An environmentally benign method for synthesis of cinnamaldehyde with near-critical water as reaction medium was proposed.The results showed that cinnamaldehyde could be synthesized successfully through the reaction of phenylaldehyde with acetaldehyde in near-critical water without adding any catalyst.The effects of temperature and reaction time on the conversion of phenylaldehyde and yield of cinnamaldehyde were determined from 220 ℃ to 300 ℃.The yield of cinnamaldehyde was up to 16.6% after 5 hours reaction time at 260 ℃

16 MPa

volume ration of reactants to water 1∶15.