Equilibrium Studies On Enantioselective Liquid-liquid Extraction Of α-amino Acids Enantiomers Using Metal BIMAP Complexes

Abstract:A new type of chiral extraction(BINAP metal complexes) is adopted to separate α-amino acid enantiomers, the influence of process variales on extraction efficiency was studied experimentally. The extraction mechanism was investigated and a reactive model was established. The model was validated by comparison of the model prediction with the experiment results. Extraction performances were evaluated using distribution ratio, enantioselectivity, performances excess and performance factor and the extraction systems were optimized by modeling and experiment. The main contents can be summarized as follows:Theoretical part, considering BINAP metal complexes cannot be dissolved in aqueous phase, while α-amino acid enantiomers are highly hydrophilic, Therefore, we have applied the interfacial reaction mechanism here. According to the equilibrium method, the equilibrium formation constants of a-amino acid enantiomers with BINAP metal complexes at the interface can be determined. A interfacial reactive extraction model was established involving dissociation equilibrium, mass balance and Chemical equilibrium and so on.Experimental part, we have researched on chiral separation four kinds of a-amino acid enantiomers. On the basis of chiral matching principle, the three different stereoselectivity of BINAP metal complexes(BINAP-Pd, BINAP-Cu and BINAP-Ni) can be achieved by combing BINAP with palladium, copper, nickel element. Chiral separation four kinds of α-amino acid enantiomers was investigated using the best extraction performance of BINAP metal complexes as the extraction. The effects of process variables such as types of organic solvents, pH, concentration of the extraction and temperature on extraction efficiency were investigated and important parameters of the model were determined experimentally. The best suitable extraction system for each α-amino acid enantiomers was obtained by experiment. Reactive extraction model was applied for each a-amino acid enantiomers. The models were then validated by comparison of the model predicitions with the experimental results. Multivariate function models were then established based on the validated models. Modeling and optimization based on the multivariate function models were carried out to obtained the optimal extraction conditions and coefficients. Results show BINAP metal complexes can recognize all the a-amino acid enantiomers. For different kinds of a-amino acid enantiomers, BINAP metal complexes have different extraction performances. Organic solvents type, pH, concentration of extractant and temperature strongly influence on different enantiomers. Four kinds of a-amino acid enantiomers were modeled successfully by application of the reactive extraction model, which indicate the theory investigation of this thesis can be generally applied. The present data indicates that the model is a powerful tool for modeling chiral solvent extraction system and can provide information for the engineering calculation and design.