Comparison of microwave and conventional heating routes for kaolin thermal activation
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Comparison of microwave and conventional heating routes for kaolin thermal activation ZHANG Liang-jing(张良静)1, 2, HE Yuan(和媛)1, 2, LÜ Peng(吕鹏)1, 2, PENG Jin-hui(彭金辉)1, 2, LI Shi-wei(李世伟)1, 2, CHEN Kai-hua(陈楷华)1, 2, YIN Shao-hua(尹少华)1, 2, ZHANG Li-bo(张利波)1, 2 1. Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China; 2. State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, China; © Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract: The effect of activation properties of the precursors of zeolite directly prepared from kaolin influenced by microwave field and conventional heating was investigated. XRD, TG-DSC, FT-IR, SEM, particle size analysis, specific surface area (BET), pore size distribution (BJH) and N2 adsorption−desorption were discussed to determine the optimal activation temperature. It is concluded that the conversion of kaolin to metakaolin in the microwave field is at 500 °C holding for 30 min, which is 100 °C lower than that in conventional calcination and 90 min shorter, and the phase transition process of kaolin under the effect of microwave field is the same as that of conventional heating method. SEM analysis indicates that the particle size is more uniform and agglomeration appears slightly in the microwave field. The N2 adsorption−desorption isotherm, BET and BJH of kaolin indicate that the pore properties are almost invariable regardless of calcination route during the process of calcining kaolin into metakaolin. It indicates that microwave calcination is superior to conventional calcination in the activation pathway of kaolin. It is attributed to microwave heating relying on objects to absorb microwave energy and convert it into thermal energy, which can simultaneously and uniformly heat the entire substance. Key words: kaolin; thermal activation; metakaolin; microwave Cite this article as: ZHANG Liang-jing, HE Yuan, LÜ Peng, PENG Jin-hui, LI Shi-wei, CHEN Kai-hua, YIN Shao-hua, ZHANG Li-bo. Comparison of microwave and conventional heating routes for kaolin thermal activation [J]. Journal of Central South University, 2020, 27(9): 2494−2506. DOI: https://doi.org/10.1007/s11771-020-4475-y.
1 Introduction Kaolinite is a clay mineral of chemical formula Al2O3·2SiO2·2H2O contained abundant silicon and aluminum [1] (Figure 1); therefore, it is conveniently used as a silicon source and an Foundation
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aluminum source for synthetic molecular sieves. Clay minerals have been used for the synthesis of zeolites as early as 1961 [2], and now are playing a pivotal role in fabricating zeolites. Simultaneously, the direct synthesis of zeolites from natural aluminosilicate minerals, without experiencing intermediate chemicals, has attracted extensive
Projects(51604135, 51504116) supported by the National Natural Science Foundational of China; Project(YNWR-QNBJ-2018-323) supported by the Yunan Ten Thousand Tale
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