新型磷酸硅铝分子筛SAPO-53的合成与表征

以氢氧化已烷双铵(R(OH)2)为模板剂,采用水热条件合成了高结晶度的SAPO-53分子筛。并采用XRD、SEMEDX、FT-IR、MAS NMR、电泳仪、N2吸附-脱附、TG-DTG等手段对合成的分子筛进行表征。考察了硅铝比、磷铝比、模板剂的用量以及晶化时间等条件对合成SAPO-53分子筛的作用。29Si MAS NMR表明,Si主要以四配位形式进入了AlPO4-53的骨架中,SAPO-53相对结晶度先增加后开始缓慢下降,Zeta电位值先增加后保持不变,与以甲胺为模板剂合成相比,氢氧化已烷双铵的用量比甲胺减少了一半,同时缩短了晶化时间,降低了合成的难度。通过计算得到SAPO-53的表观生长速率大于成核速率,说明成核过程是速率控制步骤。

Synthesis and characterization of a new type silicoaluminophosphate SAPO-53 molecular sieves

Highly crystalline SAPO-53 molecular sieves were successfully synthesized under a hydrothermal condition by using hydroxide hexane dual ammonium(R(OH)₂) as a template. The samples were characterized by a serious of techniques,including XRD,SEM-EDX,FT-IR,MAS NMR,electrophoresis apparatus,N₂ adsorption-desorption and TG-DTG. Various preparation conditions including Si/Al ratio, P/Al ratio, the amount of template and crystallization time for the synthesis of SAPO-53 molecular sieves have been systematically studied. It shows that Si has entered the AlPO₄-53 framework mainly with a form of four ligand detected by ²⁹Si MAS NMR. The results reveal that the relative crystallinity of synthesized samples increases firstly and reduces afterward with the increase of time,while the Zeta potential value increases first and then remains unchanged. Compared with the synthesis taking methylamine as a template, the template agent of hydroxide hexane dual ammonium is only half of the amount for the sample synthesis. Furthermore, this method can shorten the crystallization time and reduce the difficulty of synthesis. The apparent growth rate of SAPO-53 molecular sieve is higher than its nucleation rate through the calculation, so the nucleation process is the rate controlling step.