Abstract:

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.

Key words: hollow fiber, molecular sieve, membrane, hydrothermal synthesis, diethylamine, separation

摘要：

采用价格低廉的二乙胺为模板剂，通过球磨晶种诱导二次生长法制备中空纤维负载型SAPO-34分子筛膜用于CO₂/CH₄气体分离。系统考察了诱导晶种大小、膜合成液中二乙胺含量、铝源含量与晶化时间对膜结构形貌以及分离性能的影响。结果表明：相比于原始晶种，球磨晶种诱导制备SAPO-34分子筛膜层更加致密。随着膜合成液中二乙胺含量增加，膜表面分子筛晶体逐渐由SAPO-11向SAPO-34转变，当二乙胺含量过高时，载体表面未形成SAPO-34膜。当合成液中铝源含量较低时，分子筛膜晶化不够完全，当铝源含量过高时，膜表面晶体粒径逐渐减小甚至难以成核，膜层厚度减薄，不易生成连续的膜层。随着晶化时间的增加，膜层厚度逐渐增加，膜表面趋于致密。当膜合成液摩尔组成为1.0Al₂O₃∶0.9P₂O₅∶0.6SiO₂∶2.0DEA∶100H₂O，晶化时间为36 h时，球磨晶种诱导制得的SAPO-34分子筛膜分离性能最佳，膜的CO₂渗透性为1.11×10^?6 mol·m^?2·s^?1·Pa^?1，CO₂/CH₄分离选择性达80。

关键词: 中空纤维, 分子筛, 膜, 水热合成, 二乙胺, 分离