A Study On The Purification Of β-methylnaphthalene By Melt Crystallization

methylnaphthalene is an important chemical raw material, there are two isomers of methylnaphthalene, namely,α- methylnaphthalene andβ- methylnaphthalene ,β- methylnaphthalene is mainly used in producing Vitamin K3, organic dyes, In this thesis, a new melt crystallization technology was developed to purifyβ- methylnaphthalene, which can provide the basic data and theoretical instruction for the engineering design, and the energy loss is low compared with the traditional purification method like distillation.First, the differential scanning calorimetry (DSC) was used to measure the solid-liquid phase diagram of methylnaphthalene system, which is appeared as the eutectic phase diagram, the same as reported, however,the experimental data exhibits some obvious distinctness,compared with literature results. Wilson model was introduced to simulate the experimental data combined with generalized equilibrium relationship.Theoretical model was developed and used in the methylnaphthalene system. Crystallization process parameters as cooling rate, initial overheating of the liquid film, irrigation density were discussed for their influence on the growth rate of crystal layer, and the model can describe distinctly the melt crystallization process of methylnaphthalene based on the comparison between the calculated and the experimental results.Based on the above fundamental researches, the melt crystallization process for manufacturingβ- methylnaphthalene was systemically investigated both in falling film crystallizer and liquid flooded crystallizer. The effects of some significant factors such as the initial crystallization temperature, cooling rate, flow quantity of mothor liquor, the final sweating temperature, the way of heating of the crystallization process on the yield and purity were studied. An optimal melt crystallization technology for manufacturingβ-methylnaphthalene was developed. By using of the new technology, the purity ofβ- methylnaphthalene higher than 96% can be obtained from the raw material of 84.7% without adding any solvent. And the mothor liquid produced by the melt crystallization process can be purifed by the last purification stage to 84%.