Making Nanosized CHA Zeolites with Controlled Al Distribution for Optimizing Methanol‐to‐Olefin Performance

Abstract

From theoretical calculations and a rational synthesis methodology, it has been possible to prepare nanocrystalline (60-80 nm) chabazite with an optimized framework Al distribution that has a positive impact on its catalytic properties. This is exemplified for the methanol-to-olefin (MTO) process. The nanosized material with the predicted Al distribution maximizes the formation of the required MTO hydrocarbon pool intermediates, while better precluding excessive diffusion pathways that favor the rapid catalyst deactivation by coke formation.

Impact of Zeolite Framework Composition and Flexibility on Methanol‐To‐Olefins Selectivity: Confinement or Diffusion?

“…However, the AIMD simulations by Cnudde et al . showed that olefins can only diffuse through empty cavities, and we recently presented an optimized H‐SSZ‐13 catalyst with a controlled Al distribution that avoids the formation of HP intermediates in all the cavities, thus facilitating the product diffusion through the empty cages . These considerations, together with the clear differences in product distribution obtained from the beginning of the reaction for H‐SSZ‐13 and H‐SAPO‐34 (see Figure and S5‐S15) and the fact that they remain constant during the whole catalyst lifetime, support our proposal that selectivity is not mainly controlled by diffusion …”

“…In contrast, CHA‐type catalysts tend to produce more ethene and much less propene and butene, but there are differences in product distribution associated to framework composition. H‐SSZ‐13 always produces more ethene than propene, 45 % and 35 % respectively, while the opposite relationship is always found for H‐SAPO‐34 …”

MOF‐derived/zeolite hybrid catalyst for the production of light olefins from CO2

“…First, different aluminosilicates as potential acid catalysts for the second CÀ C coupling step (MTO) were prepared. [41,42] Two zeolites with chabazite (CHA) structure and different acid contents (Si/Al = 15 and 30) were synthesized (see supporting information for synthesis details on all zeolites/zeotypes). A sample of benchmark SAPO-34, the commercial catalysts employed for this process, was also prepared.…”

Steering polymer growth by molding nanochannels: 1,5-hexadiene polymerization in high silica mordenite

“…The organization of objects, like molecules or clusters, in lowdimensionality nanosized structures is the key to attain materials endowed with new functionalities. [1][2][3][4] This leitmotiv in advanced material science often relies on spontaneous assembly mechanisms -such as molecular recognition or intermolecular interactions -which could be enhanced or accelerated by imparting proper external stimuli e.g. via electromagnetic fields, [5] chemical reagents, or by imposing geometric restrictions.…”

“…[13][14][15] Moreover, the fine tuning of their pore architecture and their hydrophilic/hydrophobic character can improve their performance for technological or industrial applications. [4,[16][17][18][19][20][21][22][23][24] The geometrical constraints of the zeolitic framework can be proficiently exploited to induce the formation of nanostructured arrays with the desired dimensionality. Supramolecular materials which do not require chemical reactions to form compositessuch as dye-zeolite composites/artificial antenna systems in zeolite channels, [25][26][27][28][29][30][31][32][33] biomolecules and chromophores immobilized in 1-D channels, [34][35][36][37][38][39][40][41] or low-dimensional nanoarchitectures of molecular clusters [42][43][44] -have been successfully realized.…”