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..

Maturity trends in Raman spectra from kerogen and coal

Abstract: The present work explores the potential of Raman spectroscopy to provide maturity information about catagenesis stage kerogens and coals. The first-order Raman spectra of coals and kerogens show a broad amorphous A band between 1310 and 1360 cm-1 and a graphite-like G band near 1580−1600 cm-1. As vitrinite reflectance (R0) increases, the Raman A band becomes narrower and shifts to lower frequencies while the absorption strength of the A band relative to the G band decreases. The area ratio of the A band to G band (R = fA/fG) decreases from 3.2 to 2.4 in going from the least mature sample up to R0 = 2.0%. Similar trends were observed for maturation suites of Type II and other Type III kerogens. Laboratory thermolysis produced a range of samples with well-defined laboratory R0. The changes in the Raman A and G bands from the laboratory matured samples directionally paralled the natural samples. These results demonstrate that the Raman spectra of catagenesis stage samples vary in regular ways with sample mat...

Low-flow limit in slot coating: Theory and experiments

Abstract: The region of acceptable quality in the space of operating parameters of a coating process is called coating window. Their limits are set by coating defects. For the slot-coating process the low-flow limit is important. It corresponds to the maximum web speed at a given film thickness, or the minimum film thickness at a given web speed, at which the coating bead remains stable. The available viscocapillary model is based on the Landau-Levich equation, which is limited to small Capillary and Reynolds numbers. Under these conditions, the minimum film thickness that can be coated decreases with decreasing coating speed, but many coating processes do not occur at low Capillary numbers. It is important to determine the range of validity of the viscocapillary model and find the low-flow limit outside this range. The low-flow limit was determined here theoretically and experimentally. The 2-D Navier-Stokes equations with free surfaces describe liquid flow in the coating bead. Theoretical approaches solve the Navier-Stokes system by either using Galerkin's method with finite-element basis functions or applying a long-wave expansion. The minimum layer thickness at a set of parameters was determined by the turning point on the solution path as the thickness was diminished. The minimum film thickness was measured experimentally by determining the flow rate at which the coating bead breaks, leading to stripes of coated and uncoated web. Results show that the low-flow limit of the coating bead at large Capillary and Reynolds numbers fundamentally differs from that at their low numbers. At large Capillary and Reynolds numbers, the minimum film thickness that can be coated decreases with increasing coating speed. The coating window of the process is much larger than that in the literature, broadening the applicability of this coating method.

An amido transition metal compound and a catalyst system for the production of isotactic polypropylene.

Abstract: Bridged and unbridged amido transition metal compounds of the Group IV-B metals are disclosed. They are represented by general formula (I) wherein: 'y' is 1 denoting the presence of a bridging group T between nitrogen atoms; 'Z' is - y; 'M' is zirconium, hafnium or titanium; 'N' is a nitrogen atom having three substituents; each 'X' is, independently, any univalent anionic ligand such as a halide, hydride, substituted or unsubstituted C1-C30 hydrocarbyl, alkoxide, aryloxide, amide, arylamide, phosphide, or arylphosphide; 'T' is a covalent bridging group selected from the group consisting of unsubstituted hydrocarbyl and substituted hydrocarbyls containing a Group IV-A or VI-A element; and each 'R' is, independently, a radical selected from the group consisting of singly branched hydrocarbyl radicals having between 4 and 30 carbon atoms, multiply branched hydrocarbyl radicals having between 4 and 30 carbon atoms, halogen radicals, amido radicals, phosphido radicals, silyl radicals, alkoxy radicals, alkylborido radicals, C1-C30 hydrocarbyl-substituted Group IV-A metalloid radicals; and substituted C1-C30 hydrocarbyl radicals wherein one or more hydrogen atoms is replaced by a halogen radical, an amino radical, a phosphido radical, an alkoxy radical or any other radical containing a Lewis acidic or basic functionality. These compounds may be used in a catalyst system comprising the amido transition metal compound and an alumoxane. Also disclosed is a process using the catalyst system for the production of high molecular weight polyolefins and, particularly, high molecular weight isotactic polypropylene.