Stability of Supported Amine Adsorbents to SO₂ and NOₓ in Postcombustion CO₂ Capture. 1. Single-Component Adsorption


Flue gases from coal-fired power plants typically contain not only CO₂ but other acid-gas impurities such as SOₓ and NOₓ that can dramatically influence the CO₂ capture efficiency. Whereas postcombustion CO₂ capture by aminosilica materials has been extensively studied over the past few years because of their high equilibrium CO₂ capacities, the performance of these materials under realistic conditions (in the presence of SOₓ, NOₓ, and O₂) remains relatively unexplored. In this study, the degree of irreversible binding of SO₂, NO, and NO₂ to four supported amine adsorbents is evaluated to assess the SO₂, NO, and NO₂ adsorption capacities of aminosilica sorbents and their effects on the CO₂ adsorption capacities. Adsorbents constructed using poly(ethyleneimine) and three different silane coupling agents (based on propyltrimethoxysilane linkers) with primary, secondary, and tertiary amines are evaluated. Under the experimental conditions used in this investigation, it is found that primary amines with high amine loadings displayed more affinity toward NO than their secondary and tertiary amine counterparts. However, overall, NO adsorption on the aminosilica adsorbents is low, and therefore, the CO₂ capacities of the adsorbent materials exposed to NO remained almost unchanged after the exposure. In contrast, all materials showed a very high nitrogen dioxide adsorption capacity upon exposure to NO₂. As a result, all adsorbents treated with NO₂ exhibited a dramatic reduction in CO₂ capacity, which corresponds to the deactivation of amine groups due to the irreversible binding of NO₂. In addition, our results indicate that SO₂ adsorbed significantly on supported amine adsorbents, resulting in a dramatic loss in CO₂ capacity during CO₂ capture from flue gas. With similar amine loadings, although secondary amines exhibited higher affinity to SO₂, their CO₂ capacity loss after exposure to SO₂ is lower than that of primary amines, indicating that these materials are more stable in the presence of SO₂, which implies that more SO₂ desorbs from secondary amines during the desorption step. These results suggest that for silica-supported amine materials to be useful in practical CO₂ capture applications, it is necessary to significantly reduce the SO₂ and NO₂ concentrations of the flue gas prior to the CO₂ capture process. On the other hand, the capture efficiency of these materials does not change significantly in the presence of NO. This suggests that such materials might be promising for postcombustion CO₂ capture from flue gas streams derived from natural gas combustion, as these streams typically contain reduced SO₂ concentrations but can still have significant NOₓ concentrations.


Chemical and Biochemical Engineering

Keywords and Phrases

Adsorbent Materials; Adsorption Capacities; Coal-Fired Power Plant; Experimental Conditions; Irreversible Binding; Natural Gas Combustion; Realistic Conditions; Silane Coupling Agent; Adsorbents; Adsorption; Amines; Coal; Coupling Agents; Flue Gases; Fossil Fuel Power Plants; Nitrogen Oxides; Sulfur Dioxide; Carbon Dioxide

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Article - Journal

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