Methods for synthesizing diethyl carbonate from ethanol and supercritical carbon dioxide by one-pot or two-step reactions in the presence of potassium carbonate

Carbon dioxide sequestration was studied by synthesizing diethyl carbonate (DEC) from ethanol and CO2 under supercritical conditions in the presence of potassium carbonate as a base. The co-reagent was ethyl iodide or a concentrated strong acid. This sequestration reaction occurs in two steps, which were studied separately and in a one-pot reaction. An organic-inorganic carbonate hybrid, potassium ethyl carbonate (PEC) is generated at the end of the first step. This intermediate was characterized and was found to be a target molecule for CO2 capture. Different co-reactants, such as ethyl iodide and concentrated strong Brönsted acid, were compared in the second step and used to investigate the reactivity of the hybrid. With ethyl iodide as the co-reactant, one-pot DEC synthesis gave higher yields (46%) than two-step production. The supercritical CO2 acts as a swelling solvent and compatibilizing agent in the reaction medium, favoring interactions between ethanol and CO2 and between PEC and ethyl iodide. The use of a phase transfer catalyst (PTC) increased DEC production (yield 51%) without increasing the amount of diethyl ether (DEE) produced as a by-product (yield 2%)

Modelling the kinetics of transesterification reaction of sunflower oil with ethanol in microreactors

Transesterification reaction of vegetable oil with ethanol leads to ethyl esters, used to date for applications principally in food and cosmetic industry. To open the application field to biofuels (to substitute current fuels resulting from fossil resources), the process efficiency has to be developed to be economically profitable. In this work, the sunflower oil ethanolysis was performed in a micro-scaled continuous device, inducing better control for heat and mass transfer in comparison with batch processes. Moreover, this device ensures kinetic data acquisition at the first seconds of the reaction, which was not feasible in a conventional batch process. These data were used to model occurring phenomena and to determine kinetic constants and mass transfer coefficients. A single set of these parameters is able to represent the evolution of the reaction media composition function of time for five ethanol to oil molar ratios (6.0, 9.0, 16.2, 22.7 and 45.4). The model was validated in reaction and diffusion mode. Finally, it was subsequently used to simulate reactions with other operational conditions and to propose other process implementation

Valorisation chimique de composés lignocellulosiques : obtention de nouveaux matériaux

Le développement industriel et économique de ces dernières décennies a entraîné une forte production de déchets de l'agriculture. Une des valorisations possibles de ces co-produits est leur conversion en matériaux thermoplastiques par la modification chimique des fonctions hydroxyles de la matière lignocellulosique. Une méthode d’estérification du bois par des chlorures d’acides gras en l’absence de solvant organique est proposée. Un courant d’azote a permis d’entraîner le chlorure d’hydrogène formé au cours de la synthèse et de déplacer l’équilibre de la réaction. L’optimisation des conditions expérimentales (débit d’azote, température et durée de la réaction, quantité de chlorure d’acide) a permis d’obtenir avec le chlorure d’octanoyle un gain de poids expérimental de l’échantillon estérifié de 87% et un taux d’ester de 60%. Une fraction de bois estérifié (52%) s’est solubilisée dans le milieu réactionnel lors de l’estérification. Deux pré traitements de la matière lignocellulosique ont été testés : l’ozonisation et l’hydrolyse acide douce. Ce dernier est le plus intéressant car il conduit à un gain de poids expérimental plus élevé (102%). La généralisation de la réaction d’estérification du bois à d’autres chlorures d’acides gras (décanoïque à octadécanoïque) et à d’autres déchets lignocellulosiques (bagasse d'agave, jacinthe d’eau, paille de blé, moelle de sorgho) a mis en évidence une différence de réactivité liée à la composition chimique du substrat et à la longueur de la chaîne carbonée du réactif. L’estérification du bois par les chlorures d’acides gras lui a conféré de nouvelles propriétés telles que la thermoplasticité due à la diminution de la cristallinité de la cellulose du bois durant la modification chimique, l’hydrophobicité et une meilleure stabilité thermique

On-line monitoring of the transesterification reaction carried out in microreactors using near infrared spectroscopy

Biodiesel can be produced from vegetable oils, animal fats, and waste cooking oils by transesterification with ethanol (also called ethanolysis) in order to substitute fossil fuels. In this work, the batch ethanolysis of high oleic sunflower oil was transferred into a continuous microstructured device, which induces a better control of heat and mass transfers. Various parameters were studied, notably the initial ethanol to oil molar ratio. An innovative method using NIR spectroscopy was also developed to on-line monitor the transesterification reaction of high oleic sunflower oil with ethanol in microreactors (circular PFA tube 1/1600 OD, 0.0200 ID). The reactions were monitored directly in the microreactors through sequential scans of the reaction medium by the means of an adequate probe. The asset of the method is that no sample collection or preparation is necessary. Partial Least Squares regression was used to develop calibration and prediction models between NIR spectral data and analytical data obtained by a reference method (gas chromatography with flame ionization detection, GC–FID). This method is fast, safe, reliable, nondestructive and inexpensive contrary to conventional procedures, such as gas chromatography and high performance liquid chromatography generally used to determine the composition of crude transesterification medium

Computer-aided molecular design of alternative solvents based on phase equilibrium synergism in mixtures

A systematic methodology is proposed that finds binary azeotropic mixtures as new alternative solvents for the extraction process of volatile aroma molecules widely used in perfume and cosmetic industries. We investigated the use of the reverse engineering approach with Computer Aided Product Design (CAPD) instead of the traditional ‘trial and error’ approach. First, the design problem is defined from the real functionalities of the classical solvents. They are translated into physicochemical properties and the bound values for each property are defined. The reverse engineering method coupled to CAPD consists in using optimization techniques for building molecular structures that match as best as possible the complete set of target physicochemical properties, thus defining for each candidate a performance index. Property values are evaluated by using group contribution methods of each molecular structure generated by CAPD tool or by using database values. Acknowledging the contradictory relationship between two selected physicochemical properties i.e, low boiling temperature and high flash point which is rarely found in pure components, binary azeotropic mixtures were studied in order to enhance the global performance of solvent candidates. Dimethyl carbonate (DMC) is an existing solvent for the extraction of odorous molecules from plants that exhibits a good ratio between the boiling temperature and the flash point. It is selected as the key component for designing binary azeotropic mixtures. DMC. The global performance of the binary azeotropic mixtures was verified by means of calculations of the vapour-liquid equilibrium and liquid – liquid equilibrium using Modified UNIFAC method as thermodynamic method

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

Développement de nouveaux procédés de transestérification de triglycérides en microréacteurs - Applications : biocarburants, biodétergents, biosolvants

L’objectif de la thèse est d’étudier de nouveaux types de réacteurs permettant de dépasser les limites des technologies actuelles pour la transestérification de triglycérides avec de l’éthanol (ou bioéthanol). La réaction de transestérification est équilibrée et peut s’écrire globalement de la manière suivante : Triglycéride + 3EtOH ---> 3 RCO2Et + Glycérol. Cette réaction se décompose en trois réactions successives. La première étape est la conversion des triglycérides en diglycérides ; elle est suivie de la conversion des diglycérides en monoglycérides, qui sont finalement transformés en glycérol, en formant une molécule d’ester éthylique à chaque étape

Development of continuous processes for vegetable oil alcoholysis in microfluidic devices

Biodiesel can be produced from vegetable oils, animal fats, and waste cooking oils by transesterification with ethanol (also called ethanolysis) in order to substitute fossil fuels. In this work, we were interested in the transesterification reaction of sunflower oil with ethanol, which leads to ethyl esters, used to date for applications principally in food and cosmetic industry. To open the application field to biofuels (to substitute current fuels resulting from fossil resources), the process efficiency has to be developed to be economically profitable. The batch reaction of vegetable oil ethanolysis was transposed to a micro-scaled continuous device (PFA tube of 508 mm internal diameter), inducing better heat and mass transfer. Study of the influence of the operational conditions (reactants flow, initial ethanol to oil molar ratio, temperature. . .) revealed the favourable reaction parameters necessary to reach high conversions and yields. In these conditions, it is possible to acquire kinetics data at the first seconds of the reaction, which was not feasible in a conventional batch process. These data were used to model occurring phenomena and to determine kinetic constants and transfer coefficients. The model was subsequently used to simulate reactions with other operational conditions. To acquire these data in microreactors, an on-line analysis method by Near InfraRed (NIR) spectroscopy was developed by using gas chromatography as a reference method. PLS models were then set up to quantify on-line the major compounds contents during the reaction

Transestérification éthanolique d'huile végétale dans des microréacteurs (transposition du batch au continu)

La réaction de transestérification des huiles végétales avec de l'éthanol permet la production d esters éthyliques dont les applications industrielles sont, à ce jour, essentiellement cosmétiques ou alimentaires. Pour ouvrir le champ des applications aux biocarburants (pour substituer les carburants actuels issus de ressources fossiles), il est apparu nécessaire de développer un procédé de transestérification plus performant pour être économiquement rentable. Selon le schéma réactionnel et les propriétés thermocinétiques du système, les limites des procédés batchs existants pourraient être franchies en utilisant des procédés continus. Le système étudié est complexe en raison des changements d équilibres de phase notamment et de la présence simultanée de différents phénomènes (mélange, transferts de chaleur et de matière, réactions principales et compétitives) qui doivent être précisément contrôlés. Pour concevoir correctement un procédé continu et acquérir de nombreuses données, les microréacteurs apparaissent comme un outil approprié à cette transposition. Dans ce travail, nous avons transposé la réaction batch dans un dispositif microstructuré continu (tube PFA de diamètre interne 508 m) induisant un meilleur contrôle des transferts de chaleur et de matière. L étude de l influence des conditions de fonctionnement (débits des réactifs, rapport molaire initial huile/éthanol, température ) a permis de trouver des paramètres réactionnels favorables qui permettent d atteindre des conversions et rendements élevés. Dans ces conditions, nous avons montré qu il est possible d acquérir des données cinétiques dès les premières secondes de réaction, ce qui n était pas réalisable en réacteur batch conventionnel. Pour acquérir ces données en batch et en microréacteurs, nous avons développé une méthode d analyse en ligne par spectroscopie proche infrarouge en s appuyant sur la chromatographie en phase gazeuse comme méthode de référence. Des modèles PLS ont alors été établis pour quantifier en ligne les teneurs en composés majoritaires lors de la réaction de transestérification de l huile de tournesol hautement oléique avec l éthanol. A partir de ces données, les phénomènes mis en jeu ont été modélisés et les constantes cinétiques ainsi que les coefficients de transfert de cette réaction ont été déterminés. Le modèle a ensuite été utilisé pour simuler des réactions avec d autres conditions opératoires et il nous a permis de travailler sur la séparation des produits de la réaction.Transesterification reaction of vegetable oil with ethanol leads to ethyl esters, used to date for applications principally in food and cosmetic industry. To open the application field to biofuels (to substitute current fuels resulting from fossil resources), process efficiency has to be developed to be economically profitable. According to the reaction scheme and thermokinetic properties, limits of current batch processes can be overcome by carrying out continuous processes. The studied system is complex due in particular to phase equilibrium changes as well as simultaneous presence of various phenomena (mixing, heat and mass transfers, principal and competitive reactions) which have to be precisely controlled. Therefore, microreactors appear as the appropriate tool for transposition to a continuous process and acquisition of numerous data. In this work, batch reaction was transposed to a micro-scaled continuous device (PFA tube of 508 m internal diameter), inducing better heat and mass transfer. Study of the influence of the operational conditions (reactants flow, initial ethanol to oil molar ratio, temperature...) revealed the favourable reaction parameters necessary to reach high conversions and yields. In these conditions, we showed the possibility of acquiring kinetic data at the first seconds of the reaction, which was not feasible in a conventional batch process. To acquire data in batch and microreactors, an on-line analysis method by Near InfraRed (NIR) spectroscopy was developed by using gas chromatography as a reference method. PLS models were then set up to quantify the major compounds contents on-line during the transesterification reaction of high oleic sunflower oil with ethanol. These data were used to model occurring phenomena and to determine kinetic constants and transfer coefficients. The model was subsequently used to simulate reactions with other operational conditions and also to work on the separation of reaction products.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF