Aerosol-assisted Synthesis Of Small Crystal TS-1 Zeolites And Nano-sized TS-1 Zeolite Aggregates

Titanium silicalite-1?TS-1?has attracted much attention due to its excellent catalytic properties in selective oxidation reactions with H₂O₂ as oxidant.Our previous study showed that TS-1 zeolites can be synthesized by an aerosol assisted method.By the method the dosage of template agent is reduced and the utilization of the autoclave is improved.However,the size of the TS-1 zeolite is larger than that synthesized by the conventional hydrothermal synthesis,which may affect its diffusion property.In order to solve the problem,the synthesis conditions of TS-1 zeolite were improved.Firstly,the TS-1 zeolite with smaller particle size was synthesized by increasing the concentration of template agent.The distribution of titanium species can be significantly influenced by adjusting the amount of template agent.Under the following conditions:template concentration 40wt%,TPAOH/SiO₂?0.08,small crystal TS-1 zeolite with good titanium distribution and the crystal size of 230nm to 270nm can be obtained.Secondly,TPAOH solution was used to modify the TS-1 zeolite.The effect of the TPAOH concentration on the structure and catalytic performance of the TS-1 zeolite was investigated.The results show that after the TPAOH treatment the non-framework titanium species is formed.Simutaneously,the irregular voids appeared in the crystal,which significantly improves its diffusion property and catalytic performance.The best catalytic performance can be achieved when the TPAOH concentration is 0.04mol/L.Finally,mesoporous structure was introduced into the amorphous titanium silicon oxide when CTAB was added into the precursor solution.The nano-sized TS-1 zeolite aggregates were obtained by the hydrothermal crystallization of the precursor powder with the template agent.The influence of the synthesis conditions has been studied.The results show that the amorphous precursor prepared with CTAB/SiO₂=0.2 exhibits the most ordered mesopore.The obtained TS-1 zeolite aggregates exhibit uniformed size of 250nm.It has the largest external specific surface area and pore volume,and exhibits the good catalytic performance.