Study on the 3D-printed monolithic ZSM-5 catalyst to enhance CO2 desorption from amine solutions

Abstract

CO₂ desorption catalyzed by solid acid is one of the effective ways to reduce the energy consumption in the post-combustion. In this study, 3D printing technology was employed to construct a monolithic catalyst based on ZSM-5 with a direct ink writing (DIW) method. The performance of CO₂ desorption from amine solution was studied in a continuous bubbling reactor at mild temperatures (<100 °C). The physicochemical properties of the ink for 3D-printing were analyzed using XRD, NH₃-TPD, BET, and N₂ isothermal adsorption–desorption to single out the optimal preparation method. A computer vision method was established to investigate the formation of CO₂ bubbles on the surface of the 3D-printed catalyst and their evolution in the liquid bulk. The results show that the ink for 3D-printed catalysts based on ZSM-5 with a low Si/Al ratio provided more surface mesopores and active sites, leading to an increase of 46.0 %–121.6 % in the maximum CO₂ desorption rate and 16.3 %–36.0 % in the CO₂ desorption capacity, compared to the blank amine solution. A lower sintering temperature is conducive to retaining the active sites on the catalyst surface, thereby effectively enhancing the kinetics of CO₂ desorption. The optimal Si/Al ratio and sintering temperature for the ink of 3D-printed catalysts were 25 and 550 °C, respectively, which can reduce the CO₂ desorption energy by 26.5 %. And the reduction of CO₂ desorption amount for various ZSM-5 based inks did not exceed 6.0 % after multiple cyclic testing. The 3D-printed ZSM-5 monolithic catalysts increased the total CO₂ amount by 54.8 % at most compared to blank absorbents, because the grille configurations provided more specific surface area to promote the deprotonation of MEAH⁺ and the decomposition of MEACOO^-. Meanwhile, the larger pore structure of the 3D-printed channels facilitated the diffusion of desorbed CO₂ into the liquid phase. Compared to the “Square channel”, the “Diamond channel” with a lower surface Gibbs free energy enhanced the precipitation of CO₂ on the catalyst surface and the coalescence of CO₂ bubbles in the liquid phase, accelerating the desorption of CO₂ from amine solution at mild temperature. This study provides an effective approach for developing low-cost, high-performance catalysts by 3D-printing technology for CO₂ desorption from amine solutions.