Separation And Purification Of Trans-1,2-Cyclohexane

In this article the method of separation and purification of trans-1,2-cyclohexanediol and related thermodynamic data are studied based on the green synthesizing technique of trans-1,2-cyclohexanediol from cyclohexene which has been successfully developed in our laboratory. The separation technique was gained, which can save energy and raw materials and is convenient and fitted for industrial production. All these will make base for the industrial production of trans-1,2-cyclohexanediol.The saturate and supersaturate characters of trans-1,2-cyclohexanediol in water, ethyl acetate at different temperature and agitation rates were investigated with synthesis method and using laser technique, as well as those of sodium formate in water at different temperature. The crystallization metastable zone width of trans-1,2-cyclohexanediol and sodium formate was also obtained.The test results show that the solubility, supersolubility and crystallization metastable zone width (AS) of trans-1,2-cyclohexanediol in both water and ethyl acetate all increase with temperature growth, and those properties of trans-1,2-cyclohexanediol in water are larger more than those in ethyl acetate. While, the super-solubility and crystallization metastable zone width (AS) of trans-1,2-cyclohexanediol in water decrease with the raising of agitation rate. The crystallization metastable zone width ( ) of trans-1,2-cyclohexanediol in water is about 4C under high agitation rate, and about 7 C under middle agitation rate. The crystallization metastable zone width ( ) of trans-1,2-cyclohexanediol in ethyl acetate is about 3 C. The solubility, super-solubility and crystallization metastable zone width (AS) of sodium formate increase with temperature growth and the crystallization metastable zone width ( ) is between 4 C and 5C. These results offer necessary thermal data for the separation and purification of trans-1,2-cyclohexanediol, the optimization of crystallization process of trans-1,2-cyclohexanediol and the study of crystallization kinetics and batch crystallization of trans-1,2-cyclohexanediol.Trans-1,2-cyclohexanediol which has heat sensitivity, high boiling point and high coagulating point was separated and purified with batch distillation under vacuum. The distillation was operated by changing pressure and reflux ratio strategy. The optimal operating condition was acquired. Meanwhile, the recycle of the excessive formic acid in the synthesis of trans-1,2-cyclohexanediol was studied and the recycle technique of formic acid by batch distillation under common pressure was got. The operating condition with changing pressure and changing reflux ratio of batch distillation which eliminate ethyl acetate fromextracting liquid is that the operation pressure is latm at the beginning and heating voltage 140V, the beginning time of overall reflux 30 min, reflux ratio 0.3. Heating is stopped and the bottom temperature is lowered when it rises to 85 C. Vacuum distillation is employed after the bottom temperature comes down to 40 C. The vacuum distillation isn't stopped under the condition that vacuum is 0.078 ~ 0.080 MPa and reflux ratio 0.3, until all trans- 1,2-cyclohexanediol crystallizes. The operating condition with changing pressure and changing reflux ratio of batch distillation under vacuum which purifies raw trans-1,2-cyclohexanediol is that the beginning time of overall reflux is 2h and the bottom temperature 180~185C, the changing vacuum 0.086~0.092 MPa, the changing reflux ratio 5-8- 12. The production ratio of trans-1,2-cyclohexanediol is over 87% and the product purity is beyond 98% under the above operation condition. The product's color gets much more whiter than the raw's. The IR graph of the product is in agreement with that of sample imported from America, as well as it's melting point.By the recycle test, we have proved that the formic acid recycled firstly can be used for synthesis cyclically without concentration and has no effect on production ratio of trans-1,2-cyclohexanediol. The formic acid recycled cyclically is con...