Synthesis method and application of small grain silicon aluminum phosphate SAPO-34 molecular sieve

The invention discloses a synthesis method and application of a small grain silicon aluminum phosphate SAPO-34 molecular sieve. First, a raw material aluminum source, a phosphorus source, a silicon source, an organic amine and deionized water are added into a container to be evenly mixed to obtain even gel; the gel is put in a crystallized kettle, predicted crystallization treatment after warmingis conducted, after treating the temperature of the gel is reduced to a room temperature; then the crystal seeds are added to be mixed, the gel is continuously heated to heat up and crystallized; andafter crystallization, a product is centrifugally separated, washed and dried to obtain the small grain silicon aluminum phosphate SAPO-34 molecular sieve. According to the prepared small grain SAPO-34 molecular sieve, after removing an organic amine template agent by high temperature roasting, the prepared small grain SAPO-34 molecular sieve can be used as a catalyst for conversion of oxygenatedcompounds to olefins, and w