Improvement of hydrophobicity and stability of Ti-MCM-41

Abstract

In this study, Ti-MCM-41 materials with various pore sizes and Si/Ti ratios were synthesized to compare their properties. Several conditions of restructuring and silylation were investigated separately and in duality to improve the hydrophobicity and stability of Ti-MCM-41. The crystallinity change was followed up using X-ray diffraction, diffuse reflectance-UV-visible and Fourier transform infrared techniques. Low stability of large pore Ti-MCM-41 is on account of the thin wall formed around the pores. Not all silicon was completely condensed at the pore wall therefore silanol groups were left at the wall surface and can be restructured during appropriate treatment. A single treatment of restructuring in hot water results in the increase of the stability of the products, especially for small pore Ti-MCM-41, Silylation of the materials was studied under a variation of temperature, excess amount, and types of a silyl reagent. All treated samples were tested for their stabilities to hydrothermal treatment and to moisture in comparison with the untreated samples. The post-synthesis combination of restructuring in hot water and silylation is proven as the best treatment for making the highest stable Ti-MCM-41 product with great hydrophobicity.