Cancrinite hydrate

Trapping or encapsulation represents a second situation wherein guests are introduced at high temperature and at high pressure of the guest. Crystals are chilled, and then the pressure is released. The host lattice is permanent, and the windows are small. Examples are sodalite hydrate, cancrinite hydrate, and analcite. 

CAN Cancrinite Na[Pg.5096]

It is well established that cation exchange can decisively alter molecule sieving capabilities of zeolites. Stacking faults can be equally decisive, eg. ideal cancrinite hydrate and cartel in ite would be wide port sieves (Table 1). In fact stacking faults turn the cancrinite into a non-sorbent and the gmelinite into a narrow port sorbent. 

Hydrated diameters and crystal diameter of TMA are from ref. 86 in [32]. Other crystal diameters are those of Shannon-Prewitt for sixfold coordination as listed in ref. 87 in [32] higher coordination numbers as observed in many zeolite structures (e.g., 12-fold for K in the cancrinite unit in L and offretite) increase the diameter by up to 0.5 A. 

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