**Author details**

**5. Conclusions and future possibilities**

134 Advanced Catalytic Materials - Photocatalysis and Other Current Trends

processes.

The results presented in these studies show that the best conditions established for the epoxidation of AGE to DGE on the Ti-SBA-15 catalyst in water solution are as follows: the temperature of 20°C, the molar ratio of AGE/H2O2 = 0.03:1, the content of the catalyst 3 wt%, and the reaction time of 60 min. At these mild and relatively safe conditions, the selectivity of DGE amounts to 100 mol%; the conversion of AGE and the selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed amount to 4 mol% and 1 mol %, respectively. These studies also show that this process is very complicated because of the secondary reactions which proceed in reaction medium – hydration of epoxide ring in AGE (formation of 3A12PD), hydrolysis at the epoxide group in AGE, DGE, 3A12PD, epoxidation of the formed allyl alcohol, and hydration of the epoxide ring in glycidol and formation of glycerol. However, it is possible to choose such a way of carrying up this process in which only one product – DGE (the most desirable) – is obtained. The process of obtaining DGE is performed at very mild conditions, thus the danger of the explosive decomposition of hydrogen peroxide or compounds with epoxide group is very little, mainly taking into account the very low temperature of this process which amounts 20°C. Hydrogen peroxide used in this process is a relative cheap oxidizing agent and moreover, the methods of production of hydrogen peroxide are still developed and modernized. The method of AGE epoxidation with hydrogen peroxide is also ecologically friendly because only one product of its transformation is water. The presented studies showed that for this process hydrogen peroxide should be used in excess in relation to AGE. Mainly, it is connected with the phenomenon of ineffective decomposition of hydrogen peroxide (not explosive decomposition) at the active centers of Ti in the structure of the catalyst. This phenomenon causes that only a little amount of hydrogen peroxide takes part in epoxidation process and utilization of the excess of hydrogen peroxide in relation to AGE improves effective utilization of hydrogen peroxide molecules in the process of epoxidation. On the other hand, hydrogen peroxide undergoes very easy ineffective decomposition, thus even at the excess of hydrogen peroxide its concentration in reaction mixtures is low. The main cause of this situation is high content of the Ti-SBA-15 catalyst in reaction mixture (3 wt%). There are some possible ways of improving the hydrogen peroxide conversion efficiency by, for example, (1) addition of additives (CH3COOH, KHSO4, KH2PO4, KHF2, Na2SO4, NaHCO3, K2CO3, K3PO4, K2HPO4, or KH2PO4); (2) the changing of the way of hydrogen peroxide addition; (3) choosing the appropriate solvent (methanol, acetonitrile or acetone), or co-solvent (sulfolane); (4) increasing the acidity of the catalyst by the addition of metal oxide, for example, of TiO2, and utilization of the appropriate temperature of the calcination; and 5) the surface hydrophobization of mesoporous titanium silicates. We would like to test in our future works some of the ways of improving the efficiency of hydrogen peroxide conversion: choosing of the appropriate solvent, additives, and slow addition of hydrogen peroxide. A large advantage of the presented process is also performing the process of epoxidation in water solution without any other solvents. Moreover, water was not additionally introduced in the reactor, only with the solution of the oxidizing agent it was formed during the process. Water is now regarded as a very ecological solvent for organic Agnieszka Wróblewska\* , Edyta Makuch and Ewelina Mójta

\*Address all correspondence to: Agnieszka.Wroblewska@zut.edu.pl

Institute of Organic Chemical Technology, West Pomeranian University of Technology Szczecin, Szczecin, Poland
