The first example of the silver‐NHC catalyzed cycloaddition of CO2 to terminal epoxides is reported. The choice of NHC substituents, halides and the nature of additives were determined to be important. Ionic [(Cnmim)2Ag]2[Ag2Br4] (Cnmim=1‐(CnH2n+1)‐3‐methylimidazol‐2‐ylidene; n=4–18) catalysts exhibited a high yield of styrene carbonate (77–92 %) in the presence of 4‐dimethylaminopyridine (DMAP) as a cocatalyst without needing any solvent. The catalytic activity improved as the length of the alkyl groups (n) increased, although substituents longer than C14 did not produce any further beneficial effect. For the protocol performed at 1.5 MPa pressure and 100 °C the TOF was calculated to be 440 h−1. A prolonged reaction time and increased pressure of CO2 increased the yield. Used without any additive, compound C14 was able to fix CO2 with PO (propylene oxide) quantitatively at 120 °C, 2.0 MPa and could be used at least seven times without loss of activity and selectivity. The nucleophilic nature of the anion is decisive for the formation of the product.

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In this study, the selective extraction and stripping conditions of Co(II) from acidic thiocyanate solution containing Co(II) and Ni(II) by ionic liquid based solvent extraction technique (ILBSX) using symetric and asymetric imidazolium bromide salts substituting butyl and isobutyl groups were experimentally optimized. The molecular structure effect of IMs have been determined as main factor to extract Co(II). The executive parameters on stripping and extraction processes such as IMs concentration, pH, thiocyanate concentration, stripping reagent type and concentration and etc. were experimentaly investigated. Molecular changes in the adduct consisting between IMs and Co-SCN, was illuminated by comparison of ATR-FTIR spectrums of pure and Co-SCN loaded IMs.Stochiometric rates of the adduct was verified with slope analysis. In the light of these examinations, Co(SCN) 3 -has been determined as prominent Co-SCN species in aqueous media. Symetric IMs were identified as more effective than asymetric ones on selective separation of Co(II) from Ni(II). Under optimum conditions, 99.20% of Co(II) was extracted and 93.33% of Co(II) was recovered with higher separation factors especially in diluted solution, whereas, Ni(II) extractions were negligible. We have concluded that the separation power of this study is high in Co(II)/Ni(II) containing dilute solutions and it can be used in preconcentration purposes effectively. Downloaded by [University of Connecticut] at 05

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In present study, the synergistic separation of Cr(VI) has been investigated from synthetic acidic solution containing Cr(VI), Co(II) and Ni(II) by fl at sheet supported liquid membrane (FSSLM) technique using triisooctylamine (TIOA) and tri-n-butyl phosphate (TBP) as carriers. The main goal of the study was based in the exploring of the synergistic effect of TBP on selective extraction of Cr(VI) in presence of Co(II) and Ni(II) ions. The various parameters related with membrane and aqueous solution properties were studied to identify the optimum extraction and stripping conditions of the Cr(VI) through FSSLM. In the optimum conditions, initial mass fl ux (J 0 ) and separation factors (β Cr/Co and β Cr/Ni ) were obtained as 1.49 x 10 -05 (kg/m 2.s), 382.2 and 725.3 respectively from aqueous H 2 SO 4 media through Celgard 2500 (Celgard Inc., USA) polymer support. As a result, the considerable synergistic infl uence on selective transport of Cr(VI) through FSSLM using TIOA and TBP as carriers has been identifi ed.