Gloria Del Angel

Effect of Chlorine Released during Hydrodechlorination of Chlorobenzene over Pd, Pt and Rh Supported Catalysts

Chlorobenzene hydrodechlorination in liquid phase has been studied. Chlorine released during the reaction inhibits conversion in large metallic particles. It was found comparing the behavior of Pd/SiO2, Pd/Al2O3 and Pd/C catalysts that the support plays the role of a chlorine trap. The activity for Pt, Rh and Pd at similar dispersions corresponds to the chlorine adsorption affinity of the metals.

Catalytic hydrodechlorination of chlorobenzene in liquide phase

Catalytic hydrodechlorination of chlorobenzene (CB) was carried out in the liquid phase in a mixture of methanol/water (MeOH/H2O) at 30°C and 2kg/cm2 pressure. The reaction orders with respect to CB and H2 pressure were one and zero, respectively. Addition of NH4OH in the reaction produces a decrease in the activity (TOF). Solvent effect shows the following order of activity: H2O>MeOH/H2O>EtOH/H2O>MeOH.

Gold Particle Size Determination on Au/TiO2-CeO2 Catalysts by Means of Carbon Monoxide, Hydrogen Chemisorption and Transmission Electron Microscopy

Au/TiO2 and Au/TiO2-CeO2 catalysts were prepared by the sol-gel method and carbon monoxide, hydrogen chemisorption and TEM spectroscopy have been exploited to determine the size of gold particles. The gold nanoparticles (8.1 to 2.1 nm) were deposited by using the deposition-precipitation method. The XRD characterization shows the presence of anatase as the TiO2 crystalline phase; while by XPS spectroscopy, the presence of Au°, Au2O3, Ce3+ and Ce4+ species co-existing in the Au/TiO2-CeO2 catalysts is shown. The characterizations by TPD-CO as well as by TPD-H2 (temperature programmed desorption) showed that on catalysts containing cerium, the gold particle size can be determined with great accuracy by using these chemisorption methods. The gold particle size calculated from either the CO or H2 thermodesorption values is in good agreement with that obtained by High Resolution Transmission Electron Microscopy (HRTEM) and Scanning Transmission Electron Microscopy (STEM) analyses. It was proposed that the TPD-CO and/or TPD-H2 techniques could be helpful for the characterization of the gold particles by TEM; especially when the high contrast in the pictures of the supports containing CeO2 prevents the particle size from being determined.

Selective Hydrogenation of Carvone and o-Xylene (cis-trans) on Pd/Y Exchanged Zeolites

Abstracto-Xylene and carvone hydrogenation on supported Pd on exchanged Y-zeolites was done. A controlled selectivity of hydrogen stereoaddition (cis- and trans-) in o-xylene and a large control of the multiple hydrogen addition in carvone were obtained. These effects were achieved by controlling the exchanged Y zeolites acidity.

Structure Sensitivity of Sol-Gel Alkali Tantalates, ATaO3 (A= Li, Na and K): Acetone Gas Phase Condensation

Perovskite-type compounds such as alkali tantalates, ATaO3 (A = Li, Na and K), prepared by the sol-gel method are reported as heterogeneous basic catalysts for the acetone aldol condensation. It has been proposed that the activity order and the selectivity patterns (LiTaO3 > > KTaO3 > NaTaO3) depend on the octahedral arrangements of the TaO6 tantalates.

TOTAL HYDRODECHLORINATION OF INDUSTRIAL TRANSFORMER OIL ON METAL-SUPPORTED CATALYSTS

The hydrodechlorination (HDC) of transformer oil, which consists of a mixture of chlorinated benzene compounds (ClBzs) and polychlorinated biphenyls (PCBs), was carried out in liquid phase by using Pd/C, Ru/C, Rh/C, and Pd/Al2O3 catalysts under mild reaction conditions: 25°C and hydrogen pressure of 2 bar. On the Pd/Al2O3 catalysts, the total hydrodechlorination of the ClBzs and PCBs was reached after 50 h of reaction. Benzene and biphenyl aromatic compounds as well as total and partially hydrogenated products such as cyclohexane, bicyclohexane, and cyclohexylbenzene were obtained.

Effect of the Mg/Al Ratio on Activated Sol-Gel Hydrotalcites for Photocatalytic Degradation of 2,4,6-Trichlorophenol

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.