TiF4 : An original and very interesting precursor to the synthesis of titanium containing silicalite-1

A new titanium precursor, TiF₄, has been used to synthesize titanium silicalite-1 (TS-1). In contrast to the commonly used alkoxides, TiF₄ is stable in air, water, and even basic TPAOH solutions, which offers considerable advantages as compared to conventional synthesis routes. In particular, TS-1 can be obtained with commercial TPAOH solutions, containing alkali cations, without formation of extraframework species. For samples synthesized with alkali-free TPAOH solutions, the maximum Ti incorporation that can be achieved corresponds to about 2.05 Ti/u.c., and TS-1 samples are similar to previously reported solids prepared with titanium alkoxides. In particular, they are very active in the ammoximation of cyclohexanone and the hydroxylation of phenol with hydrogen peroxide. When TS-1 is prepared with commercial TPAOH solutions, alkali cations can be removed by washing the solid with dilute acid, and the catalytic performance of the washed zeolite is similar to that of samples synthesized with alkali-free TPAOH.