Study On The Synthesis Of Nanometer Titanium Silicon Molecular Sieve (TS-1) And Membrane Properties

Nano TS-1 molecular sieve's large external surface area and remarkable physical and chemical properties make it very different from amorphous or non-porous materials and conventional sub-micron molecular sieve.In particular,the nano-TS-1 molecular sieve with a particle size of less than 100 nm can exhibit excellent performance in the field of electrorheology.Nano TS-1 molecular sieve has excellent dispersion performance and narrow particle size distribution range,so the grown TS-1 molecular sieve membrane is thinner and denser,and has outstanding performance in permeability and selectivity.However,the preparation process of nano-TS-1 is complicated,and the crystallization time is long and the yield is low.Therefore,this article aims to improve the traditional hydrothermal method to realize the rapid and efficient preparation of nano-scale TS-1molecular sieve with a particle size of less than 100 nm;simply explore its crystallization mechanism and process;study the nanocrystalline TS-1 molecular sieve membrane performance.The specific research contents are as follows:1.Explore the factors affecting the formation of nano-scale TS-1 molecular sieve,such as crystallization temperature,crystallization time,titanium source,and water content in the precursor of synthetic liquid.The mother liquor contains a large number of secondary structural units.These structural units are not only the basic materials for nucleation of molecular sieves,but also the concentrated mother liquor increases the supersaturation of the precursor,which facilitates the rapid generation of nano-sized molecular sieves.Compare the structural and performance differences between nano-TS-1 and sub-micron TS-1,such as electro-rheological properties.2.Through the analysis of the precursor composition of the synthetic liquid,the main components of the solid seed crystal and the liquid seed crystal and their influence on the nucleation and growth of the molecular sieve during the crystallization process were explored.The presence of seed crystals can promote synthesis,and the secondary structure unit size of liquid seed crystals is smaller,and the fragment particle effect generated by it is conducive to the rapid nucleation of TS-1 and rapid crystallization and separation from the gel to form nano TS-1 molecular sieve.Through the analysis of growth kinetics,the molecular sieve formation model was drawn.In addition,the composition of TS-1 molecular sieve is mainly SiO₂ and a certain amount of TiO₂,which makes it have insulating and polarizing properties.Nano TS-1 has a higher Ti/Si molar ratio than traditional submicron TS-1 and Excellent dispersion performance,so this provides a new idea for the nano TS-1 molecular sieve used in the field of electrorheology.3.The nano-seed TS-1 molecular sieve membrane is prepared by periodic secondary growth,and on this basis,the growth cycle time is shortened.The traditional growth method is inefficient and the growing molecular sieve membrane is thick,which affects the overall permeability and selectivity of the membrane.Pre-treat the alumina carrier with chitosan quaternary ammonium salt,adjust the periodic secondary growth method on the basis of the predecessors,and shorten the time of the first two cycles.Combined with SEM and CO₂/N₂ gas permeation experiments,it was found that the molecular sieve membrane prepared by the periodic secondary growth method is thinner and dense without defects,and the molecular sieve membrane performance is more superior.