Stéphane Bostyn

Optimization by the simplex method of the separation of phenolic acids by high-performance liquid chromatography in wastewater olive and sugar beet vinasse

Optimization of a high-performance liquid chromatography separation has been developed for nine polyphenols by application of the simplex method. The nine polyphenols selected were mainly phenolic acids that can be present in wastewater and they can be removed by adsorption on activated carbon and resins. After the organic solvent (MeOH) had been chosen, a linear gradient in three stages and the furnace temperature were retained as parameters of optimization. The optimal conditions were determined by the super modified simplex and, in order to measure them a Chromatographic Response Function (CRF) was chosen. With the optimal conditions, the time of analysis was decreased from 69 to 40 min. The validation of the method was made on wastewater olive oil (WWOO) and sugar beet vinasse.

Kinetic modelling of the degradation of the α-tocopherol in biodiesel-rape methyl ester.

The aim of this work was to study the influence of three major factors (light, atmospheric oxygen, temperature) responsible for the degradation of tocopherols. The evolution of alpha-tocopherol contents was analysed by high-performance liquid chromatography. Taguchis experimental design was applied to establish a mathematical model of alpha-tocopherols degradation in function of the studied parameters especially in a domain of temperature between 50 degrees C and 150 degrees C. The results show that the major factor is the temperature, especially above 100 degrees C. Light is a negligible factor, meaning that degradation is mainly due to an autoxidation phenomenon. Moreover, only interactions between temperature and atmospheric oxygen have been observed especially above 100 degrees C. The mathematical model was validated for a temperature of 75 degrees C and permits to calculate a predictive speed of degradation in this domain.

Optimization of the isolation and quantitation of kahweol and cafestol in green coffee oil

Kahweol and cafestol are two diterpenes that exist mainly as esters of fatty acids in green coffee oil. To recover them under their free form they have to be either saponified or trans-esterified. These two compounds are well known to be sensitive to heat, and reagents, therefore experimental conditions used in the transesterification reaction are critical. In this paper, a Doehlert experimental design plan is used to optimize the transesterification conditions using some key variables such as the temperature of the reaction, the reagent base concentration and the duration of the reaction. Therefore, the optimal parameters determined from the Doehlert design are equal to 70 °C, temperature of the reaction; 1.25 mol L(-1) concentration of the reagent base; and 60 min reaction time. The contour plots show that the extracted quantity of kahweol and cafestol can depend greatly from the experimental conditions. After transesterification, the free form of the diterpernes is extracted from the lipid fraction using liquid-liquid extraction and analyzed using GC-FID without prior derivatization. The amount of kahweol and cafestol obtained from green coffee oil obtained by cold mechanical press of Catuai coffee bean is equal to 33.2±2.2 and 24.3±2.4 g kg(-1)oil, respectively. In an attempt to streamline the process, the transesterification reaction is performed in an in-flow chemistry reactor using the optimal conditions obtained with the Doehlert experimental design. The amount of kahweol and cafestol obtained from the same green coffee oil is equal to 43.5 and 30.072 g kg(-1)oil, respectively. Results are slightly higher compared to the ones obtained with the batch procedure. This can be explained by a better mixing of the coffee oil with the reagents and a faster transesterification reaction.

Interest of a chemometric approach in understanding the retention behaviour of three columns in hydrophilic interaction liquid chromatography: Application to the separation of glycerol carbonate, glycerol and urea

A chemometric approach was used to study the retention behaviour of glycerol, urea and glycerol carbonate in hydrophilic interaction liquid chromatography (HILIC). First, a simplex method was developed to optimize the sensitivity of an evaporative light scattering detector. A mixture design was then applied to model retention factors as a function of the mobile phase content in acetonitrile, water and methanol on three columns: Atlantis HILIC Silica, ZIC-HILIC and Monochrom diol. Atlantis HILIC Silica exhibits predominantly hydrophobic interactions, while retention on the other two columns is mainly ruled by hydrophilic interactions. Finally, a desirability function is applied on the resolution factors. The use of this function enables the compositions of eluent phases to be determined in order to achieve separation between the three chemicals. Monochrom diol proved to be the most efficient column.

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.

Sugars and Fructans Separation by Nanofiltration from Model Sugar Solution and Comparative Study with Natural Agave Juice

The fructan separation from a model sugar solution and natural agave juice was studied using a stirred-cell nanofiltration unit operated in concentration mode. Hydrophilic cellulose membrane with MWCO of 1000 Da was used. The experimental conditions were varied to predict the influence of pressure (0.14–0.350 MPa) and feed concentration (0.15–0.25 g/mL) on the initial permeate flux and solute retained fraction (SRF) values of the process. Response surface plots (p < 0.05) showed that the permeate flux and SRF increased significantly with the pressure and decreased with feed concentration. The permeate flux varied from 0.5 to 4.1 L · h−1 · m−2. The fructan retained fraction in model sugar solution varied from 0.85 to 0.97 whereas fructose, glucose and sucrose presented similar SRF values ranging from 0.38 to 0.65. Promising results were obtained when natural agave juice was used.

Size-exclusion chromatography (HPLC-SEC) technique optimization by simplex method to estimate molecular weight distribution of agave fructans

Agave fructans are increasingly important in food industry and nutrition sciences as a potential ingredient of functional food, thus practical analysis tools to characterize them are needed. In view of the importance of the molecular weight on the functional properties of agave fructans, this study has the purpose to optimize a method to determine their molecular weight distribution by HPLC-SEC for industrial application. The optimization was carried out using a simplex method. The optimum conditions obtained were at column temperature of 61.7°C using tri-distilled water without salt, adjusted pH of 5.4 and a flow rate of 0.36mL/min. The exclusion range is from 1 to 49 of polymerization degree (180-7966Da). This proposed method represents an accurate and fast alternative to standard methods involving multiple-detection or hydrolysis of fructans. The industrial applications of this technique might be for quality control, study of fractionation processes and determination of purity.

Swirl Motion Effects on Flame Dynamic of Pulverized Olive Cake in a Vertical Furnace

ABSTRACT This article presents the effect of inlet swirl motion on the flow behavior and combustion dynamics of pulverized olive cake (OC) in a 3D vertical furnace. The spherical OC particles are injected perpendicularly to the coaxial air inlet jets. Three cases are studied: without swirling air flow (Ja), with swirling axial jet (Js1), and with both swirling axial and coaxial jets (Js2). The numerical approach is based on Reynolds averaged Navier–Stokes (RANS) method using the k–ε turbulence model. For turbulence-chemistry interactions of the non-premixed combustion, a mixture fraction/probability density function approach is used. The OC thermal characteristics are determined experimentally by the thermogravimetric analysis. Flow topology, velocity contours, temperature distribution, and species concentrations profiles in several locations along the burner are obtained for all cases. Results show that the flame is more stabilized and close to the air inlet section for the swirling jet cases. The temperature of the burned gases reaches its maximum value of 1560 K.

Experimental and CFD Modeling Study of Inulin-Type Fructan Purification from a Model Solution by Diafiltration on a Pilot-Scale Unit

Nanofiltration of a model inulin-sucrose solution has been studied using a pilot cross-flow unit. The aim of this work was to evaluate two operation modes: total recycle nanofiltration and diafiltration. Experiments were performed at transmembrane pressures from 0.4 to 1.45 MPa and two inlet flow rates. It was found that inulin purification is feasible within the range of the process conditions set. Furthermore, the sucrose retention coefficient is highly affected by the transmembrane pressure but the inlet flow rate does not affect this parameter significantly. Experimental results were simulated by Computational Fluid Dynamics (CFD) and a good agreement was observed between the predicted and the experimental values.

Effect of Swirl Strength on the Flow and Combustion Characteristics of Pulverized Biomass Flames

ABSTRACT This article reports on the effect of swirl intensity on the flow and combustion characteristics of pulverized olive waste (OW) burning. Numerical simulations are carried out using the computational fluid dynamics (CFD) Commercial Software “Fluent ANSYS14” by choosing appropriate model parameters. The biomass furnace consists of a vertical cylinder equipped with a swirling co-flow injection burner. The particles of pulverized biomass (OW) are injected transversally into the furnace just near the co-flow exit, via four square-shaped injection nozzles. The non-premixed combustion model with mixture fraction/PDF model for turbulence-chemistry interactions is used. Standard k-ε turbulence model closure, discrete phase model (DPM) for tracking the motion of individual particle and P-1 radiation model for flame radiation inside the combustor are used in the numerical simulation. Four different swirl numbers Sn = 0.38, 0.95, 1.2 and 1.42 are used in this study in order to investigate the swirl intensity effect on the flow and combustion behavior. The results showed that the flow and the flame characteristics such as axial velocity, streamlines, gas temperature, flame length and CO2, CO and O2 concentrations are affected by the swirl intensity.