Study Of The Separation Of 2-methylimidazole From 2-methylimidazole Mother Liquor By Salting-out Extraction

The technology of salting-out extraction is a kind of technology using salting-out process in extraction to improve the extraction rate. This paper studies three different salting-out extraction processes to separate 2-methylimidazole from 2-methylimidazole mother liquor, to make the recovery rate of 2-methylimidazole and the purity of product to reach the requirements of industrialized production, and to determine optimal operating conditions of three processes.Through the research on salting-out extraction process,the appropriate extractants and salting-out reagent are chosen: Extractants choose benzene, salting-out agent choose composite salting-out agent mixed NaCl and NaOH.Through the research on three different salting-out extraction processes, the operational conditions of each technical routes are chosen.The optimum operational conditions of direct salting-out extraction process as follows: the NaCl concentration is 3.5mol/L(the mol of NaCl:the volume of mother liquor) ,the NaOH concentration is 3mol/L,and the extraction temperature is 70℃.Under above conditions, the rate of extraction is 85.82%.The optimum operational conditions of salting-out phase-separation extraction process as follows:the salting-out time is 15min,the salting-out temperature is room temperature,the phase ratio is 2:1(O/W), the extraction time is 30min, the extraction temperature is 70℃, the NaCl concentration is 3.5mol/L ,the NaOH concentration is 3.0mol/L. After be vacuum distilled 50% volumes,the filtrate is extracted by 1:1 benzene. Under above conditions, the rate of extraction is 86.46%.The optimum operational conditions of salting-out phase-separation extraction with preconcentration process as follows: the salting-out time is 15min,the salting-out temperature is room temperature,the phase ratio is 2:1, the extraction time is 30min, the extraction temperature is 70℃, the NaCl concentration is 2.5mol/L ,the NaOH concentration is 2.6mol/L. After be vacuum distilled 12.8% volumes,the filtrate is extracted by 1:1 benzene. Under above conditions, the rate of extraction is 85.58%.A theoretical analysis is taken on the salting-out phase-separation extraction with preconcentration process. The activity coefficients(f) of 2-methylimidazole in aqueous salt solutions have been determined . In the aqueous salt solutions , NaOH concentration is 2.49 mol/L and NaCl concentration is 0 0.4 mol/L. The relation between lgf and Cs are in agreement with Setschenow empirical formula, through linear fitting, the relation between lgf and Cs is lgf = 0.3425Cs.Form the lgf = 0.3425Cs,we can get the extraction rate calculation formula E=1-(1-E₀)10^-kc_s.