Showing papers by "Mexican Institute of Petroleum published in 2006"
TL;DR: In this article, the authors used gravimetric and electrochemical techniques to investigate the effect of decylamides of α-amino acids derivatives on steel surface protection in hydrochloric acid.
299 citations
TL;DR: Four molecules that have been proven to act as corrosion inhibitors of mild steel in acidic media are studied and it is shown that the interaction energy is favored when hardness increases, in agreement with the experimentally observed inhibition efficiencies.
Abstract: Four molecules that have been proven to act as corrosion inhibitors of mild steel in acidic media are studied. The inhibitive efficiency of these molecules is explained by means of electronic structure calculations of the protonated species that seem to represent better the actual situation of the experimental conditions. By assuming that the interaction between the inhibitor and the metallic surface occurs through donation and back-donation, it is shown, with a simple charge transfer model, that the interaction energy is favored when hardness increases, in agreement with the experimentally observed inhibition efficiencies. A local analysis with Hirshfeld condensed Fukui functions, and local Fukui functions, provides further support to the donation and back-donation mechanism.
256 citations
TL;DR: In this paper, small particles of Ti/Ni have been synthesized by a bioreduction method and the controlling parameter was the pH of the solution where they were grown in.
228 citations
TL;DR: In this article, the authors evaluated the catalytic oxidative desulfurization (OD) activity of alumina-supported polymolybdates (Mo/Al2O3) using organosulfur model compounds and diesel fuel.
Abstract: The evaluation of the catalytic oxidative desulfurization (OD) activity of alumina-supported polymolybdates (Mo/Al2O3) was carried out using organosulfur model compounds and diesel fuel. Hydrogen peroxide was the oxidizing reagent. Ultra-deep desulfurization, 97.8% removal of sulfur in diesel fuel, was achieved by reaction under mild conditions followed by solvent extraction. The catalyst was prepared by equilibrium adsorption and characterized by infrared, Raman, X-ray photoelectron, 31 P and 27 Al MAS NMR spectroscopies. Our results indicate that the phosphomolybdate used during synthesis of the catalysts decomposes and forms hydrated hepta- and octamolybdates as well as phosphate ions on the surface of alumina. # 2006 Published by Elsevier B.V.
181 citations
TL;DR: The model proposed by Szargut for the calculation of the standard chemical exergy of elements and organic and inorganic substances has been revised in this article, and updated values of the chemical exergies of elements for the standard conditions (298.15 K and 1 atm) have been presented and compared with the ones estimated by the original model, and some different reference species than those used in the latest version of the Szargput model were proposed for the following elements: silver, gold, barium, calcium, cadmium, copper, mercury, magnesium, nickel
173 citations
TL;DR: Analysis of surface sediment samples from the Salina Cruz Bay indicated relatively high enrichment factors for lead during the last two decades, and spatial distribution suggests that in addition to harbor activities, a transboundary source for Pb must account for the observed trends.
Abstract: Surface sediment samples collected from the Salina Cruz Bay in the last twenty years, were analyzed for the total available trace elements (Cr, Cu, Fe, Pb, Ni, V, and Zn) to evaluate metal contamination due to possible anthropogenic inputs. Normalization of metals to iron and fine-grained fraction (< 63 microm) indicated relatively high enrichment factors for lead during the last two decades. Sediment Quality Guidelines suggest that lead must be considered as a chemical of potential concern in the marine and estuarine ecosystem. Concentration levels of lead ranged from 5-124 microg/g, while Ni and V below 70 and 30 microg/g, respectively. Geoaccumulation and enrichment factors for the rest of elements show comparable values to those reported for sites with similar activities in the world. Spatial distribution suggests that in addition to harbor activities, a transboundary source for Pb must account for the observed trends.
160 citations
TL;DR: In this article, a new combined cycle was proposed to produce both power and cooling simultaneously with only one heat source and using ammonia-water mixture as the working fluid, and the simulation of the cycle was carried out in the process simulator ASPEN Plus.
160 citations
TL;DR: This is the first study directly exploring bacterial diversity in corrosive biofilms associated to steel pipelines subjected to normal operation conditions, and it is shown that Desulfovibrio spp.
159 citations
TL;DR: A wide array of volatile organic compound (VOC) measurements was conducted in the Valley of Mexico during the MCMA-2002 and 2003 field campaigns as discussed by the authors, where four distinct analytical techniques were used: whole air canister samples with Gas Chromatography/Flame Ionization Detection (GC-FID), on-line chemical ionization using a Proton Transfer Reaction Mass Spectrometer (PTR-MS), continuous real-time detection of olefins using a Fast Olefin Sensor (FOS), and long path measurements using UV Differential Optical Absorption Spect
Abstract: A wide array of volatile organic compound (VOC) measurements was conducted in the Valley of Mexico during the MCMA-2002 and 2003 field campaigns. Study sites included locations in the urban core, in a heavily industrial area and at boundary sites in rural landscapes. In addition, a novel mobile-laboratory-based conditional sampling method was used to collect samples dominated by fresh on-road vehicle exhaust to identify those VOCs whose ambient concentrations were primarily due to vehicle emissions. Four distinct analytical techniques were used: whole air canister samples with Gas Chromatography/Flame Ionization Detection (GC-FID), on-line chemical ionization using a Proton Transfer Reaction Mass Spectrometer (PTR-MS), continuous real-time detection of olefins using a Fast Olefin Sensor (FOS), and long path measurements using UV Differential Optical Absorption Spectrometers (DOAS). The simultaneous use of these techniques provided a wide range of individual VOC measurements with different spatial and temporal scales. The VOC data were analyzed to understand concentration and spatial distributions, diurnal patterns, origin and reactivity in the atmosphere of Mexico City. The VOC burden (in ppbC) was dominated by alkanes (60%), followed by aromatics (15%) and olefins (5%). The remaining 20% was a mix of alkynes, halogenated hydrocarbons, oxygenated species (esters, ethers, etc.) and other unidentified VOCs. However, in terms of ozone production, olefins were the most relevant hydrocarbons. Elevated levels of toxic hydrocarbons, such as 1,3-butadiene, benzene, toluene and xylenes, were also observed. Results from these various analytical techniques showed that vehicle exhaust is the main source of VOCs in Mexico City and that diurnal patterns depend on vehicular traffic in addition to meteorological processes. Finally, examination of the VOC data in terms of lumped modeling VOC classes and its comparison to the VOC lumped emissions reported in other photochemical air quality modeling studies suggests that some alkanes are underestimated in the emissions inventory, while some olefins and aromatics are overestimated.
156 citations
TL;DR: This atom by atom scheme (CPaa) is based on the consideration that the proximity of the fragments may affect the intramolecular BSSE of every involved species, and artificially influences the value of the BSSE associated to the supermolecule formation.
Abstract: In the present work the intermolecular BSSE, associated to the A-B interaction, is obtained by subtracting the intramolecular BSSE of the fragments from the intramolecular BSSE of the supermolecule, and considering every atom as a fragment in the calculation of each intramolecular BSSE. This atom by atom scheme (CP aa ) is based on the consideration that the proximity of the fragments may affect the intramolecular BSSE of every involved species, and artificially influences the value of the BSSE associated to the supermolecule formation. It drastically decreases the reported counterpoise overcorrection of the A-B interaction, even though it does not deal with all the overcorrection because it includes all the orbitals, and not only the unoccupied ones. This new approach has been tested on the water dimer, some hydrogen fluoride weakly bonded complexes, the conformational analysis of 1,2-dichloroethane, and the reaction profile of formaldehyde + OH reaction.
102 citations
TL;DR: In this paper, Imidazolines and amidic precursors were synthesized with good yields through an optimized process and evaluated as corrosion inhibitors in an aqueous solution of 1.0 M HCl by gravimetric and polarization techniques.
TL;DR: In this article, high-resolution and quantitative planktic foraminiferal biostratigraphy from two SE Mexico stratigraphic sections (Bochil, Guayal) shows that the Chicxulub-related Complex Clastic Unit (CCU) is synchronous with the ejecta-rich airfall layer and the Cretaceous/Paleogene (K/Pg) catastrophic mass extinction horizon in the El Kef (Tunisia) and Caravaca (Spain) sections.
TL;DR: In this article, a multiphase (oil/gas/asphaltene/water) multicomponent hydrodynamic model is proposed to represent the phenomenon of asphaltenes deposition in producing wells.
Abstract: A multiphase (oil/gas/asphaltene/water) multicomponent hydrodynamic model is proposed to represent the phenomenon of asphaltene deposition in producing wells. The model is based on the assumption that asphaltene particles are thermodynamically formed at a given set of p−T−x conditions during the flow, and both molecular diffusion and shear removal are two competing mechanisms that define the radial diffusion and later deposition of asphaltene particles for either turbulent or laminar flows in a well. Predictions of the model are presented for the case of two problematic (plugged) wells from the southwest producing area of Mexico, where measured pressure−temperature−depth production profiles related to deposits are available.
TL;DR: In this article, the analytical form of the intermolecular pair interaction potential in a vacuum between asphaltene−asphaltenes (UAA), asphalte−resin (UAR), and resin−resins (URR) systems using density functional theory (DFT) and compass-classical force field was calculated.
Abstract: In this work, we present the calculated analytical form of the intermolecular pair interaction potential in a vacuum between asphaltene−asphaltene (UAA), asphaltene−resin (UAR), and resin−resin (URR) systems using two methods: density functional theory (DFT) and compass-classical force field. The binding energy was obtained by varying the minimum atomic distance (contact distance) between the interacting species and their relative angle; that is, by taking into account all possible interactions between the species (T-shape, face-to-face, edge-to-edge, and random configurations). For the asphaltene molecule, we used the proposed Groenzin−Mullins structure (Energy Fuels 2000, 14, 677), and for the resin molecule, we used 6-methyl-dibenzothiophene (Energy Fuels 1999, 13, 278). The binding energy between the interacting species was obtained using compass-classical force field, DFT with the Harris functional (DFT−Harris), and DFT with the self-consistent GGA Perdew-Wang 91 functional (DFT−SC). The potential c...
TL;DR: In this paper, a dynamic heterogeneous one-dimensional model of trickle-bed reactors used for catalytic hydrotreating of oil fractions is presented, which considers the main reactions in the hydroreating process.
Abstract: This paper describes a dynamic heterogeneous one-dimensional model of trickle-bed reactors used for catalytic hydrotreating of oil fractions. The model considers the main reactions in the hydrotreating process of oil fractions: hydrodesulfurization, hydrodenitrogenation, and hydrodearomatization. The dynamic model was first validated using experimental data obtained in an isothermal pilot reactor during hydrotreating of vacuum gas oil over a commercial NiMo catalyst. Then, the model was applied to predict the dynamic behavior of a commercial hydrotreating reactor. Changes in concentration, partial pressure, and temperature profiles are obtained and discussed as a function of reactor axial position and time. The simulations obtained with the proposed dynamic model showed good agreement with experimental data.
TL;DR: In this paper, the authors derived an analytical expression for P-wave attenuation in a transversely isotropic medium with horizontal symmetry axis HTI and provided a method to estimate fracture direction from azimuthally varying Q in PP-wave reflection data.
Abstract: This paper investigates Q-anisotropy for characterizing fractured reservoirs — specifically, the variation of the seismic quality factor Q versus offset and azimuth QVOA .W e derive an analytical expression for P-wave attenuation in a transversely isotropic medium with horizontal symmetry axis HTI and provide a method QVOA for estimating fracture direction from azimuthally varying Q in PP-wave reflection data. The QVOA formula is similar to Ruger’s approximation for PP-wave reflection coefficients, the theoretical basis for amplitude variation with angle offset AVOA analysis. The technique for QVOA analysis is similar to azimuthal AVO analysis. We introduce two new seismic attributes: Q versus offset QVO gradient and intercept. QVO gradient inversion not only indicates fracture orientation but also characterizes Q-anisotropy. We relate the Q-anisotropy parameter Q to fractured-medium parameters and invert the QVO gradient to estimate Q. The attenuation parameter Q and Thomsen-style anisotropy parameter V are found to be interdependent. The attenuation anisotropy magnitude strongly depends on the host rock’s VS/VP parameter, whereas the dependence on fracture parameters is weak. This complicates the QVO gradient inversion for the fracture parameters. This result is independent of the attenuation mechanism. To illustrate the QVOA method in synthetic data, we use Hudson’s first-order effective-medium model of a dissipative fractured reservoir with fluid flow between aligned cracks and random pores as a possible mechanism for P-wave attenuation.
TL;DR: The three-layer icosahedral nanorod structure is not as stable as the Pd-core/Au-shell decahedron; however it is more stable than the solid-solution dec ahedron structure up to 400 K.
Abstract: Classical molecular dynamics simulation is used for structural thermodynamic and dynamic analysis of Au-Pd bimetallic clusters. It is observed that the Pd-core/Au-shell structure is the most stable, and can be formed through annealing of other structures such as Au-core/Pd-shell, eutecticlike, or solid solution. Depending on the starting temperature and initial composition, three-layer icosahedral nanorod, face-centered cubic (fcc) nanorod, and fcc cluster can be obtained on slow cooling. The three-layer icosahedral nanorod structure is not as stable as the Pd-core/Au-shell decahedron; however it is more stable than the solid-solution decahedron structure up to 400 K. Our findings provide valuable insight into catalysis using Au-Pd and other similar bimetallic clusters.
TL;DR: The OH abstraction of a hydrogen atom from both the side chain and the ring of toluene has been studied in the range 275-1000 K using quantum chemistry methods and the best method of calculation is to perform geometry optimization and frequency calculations at the BHLYP/6-311++G(d,p) level, followed by CCSD(T) calculations of the optimized structures with the same basis set.
Abstract: The OH abstraction of a hydrogen atom from both the side chain and the ring of toluene has been studied in the range 275-1000 K using quantum chemistry methods. It is found that the best method of calculation is to perform geometry optimization and frequency calculations at the BHandHLYP/6-311++G(d,p) level, followed by CCSD(T) calculations of the optimized structures with the same basis set. Four different reaction paths are considered, corresponding to the side chain and three possible ring hydrogen abstractions, and the branching ratio is determined as a function of temperature. Although negligible at low temperatures, at 1000 K ring-H abstraction is found to contribute 11% to the total abstraction reaction. The calculated rate coefficients agree very well with experimental results. Side chain abstraction is shown to occur through a complex mechanism that includes the reversible formation of a collisionally stabilized reactant complex.
TL;DR: In this article, the authors used the indirect boundary element method to simulate 2D scattering of elastic P and SV waves in planar and elliptic cracks and cavities, where they established a system of integral equations that allows them to compute the diffracted displacement and traction fields in both frequency and time domains.
Abstract: Comprehensive studies in geophysics and seismology have dealt with scattering phenomena in unbounded elastic domains containing fractures or cavities. Other studies have been carried out to investigate scattering by discontinuities located near a free surface. In this last case, the presence of fractures and cavities significantly affects wave motion and, in some cases, large resonant peaks may appear. To study these resonant peaks and describe how they can be affected by the presence of other near-free-surface fractures or cavities we propose the use of the indirect boundary element method to simulate 2D scattering of elastic P and SV waves. The geometries considered are planar and elliptic cracks and cavities. This method establishes a system of integral equations that allows us to compute the diffracted displacement and traction fields. We present our results in both frequency and time domains. In the planar cracks located near the free surface, we validate the method by comparing results with those of a previously published study. We develop several examples of various fractures and cavities to show resonance effects and total scattered displace- ment fields, where one can observe conspicuous peaks in the frequency domain and important wave interactions in the time domain. Finally, we show how our dimen- sionless graphs can be used to deal with materials like clay, sand, or gravel and compare the response with finite-element analysis of elastic beams.
TL;DR: In this paper, a study of the carbon steel/cooling water interface was carried out using electrochemical impedance spectroscopy (EIS) and it was found that a layer of corrosion and scale products forms naturally and evolves with the immersion time modifying carbon steel and giving rise to corrosion and scaling processes.
TL;DR: In this paper, the synthesis and surface characterization of a Zr-modified mesoporous MCM-41 solid with an ordered hexagonal arrangement, prepared through a templated synthesis route, using cetyltrimethylammonium chloride as the template.
TL;DR: In this paper, an electrochemical procedure was developed to quantify the presence of secondary phases (nitride, χ, σ) in duplex stainless steel, based on anodic galvanostatic polarization in a weakly alkaline solution.
TL;DR: In this paper, the results on the removal of cadmium ions from simulated industrial wastewater using sol-gel structured nanoparticles of silica and alumina are presented, and two different core-shell nanoparticles were prepared: Al-Si particles and Si-Al particles.
Abstract: Some results on the removal of cadmium ions from simulated industrial wastewater using sol–gel structured nanoparticles of silica and alumina are presented. Two different core-shell nanoparticles were prepared: Al–Si particles (alumina core surrounded by a silica shell) with a molar composition Al:Si of 1:5, and Si–Al particles (silica core and alumina shell) with a molar composition Si:Al of 1:5. Different amounts of cadmium ions were added and the flocculation process of these particles, induced by the ions adsorption, was followed using dynamic light scattering. The efficiency of the ions adsorption was determined using atomic absorption spectroscopy. The results show that it is possible to reduce the cadmium concentration from 140 ppm to less than 5 ppb using Si–Al particles, meeting some international regulations for this contaminant (New European Directive 98-83). The Al–Si particles were not so efficient because the cadmium was only reduced from 125 ppm to less than 90 ppb. The sol–gel technique allows to synthesize model nanoparticles with different morphologies to be used as a prototypes, allowing to choose the better morphology and scaling this knowledge to an industrial level using commercially available silica and alumina nanoparticles chemically modified on the surface.
TL;DR: The diversity and relative abundance of bacteria from water pipeline biofilms may contribute to an understanding of the complexity and mechanisms of metal corrosion during marine water injection in oil secondary recovery.
TL;DR: A detailed structural analysis for small Tin (n = 2-15) clusters based on ab initio quantum mechanical calculations of their binding energies, frontier orbital gaps, and second energy derivatives revealed that while the smaller clusters (n < or = 8) prefer hexagonal atomic arrays with bulklike crystal symmetry, the bigger clusters prefer pentagon atomic arrays.
Abstract: We present a detailed structural analysis for small Tin (n = 2−15) clusters based on ab initio quantum mechanical calculations of their binding energies, frontier orbital gaps, and second energy derivatives. Local density approximation calculations revealed that while the smaller clusters (n ≤ 8) prefer hexagonal atomic arrays with bulklike crystal symmetry, the bigger clusters prefer pentagonal atomic arrays. From the stability criteria of the magic number clusters we could identify three magic number clusters Ti7, Ti13, and Ti15. While the most stable configuration of Ti7 is a decahedral bipyramid induced by tetrahedral atomic arrays, the most stable configuration of Ti13 is an icosahedron. The other stable cluster Ti15 takes a closed-shell icosahedron-like configuration with both pentagonal and hexagonal symmetries. The stability of the Tin clusters strongly depends on their geometries and charge states. The HOMO−LUMO gap of the Tin clusters approaches its bulk value for n > 8. While there is not much ...
TL;DR: In this paper, the experimental results of the density and viscosity for aqueous solutions of three alkanolamines composed of N-methyldiethanolamine (MDEA) and 12.5 mass % diethanolamines (DEA), with 2, 4, 6, 8, and 10 mass % 2-amino-2-methyl-1-propanol (AMP) have been determined in the temperature range of (303.15 to 343.15) K.
Abstract: Experimental values of the density and viscosity for aqueous solutions of three alkanolamines composed of 32.5 mass % N-methyldiethanolamine (MDEA) and 12.5 mass % diethanolamine (DEA) with 2, 4, 6, 8, and 10 mass % 2-amino-2-methyl-1-propanol (AMP) have been determined in the temperature range of (303.15 to 343.15) K. The experimental results of the density and viscosity are given as a function of both temperature and AMP concentration. In the range of temperature studied, the experimental density values of the aqueous blends of alkanolamines decrease as the AMP concentration increases while the viscosity values increase as the AMP concentration increases. Correlation equations were obtained to allow the calculation of density and viscosity for aqueous solutions of MDEA and DEA as a function of AMP concentration and temperature.
TL;DR: In this paper, Ni-B coatings have been deposited on the surfaces of commercial steels (SAE-1026) using the electroless plating technique employing a nickel chloride solution with borane-dimethylamine as the reducing agent.
TL;DR: In this article, the authors evaluated the corrosion resistance of commercial aluminium alloy (2024) and binary Al-Mg and Al-Cu x 1.5% NaCl solution using potentiodynamic polarization curves and linear polarization resistance measurements.
Abstract: The corrosion resistance of commercial aluminium alloy (2024) and binary Al–Cu
x
and Al–Mg
x
alloys reinforced with TiC particles using a pressureless infiltration method has been evaluated in 3.5% NaCl solution using potentiodynamic polarization curves and linear polarization resistance measurements. The TiC preforms were sintered at 1250, 1350 and 1450 °C and infiltrated in the range of 900–1200 °C under argon atmosphere. Some specimens were heat treated at 530 °C for 150 min, water quenched and subsequently artificially aged at 190 °C for 12 h in an argon atmosphere and naturally aged at room temperature for 96 h, respectively. The corrosion resistance of the composites was evaluated as a function of the addition of Cu and Mg into the aluminium. In all cases pitting corrosion was observed with or without additions of Cu or Mg, but these elements increased the anodic corrosion current. However, it was found that addition of TiC particles in the composite without heat treatment reduced the anodic current density and the number and size of pits in the Al-2024 alloy. When the heat treatment was applied to the composite, either artificially or naturally aged, the anodic current density of the Al-2024 alloy increased.
TL;DR: In this article, the exact solutions of the Klein-Gordon equation with equal scalar and vector ring-shaped potentials were presented, and they were shown to be the same as in this paper.
Abstract: We present the exact solutions of the Klein–Gordon equation with equal scalar and vector ring-shaped potentials.
TL;DR: Detailed study is presented on the atomistic structure of Au–Cu nanoparticles so as to determine their most stable configurations and the conditions for obtaining clusters of different structural variants, and understand structural transition of clusters upon heating, supported by experimental evidences.
Abstract: Though the application of bimetallic nanoparticles is becoming increasingly im- portant, the local atomistic structure of such alloyed particles, which is critical for tailoring their properties, is not yet very clearly understood. In this work, we present detailed study on the atom- istic structure of Au-Cu nanoparticles so as to determine their most stable configurations and the conditions for obtaining clusters of different structural variants. The dynamic behavior of these nanoparticles upon local heating is investigated. AuCu nanoparticles are characterized by high re- solution transmission electron microscopy (HRTEM) and energy filtering elemental composition mapping (EFECM), which allowed us to study the internal structure and the elemental distribu- tion in the particles. Quantum mechanical approaches and classic molecular dynamics methods are applied to model the structure and to determine the lowest energy configurations, the corre- sponding electronic structures, and understand structural transition of clusters upon heating, sup- ported by experimental evidences. Our theoretical results demonstrate only the core/shell bimetal- lic structure have negative heat of formation, both for decahedra and octahedral, and energetically favoring core/shell structure is with Au covering the core of Cu, whose reverse core/shell structure is not stable and may transform back at a certain temperature. Experimental evidences corrobo- rate these structures and their structural changes upon heating, demonstrating the possibility to manipulate the structure of such bimetallic nanoparticles using extra stimulating energy, which is in accordance with the calculated coherence energy proportions between the different configura- tions. Microsc. Res. Tech. 69:522-530, 2006. V C 2006 Wiley-Liss, Inc.