Sapo-34 molecular sieve having both micropores and mesopores and synthesis methods thereof

Abstract

The present invention relates to a SAPO-34 molecular sieve having both micropores and mesopores and synthesis method thereof. The mesopore diameter in the molecular sieve is in a range of 2-10 nm and the mesopore volume thereof is 0.03-0.3 cm 3 /g. Triethylamine is used as a template agent and the pore size modifiers are added to the synthesis gel at the same time in the synthesis process, thereby the prepared molecular sieve crystals have mesopore distribution besides micropores. The SAPO-34 molecular sieve synthesized in the present invention can be used as catalysts for conversion of oxygen-containing compounds to lower olefins.

1 . A SAPO-34 molecular sieve having both micropores and mesopores, characterized in that the mesopore diameter of the molecular sieve is 2-10 nm and the mesopore volume thereof is 0.03-0.3 cm 3 /g. 
   
   
       2 . The SAPO-34 molecular sieve according to  claim 1 , characterized in that the cubic crystal surface of the molecular sieve is rough or broken. 
   
   
       3 . A synthesis method for the SAPO-34 molecular sieve according to  claim 1 , characterized in that triethylamine is used as a template agent and a pore size modifier is added into a synthesis gel. 
   
   
       4 . The synthesis method according to  claim 3 , characterized in that the method includes the following steps:
 a) Formulating an initial gel mixture for synthesizing SAPO-34 molecular sieve;   b) Adding a pore size modifier into the initial gel mixture obtained in step a) and stirring sufficiently;   c) Sealing and heating the gel mixture obtained in step b) to crystallization temperature, and performing a thermostatic crystallization under autogenous pressure; wherein after the crystallization is completed, a solid product is separated, washed to be neutral and dried, thus obtaining as-synthesized SAPO-34 molecular sieve   d) Calcining the as-synthesized SAPO-34 molecular sieve obtained in step c) in air to remove the organics contained in the material, and obtaining a SAPO-34 molecular sieve having both micropores and mesopores.   
   
   
       5 . The synthesis method according to  claim 4 , characterized in that the oxide molar proportions of all components in said initial synthesis gel mixture are:
 SiO 2 /Al 2 O 3 =0.1˜2.0;   P 2 O 5 /Al 2 O 3 =0.5˜15;   H 2 O/Al 2 O 3 =10˜100;   TEA/Al 2 O 3 =1˜5, wherein TEA is triethylamine;   T/TEA=0.01˜2, wherein T is the pore size modifier.   
   
   
       6 . The synthesis method according to  claim 4 , characterized in that said pore size modifier is one or more selected from the group consisted of aqueous ammonia, tetramethylammonium hydroxide, diethylamine, tripropylamine, di-n-propylamine, n-propylamine, n-butylamine, cyclohexylamine and a mixture thereof. 
   
   
       7 . The synthesis method according to  claim 4 , characterized in that the crystallization temperature in step c) is 100-250° C. 
   
   
       8 . The synthesis method according to  claim 4 , characterized in that the crystallization temperature in step c) is 160-230° C. 
   
   
       9 . The synthesis method according to  claim 4 , characterized in that the crystallization time in step c) is 0.5°˜100 h. 
   
   
       10 . The synthesis method according to  claim 4 , characterized in that the crystallization time in step c) is 2-48 h. 
   
   
       11 . The SAPO-34 molecular sieve according to  claim 1 , characterized in that the molecular sieve is used as a catalyst for the conversion of oxygen-containing compounds to lower olefins.