高岭土水热合成ZSM-5及其在甲醇制芳烃中的应用

Hydrothermal synthesis of ZSM-5 from kaolin and its application in methanol synthesis

以高岭土为原料,采用晶种替代模板剂在水热条件下合成ZSM-5分子筛。考察了晶种质量分数、碱硅摩尔比及晶化时间对合成分子筛的影响。用XRD、FESEM、N2吸附-脱附、NH3-TPD等手段对合成样品进行了表征,并在甲醇制芳烃(Methonalto Aromatics,MTA)反应中评价其催化性能。结果表明:晶种质量分数为3%,Na OH/Si O2摩尔比为0.15,晶化时间为24 h,晶化温度为200℃时,合成出的ZSM-5分子筛相对结晶度最高为96%,晶粒为典型六棱柱状,大小约为1μm。合成的ZSM-5分子筛在MTA反应中具有较高的催化活性,BTX和芳烃选择性分别为29.7%和31.6%,较南开ZSM-5原粉分别提高1.5%和0.3%。

ZSM-5 zeolite is directly synthesized from kaolin by seeded method. The effects of crystal seed dosage, molar ratio of NaOH/SiO2 and crystallization time are investigated. The synthesized samples are characterized by means of XRD, FESEM, N2 adsorption-desorption andNH3-TPD. Their catalytic performance is evaluated by methanol to aromatic （MTA） reaction. The results show that ZSM-5 crystallites with highest crystallinity （96%） can be achieved under the following conditions ：3% of crystal seed dosage ,200℃ of the crystallization temperature ,0. 15 of molar ratio of NaOH/SiO2 and 24 hours of crystallization time. The ZSM-5 crystallite has typical hexagonal prism and the size is less than 1 μm. Moreover, the synthesized ZSM-5 exhibits better catalytic performance. The selectivity of the BTX and aromatic are 29. 7 % and 31.6%, respectively, which are increased by 1.5 % and 0. 3 %, respectively, compared with the catalytic activity of parent ZSM-5.