequently impregnated with catalytic species (Pt, Sn, and bimetallic Pt–Sn). These monoliths were tested for the deoxygenation of guaiacol and anisole (products of lignin pyrolysis), two of the most deactivating compounds present in pyrolysis oil. The main products obtained from these feeds on the monolithic catalysts were phenol and benzene. Coating with CNFs provides increased surface area and anchoring sites for the active species (Pt and Sn), thus increasing the yield of desired products. The bimetallic Pt–Sn catalysts showed higher activity and stability than monometallic Pt and Sn catalysts. These tests indicate that monoliths of Pt–Sn/CNF/Inconel are potentially effective catalysts for the vapor-phase upgrading of lignin fractions present in bio-oil.Energy & Fuels. 08/2011; 25(9).
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ABSTRACT: This article reviews different methodologies for the fabrication of monolithic ceramic components possessing multiscale porosity, i.e., with pores ranging from a few nanometers to several hundred microns. Two main strategies have been discussed: (a) the assembling of micro/mesoporous materials into components possessing also macropores; (b) the addition of micro/mesoporosity to macroporous, cellular monoliths. Both routes include one-pot and multi-step processing routes, and yield components with different properties in terms, for instance, of specific surface area values, mechanical strength, and permeability to fluids. The wide range of processing approaches available enable the fabrication of components with very varied morphology, suitable for a variety of industrial applications.Journal of Materials Science 45(20):5425-5455. · 2.31 Impact Factor
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ABSTRACT: Hes6 is a member of the hairy-enhancer-of-split family of transcription factors that regulate proliferating cell fate in development and is known to be expressed in developing muscle. Here we investigate its function in myogenesis in vitro. We show that Hes6 is a direct transcriptional target of the myogenic transcription factors MyoD and Myf5, indicating that it is integral to the myogenic transcriptional program. The localization of Hes6 protein changes during differentiation, becoming predominantly nuclear. Knockdown of Hes6 mRNA levels by siRNA has no effect on cell cycle exit or induction of myosin heavy chain expression in differentiating C2C12 myoblasts, but F-actin filament formation is disrupted and both cell motility and myoblast fusion are reduced. The knockdown phenotype is rescued by expression of Hes6 cDNA resistant to siRNA. These results define a novel role for Hes6 in actin cytoskeletal dynamics in post mitotic myoblasts.Experimental Cell Research 07/2011; 317(11):1590-602. · 3.56 Impact Factor