Mg-APO-31磷酸铝分子筛合成

Synthesis of aluminophosphate molecular sieves Mg-APO-31

采用水热法在R(OH)_2-H_3PO_4-Al_2O_3-H_2O体系中以双季铵碱型的六甲双铵为模板剂,拟薄水铝石和正磷酸为铝源和磷源,合成了AlPO-31和Mg-AlPO-31磷酸铝分子筛。通过XRD、FT-IR、TG-DTG和UV-Vis等手段对合成样品进行表征。结果表明,六方晶系Mg-APO-31晶胞参数与AlPO-31相比膨胀,说明Mg进入了AlPO-31分子筛的骨架结构中;随着Mg用量的增加,在250 nm 源于骨架氧原子的成键2p电子向骨架杂原子的空d轨道p-d跃迁,吸收峰逐渐减弱;在910 cm^(-1)附近均出现了Mg的特征振动吸收峰;n(MgO):n(Al_2O_3)在0.002～0.006随原始溶胶增加Mg的量,产品结晶度提高;Mg-AlPO-31磷酸铝分子筛经加热后失重6%～6.8%,表明双季铵碱六甲双铵为模板剂用量是常规模板剂的1/3。当晶化时间(48～72)h、晶化温度(160～180)℃和0.2<n[R(OH)_2]:n(Al_2O_3)<1.4时,可以合成纯相且高结晶度的Mg-APO-31;具有ATO型骨架的AlPO-31磷酸铝分子筛,向其中掺杂Si,得到SAPO-5和SAPO-31混晶,高n(SiO_2):n(Al_2O_3)有利于生成SAPO-5,低n(SiO_2):n(Al_2O_3)有利于生成SAPO-31。

Aluminophosphate molecular sieves AlPO-31 and Mg-APO-31 were synthesized hydrothermally in R（OH）2-H3PO4-Al2O3-H2O system [ R = （CH3）3N（ CH2 ）6N（CH3 ）23＋ ] using di-quatemary ammonium base R（OH）2 as the template,pseudo-boehmite and orthophosphoric acid as the source of Al2O3 and H3PO4, respectively. The as-prepared samples Mg-APO-31 and SAPO-31 were characterized by XRD ,FT-IR,TG-DTG and UV-Vis. The results showed that with the addition of Mg,the trait cell parameters of Mg-APO-31 molecular sieves inflated and the symmetric stretching band of Si-O-Mg appeared at about 910 cm-1 in FT-IR spectrum. UV-Vis spectrum showed that there was a characteristic peak at about 250 nm with an weakened intensity for electronic transition between O and Mg. The crystallinity of Mg-APO-31 enhanced with n（MgO）：n（ Al2O3 ） = 0.002-0. 006. The weight loss of aluminophosphate molecular sieves Mg-APO-31 was 6% -6.8% after heating. Mg-APO-31 molecular sieves with high crystallinity by the hydrothermal method were prepared under the condition as follows：crystallization time （48-72） h, crystallization temperature （160- 180） ℃ and 0.2 〈 n[ R（ OH）2 ] ： n（ Al2O3 ） 〈 1.4. The crystal transportation of ATO framework molecular sieve was studied. The mixture of SAPO-5 and SAPO-31 were attained by adding Si to the system. It was apt to get SAPO-5 at high n（ SiO2 ） ： n（ Al2O3 ） and SAPO-31 at low n（ SiO2 ） ： n（ Al2O3 ）.