微氧下低浓度磷化氢在浸渍活性炭上的吸附及表征

Adsorption of Low-concentration Phosphine on Impregnated Activated Carbon under Trace Oxygen Content Condition

要利用富含高浓度CO的工业尾气(如黄磷尾气)生产甲酸、乙酸以及甲醇等高附加值产品,净化处理成为制约其应用的瓶颈问题。采用浸渍法改性活性炭吸附净化低浓度PH3,研究了HCl、KNO3和己二醇改性活性炭吸附净化磷化氢(PH3)的性能,研究表明:质量分数7%的HCl是最佳浸渍液,70℃和氧体积分数0.8%是改性活性炭的最佳反应条件。改性后的活性炭用氮气吸附的方法测定其孔结构特征。结果表明,改性使吸附剂总孔容的减少主要发生在2nm以下的微孔直径范围内,特别是在0.3～1.5nm的微孔范围内,孔容积减小明显,经改性后,微孔容的减少占总孔容减少的87%,吸附后,微孔容减少29%,表面积减少28%。HCl改性可以显著增加活性炭对PH3的吸附能力。分析表明,存在于微孔中的HCl起了催化作用,使PH3迅速氧化成磷的氧化物(P2O3或P2O5),而磷的氧化物能较强地吸附在活性炭0.3～1.5nm的微孔中。

In order to utilize industrial tail gas containing high concentration of CO to produce valuable products, impregnated activated carbon was used as sorbent and its adsorption for PH3 had been studied in laboratory. Activated carbon was impregnated with HCl, KNO3 and hexanediol respectively. The results showed that 7 % （ mass fraction） HCl was the optimum impregnant, 70 ℃ for optimum temperature, and 0.8 % （ volume fraction） for optimum oxygen content. The structure of the impregnated activated carbon was determined using method of nitrogen adsorption. The modification resulted in a decrease in the volume of pores smaller than 2 nm, the most noticeable change was in the range of pores from 0.3 nm to 1.5 nm. After modification, decrease in volume of micropores is 87 % of decrease in volume of total pores. After adsorption, the surface area decreased 28 % with 29 % decrease in the volume of micropores. Modification with HCl significantly increases the adsorption of activated carbon for PH3 while the effects of other materials used in this study are less pronounced. It is likely that HCl presenting in the small pores acts as a catalyst for enhancing the oxidation of PH3 into P2O5 or P2O3, which can be strongly adsorbed by activated carbon in small pores from 0.3 nm to 1.5 nm.