High temperature thermal stabilization of alumina modified by lanthanum species |
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| Affiliation: | 1. Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China;2. Department of Chemistry, Fudan University, Shanghai 200433, PR China;1. Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Engineering, School of Chemical Engineering, Tianjin University, Tianjin 300072, China;2. School of Chemical Engineering, Inner Mongolia University of Technology, Huhehaot 010062, China;1. Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA;2. School of Environment, Tsinghua University, Beijing 100084, China;1. Environmental Engineering Division, School of Mechanical and Building Sciences, VIT University, Chennai 600 127, India;2. Chemistry Division, School of Advanced Sciences, VIT University, Chennai 600 127, India;1. Dipartimento di Energia, Politecnico Di Milano, via Lambruschini 4, Milano, 20156, Italy;2. ENEA, via Anguillarese 301, Santa Maria di Galeria, Roma, 00123, Italy;1. State Key Laboratory of Advanced Special Steel, Shanghai University, Shanghai 200072, China;2. Shanghai Key Laboratory of Advanced Ferrometallurgy, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China;1. Departamento de Ingeniería Química, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, México;2. Instituto de Ingeniería, Coordinación de Ingeniería Ambiental, Universidad Nacional Autónoma de México, Ciudad de México 04510, México |
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| Abstract: | The effects of precursor pretreatment and addition methods of lanthanum species on stabilization of alumina (surface area loss, phase transformations and high temperature interaction with lanthanum species) have been investigated by BET specific surface area measurements (BET), X-ray powder diffraction (XRD), N2 adsorption–desorption isotherms, thermal analysis and X-ray photoelectron spectroscopy (XPS) in the range of 600–1150°C. Although powder La2O3, which is mechanically mixed with γ-Al2O3 or pseudo boehmite, can effectively retard the α phase transformation by solid phase interaction with Al2O3, it does not show a positive effect on retarding the loss of surface area. Compared with the direct impregnation of γ-Al2O3, the gelation of pseudo boehmite by acidification accelerates phase transformations and weakens the stabilizing influence of lanthanum species. At 600°C and for atomic ratio of La/Al up to 0.1 or at 1150°C and La/Al≤0.02, the lanthanum species is highly dispersed in alumina. With the increase of calcination temperature or lanthanum content, lanthanum species is present as dispersed La2O3, LaAlO3 and crystalline La2O3. At T≤1000°C the surface area loss of alumina is mainly attributed to the sintering of particles. The follow-up loss at T>1000°C results from both sintering and phase transformations. The highly dispersed lanthanum species retard both sintering and phase transformations, and their associated surface area loss. However, the formation of LaAlO3 mainly retards the surface area loss resulting from the α phase transformation. Having considered the purely mechanical mixing effect of additive on the surface area loss of alumina, an influence criterion of lanthanum species on retarding the surface area loss whether resulting from sintering or from α phase transformation at high temperature ≥1000°C has been proposed in this paper. |
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