Study on Synthesizing Isobornyl Acetate/Isoborneol from Camphene Using α-Hydroxyl Carboxylic Acid Composite Catalyst

Abstract

This study examined the preparation of isobornyl acetate/isoborneol from camphene using an α-hydroxyl carboxylic acid (HCA) composite catalyst. Through the study of the influencing factors, it was found that HCA and boric acid exhibited significant synergistic catalysis. Under optimal conditions, when tartaric acid–boric acid was used as the catalyst, the conversion of camphene and the gas chromatography (GC) content and selectivity of isobornyl acetate were 92.9%, 88.5%, and 95.3%, respectively. With the increase in the ratio of water to acetic acid, the GC content and selectivity of isobornol in the product increased, but the conversion of camphene decreased. The yield of isobornol was increased by adding ethyl acetate or titanium sulfate/zirconium sulfate to form a ternary composite catalyst. When a ternary complex of titanium sulfate, tartaric acid, and boric acid was used as the catalyst, the GC content of isobornol in the product reached 55.6%. Under solvent-free conditions, mandelic acid–boric acid could catalyze the hydration reaction of camphene, the GC content of isoborneol in the product reached 26.1%, and the selectivity of isoborneol was 55.9%. The HCA–boric acid composite catalyst can use aqueous acetic acid as a raw material, which is also beneficial for the reuse of the catalyst.