质子化哌嗪化学吸收CO_(2)过程研究与分析

Study on CO_(2)chemical absorption with protonated piperazine

为研究有机胺吸收/解吸CO_(2)变化过程,以哌嗪(PZ)为吸收剂,利用浓硫酸调节PZ的质子化程度,通过核磁共振技术研究不同pH下的PZ溶液吸收CO_(2)情况,进一步揭示PZ和质子化PZ化学吸收/解吸CO_(2)的过程机理。结果表明,吸收过程中PZ与CO_(2)反应生成哌嗪单氨基甲酸盐和双氨基甲酸盐;当溶液pH为7.95时,溶液中哌嗪双氨基甲酸盐和部分单氨基甲酸盐发生水解,生成碳酸氢根;当溶液pH低于7.95时,溶液中CO_(2)以哌嗪单氨基甲酸盐和碳酸氢根形式共存。与PZ吸收剂相比,质子化PZ吸收CO_(2)过程中的双氨基甲酸盐相对含量降低,解吸性能提高,有利于PZ吸收剂的再生。

In order to investigate the absorption/desorption of CO_(2)by organic amine,sulfuric acid was used to adjust the protonation degree of the absorbent PZ.Nuclear magnetic resonance technology was employed to investigate CO_(2)adsorption processes under different pH values,which was used to study the mechanism of CO_(2)adsorption/desorption in piperazine(PZ)and protonated PZ.The results show that piperazine monocarbamate and biscarbamate are formed after the reaction of PZ with CO_(2).Piperazine biscarbamate and certain amount of monocarbamate were hydrolyzed to HCO_(3)^(-)when the pH value was 7.95.However,piperazine monocarbamate and bicarbonate coexisted when the pH value was lower than 7.95.The generated biscarbamate in protonated PZ is reduced during CO_(2)absorption comparing with PZ,which is beneficial for CO_(2)desorption and PZ regeneration.