Solubility of Nonionic Hydrocarbon Surfactants with Different Hydrophobic Tails in Supercritical CO₂

Abstract

The experiment utilizes a high-pressure view chamber that mainly aims at identifying the effect of surfactant architecture on solubility in CO 2 . First, when solubility pressures of three series of nonionic hydrocarbon surfactants are measured, results reveal that surfactants with a methylated tail exhibit the best solubility. Unexpectedly, surfactants with a branched tail show worse solubility than linear surfactants. This is conjectured to be caused by attractive molecule−molecule interactions. TX45 that possesses the shortest ethylene oxide chain and a highly methylated tail performs the best in CO 2 solubility. Additionally, the experimental study on the solubility of TX45 in CO 2 at T = (318 to 343) K demonstrates that solubility has a direct correlation with pressure and CO 2 density, while it is inversely related to temperature. Finally, when we look at effects of the added alcohols on surfactant TX45 solubility, the results indicate that hexanol is the most effective alcohol in enhancing solubility. The reason is assumed to be that hexanol molecules could insert themselves between surfactant tails and hinder molecule−molecule interactions.

Structural Effects of Nonionic Surfactants on Their Ability to Reduce the Dissolution Pressures of Heavy Hydrocarbons in Supercritical CO2

“…Good solubility of the surfactant in CO 2 is the evidence for its solubility‐improving property. Solubility of the surfactants in scCO 2 decreased with an increase of EO and alkyl chains, according to our previous work (Shi, Jing, Xiong, Liu, & Qiao, ). In this case, apart from the CO 2 needed to dissolve the octacosane, additional CO 2 was required to dissolve the surfactant, which masked its solubility‐improving effect.…”

Water-in-CO2 Microemulsions Stabilized by Fluorinated Cation–Anion Surfactant Pairs

“…(As such W 0 max represents the Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 maximum number of water molecules which can be solubilized by one surfactant molecule). The studies aiming to find efficient CO 2 -philic solubilizers started in the 1990s 4 and continue nowadays [5][6][7][8][9][10][11][12][13][14][15] . Therefore, exploring CO 2 -philic hydrocarbon (HC) surfactants for scCO 2 remains an important task.…”

Cleaning Efficiency of Amino‐Acid Surfactants with Polyoxyethylene Ether and Isopropanol in Liquid Carbon Dioxide

“…Furthermore, if CO 2 is combined with surfactant molecules, an effective removal of insoluble substances could be achieved (Gutiérrez, Bejarano, & Fuente, ). Therefore, four nonionic surfactants with good solubility were chosen as the cosurfactants, and their solubilities in liquid CO 2 have the following order: C12–4 > (PEG) 3 ‐TS > C16(3) ≈ TX‐45 (Shi et al, ; Shi & Qiao, ). In the experiments, the total amount of surfactants was 5.77 × 10 −6 mol, which is the same as that of single surfactant and mixed with the mole ratio of 1:1.…”

“…The chemical structures are depicted in Scheme . Cetyl alcohol‐polyoxyethylene (3) ether (C16(3)), butyl laurate (C12–4), and 3‐(methoxy polyethylene (3) glycol)propyl‐1,1,1,3,5,5,5‐heptamethyltrisiloxane ((PEG) 3 ‐TS) were also synthesized by our research group (Shi et al, ; Shi & Qiao, ). Branched polyoxyethylene (5) isooctylphenyl ether (TX‐45) with a stated purity of 95%+ was purchased from Sigma–Aldrich, St. Louis, USA.…”

“…However, the use of these surfactants at an industrial scale is not a viable option as they are expensive and environmentally unfriendly. Recent studies have shown that new hydrocarbons such as fatty alcohol‐polyoxyethylene ether (C i E j ) (Garate, ; Sandoval & Gárate, ; Sandoval, Gárate, & Olea, ; Sandoval, Gárate, Scavia, Florusse, & Peters, ; Shi, Jing, Xiong, Liu, & Qiao, ), long‐chain fatty‐acid ester (C12–4), and sodium bis‐(2‐ethyl‐1‐hexyl) sulfosuccinate (AOT) (Mohamed et al, ) are soluble and can lead to the formation of reverse micelles in liquid and scCO 2 . Garate () has reported that C i E j molecules would be good detergents in liquid CO 2 .…”