Strengthening the Connection between Science, Society and Environment to Develop Future French and European Bioeconomies: Cutting-Edge Research of VAALBIO Team at UCCS.

The development of the future French and European bioeconomies will involve developing new green chemical processes in which catalytic transformations are key. The VAALBIO team (valorization of alkanes and biomass) of the UCCS laboratory (Unité de Catalyse et Chimie du Solide) are working on various catalytic processes, either developing new catalysts and/or designing the whole catalytic processes. Our research is focused on both the fundamental and applied aspects of the processes. Through this review paper, we demonstrate the main topics developed by our team focusing mostly on oxygen- and hydrogen-related processes as well as on green hydrogen production and hybrid catalysis. The social impacts of the bioeconomy are also discussed applying the concept of the institutional compass.

Exsolution of Ni Nanoparticles from A-Site-Deficient Layered Double Perovskites for Dry Reforming of Methane and as an Anode Material for a Solid Oxide Fuel Cell.

Exsolution is a promising technique to design metal nanoparticles for electrocatalysis and renewable energy. In this work, Ni-doped perovskites, (Pr0.5Ba0.5)1-x/2Mn1-x/2Nix/2O3-δ with x = 0, 0.05, 0.1, and 0.2 (S-PBMNx), were prepared to design exsolution systems as solid oxide fuel cell anodes and for catalysis applications. X-ray diffraction and transmission electron microscopy (TEM) analyses demonstrated that correlating A-site deficiency with Ni content can effectively induce exsolution of all Ni under H2 atmosphere at T ∼ 875 °C, yielding the reduced (exsolved) R-PBMNx materials. On heating the exsolution systems in air, metal incorporation in the oxide lattice did not occur; instead, the Ni nanoparticles oxidized to NiO on the layered perovskite surface. The lowest area-specific resistance (ASR) under wet 5% H2/N2 in symmetrical cells was observed for R-PBMN0.2 anode (ASR ∼ 0.64 Ω cm2 at 850 °C) due to the highest Ni particle density in the R-PBMNx series. The best performance for dry reforming of methane (DRM) was also obtained for R-PBMN0.2, with CH4 and CO2 conversion rates at 11 and 32%, respectively, and the highest production of H2 (37%). The DRM activity of R-PBMN0.2 starts at 800 °C and is sustained for up to at least 5 h operation with little carbon deposition (0.017 g·gcat-1·h-1). These results clearly demonstrate that varying Ni-doping in layered double perovskite oxides is an effective strategy to manipulate the electrochemical performance and catalytic activity for energy conversion purposes.

Quasi-homogeneous oxidation of glycerol by unsupported gold nanoparticles in the liquid phase.

A quasi-homogeneous solution of gold nanoparticles prepared by the Turkevich method was used as an unconventional catalyst in the oxidation of glycerol (GLY) in the liquid phase. The highest obtained conversion was 100 % after 3 h of reaction at 100 °C under an oxygen atmosphere (5 bar). The main products were glyceric, glycolic, formic, tartronic, and oxalic acid with selectivities of 28, 36, 25, 9, and 2 %, respectively. Traces of hydroxypyruvic and acetic acid were also detected (combined selectivities below 1 %). To elucidate the reaction mechanism and specify the role of gold nanoparticles in the oxidation process, a series of experiments under various reaction conditions were carried out. The effect of reaction temperature, oxygen pressure, gold concentration, and GLY/base molar ratio was investigated. All catalytic results were systematically compared to the corresponding noncatalytic base-induced transformations (blank tests). Such an approach allowed us to separate and clarify the respective driving parameters for the transformation of GLY (presence of a base and activity of the gold catalyst). The reaction mechanism comprised a series of oxidation and C-C cleavage reactions, whereas additional oxidation-reduction reactions (of the Cannizzaro type) could also occur in the presence of the base.

Transesterification of diethyl oxalate with phenol over sol-gel MoO(3)/TiO(2) catalysts.

The transesterification of diethyl oxalate (DEO) with phenol to form diphenyl oxalate (DPO) has been carried out in the liquid phase over very efficient MoO(3)/TiO(2) solid-acid sol-gel catalysts. A selectivity of 100 % with a remarkable maximum yield of 88 % were obtained, which opens the route to downstream phosgene-free processes for the synthesis of polycarbonates. Interpretation of the results of various acidity measurements (NH(3) and pyridine desorption, methanol oxidation as a probe reaction) allowed us to identify the catalytic sites as Lewis acid sites.