Thermodynamics, Kinetics, and Hydrodynamics of Mixed Salt Precipitation in Porous Media: Model Development and Parameter Estimation

Demands for hydrocarbon production have been increasing in recent years. Today many oilfields around the world are afflicted by the problem of scaling leading to severe formation damage and hampering of petroleum production from hydrocarbon reservoirs. In current study, a mathematical model for prediction of permeability reduction due to scale deposition is developed based on thermodynamics, kinetics, and hydrodynamics of mixed salt precipitation during flow through porous media. Model predictions are compared with sound experimental data for single deposition of barium sulfate and most importantly, for simultaneous precipitation of barium sulfate and strontium sulfate onto rock surface. Owing to high nonlinearity of the proposed model, kinetic parameters embedded in the mathematical model were tuned employing a new approach based on a hybrid algorithm consisting of particle swarm optimization (PSO) technique and pattern search (PS) algorithm. The average absolute deviations ranging from 1.03 to 9.3 % were observed between model forecasts and experimental data which corroborate the suitability and applicability of the model and also confirm the capability of PSO–PS hybrid algorithm as a highly efficient optimization tool. Estimated values for kinetic parameters are also in accordance with collision theory of chemical reactions.     

Effect of axial ligand on the electronic configuration, spin states, and reactivity of iron oxophlorin

Iron-oxophlorin is an intermediate in heme degradation, and the nature of the axial ligand can alter the spin, electron distribution, and reactivity of the metal and the oxophlorin ring. The structure and reactivity of iron-oxophlorin in the presence of imidazole, pyridine, and t-butyl isocyanide as axial ligands was investigated using the B3LYP and OPBE methods with the 6-31+G* and 6-311+G** basis sets. OPBE/6-311+G** has shown that the doublet state of [(Py)(2)Fe(III)(PO)] (where pyridines are in perpendicular planes and PO is the oxophlorin trianion) is 3.45 and 5.27 kcal/mol more stable than the quartet and sextet states, respectively. The ground-state electronic configuration of the aforementioned complex is π(xz)(2) π(yz)(2) a(2u)(2) d(xy)(1) at low temperatures and changes to π(xz)(2) π(yz)(2) d(xy)(2) a(2u)(1) at high temperatures. This latter electronic configuration is consistently seen for the [(t-BuNC)(2)Fe(II)(PO(?))] complex (where PO(?) is the oxophlorin dianion radical). The complex [(Im)(2)Fe(III)(PO)] adopted the d(xy)(2) (π(xz) π(yz))(3) ground state and has low-lying quartet excited state which is readily populated when the temperature is increased.     

BF3·nano SiO2 as a catalytic system for one-pot green synthesis of pyrophthalone derivatives under microwave conditions: 1st Nano Update

The expeditious and solvent-free approach that involves the exposure of neat reactants to microwave (MW) irradiation in conjunction with the use of supported catalysts was described. A simple one-pot and green reaction of methylpyridine derivatives and phthalic anhydride derivatives on the surface of a nano silica gel impregnated with BF₃ as solid supported catalysts under microwave irradiation without any solvent according to green chemistry was developed. The salient features of these high yield protocols are the enhanced reaction rates, greater selectivity and the experimental ease of manipulation.     

Darstellung und Eigenschaften von Trimethyl-(dialkylamidosulfonyl)-ammoniumhalogeniden

Zusammenfassung Aus Dialkylamidosulfochloriden oder-bromiden und Trimethylamin werden thermisch stabile kristalline 11-Additions-verbindungen (Tab. 1) erhalten, die auf Grund von IR-Spektren due Sulfonylammonium-Struktur [R₂NSO₂N(CH₃)₃]⁺ X ^– besitzen. Verglichen mit den zugrunde liegenden Sulfohalogeniden sind sie durch eine erhöhte Reaktionsfähigkeit der Halogenatome gekennzeichnet. Beschrieben werden die Thermolyse und die Reaktionen dieser Verbindungen mit einigen protonenaktiven Stoffen (Wasser, Äthanol, Phenol, Thiophenol). Mit Hexamethyldisilazan liefern sie N,N-Dialkyl-N-trimethylsilylsulfamide, während die freien Sulfohalogenide auch bei erhöhter Temperatur nicht mit dem Disilazan reagieren.

---

Synthesis and properties of trimethyl-(dialkylamidosulphonyl)-ammonium halides

Treatment of dialkylamidosulphonyl chlorides or bromides with trimethylamine affords stable crystalline 11 addition compounds of the general formula [R₂NSO₂N(CH₃)₃]⁺ X ^– (cf. Table 1). Evidence for this formulation is obtained from IR spectra. A striking difference between these compounds and the parent sulphonyl halides is the enhanced reactivity of the halogen groups. The thermal degradation and the reactions of the complexes with water, ethanol, phenol, thiophenol, and hexamethyldisilazane are reported. The latter reaction yields N.N-dialkyl-N-trimethylsilyl sulphamides, whereas the corresponding free dialkylamidosulphonyl chlorides are recovered unchanged from refluxing hexamethyldisilazane.

     

Characterization and optical properties of sol-gel processed PMMA/SiO2 hybrid monoliths

Organic-inorganic hybrid monoliths consisting of poly(methyl methacrylate) and SiO₂ were synthesized by the sol-gel process. Three PMMA/TEOS ratios by weight were prepared, namely PMMA/TEOS = 80/20, 50/50 and 20/80. The effects of the ratio of PMMA/TEOS on thermal stability, microstructure, morphology and optical properties were systematically studied. In particular, scanning electron microscopy (SEM) demonstrated morphological variation corresponding to the degree of miscibility between organic and inorganic components. Energy dispersive spectroscopy (EDS) clearly revealed that the SiO₂ was more uniformly distributed in the hybrids with increasing PMMA content. The refractive index could be adjustable in the range of 1.474-1.486. The 80/20 monolith had the similar transparency to pure PMMA in the visible region and lower absorption than PMMA in the near infrared region, suggesting its potential applications for optical devices.     

Interesterification of butter fat by lipase fromRhizopus niveus in cosurfactant-free microemulsion system

Butter fat was interesterified in a cosurfactant-free microemulsion system containing nonionic and ionic surfactants, using commercial lipase obtained fromRhizopus niveus, at different concentrations of surfactant mixtures and hydrophilic-lipophilic balance (HLB) values. The results indicated that the interesterification yield (IY) of lipasecatalyzed interesterified butter fat reached its maximum in the microemulsion system prepared with the surfactant mixture of HLB value of 9, followed by that of HLB value of 10. In addition, increasing concentrations of surfactant mixtures, from 3 to 6 mM, resulted by an increase in the IY. The interesterification of butter fat in the microemulsion prepared with 3 mM of surfactant mixture of HLB value of 10 showed a minimum hydrolytic activity. The results showed that the interesterified selected triacylglycerol molecules were enriched with the hypocholesterolemic fatty acid C18:l, originally located onsn-1,3 positions, on theirsn-2 positions; this fatty acid was favorably interchanged with the hypercholesterolemic fatty acid C16:0, originally located onsn-2 position. The results also indicated that the use of 6 mM of surfactant mixtures increased the acyl exchange reaction toward the long-chain saturated fatty acid C16:0 on the sn-2 position of triacylglycerol molecules.     

Rotational Energy Barrier of the Polarized Carbon–Carbon Double Bond in Quinophthalone

 A dynamic NMR effect is observed in the ¹³C NMR spectra of anhydrous quinophthalone (quinoline yellow) and its monohydrate in the vicinity of 47°C and 0°C, respectively, and is attributed to a restricted rotation around the polarized carbon–carbon double bond. The free energy of activation for this process in anhydrous quinophthalone and the monohydrate is 65±2 and 55±2 kJ · mol⁻¹, respectively, in CDCl₃.     

One-pot synthesis of α-aminonitriles using a highly efficient and recyclable silica-based scandium (III) interphase catalyst

Both aryl and alkyl imines, which formed in situ from aldehydes and amines undergo smooth nucleophilic addition with trimethylsilyl cyanide in the presence of a catalytic amount of a silica-based scandium (III) interphase catalyst under mild reaction condition to furnish the corresponding α-aminonitriles in good to excellent yields. The catalyst shows high thermal stability (up to 300 °C) and it could also be recovered and reused for at least 6 reaction cycles without considerable lose of its reactivity.     

Monte Carlo Simulation of a Segmented Detector for Low-Energy Electron Antineutrinos

Detection of low-energy electron antineutrinos is of importance for several purposes, such as ex-vessel reactor monitoring, neutrino oscillation studies, etc. The inverse beta decay (IBD) is the interaction that is responsible for detection mechanism in (organic) plastic scintillation detectors. Here, a detailed study will be presented dealing with the radiation and optical transport simulation of a typical segmented antineutrino detector withMonte Carlo method using MCNPX and FLUKA codes. This study shows different aspects of the detector, benefiting from inherent capabilities of the Monte Carlo simulation codes.