The Efficient and Environmentally Friendly Chlorination of Arene, Alcohol, Halobenzene, and Peroxide Catalyzed by Fe-Ba Binary Oxides Using Hydrochloric Acid as Chlorine Source and Aqueous H2O2 as Oxidant

A series of Fe-Ba mixed oxides, including a pure Fe-containing sample as a reference, have been synthesized via a sol-gel process using Fe3+ or Fe2+ salts and BaSO4 as raw materials, with Pluronic P123 serving as a template. These oxides have been thoroughly characterized and subsequently utilized as catalysts for the chlorination of various organic molecules. Commercial hydrochloric acid, known for its relative safety, and environmentally friendly aqueous hydrogen peroxide were employed as the chlorine source and oxidant, respectively. The pure Fe-containing catalyst displays excellent thermal stability between 600 and 800 degrees C and exhibited moderate to high conversions in the chlorination of toluene, benzene, and tert-butyl hydroperoxide, with remarkable ortho-selectivity in chlorination of toluene. The combination of Fe3+ salt with BaSO4 in the sol-gel process results in a Fe-Ba mixed oxide catalyst composed of BaO2, BaFe4O7, and Fe2O3, significantly enhancing the chlorination activity compared to that displayed by the pure Fe catalyst. Notably, the chlorination of tert-butyl hydroperoxide (TBHP) does not require additional oxidants such as H2O2, and involves both electrophilic substitution and nucleophilic addition. Notably, the chlorination of bromobenzene yields chlorobenzene as the sole product, a transformation that has not been previously reported. Overall, this catalytic chlorination system holds promise for advancing the chlorination industry and enhancing pharmaceutical production.