Stoichiometric formation of benzene and ketones by photocatalytic dechlorination of chlorobenzene in secondary alcohol suspensions of palladium-loaded titanium(iv) oxide powder in the presence of sodiumion sources

Abstract

Photocatalytic dechlorination of chlorobenzene in alcohol suspensions of metal-loaded TiO₂ in the presence of sodium ion sources under irradiation of UV light was examined. When palladium (Pd) (or rhodium), 2-propanol and NaOH were used as the metal co-catalyst, alcohol and Na⁺ source, respectively, benzene and acetone were obtained almost quantitatively and stoichiometrically in a very short time. Chloride ions eliminated from chlorobenzene were immediately solidified as NaCl by NaOH dissolved in 2-propanol and separated from other products such as benzene and acetone dissolved in 2-propanol. Effects of the physical properties of TiO₂ and addition of water on photocatalytic dechlorination of chlorobenzene were examined. A more useful oxidized product, i.e., butanone, was successfully obtained in addition to benzene as the reduction product when 2-butanol was used as the alcohol solvent. To avoid formation of water in dechlorination of chlorobenzene in 2-propanol and 2-butanol, a Na⁺-containing LTA-type zeolite (molecular sieves 4 Å) was used as the Na⁺ source, and almost quantitative recovery of benzene was achieved along with stoichiometric formation of the corresponding ketones.