Preparation of TS-1 by wetness impregnation of amorphous SiO2—TiO2 solids: influence of the synthesis variables Original Research Article

TS-1 has been synthesized by wetness impregnation of amorphous SiO2single bondTiO2 solids with TPAOH solutions and subsequent crystallization under autogenous pressure, the influence of the different variables involved being studied. The SiO2single bondTiO2 cogel used as raw material has been prepared following a two step (acid-base) sol-gel process which leads to the formation of Sisingle bondOsingle bondTi bonds previously to the zeolite crystallization. The titanium content of TS-1 can be controlled through the variation of the raw SiO2single bondTiO2 composition, although a limit of the Ti/(Ti + Si) × 100 molar ratio around 2.3% in titanium effectively incorporated to the zeolite framework has been observed, even when starting from cogels with low Si/Ti ratios. The size and morphology of the crystals depend on the synthesis variables, small crystallites with 0.2 μm of diameter being obtained at high TPAOH concentration. The kinetics of TS-1 crystallization by this method is very fast in spite of taking place in static conditions. Thus, pure TS-1 can be achieved at 170°C in just 6 h of synthesis. All TS-1 samples were tested as catalysts for n-hexane oxyfunctionalization, high activities and selectivities being obtained with most of them.