Zhang Handan, Kong Ming, Cai Zelong, Liu Qingcai, Zeng Jingsong, Duan Minghua, Yang Jian, Ren Shan, Li Jiangling
Engineering Research Center for Energy and Environment of Chongqing, College of Materials Science and Engineering, Chongqing University, Chongqing 400044, P. R. China.
Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials, Chongqing University, Chongqing 400044, P. R. China.
ACS Omega. 2020 Sep 18;5(38):24195-24203. doi: 10.1021/acsomega.0c01734. eCollection 2020 Sep 29.
The role of vapor- and liquid-phase AsO in deactivating commercial VO-WO/TiO catalyst during the NH-selective catalytic reduction (SCR) process was explored and compared. AsO was loaded via vapor deposition (As(vap)) and the wet impregnation (As(imp)) method, respectively. Results demonstrated that the poisoning extent of vapor arsenic was much stronger than in the liquid state. Differences in As distribution on the catalyst surface was one of the main causes. Most vapor AsO could be oxidized to AsO, which underwent stacking and formed a dense covering layer on the catalyst surface. In comparison, liquid AsO could also be oxidized but distributed uniformly and did not change the catalyst pore structure. Loading arsenic would destroy the V-OH and V=O active sites of the catalyst, and less reactive As-OH was generated. Catalyst oxidizability was also enhanced, resulting in NH oxidation enhancement, decreased N selectivity, and a decline in SCR activity. Importantly, the intermediate of NH oxidation, NH-amide, also could react with NO + O, and more NO was generated on the poisoned catalyst during the SCR process, especially on As(imp). Finally, two mechanisms of arsenic poisoning were proposed, in which the role of vapor and liquid AsO over the VO-WO/TiO catalyst was compared.
研究并比较了气相和液相AsO在NH选择性催化还原（SCR）过程中使商用VO-WO/TiO催化剂失活的作用。分别通过气相沉积（As(vap)）和湿浸渍（As(imp)）方法负载AsO。结果表明，气相砷的中毒程度比液相砷强得多。催化剂表面As分布的差异是主要原因之一。大多数气相AsO可被氧化为AsO，后者发生堆积并在催化剂表面形成致密的覆盖层。相比之下，液相AsO也可被氧化，但分布均匀且不改变催化剂的孔结构。负载砷会破坏催化剂的V-OH和V=O活性位点，生成的活性较低的As-OH较少。催化剂的氧化性也增强，导致NH氧化增强、N选择性降低以及SCR活性下降。重要的是，NH氧化的中间体NH-酰胺也可与NO + O反应，在SCR过程中，中毒催化剂上会生成更多的NO，尤其是在As(imp)上。最后，提出了两种砷中毒机制，并比较了气相和液相AsO在VO-WO/TiO催化剂上的作用。
