离心干燥制备含镧钼酸铵的焙解机制研究

The Study on the Mechanism of Calcination of Ammonium Molybdate with Lanthanum by CentrifugalDrying MethodZhang Xiao1,2,3,4,Wang Kuaishe1,2,Niu Shuai3,4,Ren Baojiang3,4, Liu Xuyang3,4

摘要:

本文以离心干燥制备含镧钼酸铵为原料，将其焙解为含镧三氧化钼。通过XRD和TG-MS对含镧钼酸铵在空气中的热分解过程进行了分析，并研究了不同焙解温度制备含镧三氧化钼的形貌及理化性能。结果表明，含镧钼酸铵为非晶态、中空近球形颗粒，在热分解过程中经历了3个阶段：室温至196.5℃，离心干燥粉发生从非晶态到晶态的转变；196.5～337.8℃，铵根离子完全分解，有亚稳态β-MoO3生成；337.8～410.1℃，β-MoO3发生相变生成α-MoO3。含镧三氧化钼“遗传”了离心干燥粉形貌，为近球形，随着焙解温度升高，颗粒表面越粗糙，破碎颗粒增多，内部小颗粒由不规则的粘结颗粒向规则的片状转变。焙解温度对含镧三氧化钼杂质元素含量影响不大，但随着温度升高，含镧三氧化钼的粒度和松装密度稍有减小。

Abstract:

Ammonium molybdate with lanthanum was prepared by centrifugaldrying, which was calcined to molybdenum trioxide with Lanthanum. The thermal decomposition of ammonium molybdate with lanthanum inairwasanalyzed by XRD and TG-MS, and the morphology and physicochemical properties of molybdenum trioxide with lanthanum were studied at different calcinationstemperature.The result shows that the structure of molybdenum trioxide with lanthanum is amorphous and microspheres withhollowspace inside. There were three stages in the process of the thermal decomposition of ammonium molybdate with lanthanum. Firstly, the centrifugaldrying powder changed from amorphous to crystalline states due to heat-treatment from room temperature to 196.5℃. Secondly, the residual ammonia ion in ammonium molybdate was decomposed from 196.5℃ to 337.8℃, and metastable molybdenum trioxide was formed, finally, metastable β-MoO3 turned into α-MoO3 from 337.8 ℃ to 410.1℃. Molybdenum trioxide with lanthanum prepared at different calcinedtemperature inherited the morphology of centrifugaldrying powder, with the increase of temperature, the surface of powder was coarser and thebreakageofpowder wasseriouser, and the internal small particles of powder changed from irregular and bonded to relatively regular flake. The change of calcinedtemperature had little effect on thecontentsof theimpurityelements in molybdenum trioxide with lanthanum, but with the increasing of calcinedtemperature, the apparent density and particle size reduced slightly.