Precipitation decane phase

An hour after the 7.7 wt% sample was cooled back down it looked as clear as at 65°C. However, Spectrum 17 shows that the surfactant molecules were no longer mobile. Evidently they had formed a phase dispersed into units so small — no larger than several hundred Angstroms, probably — that there was no visible scattering. After weeks of standing only a bit of white precipitate appeared, a small fraction of the total surfactant present. It follows that the growth of some of the submicro-scopic units to visible, settling size was the slow step in the subsequent precipitation of the surfactant-decane phase. 

Previous work has shown that binary surfactant systems containing Dowfax 8390 and the branched hydrophobic surfactant AOT can form Winsor III systems with both PCE and decane whereas DOWFAX 8390 by itself cannot (Wu et. al. 1999). This binary surfactant system was used in conjunction with hydrophobic octanoic acid to help with phase behavior and lessen the required concentration of CaCl2. Since this formulation is rather complicated, questions about field robustness arise. Thus, for the phase behavior studies presented here, we used the simple binary system of the nonionic TWEEN 80 and the branched hydrophobic AOT, and we optimized the NaCl concentration to give the Winsor Type III system. The lesser electrolyte concentration requirement for the binary TWEEN 80/ AOT system helps to decrease the potential for undesirable phase behavior such as surfactant precipitation, thereby increasing surfactant system robustness. 

The solubility of the surfactant in decane is also quite small at 25°C, about 0.04 wt%, but over a narrow temperature range around 50°C it rises dramatically, as in the Krafft point range of a single-chain surfactant in water (11a). Such a phenomenon with a surfactant in a nonpolar solvent is not uncommon (35). Incidentally, the absence of a Krafft point range for the surfactant in water between 10 and 90°C argues for the absence of micelles in solution. Abrupt change in the slope of such a property as surface tension versus concentration (9) can be due to precipitation of a new phase as well as to onset of appreciable micelle formation, and so does not constitute conclusive evidence for the latter. 

Finely divided particles of MAO are precipitated from a toluene solution by addition of /3-decane followed by evaporation. Suspension of these particles in decane followed by reaction with toluene solutions of Cp 2ZrCl2 (Cp 2 = Cp2 or Et(Ind)2 ) affords a solid catalyst which can be used in solution or gas-phase polymerization processes using ethylene or propylene as the monomers. Solids also separate from a toluene solution of MAO on addition of an equal volume of hexane or isobutane.Insoluble gels in toluene solutions of MAO, ordinarily a nuisance, can be filtered off, resuspended in aliphatic hydrocarbons, and reacted with metallocene dichlorides to produce active catalysts for olefin polymerization without reactor fouling. 

Titanium alkoxides have been used by various workers as the source of titanium for the synthesis of Ti02 particles via microemulsions. In an early work reported by Guizard et al. [260] a reverse microemulsion was prepared by mixing Triton X-100 (surfactant), decane (oil phase) and water Ti-tetrabutoxide or tetraisopropoxide was added to it for precipitation of particles. 

In another reverse microemulsion method [262], an oil phase/Triton X-35 / H2O mixture was added to an oil phase/Triton X-35/Ti-tetrapropoxide combination to obtain gel particles. Note here that the Triton X series of products can be described as alkylaryl polyether alcohols, the numbers indicating the average number of ethylene oxide units (3 in case of Triton X-35) see also Table 2.2. The oil phase was cyclohexane or decane. Yet another two-microemulsion method used non-ionic surfactants NP-5 and NP-9 (wt ratio 1 1) and cyclohexane as the oil phase [263]. As aqueous phase, the authors used a TiCl4 solution and an ammonia solution. The microemulsions were prepared and mixed at 13 C to obtain titania particles. The suspension was poured into acetone, the precipitate centrifuged, washed with acetone and vacuum dried for 2 h. The particle size was about 5 nm. 

Decantation de- kan- ta-sh3n [NL decan-tare, fr. L de- -f ML cantus edge, fr. L, iron ring round a wheel] (1633) n. Or siphoning off the liquid from a precipitate or sediment or the upper layer of two immiscible liquids as a partial means of separating the phases. 

Pedersen, W.B. Hansen, A.B. Larsen, E. Nielsen, A.B. and Ronningsen, H.P. (1991b). Wax Precipitation from North Sea Crude Oils. 2. Solid-Phase Content as a Fimction of Temperature. Energy Fuels, Vol.5, No.6, pp.908-913, ISSN 0887-0624 Radulescu, A. Schwahn, D. Richter, D. Fetters, L.J. (2003). Co-Crystallization of Poly(Ethylene-Butene) Copolymers and Paraffin Molecules in Decane Studied with Small-Angle Neutron Scattering. Journal of Applied Crystallography, Vol.36, No.4, pp.995-999, ISSN 0021-8898... 

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