Agenda de l'ENS de Lyon

Engineering the catalysis of selected metals in the oxidation of biomass derivatives using DFT calculations

ven 24 mar 2023

14 heures


Soutenance de M. OYEGOKE Toyese sous la direction de Mme MICHEL Carine et sous la codirection de M. BABA El-Yakubu Jibril

Langue(s) des interventions
Description générale

Hydroxymethyl furfural (HMF) and furfural (FF) have been identified as key bio-refinery platforms for the synthesis of new materials. The conversion of these platform molecules into intermediates increasingly relies on heterogeneous catalysis rather than the enzymatic approach in recent years. One of these catalytic processes is the oxidation of HMF and FF to 2,5-furan dicarboxylic acid (FDCA) and furoic acid (FA), using O2 as oxidant and supported gold catalysts. However, oxidation faces degradation challenges when using heterogeneous catalysts, leading to low yield and poor selectivity for FDCA and FA. In this thesis, we proposed a redesign strategy of the Au catalyst to retard the degradation activities reported in the oxidation of biomass derivatives (HMF and FF) on Au. Our study uses a theoretical approach based on the periodic density functional theory. First, we showed that the activation of O2 when working in a liquid water environment is metal dependent: OH forms on Au, while O forms on Pt and Pd. Then, the oxidation and degradation pathways of HMF and FF on Au were identified by computing the stability of possible surface intermediates. This study shows that the alcohol function is more difficult to oxidize than the aldehyde function in HMF and this step is probably the rate-determining step. Regarding degradation, the furan ring’s C-H is the most sensitive to oxidation compared with other routes examined. Analysis of the same reaction on Pt and Pd shows the mechanism to be the same, with greater stability of intermediates leading to higher activity but also higher degradation. Finally, the effect of alloying on Au catalysis was evaluated, showing that AuPd alloy improves the kinetics, while AuPt alloy improves HMF oxidation selectivity and delays degradation activity. Our study suggests alloying Pt and Au to retard HMF degradation, the main threat. Alternatively, alloying Pt and Pd with Au to form a trimetallic alloy would improve kinetics and retard HMF degradation.


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