Mexican Institute of Petroleum

About: Mexican Institute of Petroleum is a government organization based out in Mexico City, Mexico. It is known for research contribution in the topics: Catalysis & Asphaltene. The organization has 3273 authors who have published 4170 publications receiving 87269 citations.

New Gallium-substituted hydrotalcites: [Mg1-xGa x (OH)2](CO3)x/2 ·mH2O

Abstract: A series of Ga-containing hydrotalcite-like materials (GaHTs), [Mg1-xGa x (OH)2](CO3)x/2 ·mH2O wherex = 0.072 ∼ 0.35 (Mg/Ga = 12.9 ∼ 1.8), was synthesized by a coprecipitation method. The resulting solids were characterized by means of X-ray diffraction, thermal gravimetric and infrared analyses. All GaHTs showed diffraction patterns typical of Mg-Al hydrotalcites. Small amounts of brucite, Mg(OH)2, were detected only in the GaHT with Mg/Ga = 12.9. Attempts to obtain Ga-richer hydrotalcites, Mg/Ga < 1.8, resulted in solids with an invariably constant Mg/Ga = 1.8 ratio, which appears to be the maximum Ga content limit. Judging from the TGA pattern of a GaHT (Mg/Ga = 7.7), the layered structure is stable up to ca. 573 K, and at 873 K the resulting solid shows a MgO-like diffraction pattern, suggesting that Ga3+ may be replacing some Mg2+ ions in MgO. Once their layered structure collapses (i.e., at 873 K), GaHT can be easily converted back into the original layered material by treating in a carbonate-containing aqueous solution, i.e., they show the “memory effect” typical of Mg-Al hydrotalcites.

Influence of Synthesis Methods on Tungsten Dispersion, Structural Deformation, and Surface Acidity in Binary WO3−ZrO2 System

Abstract: WO3−ZrO2 catalysts were synthesized by precipitating the aqueous solutions of zirconium oxynitrate and ammonium metatungstate with ammonium hydroxide. The white slurry precipitate was treated under three different conditions. In the as-made materials, the amorphous phase was formed in the aged and refluxed samples, while well-crystallized tetragonal and monoclinic phases were obtained in the hydrothermally treated sample. The real amount of tungsten loaded in the samples was similar for the three samples, independently of the treatments; however, the tungsten surface atomic density in the annealed WO3−ZrO2 samples varied between 6 and 9 W atoms/nm2. Two different contrast types of aggregates were determined by scanning electron microscopy, the white particles which are rich in W, and the gray ones which are rich in zirconium; both of them were formed in the calcined solids prepared under aging or reflux condition. A very high dispersion of tungsten species on the zirconia surface was achieved in the hydro...