Study on the efficient removal of trace PCl3 by acetic acid-modified γ-Al2O3
It is necessary to reduce the amount of PCl3 to ppb levels during polysilicon production in order not to affect product perform-ance.However,the removal of PCl3 impurities to the ppb levels remains a big challenge.In this work,we present a highly effective adsorbent for the efficient removal of trace PCl3,that is,acetic acid modified γ-Al2O3,which can remove PC13 at ppb levels with a removal rate of up to 84.2%.The Boehm titration experiments revealed a substantial increase in the carboxyl group content on the sur-face of γ-Al2O3 after modification,thereby facilitating an augmented number of adsorption sites for PCl3 and consequently enhancing its removal efficiency.By means of characterization analysis and DFT simulations,it is suggested that the predominant interaction between acetic acid and γ-Al2O3 occurs through the establishment of hydrogen bonds between the hydroxyl H of acetic acid and O in Al2O3.In addition to simple physical adsorption,it has been found that the interaction by charge transfer between Al in γ-Al2O3 and Cl in PCl3,as well as between carbonyl oxygen in acetic acid and P in PCl3,play a significant role in enhancing the removal of PCl3.Five consec-utive cycle experiments show that the adsorbent has excellent regeneration properties at low regeneration temperature.The adsorbent de-veloped in this work is promising for applications in the removal of trace amounts of PCl3 due to its efficiency,ease of regeneration and low cost.
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