Protonic conduction in tin zeolites

The tin mordenites were analysed for sodium, potassium, soluble tin, and tin(IV) oxide. With certain assumptions (Si/Al ratio not changing during the preparations, all tin in the zeolite associated with two positive charges, but not necessarily in oxidation state (II)) the formula for the R = 0.2 preparation was calculated to H2.7Nao.5Ko.o5Sn2.4Al8Si4o096 

For R values less than 0.2, the amount of separate tin(IV) oxide was negligible. 

In order to evaluate the influence of the amount of tin in the samples on the conductivity, four samples with different R were measured at temperatures from 35 °C to 130 °C. The cells were closed and 1 ml of water was placed in them. In this manner, the measurements were made at 100% RH. The results are shown in Fig. 14.7. The conductivity, 0.6 x 10 cm at 120 °C for material with R = 0.7, is the highest conductivity measured for zeolites. 

From the conductivity measurements made until now, it is to be expected that all hydrated zeolites conduct protons (or hydroxyl ions). The conduction mechanism is most likely to involve a vehicle, either water or ammonia. In some experiments, small molecule amines and alcohols may have acted as vehicles. 

Conductivities in the range from 10 to 10 Q cm have been observed most zeolites tested for proton conduction have conductivities in the range 10 to cm . 

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