Abstract:Evaluation of the physical-chemical properties of aqueous solutions of nonionic surfactants based on polyoxides can be performed by different methods. Depending on the technique used, there can be a significant variation in the critical micelle concentration (CMC) found. This is related to the sensitivity of the technique regarding the unimers and micelles present in the solution as well as the structure of the surfactant evaluated. In this work, the CMC values of aqueous solutions of linear and branched pol… Show more
“…The linear (L) and branched (B) PEO-PPO block copolymers used here were employed in a previous work 28 as demulsifiers, and it was observed that the branched copolymer was more efficient in breaking the synthetic water-in-oil emulsions tested. This efficiency was associated with: (i) their branched structure, where the EO and PO groups are more distributed in the chains, thus facilitating their dispersion between the phases of the W/O emulsion, and (ii) their average molar mass, since too long chains cannot diffuse through the oil phase because they form agglomerates and too short polymer chains diffuse too slowly, so requiring a molar mass near to an optimal value.…”
Section: Tests In the Presence Of The Demulsifier Additivesmentioning
O petróleo é produzido na forma de emulsão água em óleo e os asfaltenos são considerados os principais responsáveis pela estabilização dessas emulsões. O objetivo deste trabalho foi avaliar a influência de diferentes frações asfaltênicas sobre a estabilidade de emulsões modelo de petróleo (salmoura em asfaltenos/tolueno) e sobre a eficiência de desemulsificantes. A estabilidade das emulsões foi acompanhada pelo ensaio de garrafa, com e sem a adição de desemulsificante. Os resultados mostram que a amostra de asfaltenos com larga distribuição de polaridade promove maior estabilidade da emulsão do que a amostra com distribuição mais estreita e polaridade intermediária. Além disso, a eficiência do desemulsificante na separação das emulsões está diretamente relacionada à estabilidade original da emulsão. Resultados de tensão interfacial evidenciaram a eficiência de deslocamento dos asfaltenos pelos tensoativos desemulsificantes, o que ocorreu com maior eficiência para as emulsões contendo frações de asfaltenos com distribuição estreita e polaridade intermediária.Crude oil is produced as water-in-oil emulsion, and asphaltenes have been considered the main responsible by their stabilization. The aim of this work was to evaluate the influence of the asphaltenes subfractions on the stability of petroleum model emulsions and on the efficiency of demulsifiers. Model water-in-oil emulsions were prepared: aqueous phase of brine and oil phase of asphaltenes in toluene. Different asphaltenes fractions were used. The emulsions' stability was assessed by the bottle test, with and without adding demulsifier. The results show that a sample of asphaltenes with broad polarity distribution promotes greater emulsion stability than a sample with narrow distribution and intermediate polarity. Besides this, the efficiency of demulsifiers in separating the emulsions is directly related to the original stability of the emulsion. Measurements of the interfacial tension revealed the efficiency of displacement of the asphaltenes by the demulsifiers, which occurred more efficiently for the emulsions containing asphaltenes fractions with narrow distribution and intermediate polarity.
“…The linear (L) and branched (B) PEO-PPO block copolymers used here were employed in a previous work 28 as demulsifiers, and it was observed that the branched copolymer was more efficient in breaking the synthetic water-in-oil emulsions tested. This efficiency was associated with: (i) their branched structure, where the EO and PO groups are more distributed in the chains, thus facilitating their dispersion between the phases of the W/O emulsion, and (ii) their average molar mass, since too long chains cannot diffuse through the oil phase because they form agglomerates and too short polymer chains diffuse too slowly, so requiring a molar mass near to an optimal value.…”
Section: Tests In the Presence Of The Demulsifier Additivesmentioning
O petróleo é produzido na forma de emulsão água em óleo e os asfaltenos são considerados os principais responsáveis pela estabilização dessas emulsões. O objetivo deste trabalho foi avaliar a influência de diferentes frações asfaltênicas sobre a estabilidade de emulsões modelo de petróleo (salmoura em asfaltenos/tolueno) e sobre a eficiência de desemulsificantes. A estabilidade das emulsões foi acompanhada pelo ensaio de garrafa, com e sem a adição de desemulsificante. Os resultados mostram que a amostra de asfaltenos com larga distribuição de polaridade promove maior estabilidade da emulsão do que a amostra com distribuição mais estreita e polaridade intermediária. Além disso, a eficiência do desemulsificante na separação das emulsões está diretamente relacionada à estabilidade original da emulsão. Resultados de tensão interfacial evidenciaram a eficiência de deslocamento dos asfaltenos pelos tensoativos desemulsificantes, o que ocorreu com maior eficiência para as emulsões contendo frações de asfaltenos com distribuição estreita e polaridade intermediária.Crude oil is produced as water-in-oil emulsion, and asphaltenes have been considered the main responsible by their stabilization. The aim of this work was to evaluate the influence of the asphaltenes subfractions on the stability of petroleum model emulsions and on the efficiency of demulsifiers. Model water-in-oil emulsions were prepared: aqueous phase of brine and oil phase of asphaltenes in toluene. Different asphaltenes fractions were used. The emulsions' stability was assessed by the bottle test, with and without adding demulsifier. The results show that a sample of asphaltenes with broad polarity distribution promotes greater emulsion stability than a sample with narrow distribution and intermediate polarity. Besides this, the efficiency of demulsifiers in separating the emulsions is directly related to the original stability of the emulsion. Measurements of the interfacial tension revealed the efficiency of displacement of the asphaltenes by the demulsifiers, which occurred more efficiently for the emulsions containing asphaltenes fractions with narrow distribution and intermediate polarity.
“…42 To study the micellar behaviors of the heterograft copolymers herein with different compositions of PCL and PEG, the fluorescence technique has been employed and pyrene was used as a probe. As reported by Wilhelm et al, 47,48 pyrene molecules will transfer into hydrophobic microdomains with a concurrent change in the molecule's photophysical properties. In the excitation spectra, a sharp rise in the intensity ratio of the peaks at 338 and 333 nm of pyrene indicates the onset of micellization (CMC) for the amphiphilic copolymers.…”
Section: Micellization Of Heterograft Copolymersmentioning
confidence: 83%
“…Fluorescence excitation spectra were recorded on a HITACHI F-4500 fluorescence spectrometer at 390 nm emission wavelength and 2.5 nm slit width. Sample solutions for fluorescence investigation were obtained according to the literature, 47,48 and the concentration of the aqueous solutions ranged from 1.0 Â 10 À7 to 0.5 mg/mL. The pyrene concentration in the micellar solution was 6.0 Â 10 À7 mol/L.…”
Novel amphiphilic heterograft copolymers consisting of phosphoester functionalized PEG (phosPEG) and PCL (phosPCL) were synthesized by the ring-opening polymerization via ''grafting through'' method. The heterograft structure and thermal properties of these copolymers with various compositions were characterized by 1 H-NMR, 31 P NMR, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC) in detail. These amphiphilic copolymers could self-assemble into micellar structures in aqueous solution, and their critical micellization concentrations (CMC) were determined to be 0.69-1.25 mg/L by fluorescence technique. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements show that these heterograft copolymer micelles are spherical in shape with the particle size ranging from 20 to 60 nm, which has potential in biomedical application.
“…As mentioned already, the PEO-PPO block copolymers and silicon polyethers grafted with PEO and PPO chains have a peculiar behavior when dissolved in water, because these solutions cloud when submitted to temperature variations, according to their affinities and interactions with the water molecules (Mansur et al, 2007;Silva et al, 2009).…”
Section: Solubility Tests Of the Additivesmentioning
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