Carmen Vecchi

Sorption of aromatic compounds in water using insoluble cyclodextrin polymers

Insoluble β-cyclodextrin (β-CD) polymers have been used for the recovery of various organic pollutants from aqueous solutions. These resins have been prepared by polymerization using epichlorohydrin (Epi) as a crosslinking agent. Several crosslinked polymers with various degrees of β-CD were used. Several studies (time, concentration, kinetics, and pH) are presented here. The results show that these sorbents exhibit high sorption capacities toward substituted benzene derivatives. The mechanism of sorption is both physical adsorption in the polymer network and/or the formation of an inclusion complex and/or the formation of hydrophobic guest–guest interactions.

SOLID STATE NMR SPECTROSCOPY STUDY OF MOLECULAR MOTION IN CYCLOMALTOHEPTAOSE (BETA -CYCLODEXTRIN) CROSSLINKED WITH EPICHLOROHYDRIN

Dry and hydrated insoluble cyclomaltoheptaose (beta-cyclodextrin, beta-CD) polymers have been investigated by solid state 13C NMR spectroscopy techniques such as cross polarization/magic angle spinning with dipolar decoupling (CP/MAS), magic angle spinning both with (DD-MAS) and without (MAS) dipolar decoupling and CP/MAS dipolar dephasing (dd-CP/MAS) to allow the assignment of the main 13C signals. In the solid state, the presence of water in the samples resulted in a better resolution reflecting increased mobility. Two distinct components (crosslinked beta-CD and polymerized epichlorohydrin) have been found. The molecular mobility of these two components has been analyzed in terms of relaxation parameters such as 13C spin lattice relaxation (T1) and 1H spin lattice relaxation in the rotating frame (T1 rho). The T1 values of the polymers show that the beta-CD trapped inside the polymers does not seem to undergo changes in its mobility whatever the amount of epichlorohydrin. The addition of water to beta-CD significantly increases the T1 values reflecting strong interaction between beta-CD and the solvent. The T1P values obtained reflect the homogeneous nature of the materials.

New sorbents containing beta-cyclodextrin. Synthesis, characterization, and sorption properties

Abstract New hydrophilic and insoluble polymers containing β-cyclodextrin (βCD) have been prepared by simple radical polymerization in water using 2-hydroxyethyl methacrylate (HEMA) as comonomer. Several copolymers with various degrees of βCD were synthesized. A characterization was carried out using infra-red spectroscopy and Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance 13C (CP/MAS NMR). The molecular mobilities of these polymers have been analyzed in terms of nuclear relaxation parameters such as 13C spin lattice relaxation (T1) and 1H spin lattice relaxation in the rotating frame (T1ρ). These new sorbents containing βCD were then used for the recovery of various organic pollutants from aqueous solutions. The results of sorption experiments show that they exhibit high sorption capacities toward substituted benzene derivatives. The mechanism of sorption is due to the formation of an inclusion complex between βCD and guest molecules.

Macroporous polyamines containing cyclodextrin : Synthesis, characterization, and sorption properties

Macroporous beads containing N-vinyl-tertio-butyl carbamate (NVTBC) have been prepared by suspension copolymerization using divinylbenzene as crosslinking agent. After solvolysis, parent copolymers containing vinylamine (VA) were functionalized by β-cyclodextrin (β-CD) using the mono-tosyl derivative of β-CD as the intermediate (β-CDOTs). Several copolymers with various degrees of substitution were synthesized. Several factors (reaction time, amounts of the reactants, composition of solvent, and temperature) were studied. Characterization was achieved by crosspolarization magic angle spinning nuclear magnetic resonance spectroscopy ( CPMAS NMR). The textural features (specific area and porous volume) of the beads were also determined. These insoluble macroporous copolymers containing β-CD were then used for the recovery of various organic pollutants from aqueous solutions. Some preliminary studies (time, concentration, kinetics, and β-CD content) are presented here. The results of sorption experiments show that they exhibit high sorption capacities toward substituted benzene derivatives. The mechanism of sorption is an acid-base interaction due to the amino groups of the polymer network and/or the formation of an inclusion complex due to the β-CD molecules.

Grafting of cyclodextrins onto polypropylene nonwoven fabrics for the manufacture of reactive filters. II. Characterization

A novel method for the preparation of immobilized α, β, or γ-cyclodextrins on polypropylene nonwoven supports has been previously presented. The obtained new materials were prepared by graft-polymerization of glycidyl methacrylate onto polypropylene after activation of the support by the electron beam technique, followed by the coupling of cyclodextrins with the epoxide groups. The structure of the resulting materials is characterized in detail using Fourier transform infrared spectroscopy, solid state nuclear magnetic resonance analysis, differential scanning calorimetry, thermogravimetric analysis, and optical microscopy.

Characterization of visbreaker bitumens by n.m.r. spectroscopy

Abstract A study was made using n.m.r. spectroscopy on visbreaker and straight-run bitumens to find structural differences. The results show that C ar and H ar contents are appreciably higher in VB bitumens, thus aiding characterization.

MODIFICATIONS INDUCED BY VISBREAKING ON COMPOSITION AND STRUCTURE OF ATMOSPHERIC RESIDUES

ABSTRACT The atmospheric residues, the corresponding visbroken residues and the related asphaltenes have been characterized by elemental analysis, liquid and gel permeation chromatography (LC, GPC), nuclear magnetic resonance (NMR) and pyrolysis/gas chromatography/mass spectrometry ( Py/GC/MS) before and after the thermal process. The results show that visbreaking (VB) increases the aromaticity (Car) of the residues and decreases their resins/ asphaltenes ratio. A relationship between δCar and resins/as-phaltenes ratio has been found. The cracking of aliphatic chains which takes place during the thermal process produces asphalthenes with lower molecular weight and more condensed aromatic structures. The rise up to 60% of the ratio of aromatic to paraffinic carbon (Car/Cp ( greatly affects the solubility of VB asphaltenes in a oily medium.

Characteristics of bitumens extracted from Italian bituminous rocks and shales

Abstract The soluble portion of representative samples from Italian bituminous rocks and shales were studied by n.m.r. spectrometry in the liquid state and by thermoanalytical techniques. The extracted bitumens have a variety of characteristics and also differ from analogous foreign material. One of the samples, from the Ragusa, Sicily area, is of considerable interest from the point of view of exploitation, as it is soluble in benzene and almost totally distillable in the 150–500 °C range.

Contribution of n.m.r. spectroscopy to the study of catalyst functionality : structural investigation on hydrotreated petroleum fractions

Abstract 1H and 13C n.m.r. spectroscopy were combined with liquid-solid chromatography, and used in the structural characterization of feedstock and products from catalytic hydrotreatment of two petroleum fractions. In the hydrotreatment of a visbreaker gas oil with a cobalt molybdate catalyst, the structural changes were mainly associated with sulphur removal from both non-thiophenic and thiophenic compounds. The length of paraffinic chains remained almost unchanged and the degree of aromatic saturation was low. A significant product upgrading in terms of density, stability and sulphur content was achieved under mild conditions with limited hydrogen consumption. Hydrotreatment of a heavy petroleum residuum with activated iron-rich bauxite produced deep demetallation and a remarkable enrichment of the saturate fraction through transfer of naphthenic compounds from the aromatic fraction. Hydrogenolysis of paraffinic chains in the β position on aromatic rings was also noted. Addition of molybdenum to this catalyst promoted selectivity in sulphur removal and lowered hydrogenolysis activity.

New Sorbents Containing ß-Cyclodextrin: Synthesis, Characterisation, and Sorption Properties

There has been considerable interest in the preparation, properties and applications of insoluble polymer and copolymers containing scyclodextrin (sCD). These materials which form water insoluble crosslinked polymers are obtained using polyfunctional crosslinkers such as aldehydes, ketones, isocyanates or epoxides. For example, the utility of sCD containing polymers obtained by condensation between sCD and epichlorohydrin has been recognized in many applications: catalysis, chromatography (M. Morcellet and al 1995a, 1995b, 1996), pharmaceutical and food industries, and in the clean-up of industrial waste effluents. These operations use the property of sCD to form inclusion complex with various compounds, especially aromatics.