18 research outputs found
Widely adaptable oil-in-water gel emulsions stabilized by an amphiphilic hydrogelator derived from dehydroabietic acid
A surfactant, R-6-AO, derived from dehydroabietic acid has been synthesized. It behaves as a highly efficient low-molecular-weight hydrogelator with an extremely low critical gelation concentration (CGC) of 0.18 wt % (4 mm). R-6-AO not only stabilizes oil-in-water (O/W) emulsions at concentrations above its critical micelle concentration (cmc) of 0.6 mm, but also forms gel emulsions at concentrations beyond the CGC with the oil volume fraction freely adjustable between 2 % and 95 %. Cryo-TEM images reveal that R-6-AO molecules self-assemble into left-handed helical fibers with cross-sectional diameters of about 10 nm in pure water, which can be turned to very stable hydrogels at concentrations above the CGC. The gel emulsions stabilized by R-6-AO can be prepared with different oils (n-dodecane, n-decane, n-octane, soybean oil, olive oil, tricaprylin) owing to the tricyclic diterpene hydrophobic structure in their molecules that enables them to adopt a unique arrangement in the fibers
Dioctyl Glyceryl Ether Ethoxylates as Surfactants for Surfactant–Polymer Flooding
Enhanced
oil recovery by chemical flooding has been a main measure for postponing
the overall decline of crude oil output in China, and surfactant–polymer
(SP) flooding may replace alkali–surfactant–polymer
flooding in the future for avoiding the undesired effects of using
caustic alkali. In this paper, a series of double alkyl non-ionic
surfactants, 1,3-dioctyl glyceryl ether ethoxylates (diC<sub>8</sub>GE-E<sub><i>n</i></sub>, where <i>n</i> = 4.6–15.8),
were synthesized and characterized and the effects of the ethylene
oxide (EO) number on their properties were evaluated. The results
show that diC<sub>8</sub>GE-E<sub><i>n</i></sub> are highly
surface-active, as reflected by their low critical micelle concentration
(cmc) (<2 × 10<sup>–5</sup> mol/L) and low γ<sub>cmc</sub> (<30 mN/m). Specifically, the member with the shortest
EO chain (diC<sub>8</sub>GE-E<sub>4.6</sub>), which gives a saturated
adsorption (5.81 × 10<sup>–10</sup> mol/cm<sup>2</sup>) nearly double that of others (2.94–2.63 × 10<sup>–10</sup> mol/cm<sup>2</sup>) at the air/water interface, can reduce
Daqing crude oil/connate water interfacial tension (IFT) to ultralow
(<0.01 mN/m) solely at 5 mM at 45 °C.
The members with larger EO numbers, although cannot reduce Daqing
crude oil/connate water IFT to ultralow solely, are very good hydrophilic
components superior to a typical monoalkyl non-ionic surfactant, such
as polyoxyethylene (10) monododecyl ether (C<sub>12</sub>E<sub>10</sub>), when mixed with a hydrophobic surfactant, didodecyl methyl hydroxylpropyl
sulfobetaine (diC<sub>12</sub>HSB), for SP flooding free of alkali.
At optimum formulation, the molar fraction of diC<sub>8</sub>GE-E<sub><i>n</i></sub> can be decreased from 0.85 to 0.45 with
increasing <i>n</i> from 8.0 to 15.8 and ultralow IFT can
be easily achieved at a wide effective concentration range (0.3–10
mM) thanks to the larger interaction of the double alkyl chains in
the molecules with the oil. Derived from commercially available materials
and produced by commercially realizable technology, these surfactants
are therefore practically significant for SP flooding
Inhibiting Hydrophobization of Sandstones via Adsorption of Alkyl Carboxyl Betaines in Surfactant–Polymer Flooding Using Poly Alkylammonium Bromides
Alkyl carboxyl betaines are good
surfactants for reducing crude
oil/connate water interfacial tension (IFT) in the absence of alkali
and are therefore potential surfactants for surfactant–polymer
(SP) flooding. However, they suffer from high adsorption retention
and hydrophobizing sandstones by forming a monolayer at the sandstone/water
interface with head-on configuration, which brings a risk of making
the sandstone surfaces oily wet. In this paper, a poly alkylammonium
bromide, <i>N</i><sup>1</sup>,<i>N</i><sup>1</sup>′-(propane-1,3- diyl) bisÂ(<i>N</i><sup>1</sup>,<i>N</i><sup>1</sup>,<i>N</i><sup>3</sup>,<i>N</i><sup>3</sup>,<i>N</i><sup>3</sup>-pentaÂmethylÂpropane-1,3-diaminium)
bromide, abbreviated as tetra-<i>N</i>(3)-Br, was synthesized
and its properties in inhibiting the hydrophobization of sandstones
via adsorption of alkyl carboxyl betaines were examined. The results
indicate that alkyl carboxyl betaines with either single or double
long alkyl chains can hydrophobize significantly the negatively charged
solid surfaces even in neutral aqueous media by forming a monolayer
at solid/water interface with head-on configuration. The tetra-<i>N</i>(3)-Br, which has a high positive charge density, can adsorb
strongly at negatively charged solid/water interface with the adsorption
depending only on its equilibrium concentration regardless of the
presence of alkyl carboxyl betaines. The negative charges on the solid
surfaces are neutralized, the adsorption of alkyl carboxyl betaines
is significantly inhibited, and the effective concentration of the
tetra-<i>N</i>(3)-Br is as low as 10<sup>–6</sup> mol/L. On the other hand the presence of tetra-<i>N</i>(3)-Br in aqueous solution does not affect the IFT behavior of alkyl
carboxyl betaines in a wide concentration range up to 0.1 mM. Tetra-<i>N</i>(3)-Br is thus an excellent agent in inhibiting hydrophobization
of sandstones via adsorption of alkyl carboxyl betaines in SP flooding