Probleemstelling:

Zeolites have received significant attention for their roles in the methanol-to-olefin (MTO) and biomass conversion processes. Zeolites with engineered transition metal sites are also an emerging yet comparatively less explored concept in heterogeneous catalysis.[1] A reaction of high interest and industrial relevance that could benefit from this concept are palladium-catalyzed arene couplings, as biaryl motifs are extensively found in fine chemicals. Homogeneous catalysts are well developed for this purpose,[2–4] but can be inefficient at industrial scales. Therefore zeolite-supported Pd systems are highly promising as they can combine the strengths of homogeneous and heterogeneous catalysis to provide superior selectivity, scalability and sustainability in fine chemicals production. Moreover, the Brønsted acidic sites within the zeolites may enhance the reactivity at the Pd centre, while the pores and channels may direct the process for regioselective outcomes in a manner that’s superior to current homogeneous processes.

Figure 1. Illustrative figure of arene cross-coupling catalyzed by cationic palladium in a zeolite.

Research is already underway in developing such catalytic systems, but a clear understanding of the underlying mechanisms is crucial for future developments. Experimental techniques such as spectroscopy and kinetic analyses can offer some insight, but a complete picture from experiment is often lacking due to the short lifespans and high reactivities of the intermediates in catalysis. State-of-the-art molecular modelling can fill this void by providing crucial insight into the reaction mechanism to assist with experiment, and thus drive the engineering of these processes forward for fine chemicals production.

Doelstelling:

The goal of this project is to characterize how the oxidative coupling of arenes takes place at the palladium sites within the zeolites, and how the zeolite-supported reactions compare with analogous homogeneous systems. The key catalytic steps under investigation will be arene adsorption and coordination, C-H activation, C-C coupling, reductive-elimination and Pd(0) re-oxidation, where a combination of static and dynamic simulations from first-principles will be employed to yield accurate energetics. Kinetic models can be constructed from these results, which in turn can be used to rationalize observed product selectivity, and make future predictions for reactivity.

The Center for Molecular Modeling has a wealth of experience in modelling zeolite catalysis with the aforementioned modelling techniques, and the student will be actively trained in them to address the problems at hand. The CMM also has access to large scale computational infrastructure for studying these complex systems, which the student will have ongoing access to assist with their project. Moreover, the student will be actively involved with an ongoing collaboration with the group of Professor Dirk De Vos at KU Leuven surrounding this topic.