A series of MgAl hydrotalcites (HTs) were synthesized by a sol-gel procedure with ethanol, 2-propanol, and 1-butanol as solvents. Particular attention was paid to controlling hydrolysis reactions by means of using a substoichiometric H 2 O/Al molar ratio equal to 1. The sol-gel HTs were characterized by means of thermogravimetry, mass spectrometry (MS) of the decomposition products, X-ray diffraction, diffuse reflectance infrared spectroscopy (DRIFT), electron microscopy, and N 2 adsorption-desorption. Decomposition products of sol-gel HTs were identified by MS and included, among others, C x H y fragments from alkoxy groups, which were partially withdrawn between 250 and 450 °C. Alkoxy groups, from the alcohols employed as solvents, are probably intercalated within the HT layers, as indicated by XRD and DRIFT analyses. C x H y groups in these alkoxy groups were detected by DRIFT at ∼2945 and ∼2831 cm -1 in dried HTs, even after annealing at 500 °C. The HTs obtained by the sol-gel procedure described in this work showed nanocapsular morphology. Transmission electron microscopy and Rietveld refinement techniques evidenced the curvature of the HT layers. In comparison with coprecipitated MgAl-CO 3 HT particles (>10 µm), sol-gel HTs showed very small particle aggregates (ca. 300∼350 nm). Calcined HTs presented specific surface area and pore volume values between 254∼332 m 2 /g and 0.81∼1.39 cm 3 /g, respectively, depending on the alcohol used in the sol-gel procedure.

Sulfur oxides are one of the most hazardous atmospheric pollutants since they contribute directly to acid rain formation. Consequently, stringent environmental regulations limit atmospheric SOx emissions, motivating research on efficient ways to reduce them. To supply an alternative to reduce these emissions in fluid catalytic cracking units, this study discloses efficient SOx reducing materials based on calcined MgAlFe hydrotalcite-like compounds (HT's). Thus, HT materials were synthesized by several methods including cerium addition. The adsorption of SO2 was carried out by contacting the calcined solid with a mixture of SO2 (1%) in air at 650 degrees C. It was demonstrated that the isomorphic incorporation of iron increased its reduction capability which was reflected in higher reduction rates and metal sulfate reduction grade at 550 degrees C. Moreover, when cerium was present in the iron-containing materials the saturation rate was improved, because cerium oxide promotes the oxidation of SO2 to SO3. The way cerium is incorporated influences the SO2 adsorption capacity.

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International audienceSilica supported sulfated zirconia catalysts were synthesized via a new method by grafting sulfated zirconia on the surface of a silica aerogel previously prepared. The main parameters studied in this work were the S/Zr, Zr/Si molar ratios and the support nature. The synthesized solids were characterized using XRD, N2 physisorption at 77 K, TG-DTA/SM, sulfur chemical analysis and adsorption–desorption of pyridine followed by infrared spectroscopy. These solids were tested in the n-hexane isomerization reaction. Two types of mesopores were observed on the silica aerogel. This mesoporosity was affected depending on the preparation parameters. The increase of the Zr/Si molar ratio induces the decrease of the size of zirconia particles deposed on the support. In this case, appreciable amounts of sulfur are retained with the presence of a relatively strong Brönsted and Lewis acid sites on the catalyst surface. A high density of Brönsted sites seems to be interesting in the n-hexane isomerization reaction