Characterization and Mechanisms of H2S and SO2 Adsorption by Activated Carbon

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• 作者：Lei Shi ; Ke Yang ; Qiaopo Zhao ; Haiyan Wang ; Qun Cui
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：October 15, 2015
• 年：2015
• 卷：29
• 期：10
• 页码：6678-6685
• 全文大小：466K
• ISSN：1520-5029

文摘

Coconut-shell-based activated carbon (ACS-1) was used as a sorbent to simultaneously remove H₂S and SO₂ from simulated Claus tail gas. Adsorption and regeneration tests were performed to systematically investigate the desulfurization performance, regenerability, and stability of the ACS-1 sorbent. The physicochemical properties of ACS-1 before and after adsorption were characterized by nitrogen adsorption, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The experimental results revealed that the ACS-1 sorbent exhibited good desulfurization performance under a feed gas of H₂S (20鈥?00 ppmv), SO₂ (10鈥?00 ppmv), and N₂ (balance), and the concentrations of H₂S and SO₂ in the simulated Claus tail gas could be reduced to less than 10 mg/m³ by ACS-1. The breakthrough sulfur capacity of ACS-1 is 64.27 mg of S/g of sorbent at an adsorption temperature of 30 掳C and a gas hourly space velocity of 237.7 h^鈥?. The micropores with sizes of around 0.5 nm in ACS-1 are the main active centers for adsorption of H₂S and SO₂, whereas mesopores have little desulfurization activity for deep removal of H₂S and SO₂. Both physical adsorption and chemical adsorption coexisted in the process of desulfurization. The majority of sulfides were removed by physical adsorption, and 11% of the sulfur compounds existing in the form of elemental sulfur (ca. 20 atom %) and sulfate (ca. 80 atom %) were derived from the chemical adsorption. The mechanism of H₂S and SO₂ adsorption on the ACS-1 sorbent is also discussed. H₂S and SO₂ are first adsorbed on ACS-1 by physical adsorption and then partially oxidized to elemental sulfur and sulfate, respectively, by the oxygen adsorbed on ACS-1. At the same time, the Claus reaction between H₂S and SO₂ occurs. In addition, the ACS-1 sorbent can be completely regenerated using water vapor at 450 掳C with a stable breakthrough sulfur capacity during five adsorption鈥搑egeneration cycles.