In this study, a systematic approach was applied to the hydrothermal synthesis of Zn 2 SnO 4 (ZTO) nanocrystals to gain insight into the fundamental factors controlling phase composition, particle size, crystal morphology and photocatalytic activity. The influence of various operating conditions, such as reaction temperature, alkaline concentration, duration time, and additive surfactants on the treatment process were investigated. By combining the results of X-ray diffraction (XRD), electron microscopy (SEM/TEM/ED/HRTEM), Raman and FT-IR spectroscopy, a complete structural and morphological characterization of the products was performed. The results indicated that the phase transformation probably evolved via a "dissolution-recrystallization" mechanism and accompanying the "Ostwald ripening" process. Furthermore, a correlation between the photocatalytic activity in the UV photodegradation of MB solutions and the particle properties was established.
ZSM-5 zeolites, Ga modified via different
methods (in situ hydrothermal
synthesis, mechanical mixing, incipient wetness impregnation, solid-state
ion exchange, and liquid phase ion exchange), were systematically
investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy
(XPS), 29Si, 27Al, and 71Ga magic-angle
spinning (MAS) NMR, and H2 temperature-programmed reduction
(H2-TPR). It is important to prove that both impregnation
and liquid phase ion exchange could facilitate the incorporation of
Ga species into the framework in addition to in situ hydrothermal
synthesis. The liquid phase ion exchange method drove part of the
Ga species into the framework, and it was further migrated into the
framework by drying, while the incipient wetness impregnation method
promoted part of the Ga species into the framework only during the
calcination process. In the n-heptane catalytic aromatization
procedure on the fixed bed, Ga modified ZSM-5 by in situ hydrothermal
synthesis showed the highest benzene, toluene, ethylbenzene and xylene
(BTEX) selectivity, owing to the increased strong Lewis acidic sites
and mesopore volumes induced by the framework Ga species.
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