Separation of 2-butanol–water mixtures by pervaporation through PVA–NYL 66 blend membranes

Blend membranes of poly(vinyl alcohol) (PVA) and nylon 66 (NYL) were synthesized and crosslinked with glutaraldehyde (GA) and assessed for their suitability in dehydrating 2-butanol by pervaporation (PV). These blends were subjected to sorption studies to determine the extent of interaction and degree of swelling in pure liquids as well as binary mixtures. Wide-angle X-ray diffraction (WAXD) and thermal gravimetric analysis (TGA) were carried out to investigate changes in crystallinity and thermal stability, respectively. The effect of experimental parameters such as feed water concentration, permeate pressure and barrier thickness on membrane flux and selectivity was evaluated. The membranes were found to have good potential for breaking the azeotrope of 27.6 wt.% water with a flux of 3.07 kg/m² h 10 μm and selectivity of 26.5. Selectivity was found to improve with decreasing feed water concentration and increasing membrane thickness, whereas opposite trends were observed in case of flux. Higher permeate pressure caused a reduction in both flux and selectivity. These effects were clearly elucidated.     

Proton conducting composite membranes from polysulfone and heteropolyacid for fuel cell applications

The viability of using composite membranes of heteropolyacid (HPA)/polysulfone (PSF), HPA/sulfonated polysulfone (SPSF) for use in proton exchange membrane fuel cells (PEMFC) was investigated. PSF and its sulfonated polymer, SPSF was solution‐blended with phosphotungstic acid, a commercially available HPA. Fourier transform infrared (FTIR) spectroscopy of the HPA–40/SPSF composite exhibited band shifts showing a possibility of intermolecular hydrogen bonding interaction between the HPA additive and the sulfonated polymer. The composite membranes exhibited improved mechanical strength and low water uptake. The conductivity of the composite membrane, HPA–40/SPSF, consisting of 40 wt % HPA and 60 wt % SPSF [with a degree of Sulfonation (DS) of 40%] exhibited a conductivity 0.089 S/cm at room temperature that linearly increased upto 0.14 S/cm at 120 °C, whereas the widely used commercial membrane Nafion 117, exhibited a room temperature conductivity of 0.1 S/cm that increased to only 0.12 S/cm at 120 °C. In contrast, the composite of HPA–40/PSF exhibited a proton conductivity of 0.02 S/cm at room temperature that increased only to 0.07 S/cm at a temperature of 100 °C. The incorporation of HPA into SPSF not only rendered the membranes suitable for elevated temperature operation of PEMFC but also provides an inexpensive alternative compared to Nafion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1538–1547, 2005     

A convergent route to β-hydroxy δ-lactones through Prins cyclisation as the key step: synthesis of (+)-prelactones B, C and V

Reactions of homoallylic alcohols with aldehydes in the presence of acid catalysts gave multisubstituted tetrahydropyrans with the creation of one to three new stereogenic centres in a single-pot process. The utility of this approach is extended to the enantioselective syntheses of (+)-prelactones B, C and V.     

Ropinirole hydro­chloride,a dopamine agonist

Ropinirole hydro­chloride, or diethyl[2‐(2‐oxo‐2,3‐dihydro‐1H‐indol‐4‐yl)ethyl]ammonium chloride, C₁₆H₂₅N₂O⁺·Cl⁻, belongs to a class of new non‐ergoline dopamine agonists which bind specifically to D2‐like receptors with a selectivity similar to that of dopamine (D3 > D2 > D4). The N atom in the ethyl­amine side chain is protonated and there is a hydrogen bond between it and the Cl⁻ ion. In the crystal structure, two cations and two anions form inversion‐related cyclic dimers via N—H⋯Cl hydrogen bonds.     

The generalized linear complementarity problem revisited

Given a vertical block matrixA, we consider in this paper the generalized linear complementarity problem VLCP(q, A) introduced by Cottle and Dantzig. We formulate this problem as a linear complementarity problem with a square matrixM, a formulation which is different from a similar formulation given earlier by Lemke. Our formulation helps in extending many well-known results in linear complementarity to the generalized linear complementarity problem. We also show that the class of vertical block matrices which Cottle and Dantzig's algorithm can process is the same as the class of equivalent square matrices which Lemke's algorithm can process. We also present some degree-theoretic results on a vertical block matrix.     

An integral equation and a representation for a Green's function

The final step in the mathematical solution of many problems in mathematical physics and engineering is the solution of a linear, two-point boundary-value problem such as $$\begin{gathered} \ddot u - q(t)u = - g(t), 0< t< x \hfill \\ (0) = 0, \dot u(x) = 0 \hfill \\ \end{gathered} $$ Such problems frequently arise in a variational context. In terms of the Green's functionG, the solution is $$u(t) = \int_0^x {G(t, y, x)g(y) dy} $$ It is shown that the Green's function may be represented in the form $$G(t,y,x) = m(t,y) - \int_y^x {q(s)m(t, s) m(y, s)} ds, 0< t< y< x$$ wherem satisfies the Fredholm integral equation $$m(t,x) = k(t,x) - \int_0^x k (t,y) q(y) m(y, x) dy, 0< t< x$$ and the kernelk is $$k(t, y) = min(t, y)$$      

Solvent extraction of zinc(II) with ethylthioacetoacetate into ethyl acetate

A method has been developed for the extraction of Zn(II) with ethylthioacetoacetate (HETAcAc) into ethyl acetate from an alkaline medium. Various parameters affecting the extraction of Zn(II) have been investigated. The stoichiometry of the extracted species has been determined by the slope-ratio method.     

Cauchy and Fredholm methods for Euler equations

The mathematical treatment of many problems in mathematical physics requires the minimization of a quadratic functional. It is shown that the optimizing function can be viewed as the solution of the familiar Euler equation, subject to boundary conditions, or as the solution of a certain Fredholm integral equation, or as the solution of an initial-value (Cauchy) problem. Each formulation has certain analytic and computational advantages and disadvantages.