One-step fabrication of NiSO4/NiO solid acid catalyst for rapid CO2 desorption in CO2-loaded amine solutions

Abstract

CO₂ absorption by the organic amine solvent is currently the most promising method for CO₂ capture, while this process suffers from high solvent regeneration heat duty. The catalyst-assisted regeneration is an effective mean to reduce the energy consumption of amine solution regeneration. However, the catalysts reported so far still have shortcomings with insufficient performance, difficult preparation, and high cost. In this study, four solid acid catalysts, Fe₂(SO₄)₃/Fe₂O₃, NiSO₄/NiO, CuSO₄/CuO, Zr(SO₄)₂/ZrO₂ were prepared using a simple one-step synthesis method. These catalysts were then utilized to catalyze CO₂ desorption at 88 °C in a rich 5 M monoethanolamine (MEA) solution to lower the regeneration heat duty. All the prepared catalysts showed superior ability to promote CO₂ desorption, with the NiSO₄/NiO catalyst presenting the best activity. Notably, the NiSO₄/NiO catalyst enabled a 360 % enhancement in the maximum CO₂ desorption rate, a 118 % increase in the CO₂ desorption amount, and a 46 % reduction in the relative energy penalty. After 18 absorption–desorption tests, NiSO₄/NiO proved remarkable stability. The NiSO₄/NiO catalyst contains both B and L acids, and the addition of sulfate also enhances the acidity of the metal oxides, thereby accelerating the CO₂ desorption. A potential NiSO₄/NiO-catalyzed reaction mechanism is proposed based on FT-IR characterization and DFT calculations. This work provides a simple and inexpensive strategy to facilitate the rich amine solution regeneration process with low temperature and energy consumption.