ExxonMobil

About: ExxonMobil is a company organization based out in Irving, Texas, United States. It is known for research contribution in the topics: Catalysis & Polymerization. The organization has 16969 authors who have published 23758 publications receiving 535713 citations. The organization is also known as: Exxon Mobil Corporation & Exxon Mobil Corp..

Gold clusters: reactions and deuterium uptake

Abstract: We have examined the reactivity and saturation of small gold clusters (cations, neutrals and anions) towards several molecules and find that specific small gold clusters exhibit a pronounced variation in their reactivity towards hydrogen, methane and oxygen. The reactivity not only depends strongly on cluster size but also on the cluster charge state. For example, small (n<15) gold cations react readily with D2, but no evidence of reaction is observed for the anions under our experimental conditions. Similar behavior is seen for methane. With oxygen only even atom (odd electron) anions are reactive, and Au 10 + is the only cation which exhibits evidence of reaction. The global features (small cluster cations reactive towards H2, CH4, but large ones not reactive, odd electron anions reactive towards O2) are qualitatively explained by appealing to a simple frontier orbital picture. The uptake of deuterium and methane on gold clusters also exhibits a pronounced size dependence with D/Au varying from a high of 3 for the dimer to zero for clusters containing more than 15 Au atoms. Comparison of the methane and deuterium saturation behavior leads us to suggest that methane is dissociated and bound as CH3 and H.

Shear-Induced Molecular Orientation and Crystallization in Isotactic Polypropylene: Effects of the Deformation Rate and Strain

Abstract: Studies of dilute polymer solutions in shear flow suggest that the mean fractional extension of molecules increases gradually with the Weissenberg number (Wi = shear rate × longest relaxation time) and approaches an asymptotic value of 0.4−0.5, while in elongational flow it approaches full contour length above a certain critical strain rate. In an entangled polymer melt, this behavior is more complex due to inter- and intramolecular interactions. In situ rheo-SAXS (small-angle X-ray scattering) and -WAXD (wide-angle X-ray diffraction) experiments were performed to investigate the effects of shear rate, shear duration, and Wi on the extent of molecular orientation/extension and crystal orientation in an isotactic polypropylene (iPP) melt. Two series of experiments were designed: (1) variation of shear rate (30, 45, and 60 s-1) at a constant shear duration (5 s) and (2) variation of shear duration (1.3, 3, and 5 s) at a constant rate (60 s-1). The degree of crystal orientation (Herman's orientation functio...

Some physicochemical aspects of microemulsion flooding: a review

Abstract: Injection compositions for a variety of microemulsion and surfactant floods can be represented on equilibrium ternary diagrams with coordinates surfactant-cosolvent, brine, and oil. That portion of such a diagram having economic significance, divides into a single-phase region and a multiphase region. Within the single-phase region, micellar structure is studied in relation to effects of salinity and cosolvent on viscosity, optical birefringence and electrical resistivity. Within the multiphase region, effects on phase behavior, interfacial tension and solubilization parameter are determined as functions of salinity, brine composition, temperature, surfactant structure, cosolvent, and oil aromaticity. Correlations are found between interfacial tension and solubilization parameter that are useful in preliminary screening of surfactants for oil recovery potential. When, by any means, extent of the multi-phase region is reduced, a circumstance favorable to displacement in the miscible mode; a concomitant effect is that interfacial tensions are also reduced, favoring displacement in the immiscible mode.