Low Concentrations Of Ph <sub> 3 </ Sub> Liquid Phase Catalytic Oxidation Of Experimental Research

This dissertation is about the purification of phosphine (PH₃) with low concentration. After a comprehensive research of all kinds of current purifying methods, a liquid catalytic oxdative purifying method, in which Cu²⁺ and phosphate ammonium were respectively primary and auxiliary catalyst, was proposed to purify phosphin. Experiments of optimum condition and regeneration were carried out in this dissertation. Following results have been concluded.[1] Under the condition of 1275～1300mg/m³ for initial PH₃ concentration and 21% for oxygen content, PH3 can be catalytic oxidative purified by ions of Zn²⁺,Mn²⁺,Fe³⁺ and Cu²⁺ with the effect of the higer pH value the better purification. For the sequence of purifying efficiency for four ions was Cu²⁺>Fe³⁺>Zn²⁺>Mn²⁺, Cu²⁺ was chosen as the primary catalyst. Adsorbing efficiency increased with the increase of Cu²⁺ concentration; and a slow increasing trend has been found out at the concentration of 0.15mol/L[2] Citric acid, EDTA, ethylenediamine and phosphate ammonium were added into solution with Cu²⁺ to evalueate their auxiliary pufying efficiency. Under the alkaline condition, phosphate ammonium had more positive influence on improving purifying efficiency, so phosphate ammonium was chosen as auxiliary catalyst.(3) Adsorbing efficiency increased when reaction temperature increased from 25℃ to 65℃; and a downtrend has been found out at the temperature of 85℃; so the appropriate reaction temperature should be between 65℃ and 75℃. Adsorbing efficiency decreased with increase of flow rate; and duration time of high purifying effecienvy was also short; so the appropriate flow rate was 0.3L/min. Under a constant flow rate, adsorbing efficiency decreased slowly with the increase of inlet concentration of PH3; when inlet concentration of PH3 was < 1556.5mg/L, purifying efficiency can maintain at more than 85%. When pH value of solution was between 8 and 11, adsorbing efficiency can stably matained at around 85%; between 8 and 7, adsorbing efficiency decreased obviously; duration time of high purifying effecienvy decreased with decrease of pH value; and also, there would be a better purifying efficiency when sodium carbonate was chosen as buffer solution to make pH value being around 10. Adsorbing efficiency increased obviously with the increase of oxygen content; it was 5% for increase amplitude when oxygen content increased from 0.5% to 10%, and 10% for that from 10% to 21%; in practicaloperation, when oxygen content is lower, outer oxygen can be added to increase purifying efficiency.[4] The optimum experiment conditions were as following: reaction temperature, 65℃; gas flow rate, 0.3 L/min; oxygen content, 21%; primary catalyst concentration, 0.15 mol/L; auxiliary catalyst concentration, 0.15 mol/L; and initial pH value, 10. Under optimum conditions, it was 89.5% and 4.5gPH3/L(soulution) respectively for initial purifying efficiency and saturated phosphorus capacity. Saturated adsorbing solution can be regenerated through firstly adding NH₃ into solution to neutralize phosphoric acid and then adding air to odidize Cu⁺ to Cu²⁺; there would be a little decrease of adsorbing efficiency for regenerated adsorbing solution, but still higer than 80%.