J.F. Cambra

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.

DEEP HYDRODESULFURIZATION OF DBT AND DIESEL FUEL ON SUPPORTED PT AND IR CATALYSTS

Abstract Deep hydrodesulfurization (HDS) of dibenzothiophene (DBT) and diesel fuel (0.08 wt.−% S) has been carried out on Pt and Ir supported on amorphous silica-alumina (ASA) and on a stabilized HY zeolite under standard industrial conditions. The effect of temperature, two different supports and feedstocks on HDS and hydrogenation (HYD) product selectivities are investigated. Normalized activity data indicate that in the HDS of DBT and of diesel fuel, the platinum catalysts are much more active than the iridium counterparts. In HDS of diesel fuel (at 623 K), both Pt HY and Pt ASA are a little more active than a commercial Co-Mo Al 2 O 3 catalyst. The normalized activity in the HDS of DBT (593 K) increases in the following order: Pt HY > Pt ASA ⪢ Ir HY > Ir ASA , and in the HDS of diesel fuel (623 K), increases according to: Pt HY ⪢ Pt ASA ⪢ Ir HY > Ir ASA . All spent catalysts were characterized by X-ray photoelectron spectroscopy (XPS). In view of their superior performance, both platinum catalysts were characterized by FTIR spectroscopy of CO probe.

Recycling of the Products Obtained in the Pyrolysis of Fibre-Glass Polyester SMC

An SMC (Sheeting Moulding Compound) of fibre-glass and orthophthalic polyester has been pyrolysed in a 3·5 dm3 autoclave for 30 min in a nitrogen atmosphere at 300, 400, 500, 600 and 700°C. Gas yields of 8–13 weight%, liquid yields of 9–16 weight% and solid residues of 72–82 weight% were obtained. The suitability of the pyrolysis process for recycling SMC is discussed. The characteristics, compositions and possible ways of reusing the liquid and gaseous fractions are presented. The solid pyrolysis residue has been recycled in another thermoset composite (Bulk Moulding Compound, BMC) and its mechanical properties have been compared with those of virgin BMC. The main conclusion is that pyrolysis can be an appropriate method for recycling thermoset polymeric composites such as SMC. The pyrolysis gas fraction can be sufficient to provide the energy requirements of the process plant. The pyrolysis liquids have high gross calorific values (36·8 MJ kg−1) and are non-polluting liquid fuels; about 40 weight% of such liquids could be used as petrols, and the remaining 60% could be mixed with fuel oils. The solid pyrolysis residue can be recycled in BMC with no detrimental effect on the BMC mechanical properties. Concerning temperature, it has been concluded that 400–500°C are the most suitable temperatures for recycling SMC by pyrolysis.

Dibenzothiophene hydrodesulfurization on HY-zeolite-supported transition metal sulfide catalysts

Noble and semi-noble metals (Pt, Pd, Ru, Ir, Ni) were incorporated on a HY zeolite support, and tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). Under steady-state conditions, the intrinsic activity of the catalysts was found to display the following order of reactivity: Ir>Pt>Pd≫Ni. While deactivation on Ir, Pt and Pd catalysts was very low, the significant differences in the activity of Ni and Ru zeolites could be attributed to catalyst deactivation. Temperature-programmed reduction studies revealed that noble metals were reduced at moderately low temperatures, whereas Ni catalyst was much more difficult to reduce as a consequence of the much stronger interaction with the zeolite substrate. For the most active Pt/HY and Ir/HY zeolites, photoelectron spectra of the used catalysts revealed that Pt is in metallic state (100% Pt°) and Ir is present as a mixture of metal (62% Ir°) and sulfide.

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.

Recent Improvement on H 2 Production by Liquid Phase Reforming of Glycerol: Catalytic Properties and Performance, and Deactivation Studies

Recently new Pt/Ni-based γ-Al2O3 catalysts have been developed in our laboratory with a good performance for H2 production by aqueous phase reforming of glycerol. This paper reviews these developments based on the study of the catalytic properties and performance, as well as their deactivation mechanisms. These works have led to set new perspectives related to the enhancement of catalysts hydrothermal stability and to the reduction of the deactivation processes.

Mo-USY zeolites for hydrodesulphurization: II. Surface properties of sulphided catalysts and activity for thiophene hydrodesulphurization

Abstract Molybdena-containing ultrastable (USHY) zeolite catalysts were prepared using different molybdenum precursors and activation procedures and the sulphided catalysts were characterised by nitric oxide and pyridine adsorption. X-ray photoelectron spectroscopy and tested in the hydrodesulphurization (HDS) of thiophene at 3 MPa pressure and a reaction temperature of 623 K. MoUSY catalyst exhibited decreasing conversions as a function of time-on-stream due to coking while thiophene conversion over MoNaY remained constant. No relationship between dispersion and HDS or hydrogenation selectivity was found. Differences between hydrogenation selectivities over MoUSY and MoNaY catalysts were attributed to the low concentration of support bound molybdenum species in the oxide form of the latter catalyst.

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.

Surface properties and hydrocracking activity of NiMo zeolite catalysts

The hydrocracking properties of Ni, Mo and NiMo sulphides supported on an ultrastable HY zeolite were examined by studying the hydroconversion of n-decane at moderate pressure (3 MPa). All catalysts were found to deactivate during the first hours on-stream, then reaching almost constant conversion values. Their cracking conversions are significantly higher than that of the HY support. A strong imbalance between the hydrogenation and the acidic function of catalysts was observed. The product selectivities did not depend on the conversion and the secondary cracking occurred. In the binary NiMo samples no synergetic effect between the individual Ni and Mo phases was observed. A reasonable correlation between the n-decane steady-state conversions at 598 K, the sulphidation degree of the metals and Bronsted acidities of catalysts were found.

Bioenergy II: The Development of a Reactive Distillation Process for the Production of 1,1 Diethoxy Butane from Bioalcohol: Kinetic Study and Simulation Model

1,1 Diethoxy butane was produced carrying out the reaction between ethanol and butanal in a batch stirred reactor using Amberlyst cation-exchange resins as catalyst. The kinetics of this reaction was studied working at different temperatures, feed compositions and catalyst type and loadings. Due to thermodynamic limitations, maximum conversions are quite low for kinetically acceptable temperatures. That is why the kinetic information gathered has been used to develop a model for reactive distillation, which has predicted promising results.