Mamedov A.K.,Sabic Technology Center
European Journal of Scientific Research | Year: 2010
In this paper two time dimensional physics and scale invariance frequency based space-time discrete symmetry model has been introduced for unification of dynamical laws of microscopic and high scale objects of nature within one unified concept of classic physics. The physics with two time dimensions involves a new kind of discrete space-time dynamic symmetry with 2+2 D symmetric space and time dimensions forming background state for all of the forces. By discrete space-time symmetry concept gravitation is the conservation of energy distributed in the dynamic space-time frame, therefore it is time related phenomenon and can not be described by one time dimension. The two time dimensional physics is the necessary conceptual foundation for cyclic nature of events with conservation of energy and momentum within one conserved spacetime framework. Formation of space-time frame from uniform space-time annihilations generates an energetic field which through consequences of interactions of forces and particles moves the space-time portion back to the initial state of space-time annihilation. The model involves the correlation of the space-time discrete symmetry with the energy/momentum conservation which leads to the fundamental dynamic super symmetry concept for unification of forces. The concept that energy cannot be created and destroyed, following from Neother's theorem, in the case of dynamical events is to be extended with time translational symmetry of 2+2 D space-time frame to 3+1D with energy/momentum conservation. This concept involves a new mathematical idea of correlation of the space/time derivative operator with original space/time function as an extension of mathematical tool of differentiation. By space-time discrete symmetry concept the performance of nuclear is not regulated by continuum rotation of an electron around the nuclear, described by quantum model, but stable existence of nuclear is due to the cyclic high frequency discrete protonneutron annihilations. The discrete performance of proton/neutron pair involves the correlation and exchange of electromagnetic and gravitation forces with dynamic 2:1 resonance of "elementary quark ingredients" of nuclear and discrete isospin rotation of electron family ingredients. The classic discrete space-time symmetry concept of an electron presented in this paper describes the dynamics of appearance/disappearance model of universe in its cyclic performance. The phenomenal behavior of the background 2+2D space-time discrete symmetry generates the cyclic performance of nuclear and natural events. © EuroJournals Publishing, Inc. 2010.
Alshaiban A.,Sabic Technology Center |
Soares J.B.P.,University of Waterloo
Macromolecular Reaction Engineering | Year: 2013
The effect of adding hydrogen and/or electron donor on the microstructure of polypropylene polymerized with a 4th generation Ziegler-Natta catalysts at two temperatures on the molecular weight distribution, tacticity, and crystallinity of polypropylene is thoroughly investigated in this article. Polypropylene tacticity and crystallinity increases not only when external donors are added, but also when hydrogen is used as a chain transfer agent. The molecular weight distribution of the resins is deconvoluted into several Flory's most probable distributions to show how different active site types respond to the presence of electron donor and hydrogen. The effect of adding hydrogen (H) and/or an electron donor (D) on the microstructure of polypropylene produced with a 4th generation Ziegler-Natta catalysts at two temperatures on the molecular weight distribution and tacticity of polypropylene is thoroughly investigated in this paper. The figure shows how CEF (tacticity) profiles of polypropylene are significantly affected as these conditions are varied at 70°C. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Sasaki K.,Brookhaven National Laboratory |
Naohara H.,Toyota Motor Corporation |
Choi Y.,Brookhaven National Laboratory |
Choi Y.,Sabic Technology Center |
And 4 more authors.
Nature Communications | Year: 2012
Stability is one of the main requirements for commercializing fuel cell electrocatalysts for automotive applications. Platinum is the best-known catalyst for oxygen reduction in cathodes, but it undergoes dissolution during potential changes while driving electric vehicles, thus hampering commercial adoption. Here we report a new class of highly stable, active electrocatalysts comprising platinum monolayers on palladium-gold alloy nanoparticles. In fuel-cell tests, this electrocatalyst with its ultra-low platinum content showed minimal degradation in activity over 100,000 cycles between potentials 0.6 and 1.0 V. Under more severe conditions with a potential range of 0.6-1.4 V, again we registered no marked losses in platinum and gold despite the dissolution of palladium. These data coupled with theoretical analyses demonstrated that adding a small amount of gold to palladium and forming highly uniform nanoparticle cores make the platinum monolayer electrocatalyst significantly tolerant and very promising for the automotive application of fuel cells. © 2012 Macmillan Publishers Limited. All rights reserved.
Muir J.N.,University of Aberdeen |
Choi Y.,Sabic Technology Center |
Idriss H.,University of Aberdeen |
Idriss H.,Sabic Technology Center
Physical Chemistry Chemical Physics | Year: 2012
Studies of the modes of adsorption and the associated changes in electronic structures of renewable organic compounds are needed in order to understand the fundamentals behind surface reactions of catalysts for future energies. Using planewave density functional theory (DFT) calculations, the adsorption of ethanol on perfect and O-defected TiO 2 rutile (110) surfaces was examined. On both surfaces the dissociative adsorption mode on five-fold coordinated Ti cations (Ti 4+ 5c) was found to be more favourable than the molecular adsorption mode. On the stoichiometric surface E ads was found to be equal to 0.85 eV for the ethoxide mode and equal to 0.76 eV for the molecular mode. These energies slightly increased when adsorption occurred on the Ti 4+ 5c closest to the O-defected site. However, both considerably increased when adsorption occurred at the removed bridging surface O; interacting with Ti 3+ cations. In this case the dissociative adsorption becomes strongly favoured (E ads = 1.28 eV for molecular adsorption and 2.27 eV for dissociative adsorption). Geometry and electronic structures of adsorbed ethanol were analysed in detail on the stoichiometric surface. Ethanol does not undergo major changes in its structure upon adsorption with its C-O bond rotating nearly freely on the surface. Bonding to surface Ti atoms is a σ type transfer from the O2p of the ethanol-ethoxide species. Both ethanol and ethoxide present potential hole traps on O lone pairs. Charge density and work function analyses also suggest charge transfer from the adsorbate to the surface, in which the dissociative adsorptions show a larger charge transfer than the molecular adsorption mode. This journal is © 2012 the Owner Societies.
Hudson M.R.,U.S. National Institute of Standards and Technology |
Hudson M.R.,University of Maryland University College |
Queen W.L.,U.S. National Institute of Standards and Technology |
Mason J.A.,University of California at Berkeley |
And 5 more authors.
Journal of the American Chemical Society | Year: 2012
Low-pressure adsorption of carbon dioxide and nitrogen was studied in both acidic and copper-exchanged forms of SSZ-13, a zeolite containing an 8-ring window. Under ideal conditions for industrial separations of CO 2 from N 2, the ideal adsorbed solution theory selectivity is >70 in each compound. For low gas coverage, the isosteric heat of adsorption for CO 2 was found to be 33.1 and 34.0 kJ/mol for Cu- and H-SSZ-13, respectively. From in situ neutron powder diffraction measurements, we ascribe the CO 2 over N 2 selectivity to differences in binding sites for the two gases, where the primary CO 2 binding site is located in the center of the 8-membered-ring pore window. This CO 2 binding mode, which has important implications for use of zeolites in separations, has not been observed before and is rationalized and discussed relative to the high selectivity for CO 2 over N 2 in SSZ-13 and other zeolites containing 8-ring windows. © 2012 American Chemical Society.
Kuttiyiel K.A.,Brookhaven National Laboratory |
Sasaki K.,Brookhaven National Laboratory |
Choi Y.,Brookhaven National Laboratory |
Choi Y.,Sabic Technology Center |
And 3 more authors.
Nano Letters | Year: 2012
We describe a route to the development of novel PtNiN core-shell catalysts with low Pt content shell and inexpensive NiN core having high activity and stability for the oxygen reduction reaction (ORR). The PtNiN synthesis involves nitriding Ni nanoparticles and simultaneously encapsulating it by 2-4 monolayer-thick Pt shell. The experimental data and the density functional theory calculations indicate nitride has the bifunctional effect that facilitates formation of the core-shell structures and improves the performance of the Pt shell by inducing both geometric and electronic effects. Synthesis of inexpensive NiN cores opens up possibilities for designing of various transition metal nitride based core-shell nanoparticles for a wide range of applications in energy conversion processes. © 2012 American Chemical Society.
Al-Dughaither A.S.,Sabic Technology Center |
Al-Dughaither A.S.,University of Western Ontario |
De Lasa H.,University of Western Ontario
Industrial and Engineering Chemistry Research | Year: 2014
This article reports the influence of the SiO2/Al2O3 ratio (30, 80, and 280) on HZSM-5 zeolite properties. XRD patterns show a decrease in the XRD peak intensity at low 2θ angles for low SiO2/Al2O3 ratio zeolites. N2 adsorption and desorption isotherms display hysteresis with both micropores and mesopores likely contributing to the particles network. The NLDFT cylindrical model confirms the characteristic 5.5 Å micropores in the zeolite pore framework. Furthermore, specific surface area, pore volume, and pore size distributions demonstrate that changes in the SiO2/Al2O3 ratio do not influence HZSM-5 structural properties. NH3-TPD shows both weak and strong acid sites. Pyridine-FTIR also confirms that, in HZSM-5, the weak acidity encompasses Lewis and hydrogen-bonded sites, while the strong acidity mainly involves the Brönsted acid sites. It is proven that the ratio of weak to strong acid sites as measured by NH3-TPD and Pyridine-FTIR displays similar changes to the SiO2/Al2O3 ratio. Furthermore, NH3 desorption kinetics and numerical regression allow the establishment of energies of activation for both strong and weak acid sites. It is also found that the kinetic desorption rate constants vary in agreement with the changes in weak and strong acid sites as observed with NH3-TPD and Pyridine-FTIR. © 2014 American Chemical Society.
Almahamedh H.H.,Sabic Technology Center
NACE - International Corrosion Conference Series | Year: 2013
Sulfate-reducing bacteria (SRB) are a large group of anaerobic microorganisms that can facilitate many biochemical processes. Calcium carbonate (CaCO3) precipitation is a common phenomenon found in an environment such as marine water, fresh water and soils. In this paper, the possible role of SRB (Desulfovibrio desulfuricans) in precipitation of CaCO3 was investigated. The biogenic scale formed by Desulfovibrio desulfuricans were chemically analyzed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The chemical analyses of the formed scale indicate a possible influence of Desulfovibrio desulfuricans on the formation of CaCO3. The CaCO3 formed by the chemical reaction of bicarbonate and calcium. In the presence of SRB bicarbonate is introduced to the environments by different mechanisms. In this paper, chemical reactions explaining the possible sources of bicarbonate by SRB are proposed. © 2013 by NACE International.
Hanspal S.,University of Virginia |
Young Z.D.,University of Virginia |
Shou H.,University of Virginia |
Shou H.,Sabic Technology Center |
Davis R.J.,University of Virginia
ACS Catalysis | Year: 2015
The Guerbet coupling of ethanol into butanol was investigated using multiproduct steady-state isotopic transient kinetic analysis (SSITKA) in a comparative study between stoichiometric hydroxyapatite (HAP) and magnesia (MgO) catalysts at 613 and 653 K, respectively. The steady-state catalytic reactions were conducted in a gas-phase, fixed-bed, differential reactor at 1.3 atm total system pressure. Multiproduct SSITKA results showed that the mean surface residence time of reactive intermediates leading to acetaldehyde was significantly shorter than that of intermediates leading to butanol on both HAP and MgO. This finding may suggest that the dehydrogenation of ethanol to acetaldehyde is fast on these surfaces compared with C-C bond formation. If adsorbed acetaldehyde is a key reaction intermediate in the Guerbet coupling of ethanol into butanol, then SSITKA revealed that the majority of adsorbed acetaldehyde produced on the surface of MgO desorbs into the gas-phase, whereas the majority of adsorbed acetaldehyde on HAP likely undergoes sequential aldol-type reactions required for butanol formation. Adsorption microcalorimetry of triethylamine and CO2 showed a significantly higher number of acid and base sites on the surface of HAP compared with those on MgO. Diffuse reflectance infrared Fourier transform spectroscopy of adsorbed ethanol followed by stepwise temperature-programmed desorption revealed that ethoxide is more weakly bound to the HAP surface compared with MgO. A high surface density of acid-base site pairs along with a weak binding affinity for ethanol on HAP may provide a possible explanation for the increased activity and high butanol selectivity observed with HAP compared with MgO catalysts in the ethanol coupling reaction. © 2015 American Chemical Society.
Garcia Vargas N.,Texas A&M University |
Stevenson S.,Sabic Technology Center |
Shantz D.F.,Texas A&M University
Microporous and Mesoporous Materials | Year: 2012
The synthesis and characterization of tin(IV) containing MFI zeolites are reported. It is shown that with conventional hydroxide-mediated preparations that include sodium hydroxide it is difficult to make phase-pure Sn-MFI materials with more than approximately 3 wt.% tin in the final solid. While at low tin contents and high pH values it is possible to make materials that appear more uniform, it is generally observed that the presence of sodium hydroxide in the synthesis has a deleterious effect on the quality of the material obtained. This is manifested in several ways including the presence of a residual tin/sodium surface phase observed via scanning electron microscopy, a discrepancy between the bulk and surface Si/Sn ratios as determined by X-ray fluorescence (XRF) and X-ray photoelectron spectroscopy (XPS) respectively, and a systematic decrease in the micropore volume as determined by nitrogen physisorption. Moreover, it is observed that the tin/sodium overlayer formed is recalcitrant towards methods to dissolve it, including ion-exchange processes in acidic or basic media. In contrast, Sn-MFI materials made in the absence of sodium hydroxide do not display these trends. Rather, they appear to be phase-pure and more homogeneous based on the methods outlined above. The current work lays out an approach to the synthesis of tin zeolites that appear to be highly uniform and should be of interest to the catalysis community. © 2011 Elsevier Inc. All rights reserved.