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..

Numerical investigation of gas‐driven flow in 2‐D bubble columns

Abstract: Gas-liquid bubbly flow in 2-D bubble columns was studied by numerical simulation. A Eulerian-Eulerian two-fluid model used describes the time-dependent motion of liquid driven by small, spherical gas bubbles injected at the bottom of the columns. Such equations, numerically implemented in this work, were derived by Zhang and Prosperetti. A distinctive feature of this method is the derivation of the disperse-phase momentum equation by averaging the particle (here, the bubble) equation of motion directly, not the macroscopic equation for the particle phase. Both the time-averaged quantities and dynamic characteristics of the macroscopic coherent structures agree with the experimental data of Lin et al. and Mudde et al. The comparison of simulated results with data demonstrates that this physical model and numerical approach can provide the key features of the time-dependent behavior of dispersed bubbly flows qualitatively with reasonable quantitative accuracy. Effects of the number of injectors, magnitude of bubble-induced viscosity, and various parameters in the interphase momentum exchange were also studied by simulating various cases and comparing with measurements. The applicability of different boundary conditions and the sensitivity to the mesh system used are also examined.

P and S velocity structure of the Yellowstone volcanic field from local earthquake and controlled-source tomography

Abstract: The three-dimensional P and S velocity (from Vp/Vs ratios) distribution and improved hypocenters for the Yellowstone volcanic field have been determined from inversion of first arrival times from 7942 local earthquakes and 16 controlled-source explosions The P velocity model has an rms residual of ±009 s, whereas the Vp/Vs ratio model (calculated from 511 earthquakes) has an rms residual of ±029 s High P and S velocities outside the Yellowstone caldera represent thermally undisturbed basement and sedimentary rocks A caldera-wide 15% decrease from regional P velocities at depths of 6 to 12 km is coincident with a −60 mGal gravity anomaly and is interpreted as a hot, subsolidus, granitic batholith with a quasi-plastic rheology Localized 30% reductions from regional seismic velocities and higher Vp/Vs ratios 8 km beneath Yellowstone's resurgent domes are interpreted as partial melts and vestigial magma systems associated with youthful (less than 2 Ma) silicic volcanism Additional low seismic velocities and Vp/Vs ratios and a 20 mGal gravity low less than 4 km beneath the northeast caldera rim are interpreted as a hydrothermal fracture zone thermally driven by underlying partial melt Hypocenters relocated with the three-dimensional P velocity model show subparallel alignment with NW-SE trending postcaldera volcanic vents and normal faults northwest of the caldera Focal depths of relocated earthquakes decrease from more than 11 km outside the caldera to less than 6 km within the caldera, reflecting thinning and heating of the seismogenic crust

Catalyst particle sizes from Rutherford scattered intensities

Abstract: SUMMARY We show that the number of atoms in a small supported catalyst cluster can be estimated from the strength of electron scattering into a high angle annular detector in the STEM. The technique is related to the Z contrast methods developed by Crewe, Wall, Langmore and Isaacson. It works best for high atomic number catalyst particles when supported on low atomic number supports, such as Pt on γ-aluminium oxide. The method is particularly useful for detecting and measuring particles in the sub-nanometre size range where bright field images are unreliable. Unlike the Z contrast methods, a high angle annular detector is used, which avoids intensity modulations arising from Bragg reflections. The signal is mostly high angle diffuse scattering, which is predominantly Rutherford scattering, and is proportional to the number of atoms probed by the beam, weighted by their individual scattering cross-sections. Scattering strengths of individual clusters are computed from digitized high angle annular detector images. Data for Pt on γ-aluminium oxide, when plotted as imaged area1/2 against intensity1/3, define a straight line. Such plots provide calibration of the intensity increment per atom without the need of external calibration, although assumptions about particle morphology must be made. Reliable results require high signal-to-noise and optimum sampling of the specimen. For an STEM probe size of 0.35 nm, Pt clusters containing as few as three atoms can be detected when supported on typical, 20 nm thick, γ-aluminium oxide supports.

X-ray flux enhancement in thin-film waveguides using resonant beam couplers.

Abstract: We present experimental evidence for achieving significant x-ray flux enhancement by coupling a highly collimated and monochromatic synchrotron x-ray beam into a Si/polyimide/SiO 2 thin-film waveguide. The observed 20-fold flux increase agrees with theoretical predictions and was limited only by absorption of the 1 A x rays in the waveguide structure

Membrane separation in solvent lube dewaxing

Abstract: Exxon Mobil Corporation and W.R. Grace have developed an enhanced process for recovering solvents used in the refining of lubricants. The membrane-based process provides higher yields of lube oil, while simultaneously consuming less energy, decreasing cooling water use, and potentially reducing the level of volatile organic emissions from the dewaxing operation. The yield increase equates to a process savings, for a typical commercial plant, of about 2 million barrels of crude oil per year. By recovering and recycling the dewaxing solvent while bypassing the energy intensive parts of the plant, a single facility could reduce fuel oil consumption by 36,000 barrels/year, and greenhouse gas emissions by about 20,000 tons/year for each plant. The same plant would reduce cooling water use by nearly 4 million gallons/day, and, the release of dewaxing solvents, which are volatile organic materials, could be decreased by 50–200 tons/year per plant depending on the mechanical condition of its equipment. This technology was first implemented commercially at Exxon Mobil's Beaumont, Texas, Refinery. It can be easily retrofitted into existing plants or incorporated into new plant designs, and is currently available for license as the trademarked process MAX-DEWAX®.