Mesoporogen-free synthesis of single-crystalline hierarchical beta zeolites for efficient catalytic reactions

Abstract

Single-crystalline hierarchical zeolites possess fast mass transfer, good active site accessibility, and enhanced hydrothermal stability for improved catalytic performance, which are highly desired in petro-, coal-, and fine-chemical industries. Here,...

Amino‐Acid‐Assisted Synthesis of Hollow Hierarchical FER Zeolite with Improved Catalytic Performance

“…The presence of amino acid (i. e. L-lysine) in the synthesis gel contributes to the aggregation of the primary nanoparticles, which has been reported in other hierarchical structures. [11,13] The chelation between L-lysine and silicon and aluminum species could efficiently modulate the interactions between primary nanoparticles and thus promote the formation of the agglomerates. The preferential nucleation and crystal growth at the external surfaces together with the lagged crystallization of the inner core of the agglomerates led to the formation of hierarchical urchin-like spherical crystals with hollow inner cavities.…”

“…Herein, we report on a simple direct synthesis of hollow hierarchical FER zeolite through an amino-acid-assisted approach without the use of mesoporogens. Amino-acid-assisted syntheses of hierarchical zeolites have been reported, [11] while hollow hierarchical structures that are more conducive to mass transfer are still relatively rare. In this work, a small amount of Llysine is added to induce the aggregation of gel nanoparticles during the initial crystallization stage.…”

Regulation of the Si/Al ratios and Al distributions of zeolites and their impact on properties

“…107,181 The performances of the zeolite catalysts for these reactions strongly depend on the concentration and strength of the BASs. 107,[187][188][189] The quantity/concentration of the BASs determining the number of active sites and the strength of the BASs governs the type of reaction. For example, the dealuminated Beta zeolite can catalyse the isobutyl alcohol oligomerization and the conversion of the isobutyl alcohol increases with the increase of the Si/Al ratios of Beta zeolite, which is controlled by the dealumination time.…”

Intraparticle ripening to create hierarchically porous Ti-MOF single crystals for deep oxidative desulfurization

“…S6c †), indicating that such a high crystallization temperature leads to Ostwald ripening. [25][26][27]37 Ostwald ripening is a process in which smaller crystals in solution gradually dissolve in the surrounding medium, and subsequently recrystallize into larger crystals, which is widely reported to exist in the crystallization process of MOFs. 35,[38][39][40][41][42] The Ostwald ripening process is much more intense than intraparticle ripening and the stacking voids of nanoparticle precursors cannot be preserved in such a dynamic transformation process.…”

“…The ripening (including intraparticle ripening and Ostwald ripening) method was reported to be able to achieve the simultaneous formation of mesopores and intact frameworks in zeolite crystals. [25][26][27] Intraparticle ripening refers to monomer migration from small ones to larger ones. 28 For example, by the addition of an amino acid (lysine), the ripening process of zeolite crystals was controlled to be intraparticle ripening and stacking voids created by lysine turned into intracrystal mesopores during zeolite precursor migration.…”