Synthesis of hierarchical silica zeolites for heterogenous catalysis and adsorption

Abstract

Novel pure-silica hierarchical zeolite molecular sieves have emerged within the field as ideal platforms for adsorption and heterogenous catalysis. Mesoporous/extra-large pure-silica zeolites (MPS) collectively adopt properties of both pure-silica and hierarchical frameworks, significantly surpassing the diffusion and reusability properties of conventional zeolites. Novel synthesis routes and methods reviewed within this work, range from the use of porous precursor silica seeds, green organic templating methods, supramolecular-assembly routes, to modern mesoporogen free approaches. Five novel MPS zeolite framework families (EL-SSZ, EL-EMM, M-NUD, M-Si-Beta and M-Silicalite-1) were discussed in comprehensive fashion in relation to their synthesis methods, architectural components, and applications in the fields of catalysis and mass transport. Synthesis principles and mechanisms related to mesoporous pure silica zeolite production were addressed in comprehensive fashion with relevant mechanisms schematically represented. Applications for these materials in heterogenous catalysis exhibited high catalytic activity in high-energy conditions while maintaining their structural stability and lifetime of the matrix phase, avoiding interference with the reaction phases. The reusability and high surface area of these materials offers an eco-friendly alternative to the use of non-durable catalytic platforms such as Palladium on Carbon, while performing with equal or superior activity. Due to the outstanding architectural porous features as well as their ultra-reusable nature, MPS zeolites herald a bright future in different sectors with possible solutions to unresolved problematics.