ExxonMobil

About: ExxonMobil is a company organization based out in Irving, Texas, United States. It is known for research contribution in the topics: Catalysis & Polymer. 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..

Pore Pressure Estimation From Velocity Data: Accounting for Overpressure Mechanisms Besides Undercompaction

Abstract: A new method for estimating pore pressure from formation sonic velocity data is presented. Unlike previous techniques, this method accounts for excess pressure generated by both undercompaction, and fluid expansion mechanisms such as aquathermal pressuring, hydrocarbon maturation, clay diagenesis, and charging from other zones. The method is an effective stress approach; the effective stress is computed from the velocity, and the result is subtracted from the overburden stress to obtain pore pressure. to include multiple sources of overpressure, a pair of velocity-vs.-effective-stress relations are introduced. One relation accounts for normal pressure and overpressure caused by undercompaction. The second is applied inside velocity reversal zones caused by fluid expansion mechanisms. Example applications of the method are presented from the U.S. gulf coast, the Gulf of Mexico, and the Central North Sea. some other pore pressure estimation approaches are also examined to demonstrate how these techniques have unknowingly accounted for overpressure mechanisms other than undercompaction. It is also explained how velocity-vs.-effective-stress data can be used to identify the general cause of overpressure in an area. For instance, the empirical correlation of Hottman and Johnson indicates that overpressure along the US gulf coast cannot be due only to undercompaction.

Catalysts, method of preparing these catalysts, and polymerization processes wherein these catalysts are used

Abstract: The present invention relates to catalysts, to a method for preparing such catalysts, to a method of using such catalysts and to polymeric products produced with such catalysts. The catalysts are particularly useful in the polymerization of - olefins, diolefins and acetylenically unsaturated monomers. The improved catalysts are prepared by combining at least one first compound which is a bis(cyclopentadienyl) derivative of a metal of Group IV-B of the Periodic Table of the Elements capable of forming a cation formally having a coordination number of 3 and a valence of +4 and at least one second compound comprising a cation capable of donating a proton and a compatible noncoordinating anion comprising a plurality of boron atoms, which anion is both bulky and labile, and capable of stabilizing the Group IV-B metal cation without interfering with said Group IV-B metal cation's or its decomposition product's ability to polymerize α-olefin, diolefins and/or acetylically unsaturated monomers.

Reduction of frictional forces between solid surfaces bearing polymer brushes

Abstract: THE use of lubricants to reduce friction and wear between rubbing surfaces has been documented since antiquity1–3. Recent approaches have focused on boundary lubrication by surfactant-like species coating the surfaces, whereby the friction between them is replaced by the weaker forces required for shear of adhesive contacts between the surfactant layers3,4. An alternative approach is to tether polymer chains to the surfaces by one end which, when swollen by a solvent, then act as molecular ‘brushes’ that may facilitate sliding. The normal forces between sliding brush-bearing surfaces have been previously investigated5,6, but the lateral forces, which are the most important from the point of view of lubrication, are harder to measure. Here we report the measurement of lateral forces in such a system. We find a striking reduction in the effective friction coefficients μb between the surfaces to below our detection limit (μb < 0.001), for contact pressures of around 1 MPa and sliding velocities from zero to 450 nm s−1. We believe that this effect is due to the long-ranged repulsion, of entropic origin, between the brushes, which acts to keep the surfaces apart while maintaining a relatively fluid layer at the interface between them.

A general recursion method for calculating diffracted intensities from crystals containing planar faults

Abstract: A general recursion algorithm is described for calculating kinematical diffraction intensities from crystals containing coherent planar faults. The method exploits the self-similar stacking sequences that occur when layers stack non-deterministically. Recursion gives a set of simple relations between average interference terms from a statistical crystal, which can be solved as a set of simultaneous equations. The diffracted intensity for a polycrystalline sample is given by the incoherent sum of scattered intensities over an ensemble of crystallites. The relations between this and previous approaches, namely the Hendricks-Teller matrix formulation, the difference equation method, the summed series formula of Cowley, and Michalski’s recurrence relations between average phase factors, are discussed. Although formally identical to these previous methods, the present recursive description has an intuitive appeal and proves easier to apply to complex crystal structure types. The method is valid for all types of planar faults, can accommodate long-range stacking correlations, and is applicable to crystals that contain only a finite number of layers. A FORTRAN program DIFFaX , based on this recursion algorithm, has been written and used to simulate powder X-ray (and neutron) diffraction patterns and single crystal electron (kinematical) diffraction patterns. Calculations for diamond-lonsdaleite and for several synthetic zeolite systems that contain high densities of stacking faults are presented as examples.

Supported Ionic Liquid Catalysis

Abstract: Supported ionic liquid catalysis is a concept which combines the advantages of ionic liquids with those of heterogeneous support materials. The viability of this concept has been confirmed by several studies which have successfully confined various ionic phases to the surface of support materials and explored their potential catalytic applications. Although the majority of the evaluated supports were silica based, several studies focused on polymeric materials including membranes. The preparation of these materials was achieved by using two different immobilization approaches. The first approach involves the covalent attachment of ionic liquids to the support surface whereas the second simply deposits the ionic liquid phases containing catalytically active species on the surface of the support. Herein recent advances made in this area are described.