Mainganye Dakalo, Ojumu Tunde Victor, Petrik Leslie
Department of Chemical Engineering, Cape Peninsula University of Technology, P.O Box 652, Cape Town 8000, South Africa.
Environmental and Nano Sciences Research Group, Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
Materials (Basel). 2013 May 16;6(5):2074-2089. doi: 10.3390/ma6052074.
South African fly ash has been shown to be a useful feedstock for the synthesis of some zeolites. The present study focuses on the effect of impeller design and agitation rates on the synthesis of zeolite Na-P1 which are critical to the commercialization of this product. The effects of three impeller designs (4-flat blade, Anchor and Archimedes screw impellers) and three agitation speeds (150, 200 and 300 rpm) were investigated using a modified previously reported synthesis conditions; 48 hours of ageing at 47 °C and static hydrothermal treatment at 140 °C for 48 hours. The experimental results demonstrated that the phase purity of zeolite Na-P1 was strongly affected by the agitation rate and the type of impeller used during the ageing step of the synthesis process. Although zeolite Na-P1 was synthesized with a space time yield (STY) of 15 ± 0.4 kg dmand a product yield of 0.98±0.05 g zeolites/g fly ash for each impeller at different agitation speeds, zeolite formation was assessed to be fairly unsuccessful in some cases due the occurrence of undissolved mullite and/or the formation of impurities such as hydroxysodalite with the zeolitic product. This study also showed that a high crystalline zeolite Na-P1 can be synthesized from South African coal fly ash using a 4-flat blade impeller at an agitation rate of 200 rpm during the ageing step at 47 °C for 48 hours followed by static hydrothermal treatment at 140 °C for 48 hours.
南非粉煤灰已被证明是合成某些沸石的有用原料。本研究聚焦于叶轮设计和搅拌速率对沸石Na-P1合成的影响，这对该产品的商业化至关重要。使用修改后的先前报道的合成条件，研究了三种叶轮设计（4-平板叶片、锚式和阿基米德螺旋叶轮）和三种搅拌速度（150、200和300转/分钟）的影响；在47°C下老化48小时，并在140°C下进行静态水热处理48小时。实验结果表明，在合成过程的老化步骤中，搅拌速率和所用叶轮的类型对沸石Na-P1的相纯度有很大影响。尽管在不同搅拌速度下，每种叶轮合成的沸石Na-P1的时空产率（STY）为15±0.4 kg/d，产物产率为0.98±0.05 g沸石/克粉煤灰，但由于未溶解的莫来石的出现和/或与沸石产物形成诸如羟基方钠石等杂质，在某些情况下沸石的形成被评估为相当不成功。本研究还表明，使用4-平板叶片叶轮，在47°C下老化步骤中以200转/分钟的搅拌速率搅拌48小时，然后在140°C下进行静态水热处理48小时，可以从南非煤粉煤灰中合成高结晶度的沸石Na-P1。
