Preparation of Silicates Using HSi(OC2H5)3 and Their NOx-Adsorption Behavior
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- Katayama, S., Yamada, N. & Awano, M. J Sol-Gel Sci Technol (2004) 32: 311. doi:10.1007/s10971-004-5808-2
The preparation and NO-adsorption/desorption behavior of Li, Ca and Ba silicates were investigated aiming at the application to a NOx-absorbent. Li silicate was prepared by reaction of HSi(OC2H5)3 with aqueous lithium silicate solution (LSS). Ca and Ba silicates were prepared from gels obtained using CH3Si(OC2H5)3, Si(OC2H5)4, HSi(OC2H5)3 and alkaline-earth alkoxides. The surface of these silicates indicated the solid basicity of H0 = 9 and adsorbed the acidic gas of NO. FT-IR spectra of the silicates adsorbing NO showed the absorption peaks in the range of 1300–1600 cm− 1 corresponding to ionic and covalent nitrate NO3−. The complete desorption of adsorbed NO species occurred above 500°C in the Li silicate, above 500°C in the Ca and Ba silicates prepared using CH3Si(OC2H5)3, and above 700°C in the Ba and Ca silicates prepared using Si(OC2H5)4. Regarding the Ca and Ba silicates, the difference in siloxane structure is thought to cause the difference in adsorption state and desorption behavior of NO.