Preparation Of Macroporous/Microporous Titanium Silicalite With CaCO₃ As Hard Template

The macroporous/microporous titanium silicalite-1 was synthesized in dry-gel conversion method and hydrothermal synthesis method individually by using nanosized CaCO₃ as macroporous template.The effects of CaCO₃ adding amount,template amount and water amount on the pore size distribution,coordination states of Ti atoms and catalytic performance of phenol hydroxylation were studied systematically.The main conclusions obtained were as follows:1.The macroporous/microporous titanium silicalite-1 was synthesized in a dry-gel conversion method by using nanosized CaCO₃ and TPAOH as macroporous and microporous template,respectively.The CaCO₃ was added to the synthesis system of TS-1,leading to the growth of TS-1 along the CaCO₃ and generating the core-shell structure.The macroporous/microporous TS-1 with the macroporous diameter of⁶0 nm was then obtained after the dissolution of CaCO₃ by acid treatment.The macropores in the TS-1 gradually increase with the increase of CaCO₃ adding amount.The addition of a small amount of CaCO₃ will inhibit the generation of non-framework titanium species,but too much CaCO₃will cause the non-framework titanium species to reappear.Reducing the addition of TPAOH in the solid phase is conducive to increasing the macropores and the content of tetrahedrally coordinated Ti,thereby improving the catalytic performance of phenol hydroxylation.When only a small amount of water is added to the bottom of the kettle,the TS-1 with high crystallinity,large macropores and high catalytic performance is synthesized.It is not helpful to increase the water or TPAOH amounts in the kettle for the formation of macropores and tetrahedrally coordinated Ti.2.The macroporous/microporous titanium silicalite-1 was synthesized in hydrothermal synthesis system by using nanosized CaCO₃ and TPABr as macroporous and microporous template,respectively,the macroporous diameter of which was⁶0 nm.The macropores in the TS-1 gradually increase with the increased CaCO₃ amount.Moreover,a proper amount of CaCO₃ can inhibit the formation of anatase TiO₂ and octahedrally coordinated Ti.When the m?CaCO₃:SiO₂?is in the range of 0.2-0.4,the non-framework Ti nearly disappeared.3.The functions of CaCO₃ are not only fabricating macropores,but also varying the coordination states of Ti species.The macroporous/microporous titanium silicalite-1 shows an excellent catalytic activity in the hydroxylation of phenol,due to the reduction of diffusion resistance and the inhibition of the anatase TiO₂ formation.