Enhancing CO2 desorption rate in rich MEA solutions by metal-modified attapulgite catalyst

To overcome the high energy consumption of the CO2-rich monoethanolamine (MEA) solution regeneration process, this study proposes to catalytically promote CO2 desorption using transition metal-modified attapulgite (ATP) composite catalysts (M/ATP, M = Ni, Zr) in a 5 M CO2-loaded MEA solution at 90 °C. The catalysts were characterized by XRD, FT-IR, BET, and Py-IR. The influences of different metals and metal salts on the activity of CO2 desorption for the ATP-based composite catalyst were studied. The findings proved that the introduction of metal oxide enhanced the activity of catalytic CO2 desorption for the ATP catalyst and reduced the relative energy requirement. Ni/ATP presented the superior catalytic activity, with an increase of 195 % and 144 % in the rate of CO2 desorption and desorption amount, respectively, compared with the noncatalytic desorption process. The excellent catalytic performance of metal-modified ATP composite catalysts was mainly due to the enhanced Brønsted acid sites. After 8 cycles of CO2 absorption–desorption experiment, the Ni/ATP catalyst still showed excellent stability. The introduction of the Ni/ATP catalyst had no adverse impact on the CO2 absorption in the MEA solution. Moreover, a possible catalytic MEA solution regeneration pathway over Ni/ATP was suggested based on FT-IR and 13C NMR measurements.