Physicochemical characterization of the PEG8000-Na2SO4 aqueous two-phase system

The polyethylene glycol-sodium sulfate aqueous two-phase system has been characterized at 23 °C. Tielines for the phase diagram were obtained experimentally. Phases in equilibrium were characterized by means of the solvatochromic parameters π*, α, and β, which provide a measurement of the polarity/polarizability and the H-bond donor and acceptor abilities, respectively. The ability of the phases to participate in hydrophobic interactions was characterized by means of the free energy of transfer of a methylene group between the conjugated phases, using the partition of a homologous series of dinitrophenylated amino acids. The results show the effect of the presence of polymer and salt in the aqueous phase, and a comparison of both phases with pure water is made.LSRE-PortoUniversidade Católica PortuguesaEscola Superior de Biotecnologia do PortoFundação para a Ciência e a Tecnologia (FCT

The effect of salts on the liquid–liquid phase equilibria of PEG600 + salt aqueous two-phase systems

Six new ATPSs were prepared by combining polyethylene glycol PEG600 with potassium citrate, dipotassium hydrogen phosphate, sodium formate, potassium formate, sodium sulfate, and lithium sulfate. Complete phase diagrams, including the binodal curve and three tie-lines, were determined at 23 °C. The experimental data obtained for the binodal curve were successfully adjusted to the Merchuk equation, and the reliability of tie-line data was confirmed using the equations suggested by Othmer–Tobias and Bancroft. The ability of each ion to induce ATPS formation was investigated. Na+ proved to be more effective in ATPS formation than K+ and Li+. For potassium salts, the order observed for the effectiveness of the anions was: HPO42– > C6H5O73– > HCO2–. Regarding the sodium salts, it was found that SO42– is clearly more effective than HCO2–. The position of the ions in the Hofmeister series and their free energy of hydration (ΔGhyd) were used to explain the ability of the ions to induce PEG salting-out. Furthermore, the effective excluded volume (EEV) of the salts was determined and the following order was found: Na2SO4 > K2HPO4 > Li2SO4 > K3C6H5O7 > NaCHO2 > KCHO2. Similar order was obtained when analyzing the size of the heterogeneous regions, suggesting the practical use of EEV as a comparison parameter between different ATPSs.This work is partially supported by project PEst-C/EQB/LA0020/2011, financed by FEDER through COMPETE-Programa Operacional Factores de Competitividade and by FCT-Fundacao para a Ciencia e a Tecnologia. Sara Silverio acknowledges her Ph.D. grant from FCT (SFRH/BD/43439/2008)

Petroleum Science and Technology Publication details, including instructions for authors and subscription information: Synthesis and Characterization of Microporous Aluminophosphates of AFI Topology Synthesis and Characterization of Microporous Aluminopho

Aluminophosphates of the AFI (aluminophosphate-5) topology were synthesized and characterized in order to study the influence of acid strength and distribution for the possibility of both conversion and selectivity for oligomerization reactions. It is well known that weaker acid sites lead to a product shift to hydrocarbons of lower carbon chain length and a lower conversion, and a reduction in acid site concentration has a similar effect. However, when a silylating agent modifies the surface acidity, the overall conversion drops, associated with a reduction in sticking probability of an olefin on the silicoaluminophosphate's (SAPO) crystal surface. This is associated with a reduced ability of the surface acid sites to crack the products upon exiting the internal pore system. This research reports on the synthesis and charactizeration of microporous aluminophates of AFI topology. Catalysts' properties were characterized by a series of spectroscopic and diffraction techniques, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). All catalysts were characterized in calcined form

Some Novel Liquid Partitioning Systems: Water-Ionic Liquids and Aqueous Biphasic Systems

Article on water-ionic liquids and aqueous biphasic systems and some novel liquid partitioning systems