| Nowadays,natural perfume products can not satisfy the demand of market because of the restriction by natural conditions,unstable quality of natural flavor products and a lack of supply,which results in the arising of synthetic perfume.Myrcene is important intermediates in the perfume industry which can produce various fine chemicals and medicine and it's market demand is huge.And myrcene is usually made by the thermal isomerization of ?-pinene in industrial production.Nowadays,there exists lots of technical study on the pyrolysis of ?-pinene.Unfortunately,just a few reports on the kinetic studies of the thermal isomerization of ?-pinene have been addressed until now,and the related valid kinetic data is absent.In addition,the molar fraction of myrcene made from the pyrolysis of ?-pinene in industry remains to be further improved.To satisfy the demand of industry,the reaction kinetics and reactor simulation and optimization of the thermal isomerization of ?-pinene were studied.The contents and results of this study are mainly as follows:(1)The effects of residence time and reaction temperature on the thermal isomerization of P-pinene was studied in a micro-reactor,in which P-pinene was used as the raw material.In order to know the reaction path of pyrolysis of ?-pinene further,the experiments of pyrolysis of myrcene and limonene were investigated.In the product mixture of myrcene pyrolysis,1-ethenyl-3-methylethenyl-cyclopentane and camphene were detected and identified for the first time,then we investigated the reaction mechanism of them.A kinetic model of competitive parallel and consecutive reaction of first-order was proposed.Rate corjnstants and activation parameters for the thermal isomerization of ?-pinene were also obtained from experimental data by mathematical methods.The model data showed in good agreement with the experimental data,which means the kinetic model is reliable.The results also show that high temperature and short residence time are in favor of the yield of myrcene.(2)The properties parameters of thermal isomerization reaction of reactant and products were calculated by group contribution method.This study can provide solid foundation for numerical simulation and optimization of industrial reactors.Combined with the kinetic model of thermal isomerization of ?-pinene,the transfer process of industrial-scale thermal isomerization of reactor was studied by building a 3D computational fluid dynamics(CFD)model.The mass fraction of reactant and products and temperature at the outlet of reactor was obstained by solving the model,and exhibited a good agreement with the field data.It showed that the reactor model were reliable so that it can be used for further simulation and optimization of the reactor.(3)Comparision of the thermal isomerization effect of P-pinene between straight tube and spiral tube which are both widely used in industrial production gives the result that spiral tube has higher heat and mass transfer effect than that in straight tube.Based on spiral pipe reactor,the optimization on the structure was studied.And the S-shaped pipe reactor designed upon the spiral tube was found to has more uniform speed,temperature and concentration distribution,thus it has better effect of intensifying heat transfer and mass transfer and has more advantage on the thermal isomerization of ?-pinene to myrcene.When the heat flux was set to 16500 W/m2,the mass fraction of myrcene in the product could be up to 80.72%and the yield of it could be up to 81.07%,which are significantly higher than the existing industrial reactor.Meanwhile,the S-shaped pipe reactor is more energy-saving.With the study of kinetic,physical properties and reactor simulation of the isomerization of?-pinene,it is beneficial to gain a better understanding the characteristics and process of thermal isomerization of ?-pinene and provides guidance for the design,optimization and improvement of industrial reactor. |
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