Hierarchically‐Ordered Zeolites: A Critical Assessment

Abstract

Hierarchically‐ordered zeolites have received increasing attention in the last 15 years due to their outstanding properties, which are explored in catalytic reaction with industrial relevance. Up to now, a large number of different synthetic strategies have been reported that allow to introduce an additional meso‐ or macropore system in addition to the intrinsic microporosity of classical zeolites. Thus, hierarchical zeolites combine the intrinsic (catalytic) properties of conventional zeolites with facilitated access and transport via the additional pore system. In this critical review, the various synthesis pathways reported so far are evaluated, several physico‐chemical methods required for in‐depth characterization of the hierarchical pore system are discussed, and selective applications that are or potentially will be of technical relevance are introduced. The present review provides a critical analysis of the present achievements and discusses future opportunities and challenges for the research on hierarchically‐ordered zeolite in particular with respect to their industrial use.

Systematic analysis of the nitrogen adsorption-desorption isotherms recorded for a series of microporous – mesoporous amorphous aluminosilicates using classical methods

“…The latter, despite the humongous number of materials that follow into this category such as some amorphous silica-aluminas, 5 molecular organic frameworks 46,47,62,63 , and zeolites both classic such as ZSM-5 64,65 and hierarchical ones. 39,40 The other proposed category is type IV(c). In this instance, though the isotherm could be classified as a type IV(a), the fact that it displays unlimited adsorption at P/P0 > 0.7 makes it inadequate to classify it as such, in our opinion.…”

“…The strategies for analysis presented in the paper seem particularly handy when dealing with materials that exhibit both micropores and mesopores; a type of materials often found in many scientific and industrial applications. 19,35,36,[38][39][40][41][42][43][44][45][46][47][48] 2. Experimental and analytical methods 2.1 Analyzed materials.…”

Finite Element Modeling of Atmospheric Water Extraction by Way of Highly Porous Adsorbents: A Roadmap for Solver Construction with Model Factor Sensitivity Screening

“…To describe diffusivity it is necessary to determine conversion yields, selectivities, and the activation energies. The determination of the Thiele modulus could give model indication for the presence or absence of diffusion limitations in hierarchical zeolite . Indicators are key to developing automated algorithms which can adjust the governing diffusivity approximations in simula .…”

“…The determination of the Thiele modulus could give model indication for the presence or absence of diffusion limitations in hierarchical zeolite. 25 Indicators are key to developing automated algorithms which can adjust the governing diffusivity approximations in simula. The Thiele modulus and other potential coefficients need evaluation for incorporation into fault detection loops (described in Figure 1) that could call on "Material Properties Modeling" to rederive diffusivity approximations.…”

Synthesis of Quinolines by the Skraup Reaction: Hierarchical Zeolites vs Microporous Zeolites

“…The synthesis and application of micro-mesoporous zeolite catalysts have been described in detail in reviews. [4][5][6] The novel approach that we develop for producing granular zeolite materials with a high degree of crystallinity and a hierarchical pore structure (micro-, meso-and macropores) is based on the green synthesis strategy [7] and includes selective crystallization of preformed granules containing crystals of the parent zeolite and particles of an amorphous binder (alumi-nosilicate) to form intergrown crystal aggregates. These materials are characterized by the high degree of crystallinity (95-99 %), micro-meso-macroporous structure and high acidity.…”