Abstract
Force field-based calculations of all-silica zeolites show the role of fluoride as a structure-directing agent (SDA). Calculations of fully packed organic and fluoride SDAs were possible with an updated version of zeoTsda software, based on Monte Carlo+Lattice Energy Minimization. Comparison between fluoride-containing and fluoride-free calculations using the same organic SDA allowed us to predict which zeolite phase is obtained in fluoride and hydroxide media and also, through a new energy decomposition scheme, identify energetic contributions driving the synthesis outcome.
Highlights
Zeolites are a large and growing family of currently 255 microporous crystalline aluminosilicates, aluminophosphates, and their chemically related derivatives, formed by cornersharing tetrahedral frameworks, which find applications in catalysis and separation industrial processes.Two important hydrothermal synthetic routes differ in using either a hydroxide or a fluoride anion as a mineralizer, influencing the final microporous material obtained
The present study aims to assess separately the contributions of organic structure-directing agent (OSDA) and fluoride in the synthesis of specific zeolites
The energy decomposition allows one to (a) compare the total energies for each OSDA in zeo−OSDA systems and suggest the zeolite phase obtained with each OSDA, with and without fluoride; and (b) compare each energetic term in order to find the dominant contributions to the stability of zeo−OSDA systems in the presence and absence of fluoride
Summary
Two important hydrothermal synthetic routes differ in using either a hydroxide or a fluoride anion as a mineralizer, influencing the final microporous material obtained. The incorporation of each anion in the zeolite framework has utterly different effects. While hydroxide gives internal silanol nests leading to connectivity defects, fluoride is incorporated inside small cavities, giving defectless structures. A third aspect of the fluoride route is the structure-directing effect of fluoride, which always acts jointly to that of the organic structure-directing agent (OSDA), and it is not easy to separate both effects. This will be attempted in the present study
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
