A Cooperative OSDA Blueprint for Highly Siliceous Faujasite Zeolite Catalysts with Enhanced Acidity Accessibility

A cooperative OSDA strategy is demonstrated, leading to novel high-silica FAU zeolites with a large potential for disruptive acid catalysis. In bottom-up synthesis, the symbiosis of choline ion (Ch(+)) and 15-crown-5 (CE) was evidenced, in a form of full occupation of the sodalite (sod) cages with the trans Ch(+) conformer, induced by the CE presence. CE itself occupied the supercages along with additional gauche Ch(+), but in synthesis without CE, no trans was found. The cooperation, and thus the fraction of trans Ch(+), was closely related to the Si/Al ratio, a key measure for FAU stability and acidity. As such, a bottom-up handle for lowering the Al-content of FAU and tuning its acid site distribution is shown. A mechanistic study demonstrated that forming sod cages with trans Ch(+) is key to the nucleation of high-silica FAU zeolites. The materials showed superior performances to commercial FAU zeolites and those synthesized without cooperation, in the catalytic degradation of polyethylene.

Automated summary

A cooperative OSDA strategy was used to synthesize novel high-silica FAU zeolites with large potential for disruptive acid catalysis, exhibiting superior performance in catalytic degradation of polyethylene compared to commercial FAU zeolites and materials synthesized without cooperation.