Pilar Ramírez de la Piscina

Use of biofuels to produce hydrogen (reformation processes)

This tutorial review deals with the catalytic reformation of ethanol and glycerol to produce hydrogen that can be used as an energy carrier in a fuel cell. Both the worldwide production of ethanol in large amounts to be used as a biofuel and that of glycerol as a by-product in biodiesel manufacture are presented. The catalytic reformation processes of both ethanol and glycerol are contemplated, including thermodynamic and kinetic aspects. Catalysts are analyzed as a function of operation conditions, selectivity and stability.

In situ magnetic characterisation of supported cobalt catalysts under steam-reforming of ethanol

Various supported cobalt catalysts (Co/MgO, Co/Al2O3, Co/SiO2, Co/TiO2, Co/V2O5, Co/ZnO, Co/La2O3, Co/CeO2 and Co/Sm2O3), were characterised by magnetic measurements under ethanol steam-reforming conditions, in situ diffuse reflectance infrared spectroscopy and UV-Vis-NIR diffuse reflectance spectroscopy. Their magnetic behaviour was analysed as a function of reaction temperature and hydrogen treatment and was related to the cobalt species in the catalysts and to their catalytic behaviour in the steam-reforming of ethanol. The catalysts were prepared from Co2(CO)8 and used without previous calcination or reduction. All samples showed a paramagnetic or diamagnetic behaviour before reaction. The catalysts that performed well in the steam-reforming of ethanol presented under reaction conditions, metallic (ferromagnetic) cobalt particles and oxidised cobalt species. An easy exchange between small metallic cobalt particles (produced under H2 or under ethanol steam-reforming conditions) and oxidised cobalt species (produced under ethanol steam-reforming conditions) was found in these catalysts.

Direct production of hydrogen from ethanolic aqueous solutions over oxide catalysts

Steam-reforming of ethanol over ZnO gives highly effective production of CO-free H2: 5.1 mol of H2 per mol of reacted ethanol is formed at 723 K under 100% ethanol conversion.

Hydrogen production from the steam reforming of bio-butanol over novel supported Co-based bimetallic catalysts

This paper reports the hydrogen production through the steam reforming of a bioresource-derived butanol mixture (butanol:acetone:ethanol=6:3:1 mass ratio) over supported cobalt-based catalysts. The support plays an important role for the catalytic behavior and Co/ZnO exhibits the best catalytic performance compared to Co/TiO(2) and Co/CeO(2). Moreover, a higher hydrogen yield is obtained over bimetallic Co-Ir/ZnO, which shows an increase in H(2) selectivity and a decrease in CH(4) selectivity under steam reforming conditions, compared to Co/ZnO. Raman results of the used catalysts indicate that the addition of Ir could prevent the coke formation to prolong the catalyst stability.

Vapour phase hydrogenation of crotonaldehyde over magnesia-supported platinum–tin catalysts

Magnesia-supported bimetallic Pt–Sn catalysts with various metal contents and Pt/Sn atomic ratios were prepared using the bimetallic complex cis-[PtCl(SnCl3)(PPh3)2] or the monometallic complex cis-[PtCl2(PPh3)2] and SnCl2 as metal precursors. Catalysts were characterised by X-ray diffraction, transmission electron microscopy techniques and X-ray photoelectron spectroscopy. The bulk and surface composition of the catalysts was related to the catalytic behaviour in the vapour phase hydrogenation of crotonaldehyde (but-2-enal). It is shown that the various preparation methods produce catalysts with distinct properties and catalytic behaviour. For catalysts prepared with the bimetallic complex, the highest selectivity for the unsaturated alcohol (but-2-en-1-ol) was achieved for the catalyst containing larger bimetallic particles, which are associated with a higher surface concentration of oxidised tin species. The catalyst prepared with separate metal precursors contains a higher amount of residual chlorides, which significantly affect the catalytic activity but only slightly alter the selectivity for the hydrogenation of the carbonyl bond.

Crotonaldehyde hydrogenation over alumina- and silica-supported Pt–Sn catalysts of different composition. In situ DRIFT study

Alumina- and silica-supported bimetallic Pt–Sn catalysts with different Pt/Sn atomic ratios have been prepared by using the bimetallic complex cis-[PtCl(SnCl3)(PPh3)2], the monometallic complex cis-[PtCl2(PPh3)2] and SnCl2 as metal precursors. Catalysts have been characterised by X-ray diffraction and transmission electron microscopy techniques, including energy-dispersive X-ray microanalysis, electron diffraction experiments and lattice-fringe microanalysis. The phase composition of the different catalysts has been related to the catalytic behaviour in the vapour phase hydrogenation of crotonaldehyde (but-2-enal). Results show that catalysts containing platinum–tin alloy phases with large particles are more selective towards the hydrogenation of the carbonyl bond to yield crotyl alcohol. The presence of oxidised tin species on the surface of the large alloy particles promotes the hydrogenation of the carbonyl bond. In situ diffuse reflectance infrared spectroscopy studies of crotonaldehyde adsorption under He or H2 reveal differences between bimetallic catalysts and monometallic, and these differences have been related to the different catalytic behaviour of the catalysts.

Efficient hydrogen production from ethanol and glycerol by vapour-phase reforming processes with new cobalt-based catalysts

The aim of this study was to investigate biohydrogen production from biofuel-reforming processes using new multi-component bulk-type cobalt-based catalysts. The addition of different components to improve the catalytic performance was studied. Monometallic cobalt catalyst and catalysts containing Ru (ca. 1%) and/or Na (ca. 0.5%) were characterized and tested in the 623-673 K temperature range in ethanol steam reforming (ESR) with a steam/carbon ratio (S/C) of 3. The catalysts showed a high performance for hydrogen production and, except for H(2) and CO(2), only small amounts of by-products were obtained, depending on the temperature and the catalyst used. The catalyst containing both Ru and Na (Co-Ru(Na)) showed the best catalytic behavior in ESR. It operated stably for at least 12 days under cycles of oxidative steam reforming of glycerol/ethanol mixtures (S/C=2) and activation under O(2).

Support effect on the formation of the well-defined PtSn alloy from a PtSn bimetallic complex. Catalytic properties in the activation of CO2

Abstract Platinum-tin catalysts supported on either silica or γ-alumina have been prepared from [PtCl(SnCl 3 (PPh 3 ) 2 ] bimetallic complex. The evolution of surface species under hydrogen from 473 to 873 K has been studied by in situ FTIR spectroscopy, mass spectrometry analysis of products evolved, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), electron nanodiffraction, and X-ray photoelectron spectroscopy (XPS). The genesis of supported PtSn alloy as the only metallic phase on surface is shown for both supports. Catalytic performance and catalyst stability on the reaction between CO 2 , C 2 H 4 and H 2 O to give lactic acid is reported. The characteristics of silica-supported catalysts contrast with those of alumina-supported ones.

Efficient hydrogen production from bio-butanol oxidative steam reforming over bimetallic Co–Ir/ZnO catalysts

This paper reports, for the first time, hydrogen production from oxidative steam reforming of a bio-butanol raw mixture (n-butanol–acetone–ethanol = 6:3:1, mass ratio). The process was carried out over new bimetallic Co–Ir/ZnO catalysts using air as an oxidant. The behaviour of bimetallic catalysts was compared with that of monometallic ones. Bimetallic catalyst Co–0.3Ir/ZnO (7 wt% Co, 0.3 wt% Ir) showed higher catalytic performance than monometallic samples, giving higher hydrogen concentration in the outlet gas and lower by-product formation. Moreover, the addition of 0.3 wt% Ir to Co–ZnO prevented the formation of carbon deposits and decreased their degree of graphitization. Addition of more iridium (1 wt% Ir) did not improve the catalytic behaviour. Several techniques, such as N2 adsorption, XRD, TPR, HRTEM, TG-DTG, XPS and Raman spectroscopy, were used for characterizing the fresh and used catalysts.

Hydrogen production from oxidative steam reforming of bio-butanol over CoIr-based catalysts: Effect of the support

This paper studies the influence of the support on the behavior of bimetallic CoIr-based catalysts (6.5 wt.% Co, 0.4 wt.% Ir) for hydrogen production from the oxidative steam reforming of bio-butanol raw mixture (butanol/acetone/ethanol = 6/3/1 mass ratio). Catalytic tests were carried out at 500 °C for 60 h with raw mixture/water/air/Ar = 1/10/7.5/12 molar ratio and GHSV = 7500 h(-1). Over CoIr/18CeZrO(2) and CoIr/ZnO the main process which took place was the oxidative steam reforming of the raw mixture. CoIr/18CeZrO(2) showed the better catalytic performance. Characterization of the used catalysts indicated that both active metal sintering and coke formation was prevented on the CoIr/18CeZrO(2) catalyst.