K2CO3-catalyzed direct synthesis of salicylic acid from phenol and supercritical CO2 Original Research Article

The synthesis of salicylic acid from phenol and CO2 was studied in the presence of various base catalysts. Among the catalysts investigated, potassium carbonate was found to be the most active. The formation of p-hydroxybenzoic acid, as a by-product, was negligibly small. Salicylic acid selectivity is 99% or more in all cases. Under optimized conditions, the salicylic acid yield could reach 68.3% at a phenol conversion of 69.3%. Several parameters were studied, i.e., catalyst usage, reaction temperature and time, and CO2 pressure. Based on experimental observations, a possible reaction mechanism for the present K2CO3-catalyzed direct synthesis of salicylic acid is proposed.