Heteroaggregation and Selective Deposition for the Fine Design of Nanoarchitectured Bifunctional Catalysts: Application to Hydroisomerization

We successfully prepared bifunctional catalysts with the distance between metallic and acid sites tuned at the nanometer scale. Sols of β-zeolite nanoparticles were synthesized and mixed in optimized conditions with a γ-AlOOH boehmite suspension to yield alumina/zeolite aggregates with a nanometer scale intimacy. The composition of the aggregate could be tuned from pure alumina to pure zeolite. Then, by carefully choosing the Pt precursor and the pH conditions, we were able to selectively deposit platinum, either on alumina or in zeolite domains. A subsequent, soft thermo-reduction step was applied that produced well-dispersed Pt nanoparticles either on alumina or in the zeolite nanodomains as confirmed by 3D tomography microscopy experiments. The catalytic properties of the obtained nanostructured catalysts were studied through n-heptane conversion. Comparison of these original bifunctional catalysts with monofunctional or conventional bifunctional catalysts showed the impact of the location of the metallic particles on the selectivity.