Jean-Louis Havet

DETERMINATION OF THE METASTABLE ZONE WIDTH OF GLYCINE AQUEOUS SOLUTIONS FOR BATCH CRYSTALLIZATIONS

The aim of this study was to determine the metastable zone width of aqueous solutions of glycine for non-seeded batch crystallizations. The saturation curve was determined by studying the heating rate influence on the apparent saturation temperatures of several solutions. A linear regression was then applied to obtain the saturation temperatures. The spontaneous nucleation curve was obtained by measuring the crystallization temperatures of several solutions at different cooling rates. The results show that the apparent nucleation order of the glycine aqueous solutions was around 3.5 ± 0.5. Moreover, from the experimental data, a second-order polynomial model was established by using the experimental design method. This model enables the expression of crystallization temperature to be defined as a function of concentration and cooling rate. The results show that the model fits well (R2 > 0.99; Q2 > 0.98) and that the cooling rate is the most influential parameter.

Microwave-assisted synthesis of prebiotic di-D-fructose dianhydride-enriched caramels

The synthesis of prebiotic caramels involving the use of microwaves as the activating/heating source has been achieved. The yields in di-fructose dianhydrides (DFAs) in caramels were measured. The aim of this study was twofold: first to check the feasibility of the process, and second to determine the conditions to obtain an optimum response with microwave heating. The study showed that it was possible to obtain a yield of almost 50% of DFAs in a reaction time that was 10 times shorter than a previous study; i.e. 5-10 min for microwave activation compared to 60-120 min for conventional heating. It was shown that the radiation time and the radiation power were linked. The simultaneous determination of the values of these two factors was therefore necessary to obtain significant yields. This technique demonstrates the advantage of activation for mixtures such as caramels.

Synthesis and N-methylation of tetrabutylammonium isocyanurate

A simple and efficient method for the synthesis of ammonium salt of isocyanuric acid is set out. This process is based on the direct addition of the corresponding hydroxide to isocyanuric acid. This salt exhibits several interesting properties. Its alkylation by iodomethane in various solvents is demonstrated and leads to various substituted isocyanurate derivatives.

Modelling of influential parameters on a continuous evaporation process by Doehlert shells.

The modelling of the parameters that influence the continuous evaporation of an alcoholic extract was considered using Doehlert matrices. The work was performed with a wiped falling film evaporator that allowed us to study the influence of the pressure, temperature, feed flow and dry matter of the feed solution on the dry matter contents of the resulting concentrate, and the productivity of the process. The Doehlert shells were used to model the influential parameters. The pattern obtained from the experimental results was checked allowing for some dysfunction in the unit. The evaporator was modified and a new model applied; the experimental results were then in agreement with the equations. The model was finally determined and successfully checked in order to obtain an 8% dry matter concentrate with the best productivity; the results fit in with the industrial constraints of subsequent processes.

Synthesis of prebiotic caramels catalyzed by ion exchange resin particles: kinetic model for the formation of di-D-fructose dianhydrides

Caramel enriched in di-d-fructose dianhydrides (DFAs, a family of prebiotic cyclic fructodisaccharides) is a functional food with beneficial properties for health. The aim of this work was to study the conversion of fructose into DFAs catalyzed by acid ion-exchange resin, in order to establish a simplified mechanism of the caramelization reaction and a kinetic model for DFA formation. Batch reactor experiments were carried out in a 250 mL spherical glass flask and afforded up to 50% DFA yields. The mechanism proposed entails order 2 reactions that describe fructose conversion on DFAs or formation of byproducts such as HMF or melanoidines. A third order 1 reaction defines DFA transformation into fructosyl-DFAs or fructo-oligosaccharides. The influence of fructose concentration, resin loading and temperature was studied to calculate the kinetic parameters necessary to scale up the process.

Solvent effect modelling of isocyanuric products synthesis by chemometric methods

Chemometric tools were used to generate the modelling of solvent e¡ects on the N-alkylation of an isocyanuric acid salt. The method proceeded from a central composite design applied on the Carlson solvent classification using principal components analysis. The selectivity of the reaction was studied from the production of different substituted isocyanuric derivatives. Response graphs were obtained for each compound and used to devise a strategy for solvent selection. The prediction models were validated and used to search for the best selectivity for the reaction system. The solvent most often selected as the best for the reaction is the N,N-dimethylformamide.