Two microporous hectorites were prepared by conventional and microwave heating, and a delaminated mesoporous hectorite by an ultrasound-assisted synthesis, and these three hectorites were impregnated with copper. The characterization techniques used were XRD, N 2 adsorption, TEM and H 2 reduction after selective surface copper oxidation by N 2 O (to determine copper dispersion). The catalytic activity for soot combustion of both the copper-free and the copper-containing hectorites was tested under a gas mixture of 500 ppm NOx/5%O 2 /N 2 (and 5% O 2 /N 2 in particular cases), evaluating their stability through three consecutive soot combustion experiments. The delaminated hectorite achieved the highest surface area (353 m 2 /g) and also the highest dispersion of copper, and this copper-containing catalyst was the most active for soot combustion among those prepared and tested in this study. It has been also concluded that the Cu/hectorite-catalyzed soot combustion mechanism is based on the activation of the O 2 molecule and not on the NO 2-assisted soot combustion.
-This work reports the synthesis of titanium oxide (TiO 2 ) and sulfated titanium oxide (TiO 2 -SO 4 2-) obtained by thermal hydrolysis of titanium tetrachloride. Titanium hydroxide synthesized by this method was impregnated with a 1 N H 2 SO 4 solution, to give amounts of sulfate ions (SO 4 2-) of 3 and 7 wt%. The synthesized samples were dried at 120 °C during 24 h and then calcined for 3 h at 400 °C. Thermal analyses, X-ray diffraction, nitrogen physisorption, infrared spectroscopy, potentiometric titration with n-butylamine, U.V.-visible diffuse reflectance spectroscopy and scanning electron microscopy were used to characterize the materials. The results of physicochemical characterization revealed that a mixture of crystalline structures, anatase, brookite and rutile developed in the titanium oxide, stabilizing the anatase structure in the sulfated titanium oxides, and coexisting with a small amount of brookite structure. The synthesized mesoporous materials developed specific surface areas between 62 and 70 m 2 g -1, without detecting an important influence of sulfation on this parameter. The presence of sulfate ions improved the acidity of titanium oxide and modified the characteristics of light absorption in the 425-600 nm region, which suggests the possibility of using these materials in reactions assisted by visible light.
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