Nano silica was prepared from rice husk with high surface area.X-ray diffraction(XRD) pattern showed that the amorphous form of silica was produced.Chemical composition of the nano silica was estimated by X-ray fluorescence spectroscopy and CHN analysis.The nano silica was used as a support for H3PW12O40.The nano silica and nano silica supported H3PW12O40 were characterized by inductively coupled plasma,XRD,transmission electron microscopy(TEM),N2 adsorption-desorption,and Fourier transform infrared spectroscopy.TEM images of nano silica as well as the supported catalyst displayed average size of 6 and 7 nm,respectively.The catalyst showed excellent activity in some important organic reactions including Biginelli,Hantzsch,Mannich,and Claisen-Schmidt reactions with good reusability.Catalytic activity of this nano catalyst is an improvement over the commercially available silica that is used to support H3PW12O40.
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