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Alumina prepared by the sol-gel method, was impregnated with zirconia (5, 15 and 30 wt.%). Subsequently, the resulting Al2O3–ZrO2 supports were impregnated with 15% Ni to obtain the Ni/Al2O3–ZrO2 catalysts. The obtained catalysts were characterized by BET, SEM, XRD, H2-TPR and TPD- CO2. The catalytic activity was studied by means of dry reforming of methane (DRM) for syngas production. The catalysts displayed different physicochemical properties and trends of their catalytic activity as a function of the ZrO2 content in the mixed oxide supports. For instance, ZrO2 (5 wt %) in the catalyst, led to enhanced concentration of the medium strength basic sites and increased specific surface area, yielding thus the best performance in the DRM, with low carbon deposition after 36 h of reaction, compared with the other catalysts. This indicates that during the DRM reaction, this catalyst can provide more surface oxygen to prevent carbon deposits that could deactivate the catalyst.

Advanced oxidation processes such as photocatalysis have assumed enormous importance in the scientific field as viable sustainable alternatives to be applied to the elimination of persistent organic pollutants present in water reservoirs for human consumption. Persistent organic compounds like pesticides that belong to the chlorophenol family are a global public health priority since they are associated with serious diseases like cancer and can even cause death at low concentrations of prolonged exposure. This work proposes the use of activated Ni/Al layered double hydroxides as photocatalysts for the degradation of 2,4-dichlorophenol. The study variables associated with the properties of the catalysts were the Ni/Al metal ratio as well as the synthesis conditions. To determine the structural properties of catalytic precursors and catalysts, the techniques of XRD, FTIR, UV-DR, DGTA, TPD, SEM-EDS and TEM were used. The photodegradation tests were carried out in a Bach type reactor with a high energy uv lamp. The results of the photocatalytic degradation of 2,4-dichlorophenol in aqueous solution showed good photocatalytic activity with a degradation efficiency of up to 94% attributed to the presence of Ni in the crystalline and amorphous structures of NiO–NiAl2O4 oxides by means of a combined oxidation-reduction mechanism due to the effect of holes and superoxide and hydroxyl radicals not associated with the memory effect of reconstruction of layered double hydroxides.

The materials Al2O3:Ce3+/Ce4+ (cerium content 0.5, 1.0, 3.0, and 5.0 wt.%) were synthesized by the sol-gel method. The materials were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), N2 physisorption, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX); also, some electrochemical tests were performed for the materials characterization. The materials were evaluated in the phenol photodegradation using UV light. The photocatalyst containing 1.0 wt.% cerium (AC1.0) presented the highest photoactivity than the others synthesized samples. This catalyst was selected to photodegrade others phenolic derivatives such as 4-chlorophenol, p-cresol, and 4-nitrophenol. All the synthesized photocatalysts by the sol-gel method showed a better activity than (TiO2, P25 Degussa). The photodegradation reactions were followed by UV–Vis spectroscopy and total organic carbon TOC. A reaction mechanism is proposed involving the sensitization of the organic molecule on Al2O3:Ce3+/Ce4+ with UV light for its mineralization.

Currently, interest has grown in finding effective solutions for the treatment of water pollution by toxic compounds. Some of the latter that have acquired importance are phenols and chlorophenols, due to their employment in the manufacture of pesticides, insecticides, cords of wood, paper industry, among others. The problem is rooted in that these compounds are very persistent in the environment because they are partially biodegradable and cannot be photodegraded directly by sunlight. Chlorophenols are extremely toxic, especially 2,4,6-trichlorophenol, which is potentially carcinogenic. In this work, Mg/Al-mixed oxide catalysts were obtained from the thermal treatment of hydrotalcite-type materials, synthesized by sol-gel method with different Mg/Al ratios. Hydrotalcites and Mg/Al-mixed oxides were physicochemically characterized by X-ray diffraction, thermal analysis (DTA and TGA), and N2 physisorption. The results were obtained on having proven the photocatalytic degradation of 2,4,6-trichlorophenol as a pollutant model by water. The catalysts obtained present the hydrotalcite phase with thermal evolution until achieving Mg/Al-mixed oxides at 500°C. The catalysts are of mesoporous materials and exhibiting large surface areas. The catalysts demonstrated good photocatalytic activity with good efficiency, reaching degradation percentages with Mg/Al = 1, 2, 4, 5, and 7 ratios of 94.2, 92.5, 86.2, 84.2, and 63.9%, respectively, until achieving mineralization.

In recent years, the search for solutions for the treatment of water pollution by toxic compounds such as phenols and chlorophenols has been increasing. Phenols and their derivatives are widely used in the manufacture of pesticides, insecticides, paper, and wood preservers, among other things. Chlorophenols are partially biodegradable but not directly photodegradable by sunlight and are extremely toxic&mdash, especially 2,4,6-trichlorophenol, which is considered to be potentially carcinogenic. As a viable proposal to be applied in the treatment of water contaminated with 2,4,6-trichlorophenol, this paper presents an application study of the thermally activated Mg/Fe layered double hydroxides as photocatalysts for the mineralization of this contaminant. Activated Mg/Fe layered double hydroxides were characterized by X-ray diffraction, thermal analysis, N2 physisorption, and scanning electron microscopy with X-ray dispersive energy. The results of the photocatalytic degradation of 2,4,6-trichlorophenol in aqueous solution showed good photocatalytic activity, with an efficiency of degradation of up to 93% and mineralization of 82%, degradation values which are higher than that of TiO2-P25, which only reached 18% degradation. The degradation capacity is attributed to the structure of the MgO&ndash, MgFe2O4 oxides derived from double laminate hydroxide Mg/Fe. A path of degradation based on a mechanism of superoxide and hollow radicals is proposed.