大孔分子筛VPI-5的合成与性质

The Synthesis and Characterization of Large Pore Molecular Sieve VPI-5

以二正丁胺(DBA)为结构导向剂,合成了含18元环的VPI-5分子筛.晶化体系的化学组成为DBA·Al_2O_3·P_2O_5·40H_2O。实验发现,合成过程中的二次陈化步骤非常重要,陈化时间分别以3～7h和1.5～2h为好。适宜的晶化温度为120～130℃。晶化时间为18～24h。通过DTA-TG及XRD的研究表明;合成出的VPI-5具有较高的热稳定性,可达800℃。对VPI-5酸性的测定,表明它只有一种弱酸中心,不能作为强酸性催化剂使用。

The VPI-5 molecular sieve with 18-membered rings was synthesized by using dibutylamine(DBA) as the structural directing agent. The chemical composition of the crystallization gel was DBA·Al_2O_3·P_2O_5·4OH_O. It was found that the proper aging time for the two critical aging steps in the synthetic procedure were 3～7h and 1.5～2 h respectively. The crystallization temperature should be 120～135～℃,and the crystallization time 18～20h.The thermal stability of as-synthesized VPI-5 was high,VPI-5hold its structure even at 800℃. VPI-5 has only one kind of weak acid sites,so it can't be used in the reactions requiring strong acid sites.