Publication: High-performance titaniumfunctionalised Sba-15 adsorbent for carbon dioxide adsorption
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Date
2024-03
Authors
Shalini a/p Mahendran
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Abstract
The adverse effects of global warming have attracted the attention of the world’s public and are becoming increasingly important today. This is a consequence
of the greenhouse effect, in which greenhouse gases, especially CO2, trap heat near the Earth’s surface. Despite this, CO2 has several advantages, including the ability to generate electricity and fuel. Therefore, the use of one of the three primary methods of carbon capture is crucial to remove CO2 from the environment. CO2 adsorption when paired with a suitable adsorbent, presents itself as a promising technology for addressing the challenges posed by the rising CO2 levels and global climate change. In the sol-gel method, Santa Barbara Amorphous-15 (SBA-15) was produced using TEOS, a source of silica, and Pluronic P123, a non-ionic surfactant, with hydrochloric acid (HCl) serving as the catalyst. However, the synthesised adsorbent's potential has not yet been completely maximised, as a result, titanium isoproproxide modification was carried out, producing titanium modified SBA-15 (Ti-SBA-15). The synthesized and modified adsorbent was utilized in a fixed-bed column adsorption system to study the impacts of various factors including CO2 adsorption temperature, inlet
concentration of feed, adsorbent mass, and feed flow rate. The synthesized SBA-15 was subjected to a number of physicochemical analyses, including scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR), transmission electron microscopy (TEM), BET surface area analysis and Xray photoelectron spectroscopy (XPS). Based on experimental results, it can be concluded that the adsorbent’s ability to adsorb CO2 improved when it is modified with titanium isopropoxide. This is because titanium introduces new active sites called as the Lewis acid sites. These active sites interact with CO2 molecules through the Lewis acid-base interactions and therefore improving the CO2 adsorption capacity onto the adsorbent. Besides, the column’s ability to adsorb CO2 was enhanced when the CO2 content in the feed was raised while the adsorption temperature and feed flow rate were both lowered to 30oC. Pseudo- first-order and pseudo-second-order kinetics, as well as the Avrami model, were used to interpret the kinetics of the CO2 adsorption experiment. These three models help to understand and quantify the rate at which adsorption occurs over time and can provide insights into the adsorption mechanism and helps to optimize process conditions. This adsorbent’s ability to adsorb CO2 was improved as the CO2 feed concentration was raised, whereas it declined as feed flowrate, temperature, and adsorbent loading increased. This is due to the reduction in residence time when the flowrate is increased, the adsorption process being an exothermic process and the active sites being inaccessible to CO2 molecules. The kinetic model proposed by Avrami shows that it best fits the experimental data. Three fixed bed adsorption column models namely the Adam-Bohart model, Thomas model and Yoon-Nelson model were used to describe the behavior of an adsorption process occurring in the fixed bed. The Thomas and Yoon-Nelson models were successful in predicting how well SBA-15 adsorbs CO2 in a fixed-bed column while the Adam- Bohart model did not match the column data well, owing to the low R2 values of 0.6 and the weak correlation between experimental and model values.