二乙胺导向合成中空纤维负载型SAPO-34分子筛膜

Diethylamine (DEA) was adopted as the low-cost template to prepare hollow fiber supported SAPO-34 molecular sieve membranes for CO₂/CH₄ separation. The membranes were synthesized by the secondary-growth method using ball-milled SAPO-34 seeds. Effects of seed particle size, contents of DEA and aluminum source in precursor and crystallization time on structure, morphology and separation performance of the membranes were investigated extensively. The SAPO-34 membranes induced with ball-milled seeds were more compact than those with original seeds. The increase in DEA content was beneficial to transform SAPO-11 crystals to cubic SAPO-34 crystals in the membrane layer. When the content of diethylamine is too high, the SAPO-34 membrane is not formed on the surface of the carrier. When the content of aluminum in the synthetic liquid is low, the crystallization of the molecular sieve membrane is not complete. When the content of the aluminum source is too high, the crystal grain size on the surface of the membrane is gradually reduced or even difficult to nucleate, and the thickness of the membrane layer is thinned, and it is difficult to form a continuous film. In that case, it was seen that the membrane surface became uncompacted and the membrane thickness decreased. The increased crystallization time led to thicker and denser zeolite membrane. When the precursor composition was 1.0Al₂O₃:0.9P₂O₅:0.6SiO₂:2.0DEA:100H₂O and the crystallization time was 36 h, the as-synthesized membrane achieved the best CO₂/CH₄ separation selectivity of 80 as well as CO₂ permeance of 1.11×10^-6 mol•m^-2•s^-1•Pa^-1.