'Hierarchy' is a property which can be attributed to a manifold of different immaterial systems, such as ideas, items and organisations or material ones like biological systems within living organisms or artificial, man-made constructions. The property 'hierarchy' is mainly characterised by a certain ordering of individual elements relative to each other, often in combination with a certain degree of branching.Especially mass-flow related systems in the natural environment feature special hierarchically branched patterns. This review is a survey into the world of hierarchical systems with special focus on hierarchically porous zeolite materials. A classification of hierarchical porosity is proposed based on the flow distribution pattern within the respective pore systems. In addition, this review might serve as a toolbox providing several synthetic and post-synthetic strategies to prepare zeolitic or zeolite containing material with tailored hierarchical porosity. Very often, such strategies with their underlying principles were developed for improving the performance of the final materials in different technical applications like adsorptive or catalytic processes. In the present review, besides on the hierarchically porous allzeolite material, special focus is laid on the preparation of zeolitic composite materials with hierarchical porosity capable to face the demands of industrial application.

Zeolite crystals with an embedded and interconnected macropore system are prepared by using mesoporous silica particles as a silica source and as a sacrificial macroporogen. These novel hierarchical zeolite crystals are expected to reduce diffusion limitations in all zeolite-catalyzed reactions, especially in the transformation of larger molecules like in the catalytic cracking of polymers and the conversion of biomass.

The successfuls ynthesis of hierarchically structured titaniums ilicalite-1 (TS-1) with large intracrystalline macroporesb ys team-assisted crystallisation of mesoporous silica particlesi sr eported. The macropore topologyw as imaged in 3D by using electron tomographya nd synchrotron radiation-based ptychographic X-ray computed tomography,r evealing interconnected macropores within the crystals accounting for about3 0% of the particle volume. The study of the macropore formation mechanism revealed that the mesoporous silica particles act as as acrificial macropore template during the synthesis. Silicon-to-titanium ratio of the macroporous TS-1 samples was successfully tuned from 100 to 44. The hierarchically structured TS-1 exhibited high activity in the liquid phase epoxidation of 2-octene with hydrogen peroxide.T he hierarchically structured TS-1 surpassed ac onventional nano-sized TS-1 sample in terms of alkene conversion and showed comparable selectivity to the epoxide. The flexible synthesis route described herec an be used to prepare hierarchical zeolites with improved mass transport properties for other selective oxidation reactions.

Designing astable and selective catalyst with high H 2 utilisation is of pivotal importance for the direct gas-phase epoxidation of propylene.This work describes afacile one-pot methodology to synthesise ligand-stabilised sub-nanometre gold clusters immobilised onto az eolitic support (TS-1) to engineer as table Au/TS-1 catalyst. An on-thermal O 2 plasma technique is used for the quickremoval of ligands with limited increase in particle size. Compared to untreated Au/TS-1catalysts prepared using the deposition precipitation method, the synthesised catalyst exhibits improved catalytic performance,i ncluding 10 times longer lifetime (> 20 days), increased PO selectivity and hydrogen efficiency in direct gas phase epoxidation. The structure-stability relationship of the catalyst is illustrated using multiple characterisation techniques,s uch as XPS, 31 PM AS NMR, DR-UV/VIS,H RTEM and TGA. It is hypothesised that the ligands play ag uardian role in stabilising the Au particle size, whichi sv ital in this reaction. This strategy is ap romising approach towards designing amore stable heterogeneous catalyst.

Hierarchical MFI zeolites with differently sized macropores were synthesised and a correlation between the macropore diameter and catalyst lifetime was found.