A deep insight into arsenic adsorption over γ-Al2O3 in the presence of SO2/NO

Arsenic is easily evaporated during coal combustion, which not only raises serious environmental concerns but also results in the deactivation of catalyst in selective catalytic reduction (SCR) systems. It is a promising method to use sorbents for the capture of arsenic vapors (As2O3(g)) before As-containing flue gas entering SCR catalyst. However, arsenic has a strong affinity with sulfur in coal and SO2 in the coal combustion flue gas strongly suppresses As2O3(g) capture by typical Ca/Fe-based sorbents. This study estimated the selective capture of As2O3 (g) by gamma-Al(2)O(3 )and the effects of SO2 and NO on the arsenic adsorption were investigated. The results showed that As2O (g) adsorption over gamma-Al2O3 was effectively conducted at temperatures ranging from 300 to 400 degrees C. In the reacted gamma-Al2O3, arsenic was predominantly in the form of As3+ through reactions with Al-O bonds and positive charged alumina ions. SO2 was slightly adsorbed on gamma-Al2O3, which had a limited effect on arsenic adsorption. The adsorption of SO2 on gamma-Al2O3 mainly occurred on the sites of hydroxyl groups (Al-OH) and few adsorbed SO2 was bound with positive charged alumina ions. NO was catalytically oxidized by gamma-Al2O3 and released as NO2. Nevertheless, NO competed with As2O3(g) to adhere to positive charged alumina ions and strongly suppressed arsenic adsorption over gamma-Al2O3. Fortunately, in the presence of SO2, NO was mostly transformed into intermediate (-SO3NO) at the sites of Al-OH on gamma-Al2O3. As a result, the adverse effect of NO on the adsorption of As2O3(g) was weakened. (C) 2018 The Combustion Institute Published by Elsevier Inc. All rights reserved.