From technical lignins to aromatics: a study on oxidative depolymerization in batch and continuous reactor

SSCI-VIDE+CDFA+AHM:SMA:LDJInternational audienceLignin is nowadays very studied as potential raw material for the production of high added-value molecules. This biopolymer represents the only resource composed by aromatic monomeric units, and presents an interesting alternative in the production of several compounds. Valorization of lignin is not very extended yet and different technologies needs to be developed in order to make it more efficient and cheap. In this project, the main goals are to study and optimize the depolymerization of lignin in oxidative conditions using affordable catalyst like copper-based catalyst.The catalytic oxidizing depolymerization of lignins has been studied in alkaline conditions in the presence of heterogeneous copper-based catalyst. The reaction conditions are 150°C, 20 Bar of air and 1800 rpm. 5%CuO/TiO2 has been used as catalyst. Three main fractions have been obtained from this process: the residual lignin that exhibits various chemical modifications, an aromatic fraction mainly composed by vanillin, acetovanillone and syringaldehyde, and an aliphatic fraction mainly composed by succinic, oxalic and acetic acids.Several technical lignins obtained from different biomasses have been studied initially in batch reactor. They come from Softwood (Resinous and Pine), Hardwood (Eucalyptus) and Wheat straw and were extracted by several methods such as Kraft, Organosolv and Soda processes. Hardwood and Wheat straw lignins show higher degrees of oxidation producing an important amount of aliphatic fraction (68-55%) compared to softwood lignins (33-46%). As expected from these biomasses, it showed an important quantity of syringaldehyde in the aromatic fraction. Both softwood lignins showed the same behavior, but resinous lignin led to the lowest degree of liquefaction associated to a low quantity of phenols. Next, we observed that the extraction method played also an important role. As an example, for Wheat straw, Organosolv extraction led to increased aliphatic fraction ratio with reduced quantity of aromatics compared to Soda process. Similar observations comparing Kraft and Organosolv processes were made.Data thus obtained from batch reactor studies allowed transposition to continuous fixed bed reactor. Different aspects, incl. catalyst deactivation, mass transfer limitations, influence of time contact were evaluated. Initial data showed similar results to batch reactor using the same reaction time. The reaction conditions are being optimized to maximize the aromatic production

Transformation of Sorbitol to Biofuels by Heterogeneous Catalysis: Chemical and Industrial Considerations Transformation du sorbitol en biocarburants par catalyse hétérogène : considérations chimiques et industrielles

Decreasing oil supplies and increasing energy demand provide incentives to find alternative fuels. First, the valorisation of edible crops for ethanol and biodiesel production led to first generation biofuels. Nowadays, research is focused on lignocellulosic biomass as a source of renewable carbon (second generation biofuels). Whereas the cellulosic ethanol production is in progress, a new way consisting of the transformation of ex-lignocellulose sugars and polyols towards light hydrocarbons by heterogeneous catalysis in aqueous phase has been recently described. This process is performed under mild conditions (T La raréfaction du pétrole et l’augmentation conjointe de la demande en carburants ont conduit à la recherche de carburants alternatifs. Dans un premier temps, la valorisation de ressources agricoles alimentaires pour la production d’éthanol et de biodiesel a permis de développer les biocarburants de première génération. Aujourd’hui les travaux de recherche s’orientent vers l’utilisation de biomasse lignocellulosique comme source de carbone renouvelable (biocarburants de deuxième génération). Alors que la filière de l’éthanol cellulosique est en plein développement, une nouvelle voie consistant à transformer des sucres et polyols d’origine lignocellulosique en alcanes légers par catalyse hétérogène bifonctionnelle en phase aqueuse a été récemment décrite. Ce procédé s’effectue à basse température et pression modérée (T < 300 °C et P < 50 bar). Il nécessite, d’une part, la formation d’hydrogène par reformage catalytique de carbohydrates en phase aqueuse et, d’autre part, la déshydratation/hydrogénation de polyols conduisant à un alcane par ruptures sélectives des liaisons C-O. Un défi lié à cette thématique réside dans le développement de systèmes catalytiques multifonctionnels stables, actifs et sélectifs dans les conditions de la réaction de transformation. L’objectif de l’article est de présenter les réactions mises en jeu, les systèmes catalytiques décrits dans la littérature pour ce type de transformation ainsi que des exemples d’applications industrielles

Catalytic Liquefaction of Kraft Lignin with Solvothermal Approach

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Transformation of Sorbitol to Biofuels by Heterogeneous Catalysis: Chemical and Industrial Considerations

Decreasing oil supplies and increasing energy demand provide incentives to find alternative fuels. First, the valorisation of edible crops for ethanol and biodiesel production led to first generation biofuels. Nowadays, research is focused on lignocellulosic biomass as a source of renewable carbon (second generation biofuels). Whereas the cellulosic ethanol production is in progress, a new way consisting of the transformation of ex-lignocellulose sugars and polyols towards light hydrocarbons by heterogeneous catalysis in aqueous phase has been recently described. This process is performed under mild conditions (T < 300 °C and P < 50 bar). It requires on one hand hydrogen formation by catalytic reforming of carbohydrates in aqueous phase and on the other hand, the dehydration/hydrogenation of polyols leading to alkanes by selective C-O bond cleavages. The challenge here is to conceive multifunctional catalytic systems that are stable, active and selective under the reaction conditions. The aim of this article is to present the involved reactions, the catalytic systems described in literature for that kind of transformation and examples of industrial applications

LIGNIN DEPOLYMERIZATION IN OXIDATIVE CONDITIONS: FROM BATCH TO CONTINUOUS REACTOR

SSCI-VIDE+CDFA+AHM:LDJ:SMAInternational audienceLignin, a natural polymer synthesized by plants in structural tissues, is one of the most intriguing material for utilization across a wide range of applications. Depolymerization and fragmentation of lignin into small chemicals which can either replace current market products or be used as building blocks for new material synthesis is a focus of current lignin valorization strategies. In this work, we investigated the catalytic valorization of lignin in aqueous media under oxidative conditions with copper based heterogeneous catalysts. The ultimate goals of this project are to i) depolymerize lignin in small units usable directly after purification, ii) break lignin matrix into smaller fragments easy to convert afterword, iii) maintain a low level of over-oxidized materials, char and condensed polyquinones

Influence of Reduction-Carburization Parameters on the Performance of Supported Molybdenum Carbide Catalysts in Succinic Acid Hydrogenation

SSCI-VIDE+CDFA+ALI:CPI:NPRInternational audienceMolybdenum carbides supported on TiO2 or ZrO2 were prepared by a temperature-programmed reduction–carburization method using mixtures of hydrogen and hydrocarbon (methane or ethane). All of the materials exhibited molybdenum carbide with a cubic crystallographic structure. The carbon content and the MoC lattice parameter increased with the increase of the hydrocarbon percentage (5–40%) and temperature (600–800 °C) during carburization. All catalysts were significantly active in the hydrogenation of succinic acid to butyric acid and γ-butyrolactone. For the first time, a correlation between the degree of carburization and the catalytic activity for succinic acid hydrogenation was established. The selectivity depends strongly on the support. MoC/TiO2 favored the formation of butyric acid, while MoC/ZrO2 and bulk MoC generated γ-butyrolactone primarily. The stability of MoC/TiO2 up to 50 h on stream in a continuous reactor was demonstrated, showing the interest of carbide catalysts for future biorefinery processes