Experimental study on CO 2 desorption enhancement of DMAPA solutions using composite nanoparticles

Chemical absorption using alkanolamine solutions is an effective approach for post-combustion CO2 capture, but the regeneration process remains limited by relatively slow desorption and high energy demand. In this study, a 40 wt.% DMAPA solution was used as the base absorbent, and single and composite oxide nanoparticle nanofluids were prepared by a two-step method to enhance CO2 desorption. Among the single nanoparticles tested at a total mass fraction of 0.1 wt.%, the desorption enhancement followed the order TiO2 >MoO3 >ZnO >CuO >SiO2, with TiO2 giving an average desorption enhancement factor of 1.63 and a maximum instantaneous enhancement factor of 2.22. For the composite systems, the 50 nm SiO2–TiO2 nanofluid at a 1:1 mass ratio exhibited the best overall performance, achieving an average enhancement factor of 1.32 and a maximum instantaneous enhancement factor of 1.81. Compared with the blank DMAPA solution, its peak instantaneous desorption rate increased by 6.9 mmol·L−1 and the desorption loading increased by 2.3 mol·L−1. Operating-condition tests further showed that 450 r·min−1 provided the most favorable balance between nanoparticle dispersion and gas–liquid mass transfer, while excessively high stirring speeds weakened the enhancement effect. At 413.15 K, the average and maximum instantaneous enhancement factors reached 1.60 and 2.25, respectively. Repeated absorption–desorption cycles resulted in a gradual decline in desorption enhancement, which was associated with nanoparticle agglomeration observed by TEM. These results demonstrate that the composition, particle size, and mixing ratio of composite nanoparticles, together with dispersion stability during operation, are critical to sustaining enhanced CO2 regeneration in DMAPA-based nanofluids.