A solid-state ion-exchange method is described that introduces vanadium into zeolites BZSM-5, BBeta and their deboronated by washing forms at 773
K in hydrogen. Two types of vanadium species ...(vanadium ions in cationic position and VO
2+ complex in a silanol nest) are identified when the amount of V
2O
5 is equivalent to the framework boron. The vanadium-loaded samples have been characterised by the methods of IR-KBr, FTIR and UV-Vis spectroscopies; temperature-programmed reduction/oxidation cycles (TPR/TPO).
The incorporation of indium cations into aluminum-containing mesoporous MCM-41 by reductive solid-state ion exchange (RSSIE) was studied by XRD, FTIR spectroscopy, TPR and TPDA techniques. It is ...shown that the RSSIE process proceeds as easily as in the case of zeolites. However, some typical differences associated with the specific acid properties of these molecular sieves were observed and are discussed in terms of the peculiar structure and composition of the framework.
The incorporation of indium(
i) cations into zeolite beta by reductive solid-state ion exchange has been studied by TPR/TPO techniques, FTIR spectroscopy and a catalytic test reaction (isomerization ...of
m-xylene). Among the hydroxyl groups observed in zeolite beta, those vibrating at 3610
cm
−1 (bridged hydroxyls) were found to be preferentially involved in the exchange process, resulting in In
+ lattice cations. Reoxidation leads to the formation of cationic InO
+ species. After pyridine adsorption, In
+ and InO
+ can be distinguished by typical IR bands at 1446 and 1455
cm
−1, respectively. Details of the redox behavior of the cationic indium species are reported.
Quantitative data obtained by thermal analysis proved to be consistent with the stoichiometry expected for incorporation of indium(I) ions into Y zeolite by reductive solid-state ion exchange upon ...treatment of ground
In
2O
3
NH
4NaY
mixtures in a hydrogen atmosphere at temperatures of 620–760 K. Detailed information on the complex process was obtained by IR spectroscopy. Both high frequency (HF) and low frequency (LF) hydroxyl groups are involved in the solid-state ion-exchange process, the HF ones showing higher reactivity. Reoxidation of the formed indium(I) lattice cations was found to proceed at relatively low temperatures (300–400 K) and to result, dependent on the excess of hydroxyl groups over In
+ lattice cations, in the formation of In
3+ and/or cationic In(III) species comprising ‘extra-framework oxygen’. The cationic indium species obtained after reduction and reoxidation were characterized by their interaction with pyridine applied as probe molecule. Adsorption of water on the cationic indium(III) species results in the formation of Brönsted-acid sites (In(OH)
2
+) the acid strength of which is significantly weaker than that of ‘bridged’ hydroxyls. The reduction/reoxidation cycle proved to be fully reversible.
