Alkali metal cation exchange

Thermodynamic data for alkali metal cation exchange at 25 °C (in kJ equiv ) Camp Berteau and Wyoming Bentonite... 

Cast, R. G., "Alkali Metal Cation Exchange on Chambers Montmorillonite," Soil Sci. Soc. Amer. Proc., (1972), 36, 14. 

Gast, R. G. 1972. Alkali metal cation exchange on Chambers montmorillonite. Soil Sci. Soc. Am. Proc. 36 14-19. 

Hunger B., Klepel O., Kirschhock C., Heuchel M., Toufar H. and Fuess H., Interaction of water with alkali-metal cation-exchanged X type zeolites TPD and XRD study. Langmur, 15 (1999) pp. 5937-5941... 

Typical results for the benzylation of 1-decanol in hexane are shown in Table I. Although an insoluble base such as K2CO3 was ineffective for the reaction, alkali metal cation-exchanged Y-type zeolites efficiently induced the reaction, and the highest yield (73%) was obtained when KY was used. The... 

If selectivity were governed solely by interactions of a purely electrostatic (coulombic) nature one could anticipate negative enthalpies and entropies of exchange due to dominant contributions by A and A5ii respectively. This is indeed found for alkali metal cation exchange on styrenic sulfonate resins as illustrated by Table 5.3a. 

Figure 3.2. Dependence of f-values of adsorbed cations on the mole fraction of exchange sites occupied by Rb and Na in the NaV b and Li+/Na+ exchange reaction on smectite. Adapted from R. G. Cast. 1969. Standard free energies of exchange for alkali metal cations on Wyoming bentonite. Soil Sci. Soc. Am. Proc. 33 37-41 1972. Alkali metal cation exchange on Chambers montmorillonite. Soil Sci. Soc. Am. Proc. 36 14-19.)...

I.A. Beta, H. Jobic, E. Geidel, H. Bohlig B. Hunger (2001). Spectrochim. Acta A, 57, 1393-1403. Inelastic neutron scattering and infrared spectroscopic study of furan adsorption on alkali-metal cation-exchanged faujasites. 

R. Schenkel, A. Jentys, S.F. Parker J.A. Lercher (2004). J. Phys. Chem. B, 108, 7902-7910. Investigation of the adsorption of methanol on alkali metal cation exchanged zeolite X by inelastic neutron scattering. 

H. FSrster, H. Fuess, E. Geidel, B. Hunger, H. Jobic, C. Kirschhock, O. Klepel K. Krause (1999). Phys. Chem. Chem. Phys., 1, 593-603. Adsorption of pyrrole derivatives in alkali metal cation-exchanged faujasites comparative studies by surface vibrational techniques. X-ray diffraction and temperature-programmed desorption augmented with theoretical studies Part I. Pyrrole as probe molecule. 

The situation is entirely different when alkali metal cation exchanged zeolites of faujasites are used. The conversions are high and the selectivity to NMA is high. This is due to the reduction in acidic centres and increase in the basic sites. The consequence of such reduction is the suppression of successive alkylations and disproportionation reactions. 

On the basis of an infrared study of the adsorption and reaction of methanol and dimethyl ether over alkali metal cation exchanged zeolites, we propose a reaction mechanism for the decomposition of methanol over alkali cation exchanged zeolites. Additionally, formaldehyde adsorption is performed on these molecular sieves and attempts will be made to correlate its adsorption structure with the surface reactivity. 

WAVENUMBER [cm ] Fig. 1S. Far-infrared (FIR) spectra of alkali-metal cation-exchanged faujasites and H-Y zeolite... 

It can be seen in Fig. 15 that within the series of alkali-metal cation-exchanged faujasites the bands are shifted to lower wavenumbers with increasing cation mass. This phenomenon was recognized very early by Brodskii et al. [358,359]. In an attempt to correlate the observed band positions with physical characteristics of the cations they found the relation... 

CSxH3-xPWi2O40, H3PW12O40 Alkali-metal cation-exchanged X zeolites... 

Walton K. S., Abney M. B., Levan M. D. CO adsorption in Y and X zeolites modified by alkali metal cation exchange. Microporous and Mesoporous Materials 91(1-3), 78-84 (2006). 

---