The silanization process for the hydrothermal synthesis of hierarchical titanium silicalite-1

Abstract The silanization is an important approach for hierarchical zeolite preparation. Although the influences of the silanization conditions have been detailed studied, the differences in the reactivity of the zeolite precursor should further be analyzed. In this paper, hierarchical titanium silicalite-1 (HTS) was prepared with trimethoxy[3-(phenylamino)propyl]silane (TMPAPS) under the nTMPAPS:nSi = 0.04–0.20 and nTi:nSi = 0.005–0.04 conditions, the changes of the corresponding physicochemical properties were analyzed, and the influences of the condensation activities between silicon/titanium to the organosialne were deduced and verified by density functional theory (DFT) calculations. Generally, more supermicropores and mesopores can be created in the metastable sponge-like HTS crystals with higher TMPAPS and titanium contents. In comparison, the free energy barrier in the condensation reaction with titanium (1.31 eV) is lower than silicon (1.55 eV), it's preferential to prepare HTS with more intracrystalline secondary porosity by increasing the nTi:nSi. More importantly, the titanium can be isolated by the organosilane, and HTS with more framework titanium can be synthesized by silanization.