Zwitterionic liquids have a wide variety of applications in enhanced oil recovery (EOR). In particular, geminal zwitterionic substances have been used as wettability modifiers of limestone, ...dolomites, and sandstones at high temperatures and pressures. The understanding of the interaction mechanisms of such molecules with the limestone surface is an important step toward the comprehension of the modification in wettability. In the study here presented, the interaction energies of limestone with geminal zwitterionic liquids of the type bis-N-alkyl polyether were calculated within the framework of the density functional theory (DFT). With the use of the DMOL3 library of the Material Studio Software (a DFT-based computational code), we calculated the interaction energies of the bis-N-alkyl polyether liquids, asphaltene with the limestone rocks.
The present study attempts to examine the relationship between electronic-structure properties exhibited by 4d-transition-metal sulfides (TMSs) in connection with the hydrodesulfurization (HDS) ...catalytic activity. The electronic structure is studied by means of a periodic density functional approach using a plane-wave basis set and appropriate pseudopotentials. Both bulk and relevant surfaces of NbS, NbS2, MoS2, TcS2, RuS2, Rh2S3, PdS, and PdS2 have been analyzed. High densities of nonbonding states below the Fermi level have been found for the TMSs that exhibit good catalytic performance. Therefore, it is suggested that the incomplete filling of the band gap at exposed transition metal atoms over the catalyst surface plays a determinant role in the HDS reactions. It has also been found that the highest HDS activity occurs when the surface-metal-site density of electronic states has a local minimum at the Fermi level that enhances the donation−back-donation mechanism. Additionally, the Sabatier principle is qualitatively rationalized in terms of the position of covalent bands below the Fermi level.
Phase transitions of cylindrical structures of poly(styrene)–poly(isoprene) copolymer (PS–PI) toward spherical and gyroid structures were explored using DPD simulations and a coarse-grained model. ...Cylindrical phases were first obtained within a composition interval (“predominance region”) 0.2<fPS<0.26 (volume fraction of poly(styrene)). The predominance region of cylindrical structures was then subject to thermal heating cycles. The thermodynamic instabilities of cylindrical microdomains induce anisotropic composition fluctuations and phase transitions. A transition from the cylindrical phase at low composition limit to a spherical arrangement was observed during the thermal heating process. The cylindrical phase at the intermediate and high composition limit within the predominance region exhibits a transition towards a gyroid arrangement. The phase transition control during thermal heating on the cylindrical phases was governed by small variations in composition. The results are consistent with experimental studies.
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•Control of CaSO4 scales by a new itaconic acid–sodium vinyl sulfonate copolymer.•Theoretical–experimental research of the supramolecular assembly copolymer-CaSO4.•Evaluation of a industrial ...prospective of copolymer in incompatible water systems.
A new itaconic acid (IA)–sodium vinyl sulfonate (VS) copolymer is proposed to control the formation of calcium sulfate scales. The supramolecular interacting system IA–VS copolymer-calcium sulfate scales was characterized by means of scanning electronic microscopy, X-ray powder diffraction analysis, Fourier transform infrared spectroscopy, differential thermal analysis, density parameters, X-ray fluorescence and atomic absorption spectroscopy, as well as molecular modeling through density functional theory. Industrial potential of the IA–VS copolymer and its operation in an incompatible water system having scaling calcium salts are also evaluated. Results show that the IA–VS copolymer is able to control growing of inorganic mineral scales through the formation of supramolecular complexes, which are soluble in aqueous solution and can induce morphological changes into the precipitated material.
In order to obtain the critical micellar concentration (CMC) for sodium dodecyl sulfate (SDS) in water at 288.15, 293.15, 298.15, 303.15 and 308.15 K, two approaches were employed: the first, ...consisting of experimental Isothermal Calorimetric Titration (ITC) and the second by using Dissipative Particle Dynamics (DPD) simulations. To determine the experimental CMC the calorimetric signal was treated with the software D/STAIN, obtaining values between 8.24 and 9.22 mM, which are in good agreement with other experimental determinations. Also the SDS micellization enthalpies found agree with previous experimental reports. The pairwise aij DPD interaction parameters, needed to run the simulations, were obtained from quantum chemistry calculations under the application of the COSMO-RS solvation scheme jointly with the Flory-Huggins theory. A series of systems with variable concentration of SDS in water were simulated for each temperature. Then, the analysis of the percentage of aggregation of SDS molecules at each temperature, enable to visualized the theoretical aggregation isotherms. By delimiting an experimental CMC window, the DPD aggregation isotherms were used to identify the concentration where either the monomeric or micellar states domain. Intersection of linear fits, in the monomeric and in the micellar regime produced theoretical CMCs values from 8.1 to 8.9 mM. These results compare favorably with the experimental determinations at each temperature.
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Green mechanosynthesis, free solvent, has been used for preparing a series of supramolecular complexes. Through directional hydrogen bonds and π-cation interaction can be prepared complexes with ...different states of aggregation of matter, where stoichiometry plays an essential role. When the stoichiometric ratio between the two compounds was 1:1, a solid product is obtained. But, when the ratio is higher, products are obtained as gel or paste to reach low viscosity liquids. Also, the structure of such complexes that form three-dimensional aggregates between C12TAC and phenol derivatives can explain the different aggregation states for final products and this may be the key to understand the viscosity reduction mechanism.
Plexiform fibromyxoma (PF) is an uncommon primary tumor of the gastrointestinal tract, with a mesenchymal origin and a benign behavior. Herein, we report a case and provide a literature review. A ...41-year-old male patient underwent surgery in our unit for a PF at the gastric antrum, after being admitted due to vomiting and weight loss. As illustrated by our case, the mean age at presentation is around 40 years, the antrum is the most common location and abdominal pain the most widely reported manifestation. None of the reviewed cases involved regional or distant spread.
We prepared geminal zwitterionic liquids with the capability to obtain the chemical active species from laboratory to scalable production with pure or raw materials. Hence, a green-inspired and ...efficient process for their synthesis was developed. A performance test at reservoir conditions was conducted and it was found that the synthesized chemicals increase the oil recovery factor in an enhanced oil recovery process with properties as antiscale agents.
In this work we present the results of a mesoscopic dynamic simulation study of ordered microphases modification in asymmetric-copolymer/homopolymer binary blends, where we explore the influence of ...the composition, packing density and solubilization of homopolymer chains into the compatible microdomains of the asymmetric copolymer. The poly(styrene)–poly(isoprene) (PS–PI) and homopoly(styrene) (HPS) molecules were built and represented by Gaussian chain models. The pure asymmetric copolymer generates spherical microdomains of poly(styrene) (PS) in the matrix of majority component, poly(isoprene) (PI), and is taken as the base for the binary blends. The mesoscopic dynamic evolution of asymmetric-PS–PI/HPS blends display a coarse-grained system sufficiently large to determine the separation of the microphase and the formation of ordered structures. The HPS chains tend to be selectively solubilized in the PS microdomains of the asymmetric copolymer, the repulsive interaction forces between homopoly(styrene) and poly(isoprene) chains assure that essentially all the HPS homopolymer exists in the PS microdomains. As the asymmetric-PS–PI/HPS composition is varied the mesoscale simulations predict ordered structures with defined morphologies of body-centred-cubic (BCC), hexagonal packed cylinders (HPC), hexagonal perforated layers (HPL) and lamellar phases (LAM). Ordered microphases appear in reverse order when the homopoly(styrene) composition is increased in the binary blend. The agreement between our mesoscopic simulation results and available experimental outcome open a new strategy to modify the microphase morphology of asymmetric copolymers.
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