吕超, 殷宏鑫, 刘艳龙, 陈绪鑫, 孙铭赫. 微波热解法制备氧化铈过程的可视化研究[J]. 工程科学学报, 2023, 45(7): 1238-1245. DOI: 10.13374/j.issn2095-9389.2022.04.20.004
引用本文: 吕超, 殷宏鑫, 刘艳龙, 陈绪鑫, 孙铭赫. 微波热解法制备氧化铈过程的可视化研究[J]. 工程科学学报, 2023, 45(7): 1238-1245. DOI: 10.13374/j.issn2095-9389.2022.04.20.004
LÜ Chao, YIN Hong-xin, LIU Yan-long, CHEN Xu-xin, SUN Ming-he. Visualization study on preparation of CeO2 by pyrolysis method via microwave heating[J]. Chinese Journal of Engineering, 2023, 45(7): 1238-1245. DOI: 10.13374/j.issn2095-9389.2022.04.20.004
Citation: LÜ Chao, YIN Hong-xin, LIU Yan-long, CHEN Xu-xin, SUN Ming-he. Visualization study on preparation of CeO2 by pyrolysis method via microwave heating[J]. Chinese Journal of Engineering, 2023, 45(7): 1238-1245. DOI: 10.13374/j.issn2095-9389.2022.04.20.004

微波热解法制备氧化铈过程的可视化研究

Visualization study on preparation of CeO2 by pyrolysis method via microwave heating

  • 摘要: 针对传统液相法制备氧化铈纳米颗粒存在工艺流程复杂、高污水排放等问题,提出了一种高效绿色的实验方案,以七水合氯化铈为原料,采用微波射流热解技术制备出了高纯度氧化铈纳米颗粒。通过X射线衍射仪(XRD)、扫描电镜(SEM)和能谱仪(EDS)分析手段对产物进行了表征,借助数值模拟手段可视化分析了各物理场、各组分分布。考察了不同工艺条件(热解温度、气相速度、和添加柠檬酸)对实验产物中残余氯根含量和产物微观形貌的影响。结果表明,热解温度达到500 ℃时便可获得单相氧化铈,温度越高氧化铈纯度越高,颗粒形貌越规则。增大气相入口速度导致产物残余氯根增多,但有利于改善颗粒团聚。添加柠檬后氧化铈从球状颗粒逐渐破碎为伴有少量多孔结构的不规则形状颗粒,颗粒比表面积增大。柠檬酸浓度大于0.1 mol·L−1后利于减少氯根含量。

     

    Abstract: Preparation of cerium oxide by conventional liquid phase method has the disadvantages of complex technological process and effluent discharge. Spray pyrolysis for making CeO2 has the disadvantages of nozzle plugging, and this traditional heating method produces a significant temperature gradient that results in unevenly heated reactants. To prevent the above issues, this study proposed an effective and environmental experimental scheme. Cerium chloride heptahydrate and deionized water were utilized for the raw material. High-purity nano cerium oxide particles were prepared by jet-flow pyrolysis technology via microwave heating. Combining the technology of microwave heating with jet-flow pyrolysis, whose Venturi reactor served as the primary piece of equipment, can improve the mixing of gas and liquid, increase chemical reaction efficiency, and reduce carbon emissions. It was a new effort in the area of pyrolysis. To visually analyze the distribution of each physical field and substance, numerical simulation was combined with x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy to characterize the products. Effects of the various technological conditions (pyrolysis temperature, gas velocity, and adding citric acid) on the content of residual chloride element and microstructure of the product were examined. Results demonstrated that the temperature error between the experiment and simulation was below 20 ℃ with the condition of the same microwave power. When the pyrolysis temperature was at 500 ℃, CeO2 could be produced in a single phase, but the particle profile was unclear. The particles had sharp profiles when the temperature was 600 ℃. Nanoscale spherical CeO2 particles appeared when the average temperature reached 700 ℃. The results of the study’s simulations and experiments indicated that higher temperatures were associated with more regular microcosmic morphology and a lower content of residual chloride element. Increasing the gas velocity caused an obvious decrease in the average temperature, which led to more content of residual chloride elements. However, the gas collided with the solution more fiercely, which improved the mixing of the two phases. Experimental and simulated results showed that when gas velocity reached 1.2 m∙s−1, better dispersity and less agglomeration of the product were obtained. Additionally, the residual chloride content was less than 1%. Because a significant amount of CO2 was produced during the burning of the citric acid, the spherical cerium oxide particles broke into irregular particles. Porous structures also appeared when citric acid was added. The residual chloride content decreased with the increase of citric acid concentration when citric acid concentration was greater than 0.05 mol·L−1.

     

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