Study On Crystallization And Distillation Of 1, 8 - Eucalyptus

Eucalyptus oil is the natural plant essential oil, the main component is 1,8-cineole.Eucalyptus oil has much effect, such as bactericidal, anti-inflammatory and insecticidal. These advantages make it widely used in the chemical, food, medicine and other fields. The higher the concentration of 1,8-cineole is, the better the quality of eucalyptus oil is. The crude eucalyptus oil contained varied and complex components. In addition to the main impurities such as limonene, a-pinene, p-cymene, a-terpineol, there are a large amount of other impurities. They are similar with 1, 8-cineole in physical and chemical properties, which greatly increase the difficulty to purify the eucalyptus oil. In this research, according to the freezing point differences, the crystallization method to separate and purify the crude material eucalyptus oil was studied firstly, and then the batch vacuum distillation was used to purify the product achieved fromcrystallization. This route was compared with the common route called distillation-crystallization.The main contents in this research are listed as follow:1) Low temperature crystallization process.The crystallization was carried out with serious control of the cooling and heating rate. The influence of the cooling rate, cooling temperature, heating rate and heating temperature was investigated. The results under the best conditions were got:the concentration of the product was 79.12%, and the yield of the product was 3.41%. After adding crystal seed, the effect of the various conditions on the experiment was studied again, and the optimum operate conditions were obtained. To conduct actual production, data regression of each condition point was made and the regression equations were got. Reviewing the effect of the seed amount, particle size and added time of crystal seed, the optimum results were achieved. The experiment of re-crystallization was carried out to see if it can get better result. The experiment showed the best conditions in the crystallization: the cooling rate was 4℃/h, the cooling temperature was -25℃,the heating rate was 5℃ /h, the heating temperature was -6℃, the seed amount was 0.2%, the seed diameter was 3mm, the temperature of seed added was -17℃. Under these conditions, the concentration of the product was 89.63%, and the yield of the product was 4.05%. The re-crystallization can achieve the best result when the cooling temperature was-7℃.The concentration of the product was 95.98%, and the yield of the product was 5.99%.2) Batch vacuum distillation process. The batch vacuum distillation was carried out with the material which is similar with the product obtained from crystallization method in composition. The influence of reflux ratio, vacuum degree and the bottom temperature was researched, and the optimum value was got. The experiment showed the best conditions:the vacuum was 50mbar, the light components were collected when R=25, the main components were collected when R=9, the bottom temperature was 83℃. Under these conditions, the concentration of the product was 96.55%, and the yield of the product was 59.42%.3) Simulation of the batch vacuum distillation process with Aspen plus. The Aspen plus software was used to simulate the above batch vacuum distillation process. The accuracy of the software for simulating this process was corrected. The necessary reflux ratio and theoretical plate number to obtain high concentration eucalyptus oil (the concentration of 1,8-cineole>99%) were determined through optimization.4) The comparison of the energy consumption in the crystallization-distillation route and the common distillation-crystallization was made.