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

Abstract

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 CeO/HZSM-5. The loading of alkali potassium was found to improve the Lewis acidity of the catalyst (by increasing the amounts of surface Mn after calcination), which thus promoted the CO selectivity for catalytic chlorobenzene (CB) oxidation. The KOH with a high hydrophilicity has favored the adsorption/activation of HO 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 less secondary pollution for the catalytic chloroaromatics combustion in industry.

Recent Advances in the Catalytic Oxidation of Volatile Organic Compounds: A Review Based on Pollutant Sorts and Sources

“…Chlorobenzene (CB) is another typical chlorinated contaminant resulting from industrial processes. 878 As such it is frequently used as the model pollutant for CVOCs because it is a precursor or intermediate product of polychlorinated wastes. For example, CB is used as the model compound for highly toxic polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) due to the structural similarity to these pollutants.…”

“…Chlorobenzene (CB) is another typical chlorinated contaminant resulting from industrial processes . As such it is frequently used as a model pollutant for CVOCs because it is a precursor or intermediate product of polychlorinated wastes.…”

Efficient Photothermal Elimination of Formaldehyde under Visible Light at Room Temperature by a MnOx-Modified Multi-Porous Carbon Sphere

“…The oxygen-rich groups of C-O and O-C=O at the surface of the carbon spheres are also produced by doped MnO 2 , proving that an increase in MnO 2 content results in an increase in the C-O and O-C=O contents. The peaks at 295.3 eV and 292.7 eV in Figure 8C are characteristic of potassium oxide [31], which is generated by the residual K + of used KMnO 4 .…”

High-yield synthesis of Ce modified Fe–Mn composite oxides benefitting from catalytic destruction of chlorobenzene

“…12 By comparison, catalytic oxidation is regarded as one of the most promising techniques for elimination of chlorinated aromatic compounds at much lower temperatures (<500 C), due to its high efficiency, less harmful by-products (e.g., CO 2 , HCl, Cl 2 ), and low energy consumption. 11,[13][14][15][16] Catalysts based on noble metals, perovskites, and transition metal oxides have been developed for the catalytic oxidation of chlorinated aromatic compounds. 11,16,17 Noble metals are expensive and always deactivate owing to chlorine (Cl) poisoning during catalytic oxidation processes, which limits their practical large-scale application.…”