Mesoporous titania-silica composite from sodium silicate and titanium oxychloride. Part I: Grafting method

摘要

In this study, we report a versatile method for designing a titania-silica composite using relatively inexpensive precursors. The composite was synthesized by grafting (impregnating) a precursor of a guest component into the preformed host's solid network. The latter was prepared using sodium silicate as a silica precursor in the presence of cetyltrimethylammonium bromide (CTAB). A freshly prepared solution of titanium oxychloride (TiOCl_2, titania precursor that is relatively stable) was introduced into the host's network to develop a titania-silica composite with initial ratio of Ti:Si = 1. The final product has the overall ratio of Ti:Si = 7:3 and was obtained after calcination for 5 h at 600-1000 °C. The XRD patterns for the calcined samples indicate the presence of TiO_2, and there was a significant increase in peak intensity as the calcination temperature increased. EDS, XRF, and FT-IR analyses indicated the formation of a highly pure composite rich in Ti, Si, and O. A Si-O-Ti band at 954 cm~(-1) was observed, confirming the formation of a titania-silica composite. A composite with optimum properties (homogenous dispersion of the composite and less individual oxide phase separation) was obtained at 600 °C. A similar experiment was also conducted in the absence of CTAB. In this case, the final product was microporous, rendering it unsuitable for some applications.