粉煤灰为原料水热合成ZSM-5沸石的工艺条件

以工业废弃物粉煤灰为初始原料,经酸处理除杂、碱处理活化后,采用常规水热法合成高纯ZSM-5沸石。考察酸处理过程的温度、时间和酸浓度等对酸浸取效果的影响,以及碱处理过程的焙烧温度和碱灰质量比等对碱熔活化的影响,采用XRF、XRD、SEM以及N2吸附-脱附等手段对各阶段样品进行表征。结果表明,盐酸处理可以除去粉煤灰中氧化钙、氧化铁等绝大部分碱性氧化物杂质,最适宜酸处理条件下所得粉煤灰中氧化硅和氧化铝质量分数之和由51.51%上升到处理后的85.37%;以最适宜高温氢氧化钠碱熔活化条件下所得活性硅铝溶液为原料,水热合成类似球状结构并具有较高比表面积和相对结晶度的高纯ZSM-5沸石,进而获得粉煤灰水热合成ZSM-5沸石的最佳工艺条件。

Study on the process conditions of hydrothermal synthesis of ZSM-5 zeolite from fly ash

Pure ZSM-5 zeolites were synthesized by conventional hydrothermal method with industrial waste fly ash as raw material treated by acid to remove impurities and activated by alkali fusion.Effects of reaction temperature, reaction time and acid concentration of acid treatment on products,and effects of calcination temperature and alkali-ash ratio of alkali treatment on products were examined.The obtained materials were characterized by XRF, XRD, SEM and N₂ adsorption-desorption isotherms.The results indicated that most of the basic oxide impurities, such as calcium oxide and iron oxide in fly ash, could be removed by treatment of hydrochloric acid.Content of SiO₂ and Al₂O₃ increased substantially from 51.51% to 85.37% under the optimum condition of acid treatment. High purity ZSM-5 zeolites of high specific area and relative crystallinity with spherical-like structure were successfully synthesized via hydrothermal process using the active silicon source and aluminum source from fly ash after activating treatment and hydroxide sodium fusion under the optimal condition of alkali treatment as the raw material.Optimum process conditions of hydrothermal synthesis of ZSM-5 zeolite from fly ash were obtained.