Cr/TiO_2催化剂汞氧化的实验

Catalytic oxidation experiment of element mercury over Cr/TiO_2 catalyst

通过等体积浸渍法制备不同质量分数w（0.1%~5%）的Cr/TiO2催化剂.活性测试结果表明,Cr/TiO2催化剂在高空速、低氯条件下有很高的汞氧化活性.研究Cr负载量、反应温度、不同烟气组分对汞氧化的影响,结果表明：Cr/TiO2催化剂汞氧化活性随Cr负载量和反应温度的升高而提高.O2和HCl对Cr/TiO2催化剂上汞氧化有极强的促进作用.当只有O2存在时,Cr/TiO2催化剂上汞氧化按照Mars-Maessen机理进行,Hg0首先吸附到催化剂表面,然后与晶格氧反应生成弱吸附的HgO,消耗的晶格氧由气态O2补充.当O2和HCl同时存在时,由于在催化剂表面生成活性氯物种,反应机理发生改变,汞氧化得到促进.NO也可以促进汞氧化.SO2与Hg0在催化剂表面竞争吸附从而抑制汞氧化,H2O对汞氧化也有抑制作用.

A series of Cr/TiO2 catalysts with different Cr loading w（0.1%~5%） were prepared using im- pregnation method. Cr/TiO2 catalysts exhibit excellent mercury oxidation ability in low HCl concentration even at high gas hourly space velocity. The influences of Cr loading, reaction temperature and flue gas component on mercury oxidation were studied as well. The results indicate that mercury oxidation increase together with the increase of Cr content and reaction temperature. O2 and HC; have significant promoting effect on mercury oxidation over Cr/TiO2 catalyst. The reaction over Cr/TiO2 catalyst follows Mars-Maes sen mechanism when only O2 exists. Hg^0 initially adsorbs on the catalyst surface, then reacts with lattice oxygen to form weakly-adsorbed HgO. The consumed lattice oxygen is recovered by gas-phase oxygen. When both O2 and HC; exist, mercury oxidation is promoted due to active chlorine species generated on the catalyst surface and the mechanism alters. NO is also found to promote mercury oxidation. SO2 however inhibits the reaction due to its competitive adsorption with Hg^0 on catelytic surface. H2O is also found to have a negative effect on mercury oxidation.