(562x) New Insights of Carbon Chain Length in Cross-Linked PEI Adsorbents on CO2 Capture

Recently, many countries and international society are seriously concerned about the global warming caused by CO₂ emissions from the industry and are carrying out realistic regulatory policies. For this reason, lots of researches on CO₂ capture, utilization and storage (CCUS) have been carried out. In particular, the CO₂ capture process is the most expensive step that should be preceded before the storage and utilization in CCUS, so technological efforts have been made to reduce its operation cost. Amine-impregnated adsorbent is one of considerable options to reduce the CO₂ capture cost, however, stubborn problems such as the formation of urea and low desorption performance in practical regeneration condition have been hurdles steadily. The formation of urea and poor regeneration performance can be directly connected to lower the working capacity of the adsorbents. Amine cross-linking technique could be adopted to solve these problems. In this study, cross-linked amine-impregnated adsorbents were manufactured by using polyethyleneimine (PEI), diepoxy cross-linkers having different carbon chain length and mesostructured silica gel for support. Scanning electron microscopy (SEM) and ¹³C nuclear magnetic resonance (NMR) spectroscopy were carried out to characterize adsorbents and to investigate molecular structure of cross-linked PEI, respectively. Cross-linked PEI showed less 1° amine ratio compared to pristine PEI and the morphologies of adsorbents were almost similar to the morphology of silica support. The formation of urea was diminished in cross-linked PEI samples and desorption performance was improved as well, and it was verified via thermogravimetric analyzer (TGA) and Fourier transformed infrared (FT-IR) spectroscopy. Especially, with longer carbon chain length of cross-linker, samples figured out better working capacity and less urea formation. It is thought that the carbon chain of cross-linkers acts as a spacer which can weaken the interaction force between CO₂ molecules and amine active sites, consequently, a forward reaction which causes the formation of urea could be restrained and desorption of CO₂ also could proceed well.