Public Thesis defense - IMCN

Sol-gel routes to nanostructured bifunctional catalysts for the direct conversion of (bio)ethanol to 1,3-butadiene by Denis DOCHAIN

Pour l’obtention du grade académique de Doctorat en sciences agronomiques et ingénierie biologique

In the fight against climate change, the search for alternatives to the petro-based industry has become a priority. Heterogeneous catalysis is involved in the vast majority of our chemical processes and can become the pivotal point to shift to renewable bio-based resources as feedstocks for those chemical processes. 1,3 butadiene, a key monomer in the tyre and nylon industry, attracts a lot of attention in the research field due to a fore coming instability in its market because of shale gas exploitation. In parallel, the production of bioethanol is expected to reach 150 billion litres in 2032. Thus, sustainable alternative synthesis pathways such as the catalytic conversion of ethanol to 1,3 butadiene are under extensive research. To maximize the industrial viability of such a process, the synthesis of this new generation of heterogeneous catalysts must be straight-forward and should consist of as few steps as possible. Furthermore, the ethanol-to-butadiene reaction requires Lewis acid sites and metal nanoparticles as redox sites, hence the need for a bifunctional catalyst with highly dispersed active species. These challenges are discussed in this thesis and addressed via the use of innovative sol gel techniques.

In the first half of this thesis, an aerosol assisted sol gel approach is used to synthesize Ag Ta and Cu Ta-based catalysts. These bifunctional catalysts display advantageous mesoporous texture preventing mass transfer limitations, inserted Ta atoms inside the silica matrix serving as Lewis acid sites and well dispersed small Ag or Cu nanoparticles as redox sites. Understanding the catalyst properties and tuning them allow us to obtain remarkable catalytic performance in the ethanol to butadiene reaction.

In the second half, the non hydrolytic sol gel approach is leveraged for the synthesis of Cu Ta-based catalysts. First, two different synthesis routes, the ether route and the acetamide elimination route, are compared to better understand the active sites speciation, their proximity and the influence of those characteristics on catalytic properties. The acetamide elimination route is deemed more appropriate for the ethanol-to-butadiene reaction, as it promotes the formation of catalytic sites more active in the rate limiting step. Finally, an innovative synthesis protocol is designed to combine the best properties of the two synthesis pathways in one synthesis protocol. The mixing of both routes in a so-called “delayed addition” of a fraction of precursors yield bifunctional materials with properties originating from both distinct synthesis routes and reasonable catalytic performance.

Jury members :

• Prof. Damien Debecker (UCLouvain), supervisor
• Prof. Eric Gaigneaux (UCLouvain), chairperson
• Prof. Michel Devillers (UCLouvain), secretary
• Dr. Ales Styskalik (Masaryk University, Czech Republic)
• Prof. Stéphanie Lambert (ULiège)
• Prof. Mickael Capron (Université de Lille, France)

Pay attention :

The public defense of Denis Dochain scheduled for Wednesday 13 December at 02:00 p.m will also take place in the form of a video conference

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