Research On The Removal Of Trace Phosphorus From Silicon Tetrachloride By Means Of Complexing Adsorption

The purity of optical fiber perform in the field of optical fiber product is very strict.For gas phase silicon tetrachloride in the chemical vapor deposition of indoor,trace amounts of phosphorus trichloride impurities will seriously affect the optical performance of the optical fiber preform products.Therefore,it is very important to control the content of phosphorus trichloride impurities in the range of product requirements.There is a little difference with other impurity phosphorus test method reported in the other study using ICP-Ms.In this study through the improvement of pretreatment method for silicon tetrachloride sample containing trace phosphorus trichloride,combined with analysis experiment for phosphorus content in the water and chlorosilane raw material,the composition of hydrolysate in the silicon tetrachloride raw material pretreatment process,and the influence's law and mechanism of the phase state of silicon tetrachloride raw material on phosphorous impurity content range inspected by ultraviolet spectrophotometer were studied.On the basis of the test method,modified adsorbent for gas phase adsorption of trace phosphorus trichloride was obtained through loading copper chloride on 13X molecular sieve.In order to investigate the performance of adsorbent,the adsorbent of the breakthrough curve and adsorption capacity under different temperature within the scope of the 0⁶0?was investigated,and the best adsorption temperature was confirmed on the basis of this test.The absorbance measured by ultraviolet spectrophotometer was used to characterize the content of trace phosphorus impurities in silicon tetrachloride.Results show that when the pretreatment phase of the silicon tetrachloride raw material as gas phase and high purity nitrogen as carrier gas which were bubbled into high purity water,the inter-molecular forces of silicate molecular after hydrolysis is weak,and the hydrolysate has not formed colloid but for clear solution.The absorbance range is 0.1⁰.8 and the quality of phosphorus impurities content in silicon tetrachloride detection range is 0.0003⁰.0003.X-ray diffraction and surface analysis were used to characterize adsorbent and explore the mechanism of adsorption.The results show that the copper chloride in the form of a single molecule or the mono-layer distributes on the surface of the carrier,and the specific surface area of CuCl₂-13X adsorbent was 289.5m²/g,and in experimental conditions copper chloride changes the structure of 13X molecular sieve.After loading copper chloride,the XRD adsorption spectra of CuCl₂-13X adsorbent appeared characteristics diffraction peaks.The adsorption performance of 13X molecular sieves modified by copper chloride is geometrically increased.When the volume of mixture for CuCl₂-13X adsorbent in breakthrough experiment is 160 mL,the removal efficiency of complexation adsorbent for PCl₃ is still greater than 60%,that is,the dynamic adsorption capacity is about 20.8mg/g.However,when the volume of mixture is about20 mL,the dynamic adsorption capacity is about 2.96mg/g.the 13X molecular sieve was completely penetrated and lost adsorption capacity.