Catalyst-aided CO2 capture from exhaust gases of industrial point sources for utilization in cement-based industry

Abstract

The utilization of solid-base catalysts to improve CO2 capture in amine-based postcombustion processes represents a significant technological advance. However, addressing both cost and catalytic efficiency remains crucial. Given the inherently expensive nature of amine-based post-combustion, there is an urgent need to explore innovative strategies to alleviate financial burdens. Research has shown that costs can be reduced by eliminating the desorption tower and utilizing enriched solvent directly from the absorber column. Accelerating the capture process via catalyst introduction reduces column height and further cuts costs. The primary focus of our study was to develop an alkaline catalyst to enhance CO2 loading in Potassium Glycinate salt solution. Our ultimate goal was to apply this enriched solution in the cement-based industry for producing concrete, mortar, and grout. In the course of this research, a total of twelve super basic catalysts were synthesized and rigorously assessed using a semi-batch apparatus. Their initial absorption rates were meticulously scrutinized and juxtaposed against the baseline scenario devoid of any catalyst. Notably, the introduction of most catalysts yielded a marked acceleration in CO2 absorption, resulting in remarkably increased absorption rates. These initial absorption rates were observed to follow a discernible ascending order Ce/CaO < K/MgO < Blank < AGO* < K/MgO + AGO < K/MgO + GO < Ce/MgO < AC (H) < AC (H) + MgO < GO < AGO + AC (H) < K-MgO/AC (C) < AGO. Outstandingly, AGO exhibited the highest initial absorption rate at 5.12×10-2 (mol CO2/l.min), closely traced by KMgO/ AC (C) at 4.77×10-2 (mol CO2/l.min), while Ce/CaO and K/MgO displayed relatively lower performance at 3.56×10-2 and 3.63×10-2, respectively. Intriguingly, it was noted that Ce/CaO and K/MgO, rather than facilitating CO2 absorption by the Potassium Glycinate salt solution, reverted to their starting materials, Ca(OH)2 and Mg(OH)2 respectively, in the presence of water which formed carbonates with the CO2, diminishing the readily available CO2 for the Potassium Glycinate salt solution to capture. Considering the intricate and potentially hazardous nature of the AGO preparation process, along with environmental and safety concerns related to the chemicals used, KMgO/ AC (C) was selected as the preferred catalyst for this study. It exhibited a 25.2% enhancement in the absorption process, in contrast to the 34.4% improvement achieved by AGO. K-MgO/AC (C) underwent comprehensive characterization to determine both its chemical and physical properties, and the findings are meticulously documented in this study. Moreover, the results derived from the characterization of K-MgO/AC (C) were juxtaposed with existing data on AC (H) and K/MgO from literature, providing insights into and comparisons of the performance of these three catalysts based on their respective characteristics. In an effort to assess the stability of the K-MgO/AC (C) catalyst, two distinct approaches were employed. In the first approach, the same catalyst was utilized for three consecutive runs, with fresh solvent introduced between each run. In the second approach, the catalyst underwent washing, drying, and high-temperature calcination to eliminate any residual deposits before being reused. The stability analysis outcomes corroborated the robust stability of the K-MgO/AC (C) catalyst for up to three successive cycles of usage, a conclusion reinforced by the results obtained from thermal gravimetric analysis (TGA). Worth noting is the fact that all experiments conducted during the course of this study remained well within the acceptable margin of error, not exceeding 8%.