Hierarchical porous AlOOH hollow microspheres for efficient CO2 capture

Abstract

In order to reverse the trend of increasing carbon dioxide (CO2) emissions, the development of efficient and economical CO2 trapping agents is an urgent necessity for the sustainable development of industry. In this paper, hierarchical porous hydroxyl aluminum oxide (AlOOH) hollow microspheres with controllable structure and morphology were prepared by conventional hydrothermal synthesis using malonic acid as a structure guiding agent. Then, potassium carbonate (K2CO3) based adsorbents were prepared using AlOOH hollow microspheres as supports, and their CO2 trapping performance was assessed by simulating industrial flue gas flow in a fixed bed. The results show that the loading of K2CO3, the pore structure, and the surface basic site of the adsorbent have a significant influence on the trapping performance of CO2. Among the prepared K2CO3/AlOOH adsorbents, 30 wt% K2CO3/AlOOH adsorbent has the best CO2 capture ability, which is about 2.15 times higher than that of K2CO3/C–Al2O3 adsorbent prepared from commercial alumina (C–Al2O3). There may be two explanations for this. Firstly, it may be due to the nanostructured shell and hierarchical porous structure of the adsorbent, which reduces the intra-particle diffusion resistance of CO2, and secondly, it may be due to the suitable surface basic sites of the adsorbent. In addition, the adsorbent was regenerated at 120 °C after trapping CO2, and then CO2 was captured in a cycle. It was found that the CO2 capture capability of the adsorbent did not decrease significantly after 10 cycles. In this work, an excellent technique for preparing porous honeycomb adsorbents with suitable surface basic sites has been devised, which provides a creative strategy for capturing and utilizing CO2.