Showing papers by "ExxonMobil published in 1999"

Tailored Porous Materials

Abstract: Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form of fibers, thin films, and monoliths. These issues are addressed in the context of five specific classes of porous materials: oxide molecular sieves, porous coordination solids, porous carbons, sol−gel-derived oxides, and porous heteropolyanion salts. Reviews of these specific areas are preceded by a presentation of background material and review of current theoretical approaches to adsorption phenomena. A concluding section outlines current research needs and opportunities.

Packing Length Influence in Linear Polymer Melts on the Entanglement, Critical, and Reptation Molecular Weights

Abstract: We have shown in previous studies that the entanglement molecular weight for a polymer melt, Me, is related by a power law to p, the packing length of the polymer species. We now find that power laws also describe the molecular weights characterizing the melt viscosity, Mc marking the onset of entanglement effects and Mr the crossover to the reptation form. The packing length exponents for Me, Mc, and Mr differ significantly, however. The long-held notion that the ratio Mc/Me has the same value for all species is therefore incorrect. Further, the observed and predicted values of Mr for two species, 1,4-polybutadiene and polyisobutylene, have been found to agree, within the uncertainties, with the projected values. Finally, the variations with packing length are such that all three characteristic molecular weights would appear to converge on the same value near p = 9 A. As yet, no species with such a large packing length has been completely studied rheologically. But the range is not outlandish and is clea...

Premium wear resistant lubricant

Abstract: A premium synthetic lubricant having antiwear properties comprises a synthetic isoparaffinic hydrocarbon base stock and an effective amount of at least one antiwear additive. The antiwear additive is preferably at least one of a metal phosphate, a metal dialkyldithiophosphate, a metal dithiophosphate, a metal thiocarbamate, a metal dithiocarbamate, an ethoxylated amine dialkyldithiophosphate and an ethoxylated amine dithiobenzoate. Metal dialkyldithiophosphates are preferred, particularly zincdialkyldithiophosphate (ZDDP). The base stock is derived from a waxy, Fischer-Tropsch synthesized hydrocarbon feed fraction comprising hydrocarbons having an initial boiling point in the range of about 650-750 °F, by a process which comprises hydroisomerizing the feed and dewaxing the isomerate. The lubricant may also contain hydrocarbonaceous and synthetic base stock material in admixture with the Fischer-Tropsch derived base stock.

Chain dimensions and entanglement spacings in dense macromolecular systems

Abstract: In this article, we reexamine and extend a relationship proposed earlier between entanglement density and chain dimensions in polymer melts The power-law equation presented in the earlier work, relating the entanglement molecular weight Me, melt chain density ρ, and the packing length p is tested with additional polymer species Now included are additional polydienes and their hydrogenated derivatives, the isotactic forms of polypropylene and polystyrene, the essentially syndiotactic form of poly(methyl methacrylate), along with poly(tetrafluoroethylene), poly(vinylmethyl ether), various poly(methacrylates), and polymeric sulfur We find that within experimental uncertainties, Me/ρ and p are related through an equation (Me/ρ = 218p3) that is insensitive to temperature (25°C ≤ T ≤ 380°C) and which seems to be universal for flexible Gaussian chains in the melt state © 1999 John Wiley & Sons, Inc J Polym Sci B: Polym Phys 37: 1023–1033, 1999

Illite and hydrocarbon exploration

Abstract: Illite is a general term for the dioctahedral mica-like clay mineral common in sedimentary rocks, especially shales. Illite is of interest to the petroleum industry because it can provide a K-Ar isotope date that constrains the timing of basin heating events. It is critical to establish that hydrocarbon formation and migration occurred after the formation of the trap (anticline, etc.) that is to hold the oil. Illite also may precipitate in the pores of sandstone reservoirs, impeding fluid flow. Illite in shales is a mixture of detrital mica and its weathering products with diagenetic illite formed by reaction with pore fluids during burial. K-Ar ages are apparent ages of mixtures of detrital and diagenetic end members, and what we need are the ages of the end members themselves. This paper describes a methodology, based on mineralogy and crystallography, for interpreting the K-Ar ages from illites in sedimentary rocks and for estimating the ages of the end members.

Propylene olefin copolymers

Abstract: Improved thermoplastic polymer blend compositions comprising an isotactic polypropylene component and an alpha-olefin and propylene copolymer component, said copolymer comprising crystallizable alpha-olefin sequences. In a preferred embodiment, improved thermoplastic polymer blends are provided comprising from about 35% to about 85% isotactic polypropylene and from about 30% to about 70% of an ethylene and propylene copolymer, wherein said copolymer comprises isotactically crystallizable propylene sequences and is predominately propylene. The resultant blends manifest unexpected compatibility characteristics, increased tensile strength, and improved process characteristics, e.g., a single melting point.

Process for manufacturing improved process oils using extraction of hydrotreated distillates

Abstract: A method for producing a process oil in which a naphthenic rich distillate is processed through a single hydrotreating stage, the hydrotreated distillate is then solvent extracted to yield a process oil which passes IP-346 and AMES screening test.

Transient phase-induced nucleation

Abstract: A transient metastable rotator phase occurring on crystallization of hexadecane into its triclinic phase from the supercooled melt was directly observed with time-resolved synchrotron x-ray scattering. In this system, the limit of supercooling (the crystallization temperature) is determined by the thermodynamic stability of the transient phase with respect to the liquid. The crystallization kinetics of the homologous series of n -alkanes was measured and explained in terms of a crossover from stability to “long-lived” metastability to transient metastability. This crossover allowed further confirmation of the nature of the transient phase.

Production on synthetic lubricant and lubricant base stock without dewaxing

Abstract: A lubricating base stock useful for forming lubricants such as a multigrade automotive oils, automatic transmission oils, greases and the like is prepared by hydroisomerizing a waxy hydrocarbon feed fraction having an initial boiling point in the 650-750° F. range and an end point of at least 1050° F., synthesized by a slurry Fischer-Tropsch hydrocarbon synthesis process. The hydroisomerization forms a hydroisomerate containing the desired base stock which is recovered, without dewaxing the hydroisomerate. The hydroisomerization is conducted at conditions effective to convert at least 67 wt. % of the 650-750° F.+ waxy feed hydrocarbons to lower boiling hydrocarbons. When combined with a standard lubricant additive package, these base stocks have been formed into multigrade automotive crankcase oils, transmission oils and hydraulic oils meeting the specifications for these oils.

Prediction of the wax content of the incipient wax-oil gel in a pipeline: An application of the controlled-stress rheometer

Abstract: High molecular weight paraffins are known to form gels of complex morphology at low temperatures due to the low solubility of these compounds in aromatic or naphthene-base oil solvents. The characteristics of these gels are strong functions of the shear and thermal histories of these samples. A model system of wax and oil was used to understand the gelation process of these mixtures. A significant depression in the gel point of a wax-oil sample was observed by either decreasing the cooling rate or increasing the steady shear stress. The wax-oil sample separates into two layers of different characteristics, a gel-like layer and a liquid-like layer, when sheared with a controlled-stress rheometer at high steady shear stresses and low cooling rates. The phase diagram of the model wax-oil system, obtained using a controlled-stress rheometer, was verified by analyzing the wax content of the incipient gel deposits formed on the wall of a flow loop. Based on the rheological measurements, a law has been suggested for the prediction of the wax content of the gel deposit on the laboratory flow loop walls. The wax content of the incipient gel formed on the wall of a field subsea pipeline was predicted to be much higher than that for the flow loop at similar operating conditions. This variation in the gel deposit characteristics is due to the significant differences in the cooling histories in the two cases.

Normal and Shear Forces Between Polymer Brushes

Abstract: Surface-polymer interactions are important in many technological applications, including colloidal stablization and adherence. Recently there has been considerable progress in understanding these interactions and the resulting forces between polymer-bearing surfaces. End-grafted polymers, commonly referred to as polymer brushes, are one example of a polymer-surface complex which has many interesting properties. In this article, recent progress in understanding the normal and shear forces between polymer brushes is reviewed with emphasis on the contributions from molecular simulations. These simulations show that under steady-state shear flow, some of the individual chains of a polymer brush stretch in the direction of flow while most are buried inside of the brush and are not affected by the shear flow. The height of the brush is only weakly dependent on the shear rate in contrast with several theoretical models. When two surfaces bearing end-grafted chains are brought into contact the normal force increases rapidly with decreasing plate separation, while the shear force is in most cases significantly smaller, particularly for large compressions. However, for weak compression, the range and the magnitude of the shear force depends on both the solvent quality and shear rate. These results, first observed experimentally using the surface force apparatus and recently confirmed in simulation, suggest a way to dramatically reduce the frictional force between two surfaces. For small relative velocity of the two surfaces, the surfaces slide pass each other with almost no change in the average radius of gyration of the chains or the amount of interpenetration of chains from the two surfaces. However, for large shear rates, there is significant stretching and some disentanglement of the chains.

High temperature olefin polymerization process

Abstract: The invention is directed to olefin polymerization processes using bridged hafnocene catalyst complexes comprising highly substituted noncoordinating anions that are surprisingly stable under high temperature olefin polymerization processes such that olefin copolymers having significant amount of incorporated comonomer can be prepared with high molecular weights. More specifically, the invention is a polymerization process for ethylene copolymers having a melt index of about 0.87 to about 0.930 comprising contacting, under homogeneous polymerization conditions at a reaction temperature at or above 140° C. to 225° C., ethylene and one or more comonomers capable of insertion polymerization with a bridged hafnocene catalyst complex derived from A) a biscyclopentadienyl hafnium organometallic compound having i) at least one unsubstituted cyclopentadienyl ligand or aromatic fused-ring substituted cyclopentadienyl ligand, ii) one aromatic fused-ring substituted cyclopentadienyl ligand, iii) and a covalent bridge connecting the two cyclopentadienyl ligands, said bridge comprising a single carbon or silicon atom; and B) an activating cocatalyst, precursor ionic compound comprising a halogenated tetraaryl-substituted Group 13 anion wherein each aryl substituent contains at least two cyclic aromatic rings.

Capillary waves at liquid-vapor interfaces: a molecular dynamics simulation.

Abstract: Evidence for capillary waves at a liquid/vapor interface are presented from extensive molecular dynamics simulations of a system containing up to 1.24 million Lennard-Jones particles. Careful measurements show that the total interfacial width depends logarithmically on L{sub {parallel}}, the length of the simulation cell parallel to the interface, as predicted theoretically. The strength of the divergence of the interfacial width on L{sub {parallel}} depends inversely on the surface tension {gamma}. This allows us to measure {gamma} two ways since {gamma} can also be obtained from the difference in the pressure parallel and perpendicular to the interface. These two independent measures of {gamma} agree provided that the interfacial order parameter profile is fit to an error function and not a hyperbolic tangent, as often assumed. We explore why these two common fitting functions give different results for {gamma}.

Premium synthetic lubricants

Abstract: Premium synthetic lubricants comprise a synthetic isoparaffinic hydrocarbon base stock and an effective amount of at least one, and typically a plurality of lubricant additives such as a detergent, dispersant, antioxidant, antiwear additive, pout point depressant, VI improver and the like. The base stock is derived from a waxy, paraffinic, Fischer-Tropsch synthesized hydrocarbon feed fraction having an initial boiling point in the range of about 650-750°F and continuously boiling up to at least 1050°F, by a process which comprises hydroisomerizing the feed and dewaxing the isomerate. The waxy feed has a T90-T10 temperature difference of at least 350°F and is preferably hydroisomerized without any pretreatment, other than optional fractionation. The lubricant may also contain hydrocarbonaceous and synthetic base stock material. Lubricants, such as fully formulated multigrade automotive crankcase and transmission oils formed by adding a suitable additive package to the isoparaffinic base stock have exhibited performance superior to similar fully formulated oils based on both PAO and conventional, petroleum derived base stocks.

Statistics and Dynamics of Symmetric Diblock Copolymers: A Meolecular Dynamics Study

Abstract: Extensive molecular dynamics simulations are carried out to study static and dynamic properties of symmetric diblock copolymer melts, both in the disordered and in the lamellar phases. The lamellar phase is constructed using the natural lamellar spacing, determined from constant pressure simulations. The non-Gaussian character of the chains in the disordered phase is demonstrated and quantified. In the lamellar phase, the density profile of the separate blocks, as well as the interface thickness are determined as a function of chain length N and AB interaction parameter e, and compared with experiments and other theoretical results. Single chain and single block form factors indicate that the chains in the lamellar phase are distorted into stick-like objects. Our results in the disordered phase show a stronger dependence of the diffusion constant on the chain length than observed in previous simulations. Diffusion within the lamellar plane for systems with chains of length N ≤ 100 monomers is found to be ...

Mechanical Properties and Deformation Behavior of the Double Gyroid Phase in Unoriented Thermoplastic Elastomers

Abstract: The mechanical properties of the double gyroid (DG) cubic phase in glassy−rubbery block copolymer systems are examined. The stress−strain properties of an isoprene-rich polystyrene/polyisoprene/polystyrene (SIS) triblock and a polystyrene/polyisoprene (SI) starblock DG, both comprised of two separate interpenetrating glassy networks embedded in rubbery matrices, are compared to those of the sphere, cylinder, and lamellar morphologies. This 3-dimensionally interpenetrating periodic nanocomposite is found to have superior properties over those of its classical counterparts, attributable to the morphology rather than to the volume fraction of the glassy component, the architecture of the molecule, or the molecular weight. The DG is the only polygranular/isotropic thermoplastic elastomer morphology which exhibits necking and drawing and which requires considerably higher stresses for deformation up to 200% strain than any of the three classical microdomain morphologies. The deformation behavior of the DG is f...

Elastic blends comprising crystalline polymer and crystallizable polymers of propylene

Abstract: Improved thermoplastic polymer blend compositions comprising an isotactic polypropylene component and an alpha-olefin and propylene copolymer component, said copolymer comprising crystallizable alpha-olefin sequences. In a preferred embodiment, improved thermoplastic polymer blends are provided comprising from about 35% to about 85% isotactic polypropylene and from about 30% to about 70% of an ethylene and propylene copolymer, wherein said copolymer comprises isotactically crystallizable propylene sequences and is predominately propylene. The resultant blends manifest unexpected compatibility characteristics, increased tensile strength, and improved process characteristics, e.g., a single melting point.

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

Structure of the Molybdenum Site of Dimethyl Sulfoxide Reductase

Abstract: Molybdenum K-edge X-ray absorption and Mo(V) electron paramagentic resonance (EPR) spectroscopies have been used to probe the metal coordination in oxidized and reduced forms of both wild-type and a site-directed mutant of Rhodobacter sphaeroides dimethyl sulfoxide (DMSO) reductase. We confirm our earlier findings (George, G. N.; Hilton, J.; Rajagopalan, K. V. J. Am. Chem. Soc. 1996, 118, 1113−1117) that the molybdenum site of the oxidized Mo(VI) enzyme possesses one terminal oxygen ligand (MoO) at 1.68 A, four thiolate ligands at 2.44 A, and one oxygen at 1.92 A and that the dithionite-reduced Mo(IV) enzyme possesses a desoxo species with three or four Mo−S at 2.33 A and two different Mo−O ligands at 2.16 and 1.92 A. Mo(V) EPR indicates the presence of one exchangeable oxygen ligand, most likely an Mo−OH, in the signal-giving species, probably originating from the MoO of the oxidized enzyme (Em8.5(IV/V) = +37 mV, Em8.5(V/VI) = +83 mV). The addition of dimethyl sulfide, in the reverse of the physiological...

Low viscosity lube basestock

Abstract: The present invention is directed to an easily biodegradable low viscosity, low Noack volatility lube oil material having a viscosity index (VI) in the range of about 110-145, ⊃98 % saturates useful as lube oil basestock, automatic transmission fluid (ATF) basestock or blending stock. The lube oil material is produced by the isomerization of a wax feed having a viscosity of from 4 to 10 cSt at 100 °C and containing less than about 25 % oil in wax.

A lubricant base oil having improved oxidative stability

Abstract: The instant invention is directed to a method for producing a lubricating base stock having a preselected oxidative stability comprising the steps of: (a) separating, into a plurality of fractions based on molecular shape, a hydroisomerized hydrocarbon wax, (b) collecting the fractions of step (a) which have the preselected oxidative stability for use as a lubricating base stock, wherein the fractions to be collected are determined by measuring the oxidative stability of each of said fractions of said plurality of fractions to determine which fractions have said preselected oxidative stability. The invention is also directed to an improved lubricating base oil and a formulated lubricating composition using said lubricating base oil.

Integrated staged catalytic cracking and staged hydroprocessing process

Abstract: A catalytic cracking process includes more than one catalytic cracking step and integrates catalytic cracking steps with hydroprocessing in order to maximize olefins production, distillate quality and octane level of the cracked product In the process, a hydrocarbon feed is hydroprocessed in a hydroprocessor (23) with thishydroprocessed hydrocarbon being passed to a first catalytic cracking zone (10) to form a first cracked product This first cracked product is passed to a separator (17) in which hydrocarbon fractions including a gas oil-containing bottoms fraction are separated This bottoms fraction is then passed to a second hydroprocessor (19) to form a second hydroprocessed hydrocarbon This second hydroprocessed hydrocarbon is then passed to a second separator (20) to separate a hydroprocessed bottoms fraction and an unspent hydrogen fraction The unspent hydrogen fraction is combined with the feed and the hydroprocessed bottoms fraction is passed to a second catalytic cracker (11) to form a second cracked product

Catalytic dewaxing with trivalent rare earth metal ion exchanged ferrierite

Abstract: A process for dewaxing waxy hydrocarbonaceous materials, such as hydrocarbon fuel and lubricating oil fractions to reduce their cloud and pour points comprises reacting the material with hydrogen in the presence of a dewaxing catalyst comprising at least one metal catalytic component and ferrierite in which at least a portion of its cation exchange positions are occupied by one or more trivalent rare earth metal cations. The rare earth ion exchanged ferrierite catalyst has good selectivity for lubricating oil production, particularly when dewaxing a Fischer-Tropsch wax hydroisomerate. Preferably at least 10 % and more preferably at least 15 % of the ferrierite cation exchange capacity is occupied by one or more trivalent rare earth metal cations.

Hydroconversion process for making lubricating oil basestocks

Abstract: The process is drawn to producing a lubricating oil basestock having at least 90 wt % saturates and a VI of at least 105 in unit (42) then the hydroconverted raffinate is conducted through line (46) to heat exchanger (48).

Study of the structure development during the melt spinning of nylon 6 fiber by on‐line wide‐angle synchrotron X‐ray scattering techniques

Abstract: The melt spinning of nylon 6 has been studied with on-line wide-angle synchrotron X-ray scattering techniques. The apparatus consisted of a single screw extruder and a metering pump mounted on a horizontal platform that could be translated in the vertical direction allowing a range of distances to be sampled with the X-ray beam. The structure development, equatorial crystallinity index, and crystalline orientation were studied as a function of take-up speed and position along the spinline. For low-speed (50 mpm) situations, the nylon chains crystallize into independent hydrogen bonded sheets that start to interact with each other as their concentration starts to increase. For higher speed situations, the nylon chains crystallize directly into the interacting hydrogen-bonded sheet structure. Upon conditioning at room temperature for 24 h, this interacting hydrogen-bonded sheet structure transforms into the well-known three-dimensional alpha and gamma phases of nylon 6, probably existing in a shish-kabob structure. The equatorial crystallinity index increases as distance from the spinneret increases and as take-up speed decreases. The crystalline orientation function is constant along the spinline for a constant take-up speed, and increases as take-up speed is increased. Conditioning further increases both the crystallinity and crystalline orientation of the fibers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1277–1287, 1999

Wide-cut synthetic isoparaffinic lubricating oils

Abstract: A wide-cut lubricant base stock is made by hydroisomerizing and then catalytically dewaxing a waxy Fischer-Tropsch synthesized hydrocarbon fraction feed and comprises the entire dewaxate having an initial boiling point in the 650-750 °F+ range. Formulated lubricating oils made by admixing the base stock with a commercial automotive additive package meet all specifications, including low temperature properties, for multigrade internal combustion engine crankcase oils. The waxy feed has an initial boiling point in the 650-750 °F range and continuously boils to an end point of at least 1050 °F+. Lower boiling hydrocarbons produced by the process are separated from the base stock by simple flash distillation. The base stock comprises the entire dewaxate having an initial boiling point in the 650-750 °F range.