Middle‐phase microemulsion with CO2 responsiveness
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Abstract Crude oil is the most exploited energy source and the best way to increase the yield of oil recovery is the use of middle‐phase microemulsions. But the consecutive formation of water‐in‐oil emulsions needs oil–water separation. Reversible middle‐phase microemulsions were prepared with tetradecane (equivalent alkane for crude oil from Xinjiang oilfields, China) and aqueous solutions containing 1‐pentanol, N , N ‐dimethyltetradecylamine and NaCl, and stimulated with CO 2 . By adding and removing CO 2 , the conductivity of aqueous solutions without NaCl increases from 20 μS/cm to 3.6 mS/cm reversibly. Additionally, the surface and interfacial tensions of aqueous solution show reversible changes. The middle‐phase microemulsion is stable in CO 2 atmosphere. After removing CO 2 , it becomes separated into oil and aqueous phases. However, by sparging CO 2 and standing for 2 days, it becomes middle‐phase microemulsion again. This research is expected to launch a brand‐new avenue for the CO 2 ‐stimulated reversible microemulsification.Keywords:
Microemulsion
Aqueous two-phase system
Tetradecane
Alkane
Dodecane
In this work we discuss the oil chain length dependence of ternary DDAB microemulsions, comparing decane, dodecane, and tetradecane. With dodecane and shorter alkanes the L2 microemulsion phase extends to the oil corner, while with tetradecane the microemulsion phase forms an island in the center of the ternary phase diagram. We present new NMR self-diffusion and 14N NMR relaxation data, where the three systems are compared at similar compositions. It is argued that the disconnection of the microemulsion phase from the oil corner with longer oils is associated with the Winsor II to Winsor III transition known from nonionic microemulsions. It follows that the tetradecane microemulsion has, in a major part, a monolayer rather than a bilayer structure.
Microemulsion
Tetradecane
Dodecane
Decane
Alkane
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Hydroisomerization of n-heptane and n-tetradecane over Pt/SAPO-11 catalyst with 0.6% Pt loading was carried out in a fixed-bed, down-flow reactor at 200℃～420℃, 0.5MPa, WHSV of 2.0h-1. Under such conditions, 90% selectivity to isomers was achieved at high n-alkane conversions. When the conversion was less than 55%,C_7 and C_14 followed the same reaction pathway, which means that the relative reaction rates of isomerization to cracking were same for both alkanes. Based on the product distribution, the reaction network of the n-alkane hydroconversion over Pt/SAPO-11 was proposed. Moreover, the results of the catalytic reaction tests strongly suggest that the isomerization of paraffin occurs inside the SAPO-11 channel.
Tetradecane
Alkane
Heptane
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Tetradecane
Dodecane
Alkane
Hexadecane
Isobar
Octadecane
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Citations (21)
Measurements at 25 °C are reported for the volumes of mixing of binary mixtures of n-dodecane + 2 methyl pentane and of ternary mixtures created by mixing an equimolar mixture of (n-decane + n-tetradecane) with each of the isomers of hexane. The results are compared with the work of Hamam etal. for binary mixtures of n-dodecane with the hexane isomers and shown to be in accord with the principle of congruence within the limits of experimental accuracy of the measurements.
Tetradecane
Alkane
Pentane
Dodecane
Decane
Hexane
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The liquid–liquid equilibrium (LLE) curves for 2-phenylethan-1-ol (2-phenylethanol, 2PhEtOH) + octane, + decane, + dodecane, + tetradecane or + 2,2,4-trimethylpentane have been determined by a method of turbidimetry using a laser scattering technique. Experimental results reveal that the systems are characterized by an upper critical solution temperature (UCST), which increases linearly with the number of C atoms of the n-alkane. In addition, the LLE curves have a rather horizontal top and become skewed to higher mole fractions of the n-alkane, when its size increases. For a given n-alkane, UCST decreases as follows: phenol > phenylmethanol > 2-PhEtOH, indicating that dipolar interactions decrease in the same sequence. This has been ascribed to a weakening in the same order of the proximity effects between the phenyl and OH groups of the aromatic alkanols. DISQUAC interaction parameters for OH/aliphatic and OH/aromatic contacts in the investigated systems are reported. Phenol, or phenylmethanol or 2-PhEtOH, + n-alkane mixtures only differ by the first dispersive Gibbs energy interaction parameter for the (OH/aliphatic) contact.
Alkane
Tetradecane
Dodecane
Decane
Hexadecane
Turbidimetry
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Measurements at 25 °C are reported for the enthalpies of mixing of 2-methyl pentane with n-dodecane and with each of three pseudo n-dodecanes prepared from equimolar mixtures of n-undecane + n-tridecane, n-decane + n-tetradecane, and n-octane + n-hexadecane respectively. Measurements for mixtures of the equimolar decane + tetradecane mixture with each of the other three branched hexane isomers are also reported. The results are compared with the work of Benson and co-workers for binary mixtures of n-dodecane with the same hexanes. The deviations of 1–2% from the principle of congruence are similar to those reported previously for the ternary n-alkane mixtures.
Tetradecane
Alkane
Decane
Dodecane
Undecane
Hexadecane
Pentane
Octadecane
Hexane
Heptadecane
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Microemulsion
Dodecane
Hexane
Brine
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Liquid−liquid equilibria temperatures for systems of 2,5,8,11-tetraoxadodecane with decane and tetradecane and of 2,5,8,11,14-pentaoxapentadecane with heptane, octane, and tetradecane have been measured between 264.85 K and the upper critical solution temperature (UCST). The coexistence curves were determined visually. They have a rather horizontal top, and their symmetry depends on the size of the alkane. For a given alkane, the UCST is higher for mixtures containing the pentaether. This reveals that dipole−dipole interactions between oxaalkane molecules are stronger in such solutions.
Tetradecane
Decane
Alkane
Heptane
Liquid liquid
Dodecane
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Tetradecane
Alkane
Alkylbenzenes
Heptane
Decane
Dodecane
Cyclopentanes
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Microemulsion
Dodecane
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Citations (25)