## 3 Results
### Physical Characteristic Analysis after CO\({}_{2}\) Sorption
According to the XRD and FTIR results, the alumina-based CO\({}_{2}\) sorbent could form the KHCO\({}_{3}\) phase and KAl(CO\({}_{3}\))(OH)\({}_{2}\) phase after CO\({}_{2}\) sorption in the presence of water vapor at high pressure and 200 \({}^{\circ}\)C.  
Figure 3: XRD patterns of the PZI30 and PAI10-40 sorbents before (**I**) and after (**II**) CO\({}_{2}\) sorption according to K\({}_{2}\)CO\({}_{3}\) loading; (\(\bigtriangleup\)) K\({}_{2}\)CO\({}_{3}\), (\(\blacktriangledown\)) ZrO\({}_{2}\), (\(\blacksquare\)) y-Al\({}_{2}\)O\({}_{3}\), (\(+\)) KAl(CO\({}_{3}\))(OH)\({}_{2}\). The results of TGA/DTG of PZI30 and PAI10-40 sorbents conducted to investigate the thermal properties after CO\({}_{2}\) sorption are shown in Figure 5. PZI30 and PAI10-40 sorbents showed weight loss at temperatures between 30 \({}^{\circ}\)C and 100 \({}^{\circ}\)C. This is due to the desorption of adsorbed water on the sorbent surface. The weight loss of PZI30 sorbent after CO\({}_{2}\) sorption at 20 atm was 5% at temperatures from 140 \({}^{\circ}\)C to 200 \({}^{\circ}\)C. The DTG peak of PZI30 sorbent showed one peak at the same temperature range as the weight loss range of TGA. Figure 3 II shows that the PZI30 sorbent did not change structure after CO\({}_{2}\) sorption at 20 atm, but the TGA/DTG confirmed that the PZI30 sorbent showed weight loss at temperatures ranging from 140 \({}^{\circ}\)C to 200 \({}^{\circ}\)C, which is attributed to CO\({}_{2}\) desorption from the KHCO\({}_{3}\) phase. At temperatures ranging from 140 \({}^{\circ}\)C to 350 \({}^{\circ}\)C, the weight loss of the PAI10-40 sorbents was 5.73%, 7.28%, 10.63%, and 11.61%, respectively. The DTG peak of PAI10 and 20 sorbents showed one peak between 200 \({}^{\circ}\)C and 350 \({}^{\circ}\)C due to the decomposition of the KAl(CO\({}_{3}\))(OH)\({}_{2}\) structure. The DTG peak of PAI30 and 40 sorbents showed two peaks at 140 \({}^{\circ}\)C to 200 \({}^{\circ}\)C and 200 \({}^{\circ}\)C to 350 \({}^{\circ}\)C, respectively. In the case of 140 \({}^{\circ}\)C to 200 \({}^{\circ}\)C, it was confirmed that the temperature range of the DTG peak was the same as for the PZI30 sorbent. In the XRD analysis for PAI30 and 40 sorbents, no KHCO\({}_{3}\) structures were found after CO\({}_{2}\) sorption, but we confirmed a weight loss in the temperature range from 140 \({}^{\circ}\)C to 200 \({}^{\circ}\)C. The TGA/DTG results confirmed that for the PAI10-40 sorbents, there are two CO\({}_{2}\) sorption mechanisms involving KHCO\({}_{3}\) and KAl(CO\({}_{3}\))(OH)\({}_{2}\) structures formed with increasing K\({}_{2}\)CO\({}_{3}\) loading under water vapor at high pressure [28]. From these analysis results, it was concluded that unlike for the PZI30 sorbent, the CO\({}_{2}\) absorption mechanism of the PAI-\(x\) sorbent was due to the formation of KHCO\({}_{3}\) and KAl(CO\({}_{3}\))(OH)\({}_{2}\) structures in the presence of water vapor in the conditions of 200 \({}^{\circ}\)C and 20 atm. Figure 4: FTIR results of PZI30 and PAI10–40 sorbents after CO\({}_{2}\) sorption: (**a**) KHCO\({}_{3}\), (**b**) KZI30, (**c**) PAI10, (**d**) PAI20, (**e**) PAI30, (**f**) PAI40.