Increasing Number Of Carbon Atoms Research Articles

Thermally induced release and generation of CO2 and C1–C4 hydrocarbons in Opalinus Clay from Mont Terri (Switzerland)

Claystone formations are candidate host rocks for high-level heat-emitting nuclear waste (HLW). Temperatures from 90 to 150 °C at the canister surface are discussed internationally as potential emplacement and storage conditions. The thermal energy emitted from waste containers will be transported into the host rock formation, accelerating chemical reactions including the release of sorbed and dissolved gases and the generation of new gases. This study investigated gas release and generation in Opalinus Clay from Mont Terri (Switzerland) at elevated temperature and pressure conditions relevant for HLW storage and beyond. Hydrous pyrolysis experiments were conducted in Dickson-type flexible gold-titanium reaction cells and gold capsules in the temperature range of 80–345 °C and at 20 MPa. CO2(g) was the predominant product, followed by C1–C4 hydrocarbons, which decrease in abundance with increasing carbon atom number. Neither CO nor H2S was detected. H2 was generated only in high temperature experiments at 315 °C and 345 °C, respectively. A combination of CO2(g) quantification, stable carbon isotopic composition data, thermodynamic calculations and aqueous fluid composition (dissolved ions, pH) demonstrated that ≥80 % of the measured CO2(g) originated from carbonate mineral dissolution. The model calculations also suggest that the fraction of CO2(aq) in DIC increases from ∼50 % at 80 °C to nearly 100 % at higher temperatures. Thermal transformation of organic matter represented an additional source for CO2(g) and was the predominant process yielding the C1–C4 hydrocarbons. Our findings stress the importance of quantitative geochemical data for the safety assessment of potential host rocks for HLW storage. We demonstrated that two sources are involved in gas release and generation at temperatures relevant for HLW storage, e.g., in the Opalinus Clay – organic matter and carbonate minerals. Our data will contribute to numerical modelling studies and the refinement of feature, events, and processes (FEP) catalogues.

The solution and exsolution characteristics of natural gas components in water at high temperature and pressure and their geological meaning

The processes of solution in, and exsolution from, formation water influence the component content of natural gas by contrasting the relative contents of components before the natural gas dissolves in water and those after exsolving from water under different conditions of high temperatures and pressures. Compared with the composition of original natural gas, the relative content of methane and nitrogen increased after the natural gas dissolved in water. The increase of nitrogen content exceeds that of methane, but the content of ethane, propane, pentane etc reduced. At the same temperature and with pressure increasing the content of methane increased and that of heavier hydrocarbons reduced. At the same pressure the content of methane increased quickly from 90°C to 120°C, and the content of heavier hydrocarbons reduced. But at even higher temperatures, the increase of methane slowed down and the content of heavier hydrocarbons increased slightly. At the same temperature and different pressures, heavier hydrocarbons reduced much more with increasing carbon atom number, while with temperature increasing the content difference of heavier hydrocarbons reduced. Therefore, the influence of the solution and exsolution should be considered in the study of the migration and accumulation mechanism of natural gas.

Purification and biochemical properties of carboxylesterase from fasciola gigantica

Carboxylesterase was purified from Fasciola gigantica through ammonium sulfate precipitation, chromatography on DEAE-Sepharose and gel filtration on a sephacryl S300. Three enzymes (EI, EII and EIII) were separated. EII and EIII were purified to homogeneity. The molecular weight of EII and EIII enzyme were 66 and 50 KDa, respectively as detected by gel filtration and SDSpolyacrylamide gel electrophoresis. EII and EIII had Km 1.3 and 1.7 mM of p-nitrophenyl acetate. Affinity of esterase EII and EIII decreased as increasing carbon atom number of the substrates. Esterase EII and EIII had optimum temperature at 40 °C. Esterase EII and EIII had pH optima at pH 7.5 in phosphate buffer and pH 8.0 in Tris–HCl buffer, respectively. Studying effect of metal ions on esterase EII and EIII indicated that Li+, Mn++, Ba++ and Mg++ had activation effect on each isoenzyme. An activation effects could be detected with N- ethylmalimaide on EII and EIII). The order of inhibition on EII was β- mercaptoethanol > PMSF > DTNB > PCMB > iodoacetate. While the order of inhibition on EIII was β-mercaptoethanol > iodoacetate > DTNB> PCM > PMSF.Keywords: Carboxylesterase, Fasciola gigantica; Purification; Characterization; p-Nitrophenyl; α-Naphthyl; β-Naphthyl; Esters

Continuous Shape- and Spectroscopy-Tuning of Hematite Nanocrystals

Uniform hexagonal hematite (α-Fe(2)O(3)) nanoplates have been synthesized by a facile alcohol-thermal reaction, and a new nanostructure of α-Fe(2)O(3) has been proposed. Each nanoplate is enclosed by (0001) basal planes and {1012} side surfaces. The phase, size, shape, and growth orientation of these nanocrystals were characterized by powder X-ray diffraction and electron microscopy. The thickness and diameter of these nanocrystals could be finely tuned by the selective use of alcohol solvent with increasing carbon atom number in the linear alkyl chain. A variety of nanocrystals with systemically changeable shapes from nanoplates to nanograins have been obtained. Specific adsorption of alcohol molecules on polar (0001) facets is proposed to be the main issue to modify the growth behavior of hematite nanocrystals. The presence of distilled water and the addition of sodium acetate have also been investigated. Either of them has a great influence on the growth of hematite nanocrystals, and shape-controlled growth can be rationally achieved. In addition, the post-aging of as-grown hematite nanocrystals in alcohol and distilled water has also been described. Both vibration spectroscopy (i.e., FTIR and Raman) and electronic spectra (diffused reflectance spectra) of these nanocrystals with a continuing shape change show a highly shape-dependent nature.

Solubilities of AOT Analogues Surfactants in Supercritical CO2 and HFC-134a Fluids

A series of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) analogue surfactants [sodium dibutyl sulfosuccinate (DBSS), sodium dipentyl sulfosuccinate (DPSS), sodium dihexyl sulfosuccinate (DHSS), and sodium dioctyl sulfosuccinate (DOSS)] were synthesized and characterized with 1H NMR and elemental analysis. The solubilities of surfactants in supercritical CO2 (scCO2) and supercritical 1,1,1,2-tetrafluoroethane (HFC-134a) fluids at a temperature range from (308 to 338) K and under pressures of (10 to 30) MPa were measured using a static method coupled with gravimetric analysis. The solubilities of these surfactants are much higher in HFC-134a fluid as compared with that in scCO2. The solubilities increased with increasing temperature and pressure for both scCO2 and HFC-134a fluids. The solubilities in scCO2 increased with increasing carbon atom number of surfactant, whereas they decreased with increasing carbon atom number of surfactant in HFC-134a. The density of scCO2 was simulated with the Peng−Robinson ...

Dynamic and equilibrium surface tensions of surfactin aqueous solutions

AbstractA homologous series of surfactins containing β‐hydroxy fatty acids having 13, 14, or 15 carbon atoms were isolated from the supernatant of Bacillus subtilis strain S499 cultures. Their surface‐active properties at the air‐water interface were then evaluated. Dynamic surface tension data were analyzed by the relaxation function γt=γm+(γo−γm)/[1+(t/t*)n]. Based on various parameters t*, n, vmax, γm calculated from this equation, the dynamic surface properties of surfactin were found to depend on both bulk concentration and hydrophobic character of the alkyl chain. At low concentrations of surfactin, the dynamic surface tension (γd) decreased with increasing carbon atom number of the surfactin alkyl chain (n=13 to 15). However, at high concentrations, the maximum decrease of 41‐4 was achieved by surfactin‐C14. In contrast, more strongly hydrophobic alkyl chains in surfactins always enhanced their ability in reducing the equilibrium surface tensions and their aptitude in forming micelles.

Minimum in the temperature dependence of the Kováts retention indices of nitroalkanes and alkanenitriles on an apolar phase

The Kováts retention indices ( I) of 1-nitroalkanes and alkanenitriles were determined on polydimethylsiloxane and Innowax (polyethylene glycol) columns in a wide temperature range. The temperature dependence of the retention indices exhibits a definite minimum for the early members of the homologous series. The position of the minimum shifts to lower temperatures with increasing carbon atom number of the solute. The thermodynamic explanation of an extreme in the I vs. T function is the higher solvation heat capacities of nitroalkanes and alkanenitriles relative to those of the reference n-alkanes, owing to the deviation from the ideal state in the solution. A novel equation was derived which describes the minimum in the I vs. T function, too.

Rearrangement processes of bis-(η 5-alkylcyclopentadienyl)-zirconium dichlorides under electron impact

Rearrangement processes occurring in compounds (C 5H 4R) 2ZrCl 2 (R  H, Me, nPr, iPr, nBu, tBu) and (C 5Me 5) 2ZrCl 2 under electron impact have been studied. The structure of an alkyl substituent in a cyclopentadienyl ligand has been shown to determine the dissociative ionization direction. The availability of a hydrogen atom at a substituent α-carbon atom alone gives the possibility of preceding the rearrangement process with the elimination of an HCl molecule from a molecular ion. The role of the process above increase with increasing carbon atom number in the alkyl substituent of the normal structure. The complete substituent of hydrogen atoms by methyl groups in a cyclopentadienyl ring reduces the probability of the rearrangement process with HCl elimination occurring due to steric hindrances. On the basis of the decomposition of the compound [C 5H 5C(D)Me 2] 2ZrCl 2, direct evidence of the participation of the hydrogen atoms at the substituent α-carbon atoms in the rearrangement processes has been obtained. The elimination of a DCl molecule has been demonstrated to be one of the directions of molecular ion decomposition. The subsequent abstraction of an HCl molecule is suggested to result from deutero-hydrogen exchange or the participation of methyl groups in the substituent.

The electron spin resonance and absorption spectra of microsomal cytochrome P-450 and its isocyanide complexes

The absorption spectra of oxidized P-450-isocyanide complexes were the same in difference spectra irrespective of the isocyanide derivative tested. However, with these reduced P-450-isocyanide complexes, absorption at 455 mμ increased, and that at 430 mμ decreased, with increasing carbon atom number of the isocyanide derivative at a definite pH. The same changes were seen with individual complexes with increasing pH. The dissociation constants of oxidized P-450-isocyanide complexes decreased with increase in carbon atom number of the isocyanide. These results were confirmed by electron spin resonance (ESR) spectroscopy. However, the dissociation constants of reduced P-450-isocyanide complexes were essentially identical and the dissociation constants of the oxidized and reduced P-450-isocyanide complexes were little affected by pH. The oxidized P-450-isocyanide complexes gave magnetically specific ESR signals. The orbital energy differences of d ε orbitals of the heme iron of the complexes increased with increase in the carbon atom number of the isocyanide. Purified P-450 and its isocyanide complexes were rapidly reduced by a ferredoxin-NADP + reductase system.