High Efficient Separation Process Of Boron And Phosphorus Impurities From Liquid Chlorosilane

Presently,the main producing method of polysilicon is Modified Siemens Process.Purification of raw material chlorosilane is the key process in Modified Siemens Process.Since trace boron and phosphorus impurities share the similar volatility with chlorosilane,boron and phosphorus impurities are difficult to remove from chlorosilane,which usually need multi-stage distillation to separate that leads to low distillation product yield.Even so,product quality is not stable.As a result,high energy consumptionTo settle this problem,after analyzing the cause and the existing boron and phosphorus removal technologies,the separation of trace boron and phosphorus from chlorosilane refined material was simulated by using Aspen plus software and the optimal conditions were found.Trace boron and phosphorus removal from chlorosilane by complexation and adsorption was studied preliminarily and high efficiency complexing agents and adsorbents were found.The main research work and results are as follows:(1)Designed and simulated trace boron and phosphorus impurities removal from chlorosilane by distillation was designed and simulated.The influence of process parameters on the process was analyzed by sensitivity analysis.The optimal operating parameters,including stage number?feed stage number?reflux ratio and so on was discussed.As a result,the boron and phosphorus content can be reduced to dozens of ppb,which can basically meet the demand of solar grade chlorosilane raw materials.(2)The process of trace boron and phosphorus impurities removal from chlorosilane by complexation was studied.Combined with boron and phosphorus impurities complexation mechanism and found high efficiency complexing agent,when the mass ratio of triphenyl methyl chloride and diphenyl carbazone is 2:1,its complexation efficiency is best,can make a few ppm of boron and phosphorus impurities in chlorosilane reduced two ordes of magnitude.(3)Trace boron and phosphorus impurities removal from chlorosilane by adsorption was explored and studied.Combined with the adsorption mechanism of boron and phosphorus impurities and found high efficiency adsorbents.The adsorption efficiency of boron and phosphorus by silica gel,A21,A100 and activated alumina are better.The modification of activated carbon by surface oxidation modification method and the high efficiency complexing agent supported on activated alumina can be used to improve the adsorption ability of boron and phosphorus.