Flowerlike Hierarchical Y with Dramatically Increased External Surface: A Potential Catalyst Contributing to Improving Precracking for Bulky Reactant Molecules

Special Issue "Design, Synthesis and Applications of Macroporous, Mesoporous, and Microporous Materials"

The intention of this Special Issue was to highlight the importance of the design, synthesis, and applications of macro-, meso-, and microporous materials [...].

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

Microporous zeolites have proven to be of great importance in many chemical processes. Yet, they often suffer from diffusion limitations causing inefficient use of the available catalytically active sites. To address this problem, hierarchical zeolites have been developed, which extensively improve the catalytic performance. There is a multitude of recent literature describing synthesis of and catalysis with these hierarchical zeolites. This review attempts to organize and overview this literature (of the last 5 years), with emphasis on the most important advances with regard to synthesis and application of such zeolites. Special attention is paid to the most common and important 10- and 12-membered ring zeolites (MTT, TON, FER, MFI, MOR, FAU, and *BEA). In contrast to previous reviews, the research per zeolite topology is brought together and discussed here. This allows the reader to instantly find the best synthesis method in accordance to the desired zeolite properties. A summarizing graph is made available to enable the reader to select suitable synthesis procedures based on zeolite acidity and mesoporosity, the two most important tunable properties.

Acid Properties of Hierarchical Zeolites Y

The article reviews different strategies towards obtaining mesoporous zeolites Y: desilication; surfactant templating and assembly of zeolite crystals. The impact of those methods on physicochemical properties is covered, with a special focus on the acidity of the samples measured with infrared (IR) spectroscopy. The methods of characterization of acidity are presented. Quaternary ammonium cations used for desilication lead to obtaining crystalline; mesoporous and highly acidic zeolites. Si-OH-Al groups of extremely high acidity can be produced by calcination in a humid atmosphere. When the conditions are optimized, post-synthetic surfactant templating allows crystalline mesoporous zeolite to be obtained with no loss of material. All mesoporous zeolites Y proved to be active catalysts in liquid phase isomerization, catalytic cracking, and other reactions.

A core–shell Y zeolite with a mono-crystalline core and a loosely aggregated polycrystalline shell: a hierarchical cracking catalyst for large reactants

Increased external surface areas promote the pre-cracking of reactants, and the core–shell structure guarantees that reactants undergo a hierarchical cracking process.

Preparation of hierarchical catalysts with the simultaneous generation of microporous zeolite using a template and large mesoporous silica by gel skeletal reinforcement and their reactivity in the catalytic cracking of n-dodecane

Zeolite-containing hierarchical mesoporous catalysts prepared using gel skeletal reinforcement exhibited the superior activity and selectivity in n-dodecane catalytic cracking.