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.

Oxidative dehydrogenation of 1-butene over ZnAl ferrites

Abstract: The aluminum introduction into the zinc ferrite ZnFe 2− x Al x O 4 in the range 0.0 ≤ x ≤ 1.0 was studied. These ferrites were calcined at two temperatures, 550°C and 750°C. X-ray diffraction (XRD) patterns showed that they have a spinel structure with Al 3+ replacing Fe 3+ in octahedral sites. The crystallite size decreased as the aluminum introduction increased. At high calcination temperature, sintering and segregation processes occur. Linear correlations were found between XRD and Mossbauer parameters. Mossbauer spectra showed that the symmetry of the electron distribution decreased around the nucleus of Fe 3+ , as the aluminum content increased. Such asymmetrical distribution of the electron density may be associated to the spatial accommodation of aluminum in the neighboring octahedral sites. Oxygen atoms turn out to be more basic due to the charge transfer from Fe 3+ to O 2− in the FeO bond. Hence the acid-base type dissociation of the CH bond for the n -butenes activation is favored. The highest yield of butadiene was obtained for the samples treated at 750°C whereas for the samples calcined at 550°C, double bond isomerization of 1-butene occurs in competition with the oxidative dehydrogenation.

Effect of sampling and linkage on fault length and length–displacement relationship

Abstract: The power-law exponent (n) in the equation: D=cLn, with D = maximum displacement and L = fault length, would be affected by deviations of fault trace length. (1) Assuming n=1, numerical simulations on the effect of sampling and linkage on fault length and length–displacement relationship are done in this paper. The results show that: (a) uniform relative deviations, which means all faults within a dataset have the same relative deviation, do not affect the value of n; (b) deviations of the fault length due to unresolved fault tip decrease the values of n and the deviations of n increase with the increasing length deviations; (c) fault linkage and observed dimensions either increase or decrease the value of n depending on the distribution of deviations within a dataset; (d) mixed deviations of the fault lengths are either negative or positive and cause the values of n to either decrease or increase; (e) a dataset combined from two or more datasets with different values of c and orders of magnitude also cause the values of n to deviate. (2) Data including 19 datasets and spanning more than eight orders of fault length magnitudes (10−2–105 m) collected from the published literature indicate that the values of n range from 0.55 to 1.5, the average value being 1.0813, and the peak value of nd (double regression) is 1.0–1.1. Based on above results from the simulations and published data, we propose that the relationship between the maximum displacement and fault length in a single tectonic environment with uniform mechanical properties is linear, and the value of n deviated from 1 is mainly caused by the sampling and linkage effects.

Thermokinetic Study of the Rehydration Process of a Calcined MgAl-Layered Double Hydroxide

Abstract: The rehydration process of a calcined MgAl-layered double hydroxide (LDH) with a Mg/Al molar ratio of 3 was systematically analyzed at different temperatures and relative humidity. Qualitative and quantitative experiments were done. In the first set of samples, the temperature or the relative humidity was varied, fixing the second variable. Both adsorption and absorption phenomena were present; absorption process was associated to the LDH regeneration. Of course, in all cases the LDH regeneration was confirmed by other techniques such as TGA, solid state NMR, and SAXS. In the second set of experiments, a kinetic analysis was performed, the results allowed to obtain different activation enthalpies for the LDH regeneration as a function of the relative humidity. The activation enthalpies varied from 137.6 to 83.3 kJ/mol as a function of the relative humidity (50 and 80%, respectively). All these experiments showed that LDH regeneration is highly dependent on the temperature and relative humidity.