1. Ion Exchange of Zeolites in Polyethylene Oxide Oligomer Solutions
Susan E. Latturner, Department of Chemistry, Florida State University, Tallahassee, FL
Polyethylene oxide oligomers are inexpensive polar liquids which can be used as alternative solvents for ion exchange into porous and layered oxides. Ion exchange of transition metal or rare earth ions into zeolites using traditional aqueous exchange results in structure degradation; this does not occur in PEO solutions.
PEG-ME exchange
X-ray diffraction data shows (a) the decomposition of Zeolite X samples ion-exchanged with Fe2+ in aqueous solution; those exchanged in PEO solvents (b,c) maintain their crystallinity and are more catalytically active in deNOx reactions.
Emission spectra of Er3+ exchanged Zeolite X samples; those exchanged in aqueous solution have a shifted Er luminescence due to partial degradation and incorporation of Er3+ into framework sites.
PEO-600 exchange
Aqueous exchange
No exchange
PEO oligomers enter the pores of zeolite during ion exchange and are usually removed during calcination. However, allowing them to remain may promote CO2 adsorption by the zeolite, or reduction of noble metal ions to form nanoparticles in the cages.
(Ag nanoparticles in Zeolite X matrix, right) c b a