Study On The Synthesis Of Perillyl Aldehyde From α-Pinene By Photosensitized Oxidation And Isomerization

Myrtenal and perillaldehyde were widely used in daily chemical industries, pharmaceutical industries, food industries and so on owing to their good characteristics, and they were also important intermediate on synthesis of perillartine---a new synthetic perfume product with high sweetness and low calorific. The synthesis of perillaldehyde from α-pinene was the most difficult and important two step reaction on the preparation route of perillartine by chemical methods. Because oxidation of a-pinene need use expensive and virulent SeO2 as the catalyst in the current ways and myrtenal isomerization reaction by Cu-Zn catalyst could not be completed unless the reaction condition was very hard, at the high temperature and deep vacuum, searching novel kinds of catalyst and methods which possess high catalytic activity is meaningful to make the reaction conditions more moderate and more friendly to environment. In this paper, perillaldehyde has been synthesized through using a-pinene from our abundant turpentine oil as raw material by 2-step reactions:photosensitive oxidation and isomerization. The influence of reaction variables on the conversion and selectivity of the reactions was evaluated. Furthermore, the structures of products were characterized by GC-MS and IR, and the properties of solid superacid catalyst were characterized by the Hammett indicators method and X-ray diffraction. The conclusions in our experiment research are as follows:1. Synthesis of myrtenal from a-pinene by photosensitive oxidation in the home-made photochemical reactor was carried out by using the halogen lamp as the light source. The influence of photosensitive oxidation reaction variables on the conversion and selectivity of the reactions was evaluated. The results showed that:94.89% conversion of materials and 56.46%selectivity of myrtenal were obtained when pyridine-acetic anhydride-copper salt mixture as a catalyst was used for the reaction for 6 h at 45℃ under 0.30 L/min oxygen flow rate,0.168 mol/L catalyst concentration and 0.5 mol/L material concentration. Myrtenal is prepared with 96.71% purity. The results of MS and FT-IR almost match the standard mass spectrogram of myrtenal.2. Synthesis of perillaldehyde from myrtenal by isomerization in the cracking reactor was carried out by using Cu/ZnO as the catalyst. The influence of photosensitive oxidation reaction variables on the conversion and selectivity of the reactions was evaluated. The results showed that:88.79% conversion of materials and 54.72% selectivity of perillaldehyde were obtained when Cu/ZnO-1 as catalysts was used for the reaction at 350 ℃ under 2.0 mL/min feeding rate,4:5 weight ratio material and catalyst, and 300℃ calcination temperature. Perillaldehyde is prepared with 94.27% purity. The results of MS and FT-IR. almost match the standard mass spectrogram of perillaldehyde.3. Synthesis of perillaldehyde from myrtenal by isomerization in the cracking reactor was carried out by using solid superacid SZT as the catalyst. The influence of photosensitive oxidation reaction variables on the conversion and selectivity of the reactions was evaluated. The results showed that:87.51% conversion of materials and 40.56% selectivity of the product were obtained when SZT-15 as a catalyst was used for the reaction at 400 ℃ under 1.0 mol/L impregnation concentration,550℃ calcination temperature and 1.0 mL/min feeding rate. Perillaldehyde is prepared with 92.64% purity. The results of MS and FT-IR almost match the standard mass spectrogram of perillaldehyde.4. The acid strength of solid superacid catalyst was tested by the Hammett indicators method and its crystal structure was characterized by XRD analysis. The results showed that:the acid strength of SZT-15 catalyst prepared by low impregnation temperature can be up to Ho=-16.0. However, the acid strength of SZT+20 catalyst prepared by normal impregnation temperature is Ho=-12.0～-13.2. SZT-15 solid superacid catalyst appeared very sharp diffraction peaks of anatase crystalling phase, but SZT+20 catalyst appeared amorphous state.