Study On Salting-out1-sulfo-cyclohexanecarboxylic Acid Crude Salt And Removing Organic Amine Impurities From The Solution Of Crude Salt

The technology of the production process of caprolactam from toluene techniquein sinopec Shijiazhuang Chemical Fiber Company Ltd. is derived from SNIAcompany in Italy. Amidation reaction unit is the core of SINA’s caprolactamproduction process, and there are many side reactions comeabout.1-sulfo-cyclohexanecarboxylic acid is come from in amidation reaction unit.Itis sulfonated by-product and not separated out in subsequent process. Finally, itdischarges in the form of salt with caprolactam waste liquid. Caprolactam wasteliquid in the extraction process contain a large number of sulfonated by-products.Atpresent, the high temperature incineration method to deal with the waste liquid hasmany disadvatanges, such as high processing costs, blocking the nozzle, and cause airpollution, etc.1-Sulfo-cyclohexanecarboxylic acid with sulfonic acid groups andcarboxylic acid groups, has certain market value, and can be expected to develop intoother products. Therefore, recycling1-sulfo-cyclohexanecarboxylic acid has goodsocial benefit and economic value. Currently, the crude salt of1-sulfo-cyclohexanecarboxylic acid are generated in the process of azeotropicdistillation with toluene and azeotropic distillation combination with direct distillationdisposed of caprolactam waste. Main purpose of these two methods is to reduceCOD value and NH3-N value of waste liquid, is not directly extracting1-sulfo-cyclohexanecarboxylic acid. what’s more, the device structures is complexand the time-consuming is long, the purity of the crude salt is only about80%.Activated carbon can adsorb non-polar and low-polar impurities at room temperature.Currently. After activated carbon adsorption decolourization, the coarse salt solutionof1-sulfo-cyclohexanecarboxylic acid contains polar organic amine. The organicamine is gathering in the subsequent crystallization process. It make the yield of theproduct is not high, only84.8%.The article explores the process conditions of salting outsulfo-1-cyclohexanecarboxylic acid crude salt from the caprolactam waste solution.The experiment chooses anhydrous methanol, ethanol and acetone as salting-outagents. The effects of different salting agent、the pH value of the waste solution、 theratio of salting agents and the waste、salting time、salting-out temperature and washingtimes were investigated. The experimental results show that: compared withanhydrous methanol and ethanol, the effect of salting out 1-sulfo-cyclohexanecarboxylic acid crude salt is best by acetone, the salting outprocess is rapid process. The process of salting-out conditions is: the pH value ofcaprolactam waste is8、 V(caprolactam waste):V(acetone)=1:3、 salting-outtemperature is30℃、salting-out time is5min、the times of washing residue is3.Under the condition of the above,1-sulfo-cyclohexanecarboxylic acid waresuccessfully salted out from caprolactam waste by adding acetone. The content ofsulfo-1-cyclohexanecarboxylic acid in crude salt is as high as87.97%, the yield is71%.The paper explores the process conditions of removing organic amine impuritiesfrom the solution of sulfo-1-cyclohexanecarboxylic acid crude salt. The effects of thetype of extraction agent and diluent、the volume fractions of extracting agent anddiluent、the pH value of sulfo-1-cyclohexanecarboxylic acid crude salt solution、extraction and mixing time、the proportion of complex extraction agent and coarsesalt solution, the salt solution pH and the finally concentrated volume duringevaporative crystallization on the purification process of1-sulfo-cyclohexanecarboxylic acid were investigated. The experimental results showthat: taking15g the crude salt dissolveing in100mL distilled water to experiment,determine P204as s a complexing agent, cyclohexane as diluents, and the volumeratio of then is1:9; the crude salt solution pH value is10; the extraction stirring timeis40min; the ratio of extraction solvent and crude salt solution is1:4; evaporativecrystallization of salt solution with concentrated sulfuric acid at pH=2; heating thesolution is evaporated from100mL concentrated to15mL.Under the optimumcondition, removing organic amine impurities by complex extraction within saltsolution is feasible and effective, and the yield and the mass fractions of1-sulfo-cyclohexanecarboxylic acid respectively achieved92.3%and99.6%.