Is there an alternate way to regenerate bronsted acidity in K-modified ZSM-5 zeolite? (other than using dilute acid or NH4NO3 mixing)
Because I don't want to calcine the material again as my material is not just zeolite itself
This way you may try to use a diluted acid, better nitric. You put zeolite between quartz wool plugs, pump slowly an excess of acid (calculated to provide 10 times more protons that theoretically possible in the zeolite). This should take an hour or so. Then pump water quickly to remove acid and dry at 80-100 C. this way you use gentle drying, not calcination
Interesting approach Nikolay Cherkasov. Thanks for the suggestion. Any comment on pH? should be less than 2 or 3?
Good question !
Generally the acid stability of zeolites would be a function of the silica to alumina ratio. In any case ZSM 5 would be resistant to structural degradation at room temperature at pH of ~ 1-2 .
Your question of how to generate acidity without use of either acid or ammonium exchange is indeed interesting.
Would you like to try exchange the K with a rare earth such as Ce, Dy , or Y ?
The hydrated form of the rare earth could conceivably provide the desired acidity.
Be careful to reduce the pH of the K- ZSM to < 7.0 before ion exchanging it with the nitrate salt to avoid the precipitation of the rare earth hydroxide.
Hope this helps !
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