Alkali Potassium Induced HCl/CO2 Selectivity Enhancement and Chlorination Reaction Inhibition for Catalytic Oxidation of Chloroaromatics

作者：Pengfei Sun, Wanglong Wang, Xiaole Weng, Xiaoxia Dai, Zhongbiao Wu · 发表于：Environmental Science & Technology · 年份：2018 · DOI：10.1021/acs.est.7b06023 · 被引用次数：157 · 研究领域：Catalytic Processes in Materials Science、Toxic Organic Pollutants Impact、Environmental remediation with nanomaterials

Industrial combustion of chloroaromatics is likely to generate unintentional biphenyls (PCBs), polychlorinated dibenzo- p -dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). This process involves a surface-mediated reaction and can be accelerated in the presence of a catalyst. In the past decade, the effect of surface nature of applied catalysts on the conversion of chloroaromatics to PCBs/PCDD/PCDF has been well explored. However, studies on how the flue gas interferent components affect such a conversion process remain insufficient. In this article, a critical flue gas interferent component, alkali potassium, was investigated to reveal its effect on the chloroaromatics oxidation at a typical solid acid–base catalyst, Mn x Ce 1– x O 2 /HZSM-5. The loading of alkali potassium was found to improve the Lewis acidity of the catalyst (by increasing the amounts of surface Mn 4+ after calcination), which thus promoted the CO 2 selectivity for catalytic chlorobenzene (CB) oxidation. The KOH with a high hydrophilicity has favored the adsorption/activation of H 2 O molecules that provided sufficient hydroxyl groups and possibly induced a hydrolysis process to promote the formation of HCl. The K ion also served as a potential sink for chorine ions immobilization (via forming KCl). Both of these inhibited the formation of phenyl polychloride byproducts, thereby blocking the conversion of CB to chlorophenol and then PCDDs/PCDFs, and potentially ensuring a durable operation and l...