Investigation Of Solvent Crystallization Thermodynamics And Process For Anthracene And Carbazole

Anthracene and carbazole both are high value-added products derived from coal tar.Because of its special polycyclic structure,antharcene and carbazole along with their derivatives exhibit lots of peculiar photoelectric properties and biological activities,which are widely used in photoelectric materials,pharmaceuticals,pesticides,dyes,fuels,and many other fields.In recent years,anthracene,carbazole and their derivatives are widely applied in the field of functional polymer material,OLED and biological engineering,however,the quantity and purity of anthracene and carbazole cannot meet the demand of the domestic and international market.Solvent crystallization is a common method to get anthracene and carbazole with high purity,which is with the advantage of low energy consumption,low cost and simple technology.However,current studies have focused on the separation of anthracene and carbazole,meanwhile,the specific crystallization process seldom catches eyes.In the same time the low efficiency of solvent makes it difficult to get desired products.Aiming to solve this problem,in this paper,the solubility of anthracene and carbazole were measured in four solvents,respectively.In the same time,the effects of solvent on the crystallization of anthracene and carbazole were discussed,respectively.On the basis of optimum solvent,the crystallization process and refining method of anthracene and carbazole were studied and optimized systematically,respectively.The interaction between anthracene and carbazole in solution was also investigated.Crystals with uniform size and intact shape were finally obtained.This study provide theoretical basis for the production of anthracene and carbazole with high purity in the industry.The contents mainly include:1.Solubility determination and correlation of anthracene and carbazoleThe solubility of anthracene and carbazole in N,N-dimethyl formamide(DMF),Xylene,tetrachloroethylene(TCE),and diethylene glycol dimethyl ether(DGDE)were determined from 303.15 K to 353.15 K at atmospheric pressure using a modified liquid-solid equilibrium equipment.The solubility of both anthracene and carbazole increased with the increasing temperature.The experimental data were correlated by the modified Apelblat equation,lh equation and van?t Hoff equation,respectively.The lh equation was more precise for anthracene and carbazole than the modified Apelblat equation.Then the dissolution enthalpy,dissolution entropy and Gibbs free energy were predicted from the solubility data based on van?t Hoff equation,the dissolution processes of both anthracene and carbazole was entropy-driven,endothermic and spontaneous.2.Supersolubility measurement and metastable zone width determination of anthracene and carbazoleThe supersolubility of anthracene and carbazole in N,N-dimethyl formamide(DMF),Xylene,tetrachloroethylene(TCE),and diethylene glycol dimethyl ether(DGDE)were also measured,respectively.Compared with the solubility determination above,the metastable zone width was obtained.Moreover,the effects of solvent,stirring and cooling mode on metastable zone width were discussed.The widest metastable zone was obtained in DMF,furthermore,the metastable zone tended to be smaller with the increasing stirring speed and cooling rate,respectively.3.Effect of solvent and other factors on the solvent crystallizationThe parameters of solvent crystallization of anthracene and carbazole including solvent types,stirring speed,and cooling mode were explored,respectively.Taking the crystals with highest purity and good crystal habits as targeted products,the composition of crystals were determined by gas chromatography(GC),moreover,the morphology and size of crystals were characterized by X-ray diffraction(XRD),integrated thermal analyzer(DSC)and scanning electron microscopy(SEM),respectively.The optimal condition was determined: a controlled circulating cooling mode,along with the agitation of 450 r/min,intact anthracene and carbazole crystals in uniform size were finally obtained from DMF and Xylene,respectively.4.Co-rystallization of anthracene and carbazoleThe similarities of anthracene and carbazole crystal structure and physicochemical properties make it easy to form solid solution and difficulty to separate from each other.The crystallization of anthracene and carbazole in different ratios were performed.The solid product were characterized by GC,XRD,DSC and fluorescence spectrum,respectively.Solid solution was determined qualitatively.The interaction between anthracene and carbazole in solvent crystallization were also discussed,which lay a solid foundation for the purification of anthracene and carbazole.