含镁磷酸硅铝分子筛的合成及表征

以三乙烯四胺为模板剂,采用水热合成法，以磷酸、正硅酸乙酯、氢氧化铝、乙酸镁及三乙烯四胺为原料，各原料配比为n(P)∶n(Si)∶n(Mg)∶n(Al)∶n(H₂O)∶n(TETA)=1∶0.11∶0.38∶0.49∶82∶0.89，在(150~170) ℃、晶化时间24 h和pH=6.0~6.2条件下，合成得到纯度较高和热稳定较好的含镁磷酸硅铝分子筛。采用扫描电子显微镜和粉末X射线衍射对分子筛进行晶体结构和形貌分析，所得分子筛在合成范围内具有较高的纯度和结晶度。DSC-TG热分析表明,分子筛具有较好的热稳定性。对分子筛进行甲醇转化反应评价，结果表明，在载气流速10 mL·min^-1、进料体积空速5.0 h^-1和300 ℃条件下,甲醇转化反应中气相产物甲烷体积分数可达80%，乙烯和丙烯含量约为13%。通过Vario EL Ⅲ型元素分析仪测定C、N、H和Mg质量分数分别为6.51%、5.53%、3.19%和3.39%。

Synthesis and characterization of silicoaluminophosphate molecular sieve containing magnesium

Using phosphoric acid, tetraethyl orthosilicate, aluminum hydroxide, magnesium acetate and tri- ethylenetetramine （TETA） as raw materials, the silicoaluminophosphate molecular sieve containing magne- sium with high purity and good thermal stability was synthesized by hydrothermal synthesis method under the condition as follows ：raw materials n （P） ：n （ Si ） ： n （ng） ： n （A1） ： n （ n2 O） ： n （TETA） = 1 ： 0. 11 ： 0. 38： 0.49： 82：0.89 ,crystallization time 24 h, crystallization temperature （ 150 - 170） ℃ and pH =6.0 -6.2. The as-synthesized molecular sieve was characterized by SEM, XRD and DSC-TG and was evaluated in methanol conversion reaction. The characterization results indicated that the molecular sieve possessed high purity and crystallinity, and its framework collapsed at 600 ℃. The evaluation results indicated that under the reaction condition of carrier gas flow rate 10 mL min-1, feeding volume space velocity 5.0 h-1 and 300 ℃, methane content of gasous product reached 80% and the content of ethylene and propylene was about 13%. The results of elemental analysis by Vario EL III elemental analyzer indicated that the contents of C ,N and H were 6.51wt% ,5.53wt% ,and 3.19wt% ,respectively.