Study On Refining And Isomerization Of 3-carene

3-Carene,which mainly exists in some special turpentines,is one of the few chiral source compounds with ternary ring structure and the third largest output natural monoterpene component of turpentine preceded by?-pinene and?-pinene.Turpentines produced in China were low in 3-carene,so it did not have sufficient resources for further researches until a large area of 3-carene-riched Pinus szemaoensis was found in Yunnan province the past ten years.With these pine trees reached resin tapping period in succession,the resource of 3-carene became more and more abundant,and the studies on it aslo began to recieve more attention of researcheres.With the purpose to enhance the utilization values of 3-carene-riched turpentine,the refining of 3-carene was studied in this paper firstly,and plenty of 3-carene in high purity was obtained.Secondly,a series of researches on the isomerization of 3-carene were studied and a comperehensive analysis of the results was done,and finally an industrial application process of 3-carene was built up.All of the results would enrich the chemical utilization of3-carene and 3-carene-riched turpentine,and provide theoretical guidances and establish practical foundations for the high-valuable development of turpentine.The major achievements have been obtained as below:A new combinative method of chemical reaction and rectification was put forward and detailedly studied for the refining of 3-carene.By comparative study of three different kind chemical reactions,the method combining of nopol preparation with rectification was recongnized as the optimum process for refining of 3-carene.This process has several advantageous such as high yield conversion of?-pinene with fewer byproducts and significant differnce of boiling points between 3-carene and nopol,and it played a more excellent role in separation of 3-carene from trupentine compared to single rectification.Using this process,about 40%3-carene with a purity of above 95%could be obtained,and about 50%?-pinene with a purity of above 95%and about 70%nopol with a purity of above 95%were gotten simultaneously.Studies indicated that the thermal isomerization of 3-carene mainly take place in the range of 650?and 700?,while lower than 500?3-carene could hardly be isomerized but higher than 700?more products were furtherly cracked into smaller moleculer compounds.This reaction gave a mixed product including toluene,xylene and cymenes and so on.Studies on catalytical isomerizations of 3-carene in the presence of three different kinds catalysts were made,and the results indicated that catalyzed by inorganic acids,3-carene was converted to a mixture of four kinds of menthadienes,including?-terpinene,?-terpinene,terpinolene and m-terpinolene.Under the action of platinum,palladium and nickel,3-carene was converted to cymenes,in which the ratio between m-cymene and p-cymene was about 7:2.In the presence of aluminosilicates,3-carene was converted to three kinds of compounds that were cymenes,menthadienes and aromatics,and mild conditions such as lower temperature or less catalyst amount were helpful to the production of menthadienes.In addition,the results showed that as one of the aluminosilicates,ZSM-5 molecular sieves have a high ability to paralyze cymenes to toluene.The orientation isomerization of 3-carene was studied,and by extensive tests and process optimizations a new conversion process from 3-carene to toluene and m-cymene was built up.The optimum process conditions were shown as follows:Pt-Al₂O₃ and ZSM-5 molecular sieve?SiO₂/Al₂O₃=50?were used as complex catalysts,and the loading ratio of them was 1:1;the isomerization temperature was 280?;the conversion of 3-carene was 100%and the total yield of toluene and m-cymene was more than 90%while the yield of m-cymene was nearly 60%.