Creation of Al‐Enriched Mesoporous ZSM‐5 Nanoboxes with High Catalytic Activity: Converting Tetrahedral Extra‐Framework Al into Framework Sites by Post Treatment

Abstract

ZSM-5 zeolite nanoboxes with accessible mesomicro-pore architecture and strong acid sites are important in relevant heterogeneous catalysis suffering from mass transfer limitations and weak acidities.R ational design of parent zeolites with concentrated and non-protective coordination of Al species can facilitate post-synthetic treatment to produce mesoporous ZSM-5 nanoboxes.I nt his work, as imple and effective method was developed to convert parent MFI zeolites with tetrahedral extra-framework Al into Al-enriched mesoporous ZSM-5 nanoboxes with low silicon-to-aluminium ratios of % 16. The parent MFI zeolite was prepared by rapid ageing of the zeolite sol gel synthesis mixture.The accessibility to the meso-micro-porous intra-crystalline network was probed systematically by comparative pulsed field gradient nuclear magnetic resonance diffusion measurements,w hich, together with the strong acidity of nanoboxes,provided superb catalytic activity and longevity in hydrocarbon cracking for propylene production.

The effect of T-atom ratio and TPAOH concentration on the pore structure and titanium position in MFI-Type titanosilicate during dissolution-recrystallization process

“…S1 for the full range XRD patterns). Typically, a single peak at 2θ diffraction angle of 24.3° for MFI type framework indicates an orthorhombic structure of unit cell symmetry, which is characteristic of substituted framework metal, whereas, a doublet at the same position is characteristic of a monoclinic unit cell symmetry for silicalite-1 [13,15]. The XRD patterns of TT_30 series samples shown in Fig.…”

“…Recently, using similar approach to that of the TS-1 a method was developed to convert parent MFI zeolites (Si/Al =12) with tetrahedral extra-framework Al into Al-enriched mesoporous ZSM-5 nanoboxes with low silicon-to-aluminium ratios (Si/Al=16) [13]. The resulting hollow ZSM-5 zeolite with low Si/Al ratio exhibited excellent catalytic performance in hydrocarbon cracking, especially in the cracking of bulky molecules, with high activity, stability and selectivity to propylene [13]. These findings imply a careful control of the dissolution-recrystallization process can produce a better catalyst.…”

Cellulose nanocrystals (CNCs) as hard templates for preparing mesoporous zeolite Y assemblies with high catalytic activity

“…templating methods) or 'top-down' (i.e. postsynthetic treatments) methods, 2,7,12,13 offering practical yet effective solutions to realise the faster molecular transport within the mesoporous zeolites and the greater catalytic activity compared to the conventional microporous zeolites. However, the templating methods are generally less energy intensive than the post-synthesis methods, in which prolonged post-synthesis hydrothermal treatments such as steaming are necessary.…”

Tailoring morphology of hierarchical catalysts for tuning pore diffusion behaviour: a rational guideline exploiting bench-top pulsed-field gradient (PFG) nuclear magnetic resonance (NMR)

“…A powerful tool to probe diffusion inside porous materials is the pulsed-field gradient (PFG) NMR technique. [29][30][31][32][33][34][35] Amongst notable work done in the area of zeolites, Kortunov et al 36 have investigated the effect of introducing mesopores in microporous zeolites showing that if the introduced pores form as isolated cavities, little or no increase in diffusion coefficient is observed. Conversely, the formation of a newly formed interconnected pore network is expected to lead to significant changes in diffusion coefficients.…”