Understanding the Anion-Templated, OSDA-Free, Interzeolite Conversion Synthesis of High Silica Zeolite ZK-5

High silica zeolite ZK-5 (framework Si/Al=4.8) has been prepared by interzeolite conversion from ultrastable zeolite Y via a co-templating route using alkali metal cations and nitrate anions but without organic structure directing agents. The mechanism, which involves zeolite framework - alkali metal cation - nitrate anion ordering, has been established by a combination of chemical and thermal analyses, Raman spectroscopy, computational modelling, and X-ray powder diffraction. Ammonium exchange gives ZK-5 with occluded ammonium nitrate and subsequent heating gives microporous zeolite ZK-5.

Automated summary

High silica zeolite ZK-5 can be prepared by interzeolite conversion from ultrastable zeolite Y using alkali metal cations and nitrate anions as co-templating agents, without the need for organic structure directing agents. The mechanism, involving the ordering of zeolite framework, alkali metal cations, and nitrate anions, has been established through various analyses. Ammonium exchange followed by heating can further transform ZK-5 into microporous zeolite ZK-5.