Laurent E. Prat

Co-axial capillaries microfluidic device for synthesizing size- and morphology-controlled polymer core-polymer shell particles

An easy assembling-disassembling co-axial capillaries microfluidic device was built up for the production of double droplets. Uniform polymer core-polymer shell particles were synthesized by polymerizing the two immiscible monomer phases composing the double droplet. Thus poly(acrylamide) core-poly(tri(propylene glycol) diacrylate) shell particles with controlled core diameter and shell thickness were simply obtained by adjusting operating parameters. An empirical law was extracted from experiments to predict core and shell sizes. Additionally uniform and predictable non-spherical polymer objects were also prepared without adding shape-formation procedures in the experimental device. An empirical equation for describing the lengths of rod-like polymer particles is also presented.

On-line monitoring of the transesterification reaction between triglycerides and ethanol using near infrared spectroscopy combined with gas chromatography.

Many analytical procedures have been developed to determine the composition of reaction mixtures during transesterification of vegetable oils with alcohols. However, despite their accuracy, these methods are time consuming and cannot be easily used for on-line monitoring. In this work, a fast analytical method was developed to on-line monitor the transesterification reaction of high oleic sunflower oil with ethanol using Near InfraRed spectroscopy and a multivariate approach. The reactions were monitored through sequential scans of the reaction medium with a probe in a one-liter batch reactor without collecting and preparing samples. To calibrate the NIR analytical method, gas chromatography-flame ionization detection was used as a reference method. The method was validated by studying the kinetics of the EtONa-catalyzed transesterification reaction. Activation energy (51.0 kJ/mol) was also determined by considering a pseudo second order kinetics model.

Accurate Measurement of the Photon Flux Received Inside Two Continuous Flow Microphotoreactors by Actinometry

Abstract In this study, the photon flux received in two continuous flow microphotoreactors was measured by actinometry (potassium ferrioxalate). The microphotoreactors had two different geometries and were irradiated by either a polychromatic or a monochromatic light source. A model considering the partial absorption of photons through the reactor depth and, if required, the polychromatic character of the light source and the dependence of the actinometer properties on the wavelength were formulated to describe the variation of the actinometer conversion with the irradiation time. The photon flux received in the microphotoreactors could be thus accurately calculated as a function of the emitted wavelength. The same methodology was then applied to measure the photon flux received in a batch immersion well photoreactor. The radiant power received in each photoreactor was compared to that emitted by the lamp and major differences were found, thus confirming the need for this kind of in situ measurement. Finally, some guidelines based on a knowledge of the photon flux were proposed to compare various photoreactors. They revealed in particular that the choice of the most efficient photoreactor depended on the criteria chosen to evaluate the performances (i.e. productivity, Space Time Yield).

Dynamic models for start-up operations of batch distillation columns with experimental validation

The simulation of batch distillation columns during start-up operations is a very challenging modelling problem because of the complex dynamic behaviour. Only few rigorous models for distillation columns start-up are available in literature and generally required a lot of parameters related to tray or pack geometry. On an industrial viewpoint, such a complexity penalizes the achievement of a fast and reliable estimate of start-up periods. In this paper, two “simple” mathematical models are proposed for the simulation of the dynamic behaviour during start-up operations from an empty cold state. These mathematical models are based on a rigorous tray-by-tray description of the column described by conservation laws, liquid–vapour equilibrium relationships and equations representative of hydrodynamics. The models calibration and validation are studied through experiments carried out on a batch distillation pilot plant, with perforated trays, supplied by a water methanol mixture. The proposed models are shown by comparison between simulation and experimental studies to provide accurate and reliable representations of the dynamic behaviour of batch distillation column start-ups, in spite of the few parameters entailed.

A one dimensional model for the prediction of extraction yields in a two phases modified twin-screw extruder

Solid/liquid extraction is performed on raw plant substrate with a modified twin-screw extruder (TSE) used as a thermo-mecano-chemical reactor. Visual observations and experimental residence time distributions (RTD) are used to develop a solid transport model based on classical chemical engineering method. Modeled and experimental residence times are compared. The transport model is then coupled with a reactive extraction model in order to predict extraction yields.

Two phase residence time distribution in a modified twin screw extruder

Biomass fractionation is performed with a modified Clextral twin-screw extruder used as a thermo-mechano-chemical reactor. This new process is firstly analyzed. Visual observations, residence time distributions, and global mass balances are used to obtain information about the process phenomena and their coupling. Residence time distributions (RTD) classical models are adopted to represent the experimental plots. The influence of continuous and discrete process parameters upon the RTD of the solid and liquid phases is analyzed.

Influence of solvent choice on the optimisation of a reaction–separation operation : application to a Beckmann rearrangement reaction

In pharmaceutical syntheses, the solvent choice generally represents a complex design step. Traditionally, this choice is operated according to criteria connected with the reaction step and without any consideration on the following separation steps. The purpose of this study is to highlight the benefits of a global approach of optimisation for the solvent determination. In this way, an optimisation framework dedicated to global synthesis is applied to a simple reaction–separation operation integrating a Beckmann rearrangement reaction, leading to interesting solvent choices.

Intensification of Ester Production in a Continuous Reactor

Numerous continuous intensified reactors are now accessible on the market that offer enhanced thermal performances in a continuous reactor. Such reactors are then particularly suited to fast and highly exothermic reactions. In this paper, the ability to also manage a slow and equilibrated system, the methyl acetate esterification reaction, on condition of intensification in terms of design and operating conditions is presented. To achieve this purpose, a new kinetics model has been developed and validated from experiments carried out in a lab scale batch reactor. Implemented in a simulation framework, this model leads to an intensified design of the reactor and the associated operating conditions. All this intensification methodology has been supported and validated by experimental studies.

Optical Feedback Interferometry for Velocity Measurement of Parallel Liquid-Liquid Flows in a Microchannel

Optical feedback interferometry (OFI) is a compact sensing technique with recent implementation for flow measurements in microchannels. We propose implementing OFI for the analysis at the microscale of multiphase flows starting with the case of parallel flows of two immiscible fluids. The velocity profiles in each phase were measured and the interface location estimated for several operating conditions. To the authors knowledge, this sensing technique is applied here for the first time to multiphase flows. Theoretical profiles issued from a model based on the Couette viscous flow approximation reproduce fairly well the experimental results. The sensing system and the analysis presented here provide a new tool for studying more complex interactions between immiscible fluids (such as liquid droplets flowing in a microchannel).

Optimisation of global pharmaceutical syntheses integrating environmental aspects

Publisher Summary Pharmaceutical synthesis optimization, because of its complexity, is often reduced to the optimization of the reaction step. This chapter discusses the dynamic model, allowing simulating the different synthesis steps and, particularly start-up and shut-down phases involved. This model connected to an optimization method is able to provide the optimal operating conditions satisfying a global objective. The application to an industrial process highlights the benefits of the proposed methodology. The chapter describes the operating conditions involving the optimization of the global synthesis, satisfying economical and environmental criteria, to develop sustainable methodologies. For this purpose, a framework based on a simulation program, modeling a global synthesis (reaction and separation steps), has been developed. Besides global synthesis treatment, the main features of this work lie in the modeling of batch units and of dynamics, particularly during the start-up and the shut-down involved in the different step.