Transmission FT-IR spectroscopy allowed us to monitor the deuteration of wafers of chitosan aerog... more Transmission FT-IR spectroscopy allowed us to monitor the deuteration of wafers of chitosan aerogel and xerogel by D2O vapor at room temperature. The complete deuteration of the alcohol and amine groups of the aerogel (surface area 175 m2 g(-1) as measured by N2 volumetry) confirmed the high accessibility of the functional groups of the polymer. The xerogel (surface area 5 m2 g(-1)) was only partially deuterated in more severe conditions. The isotopic shift of the deuterated groups allowed us to confirm or revise some attributions of infrared bands of chitosan.
The microporosity of the precursor gels of zeolite synthesis is stabilized by CO2 treatment by ch... more The microporosity of the precursor gels of zeolite synthesis is stabilized by CO2 treatment by chemical condensation of the surface silanols. This effect is only observable in a given field of Si/Al ratio, corresponding to the appropriate density of silanols.
Les aérogels, préparés par séchage au CO2 supercritique, conservent la dispersion des hydrocolloï... more Les aérogels, préparés par séchage au CO2 supercritique, conservent la dispersion des hydrocolloïdes dont ils sont issus. Le conditionnement en aérogel du chitosane permet de préparer des solides poreux de surface spécifique importante (supérieure à 300 m2 g-1) avec une excellente accessibilité aux fonctions aminées du polymère. L'obtention d'aérogels de chitosane, leur caractérisation texturale et les propriétés qui en découlent sont discutées dans ce chapitre. Des exemples illustrent l'exploitation des propriétés de surface du chitosane à l'état sec dans le domaine de la catalyse.
The effectiveness of zeolites in catalysis and separation can often be improved by the textural a... more The effectiveness of zeolites in catalysis and separation can often be improved by the textural and chemical properties of the matrices in which they are imbedded. Chitosan gels issued from renewable resources are already used as supports for the preparation of heterogeneous catalysts in the form of colloids, flakes or gel beads [1, 2]. In this study we present several methods for the incorporation of zeolites in chitosan matrices and characterize the synergic effect of the components on the properties of the composite.
Wood behaviour is characterized by a high sensibility to humidity, swelling when humidity increas... more Wood behaviour is characterized by a high sensibility to humidity, swelling when humidity increases and shrinkage during drying. From green condition to ovendry condition, shrinkage ranges from 0.05 % to 0.3 % along the grain direction, however, two cases exist where longitudinal shrinkage starts to be more important: in reaction wood (tension wood of hardwoods and compression wood of conifers) and juvenile wood. In these two types of wood, axial shrinkage can reach 1 % or more. These changes in longitudinal shrinkage can be explained by the wood fibre structure. The knowledge of the wood cell structure, as a multi-layer fibre composite, allows the modelling of the longitudinal shrinkage, considering that the cell wall is reduced to S2 layer. These models give a good understanding of macroscopic axial shrinkage for different values of microfibril angle, for normal, compression and juvenile wood. However, they cannot explain the behaviour of tension wood. Tension wood cell wall is ch...
... Oran, Algeria bLaboratoire de Matdriaux Catalytiques et Catalyse en Chimie Organique, ENSCM, ... more ... Oran, Algeria bLaboratoire de Matdriaux Catalytiques et Catalyse en Chimie Organique, ENSCM, 8 rue de rEcole Normale, 34296 Montpellier, France CLaboratoire de Chimie des Matdriaux, Universit60ran Es-Senia, Oran, Algeria 1 ... [14] CGV Burgess and DH Everett, J. Colloid ...
The rheological properties of several ionotropic alginate hydrogels were investigated according t... more The rheological properties of several ionotropic alginate hydrogels were investigated according to the nature of the divalent cation (Mn(2+), Co(2+), Cu(2+)) and the guluronic fraction of the alginate (HG and LG for "high G-content" and "low G-content"). Six hydrogels (Mn-LG, Mn-HG, Co-LG, Co-HG, Cu-LG and Cu-HG) were synthesized and studied by spectromechanical analyses. On one hand, Cu-HG, Cu-LG and Co-HG behaved as viscoelastic solids: the elastic contribution was higher than the dissipative component in all the frequency range studied (G'>G"). No flow zone (G">G') was detected even at very low values of the shearing frequency. On the other, Mn-HG, Mn-LG and Co-LG presented a spectromechanical behavior that resembled that observed classically for entangled polymers. Indeed, at high frequency, these latter materials could be compared to a viscoelastic solid but at low frequency, the flow zone was described and the viscous character becam...
In this manuscript we report a critical evaluation of the ability of natural DNA to mediate the n... more In this manuscript we report a critical evaluation of the ability of natural DNA to mediate the nitroaldol (Henry) reaction at physiological temperature in pure water. Under these conditions, no background reaction took place (i.e., control experiment without DNA). Both heteroaromatic aldehydes (e.g., 2-pyridinecarboxaldehyde) and aromatic aldehydes bearing strong or moderate electron-withdrawing groups reacted satisfactorily with nitromethane obeying first order kinetics and affording the corresponding β-nitroalcohols in good yields within 24 h. In contrast, aliphatic aldehydes and aromatic aldehydes having electron-donating groups either did not react or were poorly converted. Moreover, we discovered that a number of metal-free organic buffers efficiently promote the Henry reaction when they were used as reaction media without adding external catalysts. This constitutes an important observation because the influence of organic buffers in chemical processes has been traditionally underestimated.
ABSTRACT The catalytic total oxidation of toluene at low concentrations in air over Cu1.5Mn1.5O4 ... more ABSTRACT The catalytic total oxidation of toluene at low concentrations in air over Cu1.5Mn1.5O4 catalysts synthesized via the alginate route has been investigated. Several kinetic models have been selected and tested to describe the kinetics of the total oxidation of toluene. Results showed that the power law model and Langmuir model were not enough to represent the kinetics of toluene combustion over the catalyst. On the contrary, the model based on the Mars–van Krevelen mechanism provided a good fit (R2 = 0.94) towards the experimental data and allowed to determine the kinetic parameters.
Transmission FT-IR spectroscopy allowed us to monitor the deuteration of wafers of chitosan aerog... more Transmission FT-IR spectroscopy allowed us to monitor the deuteration of wafers of chitosan aerogel and xerogel by D2O vapor at room temperature. The complete deuteration of the alcohol and amine groups of the aerogel (surface area 175 m2 g(-1) as measured by N2 volumetry) confirmed the high accessibility of the functional groups of the polymer. The xerogel (surface area 5 m2 g(-1)) was only partially deuterated in more severe conditions. The isotopic shift of the deuterated groups allowed us to confirm or revise some attributions of infrared bands of chitosan.
The microporosity of the precursor gels of zeolite synthesis is stabilized by CO2 treatment by ch... more The microporosity of the precursor gels of zeolite synthesis is stabilized by CO2 treatment by chemical condensation of the surface silanols. This effect is only observable in a given field of Si/Al ratio, corresponding to the appropriate density of silanols.
Les aérogels, préparés par séchage au CO2 supercritique, conservent la dispersion des hydrocolloï... more Les aérogels, préparés par séchage au CO2 supercritique, conservent la dispersion des hydrocolloïdes dont ils sont issus. Le conditionnement en aérogel du chitosane permet de préparer des solides poreux de surface spécifique importante (supérieure à 300 m2 g-1) avec une excellente accessibilité aux fonctions aminées du polymère. L'obtention d'aérogels de chitosane, leur caractérisation texturale et les propriétés qui en découlent sont discutées dans ce chapitre. Des exemples illustrent l'exploitation des propriétés de surface du chitosane à l'état sec dans le domaine de la catalyse.
The effectiveness of zeolites in catalysis and separation can often be improved by the textural a... more The effectiveness of zeolites in catalysis and separation can often be improved by the textural and chemical properties of the matrices in which they are imbedded. Chitosan gels issued from renewable resources are already used as supports for the preparation of heterogeneous catalysts in the form of colloids, flakes or gel beads [1, 2]. In this study we present several methods for the incorporation of zeolites in chitosan matrices and characterize the synergic effect of the components on the properties of the composite.
Wood behaviour is characterized by a high sensibility to humidity, swelling when humidity increas... more Wood behaviour is characterized by a high sensibility to humidity, swelling when humidity increases and shrinkage during drying. From green condition to ovendry condition, shrinkage ranges from 0.05 % to 0.3 % along the grain direction, however, two cases exist where longitudinal shrinkage starts to be more important: in reaction wood (tension wood of hardwoods and compression wood of conifers) and juvenile wood. In these two types of wood, axial shrinkage can reach 1 % or more. These changes in longitudinal shrinkage can be explained by the wood fibre structure. The knowledge of the wood cell structure, as a multi-layer fibre composite, allows the modelling of the longitudinal shrinkage, considering that the cell wall is reduced to S2 layer. These models give a good understanding of macroscopic axial shrinkage for different values of microfibril angle, for normal, compression and juvenile wood. However, they cannot explain the behaviour of tension wood. Tension wood cell wall is ch...
... Oran, Algeria bLaboratoire de Matdriaux Catalytiques et Catalyse en Chimie Organique, ENSCM, ... more ... Oran, Algeria bLaboratoire de Matdriaux Catalytiques et Catalyse en Chimie Organique, ENSCM, 8 rue de rEcole Normale, 34296 Montpellier, France CLaboratoire de Chimie des Matdriaux, Universit60ran Es-Senia, Oran, Algeria 1 ... [14] CGV Burgess and DH Everett, J. Colloid ...
The rheological properties of several ionotropic alginate hydrogels were investigated according t... more The rheological properties of several ionotropic alginate hydrogels were investigated according to the nature of the divalent cation (Mn(2+), Co(2+), Cu(2+)) and the guluronic fraction of the alginate (HG and LG for "high G-content" and "low G-content"). Six hydrogels (Mn-LG, Mn-HG, Co-LG, Co-HG, Cu-LG and Cu-HG) were synthesized and studied by spectromechanical analyses. On one hand, Cu-HG, Cu-LG and Co-HG behaved as viscoelastic solids: the elastic contribution was higher than the dissipative component in all the frequency range studied (G'>G"). No flow zone (G">G') was detected even at very low values of the shearing frequency. On the other, Mn-HG, Mn-LG and Co-LG presented a spectromechanical behavior that resembled that observed classically for entangled polymers. Indeed, at high frequency, these latter materials could be compared to a viscoelastic solid but at low frequency, the flow zone was described and the viscous character becam...
In this manuscript we report a critical evaluation of the ability of natural DNA to mediate the n... more In this manuscript we report a critical evaluation of the ability of natural DNA to mediate the nitroaldol (Henry) reaction at physiological temperature in pure water. Under these conditions, no background reaction took place (i.e., control experiment without DNA). Both heteroaromatic aldehydes (e.g., 2-pyridinecarboxaldehyde) and aromatic aldehydes bearing strong or moderate electron-withdrawing groups reacted satisfactorily with nitromethane obeying first order kinetics and affording the corresponding β-nitroalcohols in good yields within 24 h. In contrast, aliphatic aldehydes and aromatic aldehydes having electron-donating groups either did not react or were poorly converted. Moreover, we discovered that a number of metal-free organic buffers efficiently promote the Henry reaction when they were used as reaction media without adding external catalysts. This constitutes an important observation because the influence of organic buffers in chemical processes has been traditionally underestimated.
ABSTRACT The catalytic total oxidation of toluene at low concentrations in air over Cu1.5Mn1.5O4 ... more ABSTRACT The catalytic total oxidation of toluene at low concentrations in air over Cu1.5Mn1.5O4 catalysts synthesized via the alginate route has been investigated. Several kinetic models have been selected and tested to describe the kinetics of the total oxidation of toluene. Results showed that the power law model and Langmuir model were not enough to represent the kinetics of toluene combustion over the catalyst. On the contrary, the model based on the Mars–van Krevelen mechanism provided a good fit (R2 = 0.94) towards the experimental data and allowed to determine the kinetic parameters.
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Papers by Françoise Quignard