改性活性氧化铝的二氧化碳吸附性能研究

Study on Adsorption of Carbon Dioxide on Modified Activated Alumina

以活性氧化铝(γ-Al_(2)O_(3))为原料,不同含量五乙烯六胺(PEHA)的乙醇溶液为改性剂,使用浸渍法制备改性活性氧化铝(Al_(2)O_(3)-PEHA-X)。通过对改性活性氧化铝进行X射线粉末衍射实验(XRD)、傅里叶变换红外光谱实验(FTIR)和氮气吸附脱附实验(BET)可知,PEHA成功负载于活性氧化铝且没有破坏活性氧化铝原有结构,但导致其比表面积和孔容有所降低。当PEHA含量一定时,在吸附温度为25~70℃范围内,随吸附温度升高,改性活性氧化铝的CO_(2)吸附量下降。在吸附温度一定时,随PEHA含量增加,改性活性氧化铝的CO_(2)吸附量呈先增加后减小的趋势,当PEHA含量大于2 mL时,CO_(2)吸附量下降尤为明显。Al_(2)O_(3)-PEHA-0.5经过5次重复使用,保持了约81%的吸附能力。在第2次吸附时CO_(2)吸附量下降17.6%,随后基本保持稳定。改性活性氧化铝的CO_(2)吸附过程符合准二级动力学模型,表明吸附过程主要由化学吸附控制。吸附过程放热,反应自发进行,吸附温度升高不利于吸附反应进行。

With activated alumina(γ-Al_(2)O_(3))as raw material,ethanol solution with different contents of pentaethylenehexamine(PEHA)as modifier,the modified activated alumina(Al_(2)O_(3)-PEHA-X)is prepared by impregnation method.Through the X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FTIR)and nitrogen adsorption-desorption(BET)experiments on the modified activated alumina,it can be seen that PEHA is successfully loaded on the activated alumina and does not damage the original structure of the activated alumina,but causes its specific surface area and pore volume to be reduced.When the content of PEHA is constant,the CO_(2) adsorption capacity of modified activated alumina decreases with the increase of adsorption temperature in the range of 25-70℃.When the adsorption temperature is constant,with the increase of PEHA content,the CO_(2) adsorption capacity of modified activated alumina increases first and then decreases.When the PEHA content is greater than 2 mL,the CO_(2) adsorption capacity decreases significantly.Al_(2)O_(3)-PEHA-0.5 has maintained about 81%adsorption capacity after 5 times of reuse.During the second adsorption,the CO_(2) adsorption capacity decreases by 17.6%,and then remains basically stable.The CO_(2) adsorption process of modified activated alumina conforms to the quasi-second-order kinetic model,it shows that the adsorption process is mainly controlled by chemical adsorption.The adsorption process is exothermic,the reaction is spontaneous,and the increase of adsorption temperature is not conducive to the adsorption reaction.