Showing papers by "Francisco Rodríguez-Reinoso published in 2009"
TL;DR: In this article, activated carbon binderless monoliths with high consistency and large porosity, synthesised from a mesophase pitch, are studied as electrodes for supercapacitors.
166 citations
TL;DR: In this paper, the porosity and surface area of activated carbons with increasing porosity have been prepared by chemical activation of olive stones using ZnCl2 followed by physical activation with CO2.
109 citations
69 citations
TL;DR: In this paper, two series of activated carbons have been prepared from date pits; series C, using carbon dioxide as activating agent, and series S, prepared by activation with steam under the same experimental conditions.
69 citations
TL;DR: In this article, the effect of porosity and chemical reactivity with silicon of the carbon preforms on the properties of SiC pieces produced by reactive infiltration was focused on the effect on the porosity.
59 citations
TL;DR: Selective blocking of the microporosity with n-nonane proves experimentally that MCM-41 is exclusively mesoporous while SBA-15 exhibits both micro- and mesopores.
Abstract: The porous structure of nanostructured silicas MCM-41 and SBA-15 has been characterized using N2 adsorption at 77 K, before and after n-nonane preadsorption, together with immersion calorimetry into liquids of different molecular dimensions. Selective blocking of the microporosity with n-nonane proves experimentally that MCM-41 is exclusively mesoporous while SBA-15 exhibits both micro- and mesopores. Additionally, N2 adsorption experiments on the preadsorbed samples show that the microporosity on SBA-15 is located in intrawall positions, the micropore volume accounting for only ∼7−8 % of the total pore volume. Calorimetric measurements into n-hexane (0.43 nm), 2-methylpentane (0.49 nm), and 2,2-dimethylbutane (0.56 nm) estimate the size of these micropores to be ≤0.56 nm.
55 citations
TL;DR: In this paper, the authors used Pt/C (platinum nanoparticles supported on activated carbon) as a highly reusable catalyst for the high-yielding transfer hydrogenation of aromatic ketones in 2-propanol.
Abstract: The hydrogen-transfer reduction of organic compounds is an advantageous methodology with respect to catalytic hydrogenation and other reduction methods for various reasons: a) the hydrogen source is easy to handle (no gas containment or pressure vessels are necessary) ; b) possible hazards are minimized (molecular hydrogen is a highly flammable, explosive gas); c) the mild reaction conditions used can afford enhanced selectivity; d) catalytic asymmetric transfer hydrogenation can be applied in the presence of chiral ligands. 2-Propanol is the most widely used hydrogen donor since it is cheap, nontoxic, volatile, possesses good solvent properties, and is transformed into acetone, which is environmentally friendly and easy to remove from the reaction system. The transfer hydrogenation of carbonyl compounds has mostly been carried out with 2propanol as the hydrogen donor, under homogeneous conditions, in the presence of noble-metal complexes. Complexes of the secondor third-row transition metals, such as Ru, Rh, and Ir, are the most efficient catalysts devised to date. Among them, ruthenium complexes have been widely studied in homogeneous transfer hydrogenation, especially for the asymmetric reduction of aromatic ketones as well as from a mechanistic point of view. Much less attention has been devoted, however, to the hydrogen-transfer reduction of carbonyl compounds under heterogeneous conditions. Heterogeneous catalysts offer several advantages over the homogeneous counterparts, such as easy recovery, easy recycling and enhanced stability. With this in mind, we studied the application of reusable unsupported nickel nanoparticles to the hydrogen-transfer reduction of carbonyl compounds and to the hydrogen-transfer reductive amination of aldehydes with 2-propanol. Recently, a very efficient and chemoACHTUNGTRENNUNGselective transfer hydrogenation of carbonyl compounds, catalyzed by Au/TiO2 in 2-propanol, was reported. [10] Also recently, we described the successful application of a supported and reusable platinum catalyst (Pt/TiO2) to the transfer hydrogenation of acetophenone in 2-propanol. This catalyst was easily reused, retaining good catalytic activity over four consecutive cycles. In the search of a more effective platinum catalyst for hydrogen-transfer reactions, we report herein the use of Pt/C (platinum nanoparticles supported on activated carbon) as a highly reusable catalyst for the high-yielding transfer hydrogenation of aromatic ketones in 2-propanol. The catalyst was prepared by impregnation of an activated carbon support with an aqueous solution of H2PtCl6, and subsequent reduction under a H2 flow at 200 or 500 8C. Transmission-electron microscopy (TEM) images of the Pt/C catalyst show dark spots, which correspond to platinum nanoparticles, whereas the lighter areas are due to the amorphous carbon support (Figure 1). A good dispersion of the platinum particles on the porous carbon was detected after reduction at 200 8C, the mean size of the platinum particles being around 5 nm. Sintering to some extent was evident after reduction at 500 8C. In this case, larger particles and wider particle size distribution were observed, some particles having a diameter in excess of 100 nm. Therefore, TEM results suggest a decrease in
35 citations
TL;DR: In this article, a linear correlation between bending strength and bioSiC density for different types of softwood and hardwood has been found, and a good correlation was found when biomorphic SiC is treated as porous solid.
Abstract: Biomorphic SiC was prepared from four types of Mediterranean wood as carbon precursor. Carbon biotemplates were obtained by pyrolysis and carbonization up to 1400 °C and they were infiltrated with liquid silicon in two different directions. A linear correlation between bending strength and bioSiC density for different types of softwood and hardwood has been found. Mechanical properties were modelled according to the MSA (minimum solid area) approach. Fairly good correlation was found when biomorphic SiC is treated as porous solid. Moreover, the fabrication of bioSiC from carbon biotemplates heat-treated up to 2500 °C has been additionally studied. An improvement up to 56% in flexural strength has been reached by densification of bioC at such high temperature.
32 citations
TL;DR: In this paper preferentially oriented Pt nanoparticles supported on expanded graphite were prepared by impregnation of the support with an aqueous solution of H2PtCl6.
Abstract: (111) preferentially oriented Pt nanoparticles supported on expanded graphite were prepared by impregnation of the support with an aqueous solution of H2PtCl6. The catalyst was characterized by a number of techniques and tested in the liquid-phase hydrogenation of cinnamaldehyde. The preferential surface orientation of the metal particles favours a very high selectivity towards the hydrogenation of the carbonyl bond of cinnamaldehyde to yield cinnamyl alcohol. The performance of this catalytic system is comparable to that obtained with similar catalysts prepared by more complex methods. Furthermore, expanded graphite provides a good alternative as support to other graphitic materials such as carbon nanotubes and carbon nanofibres.
29 citations
TL;DR: In this article, a large variety of host-guest systems with both ordered and random pore networks have been studied, from microporous up to macroporous materials, and the information obtained concerns diffusivities in the various pore domains, extra resistances at the interfaces between them and the associated exchange rates.
Abstract: Detailed knowledge of the transport properties of nanoporous materials is a prerequisite for their complete characterization and optimum technological exploitation. One of the best ways to attain this information is provided by the “microscopic” techniques of diffusion measurement, in particular by the pulsed field gradient technique of NMR and by interference microscopy and IR microscopy. Starting with the measuring principles, the various types of evidence as accessible by these techniques are illustrated. A large variety of host-guest systems with both ordered and random pore networks have been studied, from microporous up to macroporous materials. The information obtained concerns diffusivities in the various pore domains, extra resistances at the interfaces between them and the associated exchange rates.
24 citations
TL;DR: In this article, the textural characterization of a series of carbon molecular sieves (CMS) prepared from different polymer precursors was investigated using N2 adsorption at 77 K and CO 2 adaption at 273 K.
Abstract: The textural characterization of a series of carbon molecular sieves (CMS) prepared from different polymer precursors has been investigated using N2 adsorption at 77 K and CO2 adsorption at 273 K, ...
TL;DR: This paper reports a CO adsorption study on a Pt/TiO(2) catalyst reduced at two different temperatures, 473 and 773 K, followed by in situ infrared spectroscopy and advertisersorption microcalorimetry.
Abstract: This paper reports a CO adsorption study on a Pt/TiO2 catalyst reduced at two different temperatures, 473 and 773 K, followed by in situinfrared spectroscopy and adsorption microcalorimetry. The study is complemented with XPS characterization of the reduced catalysts.
TL;DR: In this paper, the authors demonstrate compatibility between the evidence of classical sorption experiments and NMR cryoporometry on pore size distribution and demonstrate that the spatial extension of the regions with structural differences (as evidenced by the differences in diffusion and nuclear magnetic relaxation of the probe molecules) may be at least of the order of 20 μm.
TL;DR: In this article, carbon fibres with extremely high surface areas (ACFs) were prepared by CO2 re-activation using pitch-based ACFs having an original surface area of 1730 m2/g.
Abstract: Activated carbon fibres with extremely high surface areas (ACFs) were prepared by CO2 re-activation using pitch-based ACFs having an original surface area of 1730 m2/g. The highest surface area of the re-activated ACFs was 2930 m2/g as determined from an αS-plot analysis of the nitrogen adsorption isotherm measured at 77 K. The ACF with the highest surface area showed excellent adsorptivity towards supercritical CH4 and H2. The amounts of CH4 and H2 adsorbed were enhanced by 52% and 30%, respectively, as a result of re-activation.
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