Preparation of α-Terpinene by Isomerization of β-Phellandrene
Acid-catalyzed isomerization of β-phellandrene for the preparation of α-terpinene and relative reaction process were investigated.The results indicated that trimethylsilyl bromide(TMSBr)showed excellent catalytic activity on the isomerizationβ-phellandrene owing to its moderate acidity.However,its catalytic effects on other monoterpenes such as α-pinene,β-pinene,3-carene,limonene and terpinene were limited.The auxiliary agent of 30％(mass fraction)H2O2 greatly improved the reaction efficiency owing to its three characteristics including converting TMSBr to H+to catalyze the isomerization reaction due to the existence of water,dispersing H+to reduce the occurrence of side reactions,and assisting the reaction by its own acidity.The optimal conditions for the preparation of α-terpinene from the isomerization of β-phellandrene were β-phellandrene of 0.1 mol,TMSBr of 0.002 mol,30％H2O2 of 0.1 mol,temperature of 100 ℃,time of 6 h,and the raw material conversion and product selectivity were 88.4％and 94.0％,respectively.
β-phellandreneα-terpineneturpentine from Pinus patulacatalytic isomerizationtrimethylsilyl bromide
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