Effects of CO2 Injection on Phase Behavior of Crude Oil

CO₂ flooding is a win-win technology, sequestrating greenhouse CO₂ while producing a significant amount of crude oil to help defray the cost of CO₂ sequestrating and enhancing oil recovery. However, due to the difference of sedimentary environment and poor properties of formations, physical properties of the crude oil and the effect of CO₂ flooding are not always satisfactory in most oilfields of China. Therefore, in this article, to improve the understanding of the oil recovery mechanisms and feasibility of CO₂ flooding in China, based on the oil and gas of Mao-3 oilfields, phase behavior of the CO₂ and crude oil system was investigated. Parameters like saturated pressure, volume factor, gas oil ratio, and viscosity were measured and their relationships analyzed. Results show that crude oil of Mao-3 reservoir and CO₂ has good mutual dissolution under reservoir conditions, and CO₂ could expand the oil and reduce the oil viscosity greatly. As a result, formation energy could be enhanced and flow characteristics of the oil could be improved by CO₂ flooding.     

On the bond order of C2 and N2

The commonly adopted bond order values of C₂ and N₂ are critically investigated with a new bond order concept. Ab initio calculations with extended basis sets suggest that C₂ can be described by a double to triple bond closer to acetylene than to ethylene and N₂ by a triple bond. The basis set dependence is discussed. Also a relation between the number of basis functions, MO's and non-vanishing eigenvalues of the bond order parts of the density matrix is presented.     

The solubility of CO2 and N2O in olive oil

The solubility of CO₂ and N₂O in olive oil has been measured at temperatures of about 298, 310, and 323 K with a gravimetric microbalance under pressures up to 2 MPa. The molecular weight of olive oil has been analyzed and found to be about 882 g mol⁻¹ as a mixed oil compound. The observed solubility data have been correlated with a cubic equation of state (EOS) model. N₂O has a larger solubility than CO₂ in olive oil based on either the mole or mass fraction. The present results clarify some ambiguities from the previous N₂O solubility data in the literature.     

Encapsulation of Pd(II) by N4 and N2O2 macrocyclic ligands: their use in catalysis and biology

New macrocyclic Schiff base Pd(II) compounds were synthesized by treating N₄ and N₂O₂ macrocycles with palladium chloride in a 1 : 1 ratio. The resulting macrocyclic compounds were characterized by elemental, IR, ¹H-NMR, ¹³C-NMR, mass, molar conductance, magnetic susceptibility, electronic spectra, and thermal analysis. These compounds were used as catalysts in the development of an efficient catalytic method for reduction of organic substrates having nitro, olefinic, acetylenic, and aldehyde groups under mild reaction conditions. The biological activities of all the macrocycles and macrocyclic Pd(II) compounds have been tested against gram positive (Bacillus subtilis and Staphylococcus aureus) and gram negative (Escherichia coli and Klebsiella pneumonia) bacteria and found to be more active than commercially available antibacterial drugs like Streptomycin and Ampicillin.     

Synthesis and metal-ion binding properties of new N2S4- and N2S5-donor macrocycles

Synthetic procedures for new N₂S₄- and N₂S₅-donor macrocycles (2 and 4) were given. The ligands were prepared by the reaction of NaBH₄ with the appropriate macrocyclic diamide in the presence of boron trifluoride ethyl etherate in dry tetrahydrofuran (THF). Solvent extraction method was used to evaluate metal-ion binding properties of the new ligands. The solvent extraction experiments suggested that the reduced macrocycles have Ag⁺ and Hg²⁺ selectivities compared to Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺, Cu²⁺, Mn²⁺ and Cd²⁺ ions. The extraction constants (log K _ex) and complex compositions were determined for Ag⁺ and Hg²⁺ complex of compound (4).     

Production of N,H, and NH active species in N2-H2 dc flowing discharges

Densities of N, H, and NH active species have been detected by laser-induced fluorescence (LIF) in N₂-xH₂ dc flowing discharges. A peak value of N atom densities far x = 0.2–0.5% and a plateau value of H atom densities between x = 1% and 90% in post-discharge conditions (0.05 sec, p = 2 torr) has been found. Comparison between LIF measurements of N atoms and the trend of the N₂(B, v = II) population shows that the emission from this state can be used for monitoring N atoms. The NH radical has only been detected inside the discharge region.On leave from Instituto Tecnológico de Aeronáutica, CNPq, Brazil.     

CO2/N2-switchable viscoelastic fluids based on a pseudogemini surfactant system

We prepared a CO₂/N₂-switchable pseudogemini surfactant system composed of sodium oleate (NaOA) and N, N, N’, N’-tetramethyl-1, 6-hexanediamine (TMHDA) at a mole ratio of 2:1. The two tertiary amine groups of the TMHDA can be protonated into quaternary ammonium salt when the system was bubbled with CO₂, which can ‘‘bridge’’ two NaOA molecules via electrostatic attraction to form a pseudogemini surfactant. The formed pseudogemini surfactant can further self-assemble to wormlike micelles, causing a sharp increase in viscosity. The viscoelastic property and structure transitions of the pseudogemini surfactant system were investigated before and after bubbling of CO₂. The pseudogemini surfactant system transformed from water-like to gel-like fluid with the bubbling of CO₂, followed by white precipitate. The cryo-transmission electron microscope (cryo-TEM) characterization and rheological measurements exhibited that the sol–gel transition was attributed to a spherical-wormlike micelle transition. Moreover, this transition was switchable at least in three cycles. Finally, a reasonable mechanism of aggregate behavior transition was proposed from the viewpoint of the molecular states, micelle structures, and intermolecular interactions.     

Vibrational frequencies and force constants of N2O4 in complexes with molecules of different solvents determined by Raman spectra andAb initio calculation

The Raman spectra of N₂O₄ solutions in organic solvents have been recorded. The frequencies ofv ₁,v ₂, andv ₃ bands of N₂O₄ increase with increasing solvent electron-donor properties. Especially large changes ofv ₃ N-N stretching band have been observed (254.5 cm^–1 in n-hexane, 276.5 cm^–1 in 1,4-dioxane). The ab initio calculations have shown that the interaction between N₂O₄ and electron-donor molecules causes an increase of N-N and N-O stretching and O-N-O bending force constants of N₂O₄ in agreement with the results of Raman study.     

Nonequilibrium phase diagrams in the PbCl2−AgCl eutectic system

It is well-known that eutectics do not necessarily grow at the eutectic temperature, or with the eutectic composition. Thus, the eutectic point can be shifted due to nonequilibrium conditions in the system. This fact was observed in many experiments. We try to explain this behaviour on base of the study of phase transformation kinetics. We construct the kinetic phase diagrams of PbCl₂?AgCl within the framework as of the nucleation theory as of the theory of growth on the phase interface. Our models are based on the molecular model of the difference of chemical potential of components for the liquid and solid phases. The proposed model describes the position of the eutectic point very well and is practically applied for the study of nonequilibrium directional growth in the PbCl₂?AgCl system.     

Die Phase La2U2N5

In the system U–La–N a new phase of composition La₂U₂N₅ was observed. The differaction pattern of this phase can be indexed with a tetragonal unit cell:a=8.43 Å,c=8.50 Å andc/a=1.008. The pseudocubic sub-cell withaca/2 is closely related to the CsCl-type.

Auszug aus der von der Technisch-Naturwissenschaftlichen Fakuktät der TU Wien approbierten Diplomarbait des Herrn Dipl.-Ing.J. Waldhart.     

Some theoretical aspects of vibrational fine structure accompanying core ionizations in N2 and CO

Ab initio calculations have been carried out on CO and N₂ and the relevant core hole states with different basis sets to investigate differences in geometries and force constants. From these calculations vibrational band profiles of the core level ESCA spectra for these molecules have been interpreted, obviating the need to rely on data pertaining to the equivalent core species. The agreement with experimental profiles is excellent. The O_1s level of CO which has not been subjected to detailed theoretical analysis previously, is predicted to show substantial vibrational structure in excellent agreement with recently acquired experimental data. The effect of temperature on the band profiles has also been considered. Theoretically derived core binding and relaxation energies of these systems have been investigated both as a function of basis set, and of internuclear distance. Density difference contours have been computed and give a straightforward pictorial representation of the substantial electron reorganizations accompanying core ionizations. Small basis sets with valence exponents appropriate to the equivalent core species when used in hole state calculations describe bond lengths, force constants, core binding energies and relaxation energies with an accuracy comparable to that appropriate to the corresponding extended basis set calculations.     

Synthesis,characterization and thermal analysis of [Fe(N2H4)2(CH3COO)2]

[Fe(N₂H₄)₂(CH₃COO)₂] was synthesised and characterized for the first time by chemical analysis, magnetic measurements, electronic and IR spectral studies. Its thermal reactivity was ascertained by thermogravimetric (TG) and derivative thermogravimetric (DTG) techniques and it has been concluded that unlike some other metal carboxylate hydrazinates, it does not show any autocatalytic behaviour. The decomposition was also subjected to kinetic analysis using the equations of Coats-Redfern and Horowitz-Metzger by the method of weighted least-squares.     

N2O4 complexes with electron donor molecules. An STO-3G study

The quantum chemical calculations for N₂O₄ complexes with some electron-donor molecules: CH₃NO₂, CH₃COOH, CH₃CN, C₆H₆ and with another molecule of N₂O₄ show that the donor molecule lies under the N₂O₄ plane and its electron-donor atom points to the center of N-N bond of N₂O₄ (or near this center). The electron charge is transferred from the donor to N₂O₄ molecule, mostly to the N-N bond of N₂O₄.     

A quantum chemical study of the hydrogen bonding in the CO2⋯HF and N2O⋯HF complexes

Summary Quantum chemical ab initio calculations have been performed for the complex CO₂HF and N₂OHF. The interaction energies were computed through fourth order MBPT and were corrected for basis set superposition errors. Extended polarized basis sets were used which are constructed to give accurate values for electric moments and polarizabilities. The complex NNOHF was found to be bent, while OCOHF is linear, in agreement with experiment. The MBPT calculations give evidence for a second linear isomeric structure FHNNO, a possibility which has also been suggested by recent experimental data. The computed binding energies are: 2.5 kcal/mol for OCOHF, 2.4 kcal/mol for NNOHF, and 3.0 kcal/mol for FHNNO. At the SCF level, the FHNNO complex is less stable than NNOHF, but correlation has a large effect on the geometry and energetics of the latter complex. The NNOHF complex seems to be a system where the positive intramolecular correlation correction prevails over the negative intermolecular component.     

Formation and Crystallization Behavior of Gels in the Na2O-SiO2-TiO2-ZrO2 System

SiO₂-TiO₂-ZrO₂ and 5Na₂O·95(SiO₂ + TiO₂ + ZrO₂) gels were synthesized and role of Na₂O in gel formation and crystallization behavior of gels were studied. From Si(OC₂H₅)₄, Ti(iso-OC₃H₇)₄, Zr(n-OC₃H₇)₄ and NaOCH₃ solutions in EtOH without H₂O, transparent and opaque gels were obtained. Opaque bulk gels, rich in TiO₂ or ZrO₂ composition in Na₂O containing SiO₂-TiO₂-ZrO₂ system, contain agglomerated spherical particles of diameter small <10 m, in contrast with opaque gels having large particles <30 m in alkali-free SiO₂-TiO₂-ZrO₂ system. Crystallization temperature (Tc) was measured by DTA on dried gels. Compared with the alkali-free SiO₂-TiO₂-ZrO₂ gels, 5 mol% Na₂O containing gels gave lower Tc in SiO₂ rich compositions and higher in TiO₂ rich or ZrO₂ rich compositions.     

Ion-pair extraction of transition metal cations from aqueous media using novel N2O2-macrocyclic crown ligands

Three new macrocyclic crown ether ligands containing nitrogen–oxygen donor atoms were designed and synthesized from 1,4-bis(2′-formylphenyl)-1,4-dioxabutane and 4-nitro-o-phenylenediamine. Ion-pair extraction of metal picrates such as Ag⁺, Hg²⁺, Cd²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Co²⁺, and Pb²⁺ from aqueous phase to the organic phase was carried out using the novel ligands. The solvent effect over the metal picrate extractions was investigated at 25 ± 0.1 °C by using UV–visible spectrometry. The extractability and the values of the extraction constants (log K_ex) were determined for the extracted complexes.     

He-N2 radiofrequency discharge: Influence of N2 on discharge and afterglow

A diagnostic study q (energy transfer processes in a He-N₂ flowing discharge and afterglow has been performed in a radiofrequency-produced plasma cooled in a liquid nitrogen hath. Optical emission spectroscopy in the visible and infrared spectral range as well as Langrnuir probe diagnostics were used. The vibrational kinetics of CO injected in such an afterglow has been examined. It shows a slow cooling of the electrons in the afterglow regime. The electron kinetics responsible joy CO vibrahonal excitation is turned off when N₂ is added to the He discharge, while that for vibrationally excited N₂ molecules is turned on. The results are discussed on the basis of previous theorerical calculations and experiments on the He-N₂ system.     

Self-Assembled Structures of Diglycerol Monolaurate- and Monomyristate in Olive Oil

We have investigated the phase behavior and self-assembled structures of diglycerol monolaurate-and monomyristate (abbreviated as C₁₂G₂ and C₁₄G₂, respectivley) in olive oil over a wide range of temperatures and compositions. At lower temperatures, both the surfactants appear in solid state (α-solid), which does not swell with olive oil. The α-solid transforms into lamellar liquid crystal (L_α) phase upon heating and the solid melting temperature is practically constant at all surfactant/oil compositions, but the C₁₂G₂ melts earlier than the C₁₄G₂. There appear the dispersions of L_α phase and α-solid in the dilute regions of the C₁₂G₂/olive oil and the C₁₄G₂/olive oil systems, respectively, at 25°C. The L_α phase can solubilize some amount of olive oil, but as the oil concentration increases the excess oil separates out from the L_α phase, and there appears L_α dispersion in the dilute surfactant concentration region. The L_α phase eventually transforms into isotropic solutions (reverse micelles) with further heating. The structures (shape and size) of the reverse micelles have been characterized by small-angle x-ray scattering technique. It has found that the C₁₂G₂ and C₁₄G₂ surfactants form reverse rod-like micelles in olive oil above the L_α melting temperature and the micellar size increases with surfactant concentration, but decreases with temperatures.     

Cs2SO4-C2H5OH-H2O三元体系30℃和50℃的平衡溶解度研究

The solubilities of Cs₂SO₄-C₂H₅OH-H₂O ternary system at 30℃ and 50℃ have been studied using microe-quipment for solubility determination. There appears two phases, alcoholic phase, water phase in the liquid phase. The solubilities of Cs₂SO₄ in water, C₂H₅OH and mixed solvent have been determined. The phase diagram indicated that C₂H₅OH might be salted out by Cs₂SO₄ from this system and the equilibrium solid phase is Cs₂SO₄.     

Anodic TiO2 Nanotube Layers for Wastewater and Air Treatments: Assessment of Performance Using Sulfamethoxazole Degradation and N2O Reduction

The preparation of anodic TiO₂ nanotube layers has been performed using electrochemical anodization of Ti foil for 4 h at different voltages (from 0 V to 80 V). In addition, a TiO₂ thin layer has been also prepared using the sol–gel method. All the photocatalysts have been characterized by XRD, SEM, and DRS to investigate the crystalline phase composition, the surface morphology, and the optical properties, respectively. The performance of the photocatalyst has been assessed in versatile photocatalytic reactions including the reduction of N₂O gas and the oxidation of aqueous sulfamethoxazole. Due to their high specific surface area and excellent charge carriers transport, anodic TiO₂ nanotube layers have exhibited the highest N₂O conversion rate (up to 10% after 22 h) and the highest degradation extent of sulfamethoxazole (about 65% after 4 h) under UVA light. The degradation mechanism of sulfamethoxazole has been investigated by analyzing its transformation products by LC-MS and the predominant role of hydroxyl radicals has been confirmed. Finally, the efficiency of the anodic TiO₂ nanotube layer has been tested in real wastewater reaching up to 45% of sulfamethoxazole degradation after 4 h.