Uniform Mesoporosity Development in Incorporated β Zeolite: Dual-Template Strategy

Abstract

The hierarchical porosity of zeolite is a key factor affecting its catalytic activity and stability for bulky molecules involved reactions. However, it is still challenging to introduce mesoporosity into heteroatom-incorporated zeolites in a facile manner while maintaining the catalytic activity. In this work, a strategy for mesoporosity development in incorporated zeolites based on two templates (TEAOH and surfactants) under hydrothermal conditions was proposed, and hierarchical Zr-incorporated β zeolite was successfully prepared and used to catalyze the ETB reaction. In this process, OH– etches the zeolite framework while TEA+ preserves the microporous structure and the surfactant as the mesoporogen. The mesopore size (2.1–3.2 nm) can be tailored by changing the alkyl chain length (C10–C16) of the surfactant. During the treatment, the chemical environment of Zr in Zr-β zeolite did not change and the amount of Lewis acid was increased, showing that the mesoporosity could improve the accessibility of active sites. The hierarchical Zr-β zeolite showed better catalytic performance than the parent Zr-β zeolite in the ethanol–acetaldehyde to butadiene reaction, the conversion of ethanol and acetaldehyde can reach 63.7%, and the selectivity of butadiene can reach 76.6%. The stability of hierarchical Zr-β zeolite is significantly higher than that of microporous Zr-β zeolite, whose conversion can be maintained at 35.0% and selectivity at 70.9% at TOS = 24 h. The mesoporosity can increase the capability of coke which mitigates the deactivation.

A route to selectively increase the microporous structure of zeolite and its optimization in the ethanol to butadiene reaction

“…In this process, OH − etched the zeolite framework and the mesopore size could be tailored by changing the alkyl chain length of the surfactants. 11 Mesoporous ZSM-5 zeolite catalysts were prepared by desilication upon heating in aqueous solutions of tetrapropylammonium and tetrabutylammonium hydroxide, and compared with NaOH leaching. Silicon dissolution in organic hydroxides was much slower than in NaOH, making the demetallation process highly controllable.…”

Simultaneous Mesoporosity Generation and Lewis Acidity Enhancement in Zr‐Based Metallosilicalite for Promoting the Conversion of Ethanol‐Acetaldehyde to 1,3‐Butadiene

“…Thus developing hierarchical porosity in the zeolite matrix is a simple and efficient way for catalytic performance improvement. For example our group has developed several strategies to develop hierarchical porosity in Zr‐ β zeolite, including surfactant‐templating, [34] protective desilication, [35] dual‐template, [36] bifunctional template synthesis, [37] and IDRC [38] . Also several reports claimed that tuning Lewis acidity can sequentially improve catalytic performance [19] .…”

High accessibility to active sites of hierarchical nanocrystalline Zr-β zeolite in ethanol–acetaldehyde conversion to 1,3-butadiene

“…16,17 Likewise, hierarchical β zeolite has already been developed via base-leaching and dualtemplating synthesis in our previous studies, with improved textural properties and therefore high catalytic performances for ETB. 9,18,19 However, the secondary porosity comes at the cost of microporosity, which may have negative effects. 20 Significantly, the introduction of mesopores in zeolite may have an indefinite effect on its acidic properties since the location of acid sites might change.…”