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.

Core−Shell Polymers with Improved Mechanical Properties Prepared by Microemulsion Polymerization

Abstract: The synthesis of core−shell polymers of styrene and butyl acrylate by a two-stage microemulsion polymerization process is reported. The microemulsion polymerization was optimized by adding more monomer in a semicontinuous fashion to the latex resulting from the polymerization of the parent microemulsion to produce a high-solid-content polystyrene latex (ca. 40% solids) with small particle size ( 2 × 106 g/mol). Core−shell polymers were characterized by transmission electron microscopy, quasielastic light scattering, IR spectroscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The effect of adding a functional monomer (itaconic acid) on the mechanical properties (Young modulus, ultimate elongation, and hardness) of the microemulsion-made structured polymers is also reported. The core−shell polymers synthesized by microemulsion polymerization are more rigid and harder than core−shell polymers of similar composition made by emulsion polymerization....

Bounds For Invariants of Edge-Rings

Abstract: Let G be a simple graph with |V(G)| = n and no isolated vertices. Let α be its stability number. We study invariants of the edge-ring of G that can be interpreted as invariants of G. If G has a cover by maximum stable sets we are able to prove the inequality . As a byproduct we prove that if G is vertex-critical, then α ≤ (n − |A|)/2, where A is the intersection of all the minimum vertex covers of G. We estimate the smallest number of vertices in any maximal stable set of G to obtain a bound for the depth of the edge-ring of G. #Communicated by R. Villarreal.

Theoretical study of the initial reaction between OH and isoprene in tropospheric conditions

Abstract: The reaction of isoprene with OH radicals has been investigated by ab initio molecular orbital theory. We report the energetics of four different pathways, involving the direct addition of OH to four of the carbon atoms. Calculations have been performed using both density functional theory (BHandHLYP) and Moller–Plesset perturbation theory to the second-order (MP2). Two pre-reactive complexes have been identified, whose stabilization energy with respect to the separated reactants is about 12 kJ mol−1. Their structure is similar to the ones previously reported for OH–ethene and OH–propene adducts: the OH radical is placed over either one of the double bonds at a distance of about 2.1 A, with the H atom pointing towards the C–C bond. The geometries of the transition states corresponding to OH addition at the four different positions have been optimized. The calculated apparent activation energies are negative for addition at the terminal carbon atoms and in excellent agreement with the experimental measurements. Direct addition at the internal carbon atoms involves much higher energy barriers, and these pathways are expected to be negligible at normal temperatures. Thus, the observed formation of 3-methylfuran must occur after radical addition to the terminal carbon atoms, following a pathway such as the one proposed by R. Atkinson, S. M. Aschmann, E. C. Tuazon, J. Arey and B. Zielinska, Int. J. Chem. Kinet., 1989, 21, 594 (). Calculated overall rate constants are obtained, in excellent agreement with experimental values. The two-parameter equation for the calculated overall rate coefficient was found to be (2.12 ± 0.42) × 10−11 exp[(384 ± 55)/T] cm3 molecule−1 s−1, while the best fit for the four channels studied here correspond to the following expressions: k1 = (2.25 ± 0.51) × 10−11 exp[(253 ± 62)/T], k2 = (9.60 ± 1.18) × 10−13 exp[(−2871 ± 35)/T], k3 = (1.81 ± 0.22) × 10−12 exp[(−1567 ± 33)/T], and k4 = (2.39 ± 0.27) × 10−12 exp[(676 ± 33)/T] cm3 molecule−1 s−1.