Enhanced CO2 Capture Performance of Titanium-Modified SBA-15: Synthesis, Characterization, and Fixed-Bed Column Adsorption Study

Abstract

Global warming is widely recognized as one of humanity's most pressing challenges. It is primarily driven by the greenhouse effect, whereby greenhouse gases, predominantly CO2, trap heat close to the surface of the Earth. The accumulation of CO2 in high concentrations can have various negative effects on the environment, such as global warming, ocean acidification and reduced crop yields. Therefore, it is crucial to mitigate CO2 emissions by employing carbon capture techniques. In this study, Pluronic P123 (a non-ionic surfactant) and TEOS (a silica source) were utilized in a sol-gel process to fabricate an ordered mesoporous silica, known as SBA-15, as catalyzed by hydrochloric acid (HCl). Subsequently, the synthesized adsorbent was modified with titanium (IV) isopropoxide (TIP) to enhance its physicochemical properties and adsorption capacity, which resulted in the Ti-SBA-15. This modified adsorbent was then evaluated using a fixed-bed column adsorption system to investigate the impacts of different factors, namely CO2 adsorption temperature, inlet gas concentration, adsorbent loading, and gas flow rate. Physicochemical analyses, such as scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), BET surface analysis, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were conducted on the Ti-SBA-15. Experimental results were interpreted using the pseudo-first-order and pseudo-second-order kinetics, as well as the Avrami model, with the Avrami model showing the best fit. The Thomas and Yoon-Nelson models effectively predicted the CO2 adsorption performance in the fixed-bed column. Thermodynamic modeling confirmed the exothermic and positively spontaneous nature of the reaction. Overall, Ti-SBA-15 demonstrated a promising ability as a low-cost, high-capacity CO2 capture adsorbent, while maintaining its adsorption efficiency, even through multiple cycles of reuse.