Clean Separation And Purification Of L-hydroxyproline And L-proline Process

Wastewater problems existed in the production process of L-hydroxyproline made from hydrolysate of Gelatin,such as wastewater in large amount,high COD and NH3-N,and it’s difficult and expensive to treat the wastewater.Simulation experiment and industrial application at the foundation of theory were investigated.L-hydroxyproline single crystal was prepared and characterized.The thermodynamic properties and crystallization process were studied.Based on the theory and experimental date,the separation and purification of mixture contains L-hydroxyproline and L-proline were simulated,and the two kinds of amino acids were separated and purified from reducing solution in original process.L-hydroxyproline single crystal was prepared by dilution + solvent evaporation method,the structure of single crystal and powder were obtained by X-ray single crystal diffraction and X-ray powder diffraction,and the single crystal was poor in moisture absorption.The solubility at various p H values and temperatures from 298.15 K to 338.15 K and metastable zone of L-hydroxyproline in water were measured by gravimetric method.And the non-random two liquid(NRTL)activity coefficient model and the Henserson-Hasselbalch(HH)equation were adopted to describe the solubility.The effects of cooling rate and stirring rate on the metastable zone were investigated experimentally.Cooling crystallization of L-hydroxyproline in water were studied,the stirring rate,cooling rate,endpoint temperature and breeding time were explored in detail.The optimum process parameters were determined as stirring speed of 200 rpm,cooling rate of5 ℃/min,endpoint temperature of 25℃,breeding time of 8 h.The separation and purification of mixture contains L-hydroxyproline and L-proline were simulated,methanol was choosed as separating agent based on the different solubility of L-hydroxyproline and L-proline,and the effect of methanol addition and balance time on the separation efficiency were measured.The amino acids were analyzed by high performance liquid chromatography(HPLC)and polarimeter.Results showed that the optimum process parameters were 90% methanol addition,balance time 2 h.Based on the results of simulation,the mixture of the two kinds of amino acids were separated and purified from reducing solution in original process,the products were characterized by HPLC and polarimeter,purity of more than 99%.And the recoveries of L-hydroxyproline and L-proline were above 85% and 80% respectively.The amount of 80%-90%wastewater were reduced in the process,methanol could be reused,and L-proline were recovered at low cost,the cleaner production of L-hydroxyproline could be achieved.