V2O5/AC在含SO2气氛中对气态Hg0的吸附脱除研究

利用固定床反应器研究了模拟烟气(N_2、SO_2、O_2)气氛下,气态Hg~0在V_2O_5/AC催化剂上的吸附脱除行为.考察了V_2O_5担载量、SO_2浓度和吸附温度等对V_2O_5/AC吸附脱除Hg~0的影响,并对V_2O_5/AC上吸附汞的形态进行了XPS分析表征.研究发现,V_2O_5/AC对Hg~0的吸附能力远大于载体AC.汞的吸附量与V_2O_5/AC中V_2O_5的质量分数有关,随着V_2O_5质量分数从0.5%增加到1.0%,汞的吸附量从75.9 μg·g~(-1)增加到89.6 μg·g~(-1) (无氧) 和115.9 μg·g~(-1)增加到185.5 μg·g~(-1) (有氧),远高于相同吸附条件下的AC上的汞吸附量 (9.6 μg·g~(-1)和23.3 μg·g~(-1)).SO_2对Hg~0的吸附有促进作用,主要是由于SO_2和Hg~0在V_2O_5/AC上发生了化学反应.但是当SO_2体积分数从500×10~(-6)增加到2 000×10~(-6)时,V_2O_5/AC对汞的吸附量只增加了5%.不同温度下的实验结果表明,V_2O_5/AC催化剂在150℃左右的吸附脱除Hg~0的能力最高,汞的吸附量达到98.5 μg·g~(-1) (无氧) 和187.7 μg·g~(-1) (有氧).XPS 分析结果表明,在V_2O_5/AC催化剂表面有HgO和HgSO_4生成,证实了V_2O_5和SO_2的作用.

Adsorption and Removal of Gas-Phase Hg0 over a V2O5/AC Catalyst in the Presence of SO2

The adsorption and removal behaviors of gas-phase Hg~0 over V_2O_5/AC and AC were studied under a simulated flue gas (containing N_2, SO_2, O_2) in a fixed-bed reactor. The influences of the V_2O_5 loading, SO_2 concentration and adsorption temperature on Hg0 adsorption were investigated. The speciation of mercury adsorbed was determined by X-ray photoelectron spectroscopy (XPS). It was found that the V_2O_5/AC catalyst has a much higher capability than AC for Hg~0 adsorption and removal, mainly because of the catalytic oxidation activity of V_2O_5. The Hg~0 adsorption capability depends on the V_2O_5 content of the V_2O_5/AC catalyst. The amounts of mercury adsorbed increase from 75.9 μg·g~(-1) to 89.6 μg·g~(-1) (in the absence of O_2) and from 115.9 μg·g~(-1) to 185.5 μg·g~(-1) (in the presence of O_2) as the V_2O_5 loading increases from 0.5% to 1.0%,which are much higher than those over AC under the same conditions (9.6 μg·g~(-1) and 23.3 μg·g~(-1)). SO_2 in the flue gas enhances Hg~0 adsorption over the V_2O_5/AC catalyst, which is due to the reaction of SO_2 and Hg~0 on V_2O_5/AC. But as the SO_2 concentration increases from 500×10~(-6) to 2 000×10~(-6), the amount of mercury adsorbed has only a slight increase. The optimal temperature for Hg~0 adsorption over the V_2O_5/AC catalyst is around 150℃, at which the amounts of mercury adsorbed are up to 98.5 μg·g~(-1) (in the absence of O_2) and 187.7 μg·g~(-1) (in the presence of O_2). The XPS results indicate the formation of HgO and HgSO_4 on the surface of the V_2O_5/AC catalyst, which confirms the role of V_2O_5 and SO_2.