A.E. Palomares

Denitrification of natural water on supported Pd/Cu catalysts

Abstract The influence of the support on the catalytic hydrogenation of nitrates in liquid phase was investigated. Pd/Cu supported on hydrotalcite and Pd/Cu supported on alumina catalysts were tested for this reaction and its activity and selectivity were compared. It has been observed a higher activity and a lower production of ammonium when the metals are supported on hydrotalcite than when they are supported on alumina. When rehydrated after calcination hydrotalcite recovers its layered structure. Nitrates can be located in the interlayer space diminishing the problems associated to mass transfer limitations and increasing the activity of the material. In addition, copper can be incorporated in the hydrotalcite structure by an isomorphical replacement of magnesium, obtaining thus a high dispersion of the copper centres, that is reflected in a higher activity if compared with copper impregnated samples. A XPS study was made in order to characterise the metals supported on the hydrotalcite.

Optimization of SOx additives of FCC catalysts based on MgO-Al2O3 mixed oxides produced from hydrotalcites

Abstract A series of magnesium-rich Mg-Al spinels were prepared from hydrotalcites and characterized. When CeO2 was incorporated they showed a very good SOx absorption as FCC SOx additives, but their regeneration capacity was limited. Different transition metal oxides were tried as co-catalysts, and among them CuO, showed excellent properties to catalyze SO2 oxidation as well as catalyst regeneration. The SOx catalyst was stable when steamed at 750°C together with FCC catalysts.

Hydrotalcite-derived mixed oxides containing copper: catalysts for the removal of nitric oxide

Hydrotalcite structures containing copper, magnesium and aluminium in the metal hydroxide layers have been investigated for their potential as precursors to the formation of catalysts for the decomposition and reduction of nitrogen oxides. These CuIIMgIIAlIII hydrotalcites are catalytically active towards both the decomposition of nitric oxide and its reduction in the presence of an appropriate coreductant, such as propane. The copper centred active species, identified using EXAFS spectroscopy and combined EXAFS/XRD under operating conditions, have been found to be CuI for the decomposition and Cu0 for the reduction.

On the researching of a new zeolite structure for the selective catalytic reduction of NO: The possibilities of Cu-exchanged IM5

A new zeolite (IM5) whose structure has not been resolved yet is tested for the selective catalytic reduction (SCR) of NO with C3H8 and characterized by in situ X-ray photoelectron spectroscopy. The catalytic behavior of copper exchanged IM5 zeolite is compared with that of copper exchanged ZSM5 zeolites. The influence of the partial pressure of oxygen, reaction temperature and exchange level of the metal in the catalyst is similar to that observed with copper exchanged ZSM5 zeolite, but Cu–IM5 is a more active and hydrothermically more stable catalyst than Cu–ZSM5.

Characterisation of the active copper species for the NOx removal on Cu/Mg/Al mixed oxides derived from hydrotalcites: an in situ XPS/XAES study

In situ X-ray photoelectron spectroscopy was used to characterise Cu/Mg/Al mixed oxides derived from hydrotalcites (catalyst used for the NOx removal reaction). The active sites are the copper centres: (i) Cu(0) for NO decomposition and (ii) Cu(0) and/or Cu(I) for NO reduction with a hydrocarbon. The ability of these materials to redisperse the copper active sites without destroying the structure of the material makes them different from other catalysts such as zeolites, and is essential for suitable catalytic behaviour at high temperatures.

A new active zeolite structure for the selective catalytic reduction (SCR) of nitrogen oxides: ITQ7 zeolite: The influence of NO2 on this reaction

Abstract The activity of a new zeolite material, ITQ7, has been studied for the selective catalytic reduction (SCR) of NO. The pore topology of this material is similar to the structure of a beta zeolite, with a tridirectional system with 12-member rings. ITQ7 exchanged with copper or cobalt shows a catalytic behaviour very similar to a beta zeolite exchanged with copper or cobalt, probably due to its similar structure. The presence of oxygen, water, sulphur dioxide and NO 2 has been studied, obtaining the best results at low oxygen concentration and in the absence of water and SO 2 . Nevertheless if NO 2 is present in the reaction mixture, the maximum activity of the catalyst shifts towards higher oxygen concentration.

EXFAS electron spectroscopy as a new tool of local characterisation of copper in Cu-Beta zeolite

Abstract EXFAS spectroscopy has been applied for the first time to the study of the local characterisation of reduced copper in zeolites. The oscillating features observed beyond the Cu M2,3VV Auger transition have been isolated and analysed following the standard EXAFS procedure.