Semi-Fluorinated Trialkyltin Fluorides and Fluorinated Telechelic Ionomers as Viscosity-Enhancing Agents for Carbon Dioxide

Abstract

Direct thickeners for dense carbon dioxide were designed and synthesized. Each thickener contained “CO2-philic” fluorinated groups to impart solubility in carbon dioxide and “CO2-phobic” functionalities to promote intermolecular associations for viscosity enhancement. Semi-fluorinated trialkyltin fluorides and fluorinated telechelic ionomers were soluble to at least several weight percent in dense liquid carbon dioxide without the use of a cosolvent. Increases in solution viscosity at 297 K were measured using falling cylinder viscometry. The viscosity of liquid carbon dioxide was increased by a factor of 2−3 at thickener concentrations of 2−4 wt %. These results demonstrate that carbon dioxide viscosity enhancement is possible without the need for a cosolvent through the design of compounds with the appropriate balance of CO2-philic groups for solubility and CO2-phobic associating groups for macromolecular, viscosity-enhancing interactions. Neither compound, however, was as effective as the (29% styrene−71% fluoroacrylate) copolymer we recently developed. More substantial increases in solution viscosity were not attained with the semi-fluorinated trialkyltin fluoride because the fluorinated alkyl chains disrupted the associations that formed viscosity-enhancing, weakly associating, linear polymers. The viscosity increases obtained with the telechelic ionomer were also less than expected because of the relatively low molecular weight of the carbon-dioxide-soluble ionomers. Higher-molecular-weight ionomers would not be CO2-soluble, however.

Viscosity measurements on gas expanded liquid systems—Methanol and carbon dioxide

“…Assuming similar flow regimes within the annulus and concentric fall of the weight during calibration and subsequent viscosity determinations, correlations in the form of Eq. (2) have been widely used to determine the viscosity of other Newtonian fluids relative to the calibration fluids [9,17,20,22,29,39,[44][45][46][47][48].…”

“…The falling-weight viscometer has been used extensively in the past for the determination of viscosities in systems under high pressure [9,14,17,[19][20][21][22][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The falling-weight viscometer is relatively simple in construction, is easily adaptable for highpressure applications and typically exhibits high repeatability and accuracy.…”

“…The viscosities of mixtures under supercritical conditions have also been recently investigated [9,[14][15][16][17][18][19][20][21][22][23][24][25].…”

Shape Transitions in Supercritical CO2 Microemulsions Induced by Hydrotropes

“…The main disadvantage of using CO2 in EOR is the very low viscosity, which does not readily facilitate transport over oil bearing reservoirs, but rather through porous media (fingering) which occurs to make a pathway of least resistance 6 . There is therefore a need to develop systems that can enhance CO2 viscosity [7][8][9][10][11] .…”

Hydrophobic and oleophobic surface modification using fluorinated bis-urea and bis-amide gelators

“…For example, CO 2 is used extensively as a flooding agent for enhanced oil recovery from underground formations [28,29]. Various additives have been used to increase the viscosity of CO 2 in an attempt to improve oil recovery efficiency and production rates by more closely aligning the mobilities of the CO 2 and oil in the reservoir [30]. There are many reports on new gelators for CO 2 , and one primary criterion for their design is incorporation of CO 2 -philic functional moieties such as long chain fluoroalkyl groups in the molecular design [31][32].…”