Reducing energy consumption of CO2 desorption in CO2-loaded aqueous amine solution using Al2O3/HZSM-5 bifunctional catalysts

Abstract

The aim of this work is to find a potential way for great decrease in CO2 capture energy requirement. Here, for the first time, a series of bifunctional Al2O3/HZSM-5 catalysts (Al-ZSM) were prepared by the combined precipitation ultrasound method and used for the CO2 desorption process. All the investigated catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), N2 adsorption–desorption, ammonia and CO2 temperature programmed desorption (NH3/CO2-TPD) and pyridine-adsorption infrared spectroscopy (Py-IR). The regeneration behaviors of a 5 M monoethanolamine (MEA) solvent with four Al-ZSM catalysts were studied at an initial CO2 loading of 0.5 mol CO2/mol amine and the temperature of 96 °C. The results reveal that all the catalysts improve the CO2 desorption performance, the Al-ZSM catalysts show higher catalytic performance than the single catalysts Al2O3 and HZSM-5, and the Al-ZSM can reduce the heat duty by 23.3–34.2% as compared with the catalyst-free test. The use of Al-ZSM in the MEA regeneration process improves the desorption performance by 2–3 times in comparison with the blank run. A possible dual sites mechanism of CO2 desorption with Al-ZSM is suggested. The excellent performance of Al-ZSM can be attributed to their enhanced Brϕnsted acid sites (BAS), mesopore surface area (MSA) and basic sites, which resulted from the good synergistic reaction between the Al2O3 and HZSM-5, and the base treatment for HZSM-5. Besides, the stability test of the Al-ZSM was conducted. Based on the results, the Al-ZSM demonstrate a superior catalytic performance for the rich amine regeneration process, and present an excellent cyclic stability, explicitly have the potential to be a promising industrial catalyst for CO2 capture. Furthermore, the dual sites catalytic CO2 desorption over bifunctional catalysts will open a new path to design better catalysts for the rich amine solution regeneration process to increase the desorption performance, reduce the regeneration energy consumption, and thus further decreasing the operation costs of CO2 capture.