The Study On Crystallization And Separating Of 1,4-bis (2-hydroxypropyl)-piperazine

The solubility of 1,4-bis (2-hydroxypropyl)-piperazine in different solvents such as water, methanol, ethanol, isopropanol, n-butyl alcohol, n-hexane, cyclohexane, toluene, benzene and ethanol-water mixture were determined through dissolution equilibrium method. The results indicated that the solubility in all the solvents increased with temperature. The solubility of 1,4-bis (2-hydroxypropyl)-piperazine in solute molar fraction followed the order of methanol> ethanol> n-butyl alcohol> isopropanol> water> benzene> toluene> cyclohexane>n-hexane under the same temperature. For the water-ethanol mixture solvent, the solubility of HPP followed the order of 33% ethanol> 100% ethanol> 66% ethanol> 50% ethanol> water. The solubility data was correlated using Apelblat equation and ideal solubility equation; the parameters for each model were obtained. Van’t Hoff equation was applied to evaluate the dissolution enthalpy and dissolution entropy. The experimental solubility data and correlation results should benefit the design of HPP crystallization process. And the metastable zone widths of the HPP ethanol solution at different temperatures and agitating rate of 100 r/min,200 r/min and impurity ions Ca2+and Mg2+ (concentration range from 0%-0.08%) were investigated. The width of metastable zone increased with decreasing temperature and agitation rate. With the increase of the concentration of Ca2+ and Mg2+, the metastable zone increased slightly.The effect of solvents on the crystal habit of HPP was studied by cooling crystallization. HPP crysatls were characterizized by optical microscope, DSC, XRD and etc. The effects of crystallization conditions such as temperature, crystal seed, cooling rate and stirring rate on the crystallization of HPP were studied. The results show that the solvent has a significant effect on the crystal habit of HPP crystal. With the decrease of the dielectric constant of the solvent, the ratio of the length to diameter decreased.Optimal working conditions for HPP cooling crystallization were obtained through coreralting the shape, size and size distribution with temperature, crystal seed (sizes, adding temperature,amount),cooling rate and stirring speed in the process of cooling crystallization. Those basic data could provide valueable information for industrial applications.Study on separation effect of centrifugal filtration, vacuum filtration and drying effect under different drying methods. The results show that the centrifugal separation at 5 min, speed 1000 r/min can meet the separation requirements. Compared drying effect and energy consumption, air blast drying effect is the best. The whole cooling crystallization process of HPP was improved.