The aim of the OxCyCat-CO2 project is to use CO2 as both a reagent and a solvent (supercritical conditions) to prepare cyclic carbonates of interest starting from the corresponding olefins via a one-pot reaction with hydrogen peroxide or molecular oxygen. To achieve this, new multifunctional heterogeneous catalysts will be developed by combining, on the same mesoporous support, active phases that are able to catalyze the epoxidation of alkenes and the further cycloaddition of CO2 under the same experimental conditions.
Two ligand libraries, lacunary polyoxometalates (W-POMs) and nitrogen Schiff bases (BS-4Ns) are available within the consortium. W-POM species will be used to catalyze the epoxidation of alkenes in the presence of H2O2 and will be compared to Mn(III) complexes involving BS-4N ligands also able to catalyze epoxidations in the presence of dioxygen and of an aldehyde. The same nitrogen Schiff bases associated with zinc (II) will also be exploited for the cycloaddition reaction of CO2 onto epoxides. These different active phases will then be combined, thus allowing the definition of two classes of bifunctional catalytic systems according to whether they involve i) both polyoxometalates and complexes with nitrogen Schiff bases ("Mix POM / BS-4N ") intended for operations with H2O2 / CO2, or (ii) only complexes derived from Schiff bases (" all BS-4Ns ") intended for operations with O2 / CO2.
In a first approach, these combinations will be tested in solution. In particular, we shall ensure that the two active phases can work in synergy under comparable solvent, temperature and pressure conditions without interfering with one another. An important challenge of the project is to lower the optimum temperature of the CO2 cycloaddition reaction via the design of suitable BS-4N ligands with the help of theoretical chemistry colleagues involved in the consortium. The reactions will first be carried out in organic solvent, a priori in acetonitrile, and then transposed into supercritical CO2. This last solvent will be preferred, especially for combinations of CO2 with O2 in order to limit the risks of explosiveness. Moreover, this association suggests the possibility of using CO2 emissions that are not completely purified. Some terminal and internal alkenes representative of industrial requirements will be considered. Chiral versions of the catalytic "all BS-4Ns" system will be developed and then tested in the context of the enantioselective epoxidation of alkenes and then in the overall process.
Polyoxometalates will then be grafted by amide bonds to the surface of mesoporous silicas and complexes with BS-4N ligands by Si-O-Si bonds. For the sake of simplification, and ultimately, in the case of "all BS-4Ns", the use of a single metal / BS-4N complex to perform both reactions (epoxidation and cycloaddition) will be preferred. In the case of "Mix POM / BS-4N", the pre-association of the two entities in one edifice that will be grafted later through amide linkages will be encouraged.
Laboratoire de Réactivité de Surface (Laboratoire public)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Institut des Sciences Analytiques
Laboratoire de Réactivité de Surface
Institut de Recherches sur la Catalyse et l'Environnement de Lyon
Institut Parisien de Chimie Moléculaire
Help of the ANR 508,874 euros
Beginning and duration of the scientific project: September 2017 - 48 Months