Zeolite Catalysts Design: from the molecule, via the crystal, to the reactor scale
The development of new heterogeneous catalysts based on zeolites and related materials (POMs, SBA-15) was achieved by tailoring zeolite’s Brönsted acidity and/or adding metal cations known for their properties in homogeneous catalysis. In parallel to the molecular tailoring of zeolites, the design has also been performed at the microscopic level, by carefully controlling the size of the crystals and even their assemblies.
The combination of molecular and microscopic design remains relatively non-mature in the field of zeolite science. Crystal sizes influence the catalytic properties of zeolites. Indeed, large crystals favour shape-selective catalysis due to slow molecular diffusion, whereas small crystals enhance catalyst’s effectiveness. On the other hand, nanocrystal sizes
Our know-how acquired in the hydrothermal syntheses of zeolites either in alkaline or in fluoride medium led us to successfully apply those acid catalysts in different reactions, summarized as follows:
- Methanol-to-Hydrocarbons process: DME, MTO, MTG
- C-C coupling reaction to produce find chemicals
- Alkane activation and alkane cracking studies
- Electrophilic aromatic substitution
- Friedel-Crafts acylation
These studies allowed us to validate (to some extend) the importance of our rational approach for tailoring the zeolite properties.
Finally the main highlight consisted of developing a new Brönsted acid sites quantification in solid acids while using the H/D isotope labelling of the acid sites.