The invention discloses a CHA-RHO type composite
molecular sieve as well as a preparation method and application thereof. The preparation method comprises the following steps: uniformly mixing a
phosphorus source, an aluminum source and deionized water according to the
mole ratio being (0.5 to 3):1:(50 to 100),
drying,
roasting and crushing to obtain granular phosphorous and aluminum
dry glue; uniformly mixing the granular phosphorous and aluminum
dry glue, a template agent R, a
silicon source and the deionized water according to the
mole ratio being 1:(0.5 to 3): (0.05 to 0.25):(25 to 50), crystallizing, cooling, carrying out suction filtering, washing and
drying to obtain
molecular sieve raw
powder;
roasting the
molecular sieve raw
powder to obtain CHA-RHO type SAPO (Silicoaluminophosphate) composite molecular
sieve. The composite molecular
sieve disclosed by the invention is prepared from 90 to 99 weight percent of CHA type molecular
sieve and 1 to 10 weight percent of RHO type molecular sieve; in a composite molecular sieve framework, the
mole ratio of SiO2 to Al2O3 is (0.05 to 0.35):1. The composite molecular sieve has the advantages of small crystalline grains, low
silicon content, long service life and high catalytic activity; the composite molecular sieve is used for a catalyst for a reaction of preparing lower olefins by catalytic
dehydration of
methanol and high higher olefin selectivity; by means of the composite molecular sieve, the oligomerization of the lower olefins can be greatly reduced, so that the yield of the olefins is increased; the composite molecular sieve can be used as an adsorbent for adsorbing and separating small-molecule gases.