Ultrasound-assisted selective catalytic aqueous-phase oxidation of vanillyl alcohol under mild conditions

International audienc

Heterogeneous catalytic oxidation for lignin valorization into valuable chemicals: what results? What limitations? What trends?

International audienceLignin, a renewable polymer derived from the lignocellulosic biomass represents more than 20% of the total mass of the Earth's biosphere. However, 98% of lignin is burned as a source of energy in the pulp and paper industry, essentially due to its complex structure. Today, the valorization of lignin into the production of value-added chemicals represents a real challenge in terms of both sustainability and environmental protection. The present contribution aims to provide a critical discussion on the crucial choice of the starting material to study lignin valorization. Next, a comparison between the different oxidation routes investigated by chemists over the past several years is presented, with emphasis on the major difficulties encountered. The main current challenges regarding the heterogeneous catalytic oxidation of lignin and its derivatives are also highlighted. Particular focus is given to innovative strategies favoring mild reaction conditions. Finally, we provide some recommendations and routes worthy of interest in this studied area of research in order to generate value-added chemicals from lignin oxidation through the use of heterogeneous catalysts

Apport de la sonochimie pour l’oxydation sélective d’un modèle mono-aromatique de lignine

National audienc

Sonochemical oxidation of vanillyl alcohol to vanillin in the presence of a cobalt oxide catalyst under mild conditions

International audienceThe heterogeneous oxidation of vanillyl alcohol to vanillin was investigated on new grounds under ecofriendly conditions in the presence of hydrogen peroxide as an oxidant and water as solvent, coupled with low frequency ultrasonic irradiation. The sono-Fenton-like-assisted vanillyl alcohol oxidation was performed with a high-surface area nanostructured spinel cobalt oxide catalyst exhibiting small crystallites size. The catalytic reaction was also carried out under conventional heating conditions for comparison purposes. The influence of the reaction parameters, namely catalyst loading and hydrogen peroxide concentration was studied with the aim of determining the optimum yield and selectivity to the desired vanillin product. The chemical effects of ultrasound (ability to generate hydroxyl radicals) along with increased mass transfer appeared to be key prerequisites for enhancing the efficiency of the process, while decreasing the overall energy consumption

Qu’est-ce que la sonochimie ?

International audienceLa sonochimie, basée sur l’énergie acoustique et le phénomène de cavitation, met en œuvre les effets physiques et chimiques des ultrasons en milieux liquides. Depuis une trentaine d’années, les chimistes ont démontré que les ultrasons représentaient plus qu’un simple outil d’agitation. En fait, de nombreux travaux ont montré que la sonochimie permet d’une part l’amélioration des conditions de réactions chimiques en termes de sélectivité, rendement, quantité de catalyseur utilisé ou temps de réaction, mais également d’apporter de nouvelles solutions dans le domaine de la chimie.Après quelques rappels théoriques sur les ondes sonores et le phénomène de cavitation, ainsi qu’une parenthèse historique, cet article détaille les facteurs affectant les effets sonochimiques, l’équipement utilisé, ainsi que les paramètres sonochimiques à déterminer expérimentalement

Mechanochemical top-down preparation of active nanomaterials for the selective oxidation of lignin model compounds

International audienc

Mechanochemical preparation of nanostructured mixed oxide catalysts for selective oxidation reactions

International audienc

Selective oxidation of lignin model compounds catalyzed by cobalt titanate prepared through a mechanoactivation top-down approach

International audienc

Ultrasound-assisted synthesis of nanostructured oxide Mmaterials: basic concepts and applications to energy

International audienceThis chapter is focused on the use of high intensity ultrasound for the preparation of nanostructured materials with an emphasis on recent prominent examples of the production of dense or porous metal oxides through sonochemical and ultrasonic spray pyrolysis routes. Sonochemistry enables the synthesis of oxides that are often unachievable by traditional methods or affords known materials with shape, size, and nano/microstructure control under fast reaction conditions. The fundamental principles of acoustic cavitation, as well as the main ultrasonic parameters affecting the cavitation phenomenon, are first summarized. Next, the applications of ultrasound in the synthesis of nanostructured oxide materials following both preparation methods are reviewed. Particular focus is given to the ultrasound-assisted synthesis of metal oxide nanoparticles for energy applications

Sustainable biofuels and chemicals production using ionic liquids

International audienc