Optimization of the synthesis of mesoporous titanosilicate ETS-10: Problems and unexpected difficulties
We focused on the synthesis and subsequent use of mesoporous titanosilicate ETS-10 for industrial water purification. Numerous attempts have been made to optimize the conditions and reagents used for the synthesis of the ETS-10. The main problem we faced in the synthesis of ETS-10 is the production of “pure” phase and it was related to the type of titanium source. Various sources of titanium were used – titanium tetrachloride, anatase (anatase 92% and rutile 6%), nanosized titanium dioxide (Degussa P25) etc. The use of liquid titanium tetrachloride, due to its high hydrophilicity, leads to difficulties in reproducible control of the quantities of used reagents, which leads to the formation of unwanted crystalline phases, especially if the synthesis is carried out in small volumes. In addition, the optimized by us synthesis attempts included a reduced reaction time – up to 24 hours – and lower temperatures (up to 200 oC). For comparison standard synthesis is carried out for 72 h at 230 oC. As a result of the experiments, ETS-10 with minimal SiO2 residues was obtained in 24 hours at 200 oC using nanosized anatase.