Investigations on P zeolites: synthesis and structure of the gismondine analogue, highly crystalline low-silica CaP

A highly crystalline powder sample of NaP with a Si/Al ratio of 1.0 was synthesized and ion-exchanged against Ca, yielding a monophasic sample of a CaP zeolite, Ca 4 Al 8 Si 8 O 32 ·18.9H 2 O. The crystal structure of CaP was determined from X-ray (synchrotron) data in the monoclinic crystal system, space group P2 1 / c ( a =10.02415 A, b =10.6130 A, c =9.8333 A, β =92.292°, R p =0.0677, w R P =0.0648). It is found to be very similar to the structure of the natural occuring zeolite, gismondine. The close structural relationship between the synthetic group of P zeolites and natural zeolites with gismondine framework (gismondine, garronite, amicite and gobbinsite) is discussed.