Molecular dynamics simulations of CO₂ permeation through ionic liquids confined in γ-alumina nanopores

<p>CO₂ permeation through imidazolium-based ionic liquids (ILs, [BMIM][Ac], [EMIM][Ac], [OMIM][Ac], [BMIM][BF₄], and [BMIM][PF₆]) confined in 1.0, 2.0, and 3.5 nm γ-alumina pores was investigated using molecular dynamics simulation. It was found that the nanopore confinement effect influenced the structure of confined ILs greatly, resulting in a layered structure and anisotropic orientation of ILs. In the center of 2.0-nm pore, the long alkyl chain of [BMIM]⁺ tended to be parallel to the wall, providing a straight diffusion path benefiting the CO₂ permeation. The CO₂ diffusion coefficients in confined [EMIM][Ac], [BMIM][Ac], and [OMIM][Ac] were 2.3–4.1, 2.4–6.4, and 14.4–21.7 × 10⁻¹⁰ m² s⁻¹, respectively. This order was opposite to that in the bulk ILs, because the longer alkyl chain led to a more ordered structure, facilitating CO₂ diffusion. In addition, the CO₂ solubilities were 445–722 mol m⁻³ MPa⁻¹ for the five ILs confined in 1.0 nm pore, which were larger than those in 2.0 and 3.5 nm pores (196–335 mol·m⁻³ MPa⁻¹), due to the larger free volume. Both parallel orientation of alkyl chain and large free volume could increase the CO₂ permeability in confined ILs.</p

Critical Microemulsion Concentration and Molar Ratio of Water-to-Surfactant of Supercritical CO₂ Microemulsions with Commercial Nonionic Surfactants: Experiment and Molecular Dynamics Simulation

The critical microemulsion concentration (cμc) and the molar ratio of water-to-surfactant (<i>W</i>₀) of supercritical CO₂ (scCO₂) microemulsion that uses different nonionic hydrocarbon surfactants (LS-36, LS-45, LS-54, DYNOL-604, TMN-6) were examined at temperatures from 35 to 45 °C and pressures up to 19 MPa. The results show that the cμc mainly depends on the structure of the surfactant. The surfactant with more hydrophilic structure, such as the ethylene oxide (EO) group and hydroxyl, tends to produce a higher cμc. In addition, the cμc increases with the increase of the ratio of ethylene oxide (EO) group number to the propylene oxide (PO) group number of the surfactant. The capacity of the microemulsion system to dissolve water, which is characterized by <i>W</i>₀, is related to the concentration and structure of surfactant. It is found that a higher solubility of surfactant in CO₂ favors the system to dissolve water at lower pressure. At higher pressure, the stronger hydrophilicity of surfactant and the higher surfactant concentration are beneficial for microemulsions to contain more water. The molecular dynamics (MD) simulation, which was conducted in the NPT ensemble, shows the spontaneous evolution of a surfactant cluster and microstructure of microemulsion at different conditions. It demonstrates that the microemulsion system with more water molecules can form a larger water cluster and catch more surfactants although a few surfactants dissociate in the continuous phase. The experimental data and MD simulation results provide useful infomation for the structure regulation of the scCO₂ microemulsion and expand the study to the microscopic scale

Journal officiel du Haut-Sénégal-Niger

15 novembre 19241924/11/15 (A19,N443)

Additional file 14: Text S2. of Metabolic capability and in situ activity of microorganisms in an oil reservoir

Supplementary materials and methods. (DOCX 29 kb

Additional file 7: Figure S2. of Metabolic capability and in situ activity of microorganisms in an oil reservoir

Proposed Syntrophic model for (a) Methanosaeta and (b) Archaeoglobus. The expression level of each gene is represented by bars (pink and blue), with one bar representing FPKM value of 10. Genes for which not transcripts could be mapped (FPKM value = 0) are marked in red. (TIFF 1778 kb

Additional file 6: Figure S1. of Metabolic capability and in situ activity of microorganisms in an oil reservoir

Phylogenetic tree of amino acid sequences of assA genes. (PNG 287 kb

Additional file 8: Table S6. of Metabolic capability and in situ activity of microorganisms in an oil reservoir

Annotation and FPKM value of hydrocarbon degradation and methanogenesis related genes in GBs (separate file). Annotation of studied GBs was done by a combined effort of RAST server and KEGG database. (XLSX 429 kb

Additional file 13: Text S1. of Metabolic capability and in situ activity of microorganisms in an oil reservoir

Supplementary results and discussion. (DOCX 17 kb

Additional file 1: Table S1. of Metabolic capability and in situ activity of microorganisms in an oil reservoir

Summary of assembled contigs. (DOCX 14 kb

Additional file 12: Table S8. of Metabolic capability and in situ activity of microorganisms in an oil reservoir

Geochemical characterization of production water from three wells from the Jiangsu oil field, China. (* ND, not detected.) (DOCX 15 kb