Abstract:

 Mixed oxides TiO₂-M_xO_y(M=Fe, Si, Al, Zr）prepared by co-precipitation method were impregnated in aqueous solutions of sulfuric acid to form doped solid acid samples.These catalysts were characterized by XRD, FTIR, NH₃-TPD and H₂-TPR.Their catalytic activity was tested in the transesterification reaction between soybean and methanol.The results showed that the addition of second oxide into TiO₂/SO₄^{2 -} could improve the catalytic activity and inhibit the formation of TiOSO₄ in impregnation process except Al.The restraint effect was the strongest for silica.The doping of Si, Zr and Fe oxides could enhance surface acidity of catalysts while the addition of Al even made the acidity lower.The decrease of reduction temperature by H₂ was larger for Fe-involving sample than for Si-involving one.The Fe doped catalyst was found to be readily reusable in activity upon reuse for three times with subtle decrease conversion.