V.L. Barrio

Aromatics hydrogenation on silica-alumina supported palladium-nickel catalysts

Abstract Nickel- and palladium–nickel catalysts supported on silica–alumina have been studied in the simultaneous hydrogenation of naphthalene and toluene. These catalysts were characterised by means of X-ray diffraction, CO chemisorption, temperature-programmed reduction, NH 3 temperature-programmed desorption, diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy of adsorbed CO and X-ray photoelectron spectroscopy techniques. All the catalysts studied showed higher initial intrinsic activity in the hydrogenation of toluene than of naphthalene. Regarding the hydrogenation of toluene, the 1Pd–8Ni/SA sample displayed the strongest resistance to deactivation by coke precursors as compared with the Ni-free 1Pd/SA catalyst. For the 1Pd–8Ni catalyst, the characterisation data pointed not only to a high degree of reducibility of nickel but also the greatest exposure of Pd species. Both findings appear to be related to the development of nickel hydrosilicate species at the support interface. Indeed, a better resistance towards deactivation was obtained by Pd incorporation and by increasing Ni-loading.

Evaluation of silica-alumina-supported nickel catalysts in dibenzothiophene hydrodesulphurisation

Abstract The influence of both the nickel–support interaction and the Pd promotion on the activity and thiotolerance during the hydrodesulphurisation (HDS) of dibenzothiophene (DBT) was studied in a variety of amorphous silica-alumina-supported nickel catalysts (Ni/ASA). The catalysts were characterized by means of X-ray diffraction (XRD), N 2 adsorption–desorption measurements, temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of NH 3 , CO chemisorption and X-ray photoelectron spectroscopy (XPS) techniques. In the low-nickel-content catalysts, a difficulty in reducing the Ni 2+ –support phase was observed, whereas in the high nickel-content catalysts a major reducible NiO phase was developed. Catalysts containing low amounts of nickel exhibited higher activity and selectivity toward ring-opening (RO) products than those containing higher nickel loadings. The larger ring-opening activity and the greater resistance to deactivation of the low nickel-loading catalysts appear to be related to the morphology of the nickel phases at the catalyst surface, consisting of very small Ni clusters separated by non-reduced Ni 2+ species. The high activity of the catalysts in the ring-opening reaction can be explained assuming that non-reduced Ni 2+ species might to force DBT adsorption on Ni 0 phase via CC bonds perpendicular to the surface. In addition, the greater resistance of the catalysts to deactivation was related to H 2 S adsorption on Ni 2+ species, thus maintaining Ni 0 locations available for performing the ring-opening reaction.

Catalytic reactive distillation process development for 1,1 diethoxy butane production from renewable sources.

Some acetals can be produced from renewable resources (bioalcohols) and seem to be good candidates for different applications such as oxygenated diesel additives. In the present case the production of 1,1 diethoxy butane from bioethanol and butanal is presented. Butanal can be obtained from biobutanol following a partial oxidation or a dehydrogenation process. In this paper innovative process development about the synthesis of the mentioned acetal including catalytic reactive distillation experimental and simulation results will be presented and discussed. Katapak SP modules containing Amberlyst 47 resin were used as structured catalytic packings. This reactive system allowed reaching higher conversions than the equilibrium ones at the same temperatures. All the experimental data gathered allowed to tune a simulation model for the reactive distillation operation which showed a fairly good behavior in order to perform initial 1,1 diethoxy butane production process design studies.

Glycerol conversion into H2 by steam reforming over Ni and PtNi catalysts supported on MgO modified γ-Al2O3

Abstract The glycerol catalytic steam reforming over Ni and PtNi catalysts to produce H 2 was studied. The activity results indicate that the catalyst with the lower content of MgO, the NiA1M, provides higher H 2 molar ratios than the Ni catalyst. The behaviour of the NiA1M catalysts seems to be related to the Ni o species stabilization by nickel-magnesia interactions, which are favoured by the presence of well dispersed MgAl 2 O 4 spinels. The bimetallic catalyst, PtNiA3M named, reforms the intermediate products improving the activity of the Ni monometallic catalyst toward H 2 production. The characterization results suggest that the Pt in the Ni monometallic catalyst enhances the Ni o particles dispersion and the nickel species reducibility by H 2 spillover.

Methyl-naphthalene hydrogenation on Pt/HY–Al2O3 catalysts. An approach to hydrogenation of polyaromatic hydrocarbon mixtures

Abstract Pt particles supported on a physical mixture of alumina and HY zeolite were used in the hydrogenation of α-methyl-naphthalene (1-MeN) under conditions that approach industrial practice (P=6 MPa; T=498–548 K; WHSV=1 h−1). As compared with the Pt/alumina catalyst, the use of the hybrid support markedly enhances the activity of the platinum catalysts. A maximum in the rate of methyl tetralin formation was found using platinum supported on a mixture of 3 wt.% HY zeolite in alumina; whereas, for the catalysts with higher zeolite contents, the rate decreased. Results of catalyst characterisation by temperature-programmed desorption (TPD) of NH3, IR spectroscopy of adsorbed CO and pyridine, H2-chemisorption and X-ray photoelectron spectroscopy (XPS) revealed that methyl tetralin formation is favoured on bifunctional catalysts displaying moderate acidity. On the contrary, isomerisation and/or hydrocracking reactions of methyl tetralin are favoured in the more acidic catalysts containing higher contents (7% and 12%) of HY zeolite.

Sustainable hydrogen production from bio-oil model compounds (meta-xylene) and mixtures (1-butanol, meta-xylene and furfural)

In the present work m-xylene and an equimolecular mixture of m-xylene, 1-butanol and furfural, all of them bio-oil model compounds, were studied in steam reforming (SR) conditions. Three different nickel catalysts, which showed to be active in 1-butanol SR (Ni/Al2O3, Ni/CeO2-Al2O3 and Ni/La2O3-Al2O3), were tested and compared with thermodynamic equilibrium values. Tests were carried out at temperatures from 800 to 600°C at atmospheric pressure with a steam to carbon ratio (S/C) of 5.0. Despite the different bio-oils fed, the amount of moles going through the catalytic bed was kept constant in order to obtain comparable results. After their use, catalysts were characterized by different techniques and those values were correlated with the activity results. All catalysts were deactivated during the SR of the mixture, mainly by coking. The highest hydrogen yields were obtained with Ni/Al2O3 and Ni/CeO2-Al2O3 catalysts in the SR of m-xylene and SR of the mixture, respectively.

Natural and synthetic iron oxides for hydrogen storage and purification

In this paper, the hydrogen storage capacity of some synthetic and natural iron oxides is presented. The results of the activity tests and characterization techniques of natural and synthetic iron oxides (N2 adsorption–desorption isotherms, temperature-programmed reduction, X-ray diffraction, and plasma atomic emission spectroscopy) suggest that the use of chromium on iron oxide systems improved their hydrogen storage capacity. This is related to the capacity of chromium to modify the iron oxide reduction profile when Cr was incorporated. A direct reduction from Fe3O4 to Fe was observed as the mechanism for H2 storage. In addition, natural oxides as commercial Superfine and Densinox-L oxides are proved to be suitable materials to store and purify H2 due to their high stability during different cycles of reduction and oxidation. The best results among the natural ones were Densinox-L and among the synthetic ones Fe–10Cr.

Acetals as Possible Diesel Additives

Nowadays, oil is the source of the vast majority of fuels used for transport, heating and of the hydrocarbons used in petrochemical industry. However, oil is a fossil fuel and some experts predict that its reserves will exhaust approximately in 20–30 years. Moreover, it seems that the demand of fossil fuels will increase at rates that can be estimated from “World Energy Outlook” elaborated by the International Energy Agency (IEA, 2007). Apart from all these data, there are evidences that the climate of the planet is changing due to the global warning. The temperature of the earth is increasing and the ice of the poles is beginning to melt; all these changes are attributed to the Greenhouse Effect. Besides, it has been estimated that 82 % of the anthropogenic CO2 emissions are due to fossil fuel combustion so it is clear that alternative energy sources are needed (see Figure 1).