Abstract:

The triple acid catalyst system composed of α-hydroxycarboxylic acid represented by citric acid, phosphoric acid and low carbon chain fatty acid represented by propionic acid was applied to the catalytic hydration of α-pinene to synthesize terpineol. The effects of solvent type, fatty acid chain length, α-hydroxycarboxylic acid type, catalyst amount, water amount, reaction temperature and reaction time on the hydration reaction were investigated. The results showed that under the reaction conditions of the mass ratio of α-pinene, water, propionic acid, citric acid and phosphoric acid of 1∶1∶2∶0.05∶0.1, reaction temperature of 70 ℃ and reaction time of 24 h, the conversion of α-pinene, the GC content of terpineol and the product selectivity could reach 99.0%, 53.3% and 54.9%, respectively. Under the same conditions, the selectivity of the target product terpineol could be improved by adding the monocyclic monoterpene by-products generated during the hydration of α-pinene to the starting material. When the addition amount was 40%, the selectivity of terpineol could be increased to 76%. The product composition analysis showed that the total GC content of terpineol in the product was 53.3%, the total GC content of hydrate was 57.1%, and the total content of propionate was 8.1%.

Key words: α-pinene, terpineol, α-hydroxycarboxylic acid, triple acid composite system