New catalytic Polymeric membranes Incorporationg Ti(IV) Trialkanolamines Complexes: Synthesis, Characterization and Application in Catalysis

The incorporation of chiral homogenous catalyst, Ti(IV)/(R,R,R)-tris-(2-phenylethanol)amine, in polymeric membranes provided the first asymmetric catalytic Ti(IV)-based membranes, stable and efficient as heterogeneous catalysts for stereoselective sulfoxidations and chemoselective oxidations of secondary amines to nitrones by alkyl hydroperoxides. Polyvinylidene fluoride (PVDF) -based catalytic membranes gave the best results affording products in short reaction times, high yields and high selectivity using as little as 1% of catalyst, comparable with the performances of the corresponding homogeneous system. The PVDF-Ti stability is reasonably good and catalyst activity increases with no loss of selectivity in the subsequent uses of the same membran

Polymeric membranes modified via plasma for nanofiltration of aqueous solutions containing organic compounds

Polymeric nanofiltration membranes were prepared modifying via low temperature plasma treatment flat membranes based on a modified poly(ether ether ketone) (PEEKWC). PEEKWC membranes, prepared using wet phase inversion using methanol (M2m) and 1-butanol (M2b) as internal non-solvent, were further plasma surface modified (RF 13.56 MHz) introducing amino groups on the membrane using two different pre-treatment gases, Ar (M2bpsm/Ar/NH3 and M2mpsm/Ar/NH3) and H2 (M2bpsm/H2/NH3 and M2mpsm/H2/NH3). The performances of unmodified and plasma modified membranes M2b and M2m and of a commercial nanofiltration membrane (NFTFC50) were tested in treatment of aqueous solution containing two dyes, characterized by similar molecular weight (320 g/mol) and opposite charge, methylene blue and methyl orange, positively and negatively charged, respectively. The observed rejections resulted optimized in terms of fouling for the plasma modified membranes with respect to unmodified and commercial NFTFC50 membranes. In particular, methylene blue was retained for 100% by M2mpsm/Ar/NH3 with a relative flux of 100% compared to 100% and 95% rejections and 85% and 90% relative fluxes observed for unmodified PEEKWC M2b membrane and commercial NFTFC50, respectively

New PVDF membranes: the effect of plasma surface modification on retention in nanofiltration of aqueous solutions containing organic compounds

New nanofiltration membranes were prepared by non-solvent-induced phase inversion from a PVDF/DMF/water system. The effect of exposure time before coagulation on the membrane characteristics (morphology, thickness, overall porosity, tensile strength) was investigated. PVDF membrane prepared at a fixed exposure time of 45 s (PF45) was further plasma surface modified (RF 13.56 MHz) (PF45psm), introducing amino groups on the membrane. The performances of PF45, PF45psm and of a commercial nanofiltration membrane (N30F) were tested in the removal of two dyes from aqueous solution, characterized by different charge and molecular weight (congo red and methylene blue). The observed rejections depended more on the charge of the compound than on their molecular weights and results were optimized for the plasma modified membrane (PF45psm) with respect to unmodified (PF45) and commercial N30F membranes. In particular, methylene blue was retained for 100% by PF45psm with a relative flux of 65% compared to 38% of rejection and 59% of relative flux observed for N30F

Sodium tungstate on plasma-treated PVDF membranes: new efficient heterogeneous catalyst for oxidation secondary amines to nitrones

New heterogeneous oxidation catalysts have been obtained by immobilizing sodium tungstate (Na2WO4) on plasma-treated poly(vinyldene difluoride) (PVDF) membranes. This new generation of catalytically active membranes has been developed by coupling the advantages of low temperature plasma modification processes with surface chemical immobilization reactions of catalysts. Polymeric membranes with different thicknesses, morphologies and pore dimensions were prepared by a non-solvent induced phase inversion technique. Then the surface of the membranes have been surface modified with NH3 radiofrequency glow discharges in order to graft active amino groups for immobilizing sodium tungstate in a stable way. The new catalytic membranes were successfully used for the oxidation of secondary an-tines to nitrones in a flat membrane reactor. A conversion to nitrone of 100% in less than 3 h (comparable to the homogeneous system) was achieved with the membrane having smallest pore diameter and finger like morphology

Immobilization of tungsten catalysts on plasma modified membranes

Novel catalytic membranes were developed by coupling low-temperature plasma treatments with the chemical immobilization of W-based catalysts. Poly(vinylidene fluoride) membranes were pre-treated with Ar, and then treated with NH3 RF glow discharges in order to obtain a surface rich in amino groups, which are suitable anchor sites for the immobilization of tungsten-based heterogeneous catalysts. In particular, (WO42-), we have focused our interest on tungstate ions 4 which catalyze the oxidation of secondary amines to nitrones, and on decatungstate (W10O324-) and phospho tungstate (W12PO403-) ions, which can both be used as catalysts for the degradation of organic pollutants such as phenol

A new generation of catalytic PVdF membranes: coupling plasma treatment with chemical immobilization of tungsten-based catalysts

A new generation of catalytically active membranes for secondary amine oxidation and phenol degradation has been developed by coupling the advantages of low-temperature plasma-modification processes with surface chemical immobilization reactions of catalysts. Poly(vinylidene fluoride) membranes have been modified with NH(3) radiofrequency glow discharges in order to graft amino groups at their surface, providing active sites for stable immobilization of tungsten-based heterogeneous catalysts. Particular attention has been focused on tungstate, WO(4)(2-), and decatungstate, W(10)O(32)(4-), which act efficiently as catalysts for the oxidation of secondary amines and as photocatalysts for the degradation of organic pollutants, respectively. Plasma-modified membranes surface-tailored With WO(4)(2-) have been used in catalytic membrane reactors to activate hydrogen-peroxide for oxidizing secondary amines to nitrones; membranes modified with W(10)O(32)(4-) have been used for the complete degradation of phenol. The obtained results, in terms of amine-nitrone conversion and phenol degradation, respectively, appear extremely promising; these modified membranes can be considered as a pioneering, successful example of heterogenization of W-based catalysts on plasma-treated membranes

Ti(IV)/trialkanolamine catalytic polymeric membranes: Preparation, characterization, and use in oxygen transfer reactions

New heterogeneous oxidation catalysts have been obtained by entrapping Ti(IV)/trialkanolamine complexes within polymeric membranes. The catalytic membranes were prepared by a nonsolvent-induced phase-inversion technique. Three polymers, polyvinylidene fluoride (PVDF), a modified polyetherketone (PEEK-WC), and polyacrylonitrile (PAN), with different functional groups and chemical\u2013physical properties, were used to tune the reactivity of the catalytic polymeric membranes in the stereoselective oxidation to sulfoxide and chemoselective oxidation of secondary amines to nitrones by alkyl hidroperoxides. The chemical\u2013physical analysis of the new catalytic membranes was carried out by SEM, EDX, IR, CAM, and XPS techniques. In particular, the XPS spectra showed a very interesting orientation effect of PVDF membranes on the entrapped Ti(IV)/trialkanolamine complex. PVDF-based catalytic membranes gave the best results, affording products in shorter reaction times, higher yields, and better selectivity compared with the corresponding homogeneous systems. The membranes can be recycled up to five runs with no loss of activit