Applied Basic Research On Chromatographic Separation Of Ethylene Glycol And 1,2-butanediol

Mixed alcohol by-products are produced in the process of preparing ethylene glycol（EG）by coal-based route and bio-based route,among which EG and 1,2-butanediol（1,2-BDO）are azeotropic and near-boiling systems due to their similar physical properties.This greatly increases the difficulty in subsequent separation.In view of the problems of complicated equipment,high energy consumption and high cost in the distillation separation process,chromatographic techniques with gentle operation conditions were proposed for the separation of EG and 1,2-BDO in this thesis.The main research contents and results are as follows:（1）A series of single column pulse experiments under single factor were designed.The effects of IPE-18 adsorbent on the separation of EG and1,2-BDO at different temperatures,elution flow rates,feed volume and feed concentration were investigated.The results showed that the resolution and peak height of both reached the optimum value when the temperature was70℃and the elution flow rate was 2m L/min.With the increase of feed volume and feed concentration,the separation degree of the mixing diols gradually decreased.（2）A single column chromatographic model was established in Aspen chromatography.The adsorbent particle size,intra-particle porosity,inter-particle voidage,axial diffusion coefficient,mass transfer coefficient and adsorption isotherm parameters were measured,and embedded into the single column model for simulation.The simulation results showed that the simulated outflow curve is consistent with the experimental results,and the accuracy and universality of the chromatographic model were further verified in the single column amplification experiment.（3）In order to realize the continuous chromatographic separation of EG and 1,2-BDO,models of 8-column simulated moving bed（SMB）and sequential simulated moving bed（SSMB）were established.According to the triangle theory,the SMB simulation results at the optimal operating point showed that with the increase of feed concentration and flow rate,the separation purity of EG and 1,2-BDO decreased,especially for 1,2-BDO,the purity dropped from 97.95%to 81.22%.The simulation results of the two models at the same operating point showed that the purity and yield of1,2-butanediol were sensitive to the changes of m₂and m₃.The simulation results of SSMB in the upper part of the complete separation zone showed that it had superior performance in purity and yield,but the unit processing capacity is generally lower than traditional SMB.（4）The SSMB model was used to guide the actual separation experiment.When the model was embedded with 9.12%of the pipeline dead volume and compensated for 1.88%of the switching time,the model could accurately predict the purity of EG and 1,2-BDO separated under the feed concentration of 400g/L and 500g/L.In addition,when the operation point was outside the triangular region,it was difficult to achieve chromatographic separation of EG and 1,2-BDO.However,the purity of EG and 1,2-BDO could still reach more than 98%under the optimization of the operating parameters by SSMB model.