Role of structural properties of Ni-based catalysts towards aqueous glucose hydrogenation

Pour l’obtention du grade de Docteur en sciences

Biomass is currently the only sustainable resource for the production of organic carbon and biofuels. Among the varieties of organic molecules obtainable from biomass, sorbitol has been recognized as one of the 12 most important platform chemicals, widely applied in food industry, medical applications, cosmetic industry and other miscellaneous uses. It is usually produced by glucose hydrogenation in the presence of metal-based catalysts like Ni, Ru, Pt, Co. Noble metal catalysts such as Ru demonstrate better catalytic performance than non-noble ones like Ni, while the latter is more preferable on the industrial scale due to its low cost and availability. Optimizing non-noble catalysts systems to push their properties closer to noble metals is also crucial for gaining overall understanding on the nature and associated mechanisms of non-noble metal formulations.

Thus, in this thesis, three aspects have been considered to design Ni -based non-noble metal nanoparticles (NPs) catalysts – shape, size and composition. We first obtained bare Ni nanoparticles with different shapes, and analysed their morphologies, crystallinities and compositions. Amorphous structures and P-doping were found to be critical factors in enhancing catalytic performance of Ni, which leads to the Ni nanosphere catalyst being a very active system with a reaction barrier of only 22.5 kJ/mol for glucose hydrogenation. This value is lower than with a commercial Ru catalyst. Secondly, carbon supports - carbon black (CB) and graphite nanoplatelets (GNPs) were introduced to disperse the NPs. By controlling the sintering of Ni particles, different NPs sizes (7 nm to 24 nm) were obtained on both supports. Ni catalysts on CB support showed higher reactivities than with GNPs support. In addition, Ni particles with an average size of 17 nm were demonstrated to exhibit the highest catalytic performance compared to other sizes. Thirdly, Fe was introduced into the Ni catalysts, forming Fe-Ni alloy catalysts, which achieves more than twice the glucose conversion of a monometallic Ni catalyst. The Fe:Ni ratio 1:1 was identified as the best compromise to achieve a high catalytic activity as well as a high sorbitol selectivity. At the end of the thesis, we investigated the changes of morphology, crystallinity and composition in the catalysts before and after use. Sintering, surface oxidation and leaching were found to be the main causes of deactivation, and the mitigation of leaching was eventually achieved by changing the catalyst composition and reaction conditions and solvent.

Jury members :

• Prof. Sophie Hermans (UCLouvain), promotrice
• Prof. Michael Singleton (UCLouvain), promoteur
• Prof. Yann Garcia (UCLouvain), président
• Prof. Yaroslav Filinchuk (UCLouvain), secrétaire
• Prof. Eric Gaigneaux (UCLouvain)
• Prof. Vincent Dubois (LABIRIS, Belgique)
• Prof. Sébastien Paul (Centrale Lille, France)

Pay attention :

The public defense of Fang Yu scheduled for Tuesday 15 March at 2:00 p.m will also take place in the form of a video conference

Télécharger l'annonce