Zeolites are employed as acidic catalysts in refining, petrochemistry, pollution abatement, and biomass. These microporous materials are crystalline structures built from corner-connected SiO4 and AlO4 tetrahedra. The enhancement of the acidic properties of zeolites by specific chemical and thermal treatments proceeds through structural and chemical changes at both volume and surface scales of the mineral.
Physics and Analysis
In order to reduce the energy consumption of catalytic processes, one of the levers is to optimize catalysts. This optimization is accompanied by an ever-increasing need to characterize these solids. This is particularly the case for hydrotreating catalysts that produce fuels and chemical intermediates with low environmental impact.
Alumina remains the unavoidable catalyst support used in heterogeneous catalysis in the refining field. This material has a multi-scale hierarchical porosity that extends from nano to micron pores. It is obtained through calcination (topotactic) of boehmite pastes. Upstream, these pastes result from unit operations such as synthesis, drying, peptization, filtration and shaping (by drying, by extrusion). It has been shown that the porous structure of alumina is largely inherited from the structure of boehmite nano-crystal aggregates in aqueous phase.
The use of solar energy to convert CO2 into hydrocarbons could mitigate two main problems : global warming and future energy demand. The photocatalytic route is pertinent, but the process yield remains low even for the most efficient developed materials and many questions stay opened regarding the intrinsic properties of the photocatalyst to be optimized and about the reactional mechanisms.