Probing the Design Rationale of a High-Performing Faujasitic Zeotype Engineered to have Hierarchical Porosity and Moderated Acidity.

Stephanie Chapman,Robert Raja,Jihong Yu,Marina Carravetta,Enrica Gianotti,James D Taylor,Hannah Dixon,Ivana Miletto,Cara M Doherty

doi:10.1002/anie.202005108

Abstract

Porosity and acidity are influential properties in the rational design of solid‐acid catalysts. Probing the physicochemical characteristics of an acidic zeotype framework at the molecular level can provide valuable insights in understanding intrinsic reaction pathways, for affording structure–activity relationships. Herein, we employ a variety of probe‐based techniques (including positron annihilation lifetime spectroscopy (PALS), FTIR and solid‐state NMR spectroscopy) to demonstrate how a hierarchical design strategy for a faujasitic (FAU) zeotype (synthesized for the first time, via a soft‐templating approach, with high phase‐purity) can be used to simultaneously modify the porosity and modulate the acidity for an industrially significant catalytic process (Beckmann rearrangement). Detailed characterization of hierarchically porous (HP) SAPO‐37 reveals enhanced mass‐transport characteristics and moderated acidity, which leads to superior catalytic performance and increased resistance to deactivation by coking, compared to its microporous counterpart, further vindicating the interplay between porosity and moderated acidity.

Highlights

The emergence of hierarchical materials has led to an evolution in the design of catalysts for targeted chemical transformations
We employ a variety of probe-based techniques (including positron annihilation lifetime spectroscopy (PALS), FTIR and solid-state NMR) to demonstrate how a hierarchical design strategy for a faujasitic (FAU) zeotype can be used to simultaneously modify the porosity and modulate the acidity for an industriallysignificant catalytic process (Beckmann rearrangement)
Elemental and thermogravimetric analyses (Sections SI.2 and SI.3) indicated that the organosilane was incorporated in the assynthesized HP SAPO-37 material, and after calcination the HP

Summary

Introduction

The emergence of hierarchical materials has led to an evolution in the design of catalysts for targeted chemical transformations. The catalyst surface, or within the mesopores.[52, 54,55,56] In the FTIR region associated with 2,6-dTBP aromatic ring-modes (1700 – 1540 cm-1) two peaks were observed.[52, 54,55,56] higher energy band, centered at 1616 cm-1, characterized the protonated 2,6-dTBPH+ species, and Brønsted acid sites.

Results

Conclusion