Research Of Synthesizing Citral From Dehydrolinlool By Rearranging

Citral is an important spice and chemical raw materials. At present, most of citral in the domestic market is obtained from distillation of litsea cubeba oil under a reduced pressure. As citral use expands, the number of citral obtained by natural resources cannot meet the needs of market development. Therefore, synthesis of citral from petrochemical products has garnered particular attention. The synthesis of citral with dehydrolinalool is the most promising.The synthesization of citral through rearrangement of dehyrolinalool had been studied in this paper.[Ru(η3-C4H7)2(Ph2PCH2CH2PPh2)] was selected as the catalyst, and the preparation of the catalyst were investigated. The results showed that the optimal conditions to prepare the Grignard reagent which is a raw material for catalyst preparation are as follows:anhydrous THF was selected as the solvent while magnesite powder as the material, the dropping time was2.5hour at temperature of15℃, after dropping the reaction mixture was heated to60℃for other2hour. Moreover,[Ru(η3-C4H7)2(Ph2PCH2CH2PPh2)] showed good catalytic activity and selectivity by recrystallizing the catalyst precursor Ru(η3-C4H7)2(η4-C8H12) with a mixed solvent of petroleum ether and methanol in a volume ratio of6:1.Based on the investigation of the catalyst, the process conditions of citral synthesization were studied. The conversion of94.4%for dehydrolinalool and the yield of93.2%for citral were obtained respectively under reaction conditions as follows:[Ru(η3-C4H7)2(Ph2PCH2-CH2PPH2)] was used as the catalyst while the benzoic acid was selected as the promotor, the catalyst:dehydrolinalool=1:100(mole), benzoic acid:dehydrolinalool=1:1(mole), dehydro-linalool:toluene=1:5(mole), the reaction at70℃for1h and then heating up to120℃for4h in a nitrogen atmosphere.