The effect of low solid/liquid ratio on hydrothermal synthesis of zeolites from fly ash
The effect of low solid/liquid ratio on hydrothermal synthesis of zeolites from fly ash
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DOI：
10.1016/j.fuel.2008.06.006
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发表时间：
2008-11
期刊：
影响因子：
7.4
通讯作者：
Tom Walek;F. Saito;Qiwu Zhang
中科院分区：
文献类型：
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作者：
Tom Walek;F. Saito;Qiwu Zhang
以F级飞灰为原料，在固液比(S/L)为4g/dm~3的条件下，水热合成沸石，考察了合成沸石的初始溶解阶段。较低的S/L比使反应前4h的飞灰溶出量显著增加(最高可达85wt%)。结果表明，对于通常使用的S/L比值(50-150g/dm~3)，飞灰的溶解受到很大限制。在这些条件下，部分溶解的飞灰颗粒表面会形成沸石晶体。这阻止了进一步的溶解，并导致形成低结晶度的类沸石材料。当S/L摩尔比较低时，样品的结晶度为80wt%，并随所加氢氧化钠浓度和温度的不同，得到NaP_1、方沸石和/或羟基方钠石相。在2M氢氧化钠溶液中，溶解阶段温度保持在104℃，晶化阶段温度降至80℃，得到了单相NAP1沸石。采用较低的S/L比，可以更清楚地描述合成条件与所得产物的关系。
Hydrothermal synthesis of zeolites from class F fly ash was carried out at solid/liquid (S/L) ratio of 4g/dm3to investigate the initial dissolution stage of the process. The low S/L ratio caused a significant increase in fly ash dissolution (up to 85wt%) during first 4h of reaction. It was shown that for S/L ratios typically used (50–150g/dm3) fly ash dissolution is largely limited. In these conditions zeolite crystals are formed on the surface of partially dissolved fly ash particles. This precludes further dissolution and results in formation of a low-crystallinity zeolite-like material. At low S/L ratio, a degree of crystallization of 80wt% was observed, and NaP1, analcime and/or hydroxy-sodalite phases were obtained depending on the applied NaOH concentration and temperature. Single phase NaP1 zeolite was obtained in 2M NaOH solution at temperature maintained at 104°C during the stage of dissolution and reduced to 80°C in the stage of crystallization. Application of low S/L ratio allows a clearer description of the relationships between the synthesis conditions and the products obtained.