The Influence Of Microwave And Ultrasound On The Crystallization Process

The use of ultrasound irradiations for controlling the crystallization operation has been generally expressed to as sono-crystallization.Crystallization in microwave system has been used to make nano-crystals and mono-disperse crystal.However,the influence mechanism of microwave and ultrasound on the crystallization process was not well understood so far.Therefore,in this work,benzotriazole(BTA)was used as model compound to investigate the effect of microwave and ultrasound on crystallization processes.First of all,solubility data of benzotriazole(BTA)in fourteen solvents were measured by a static gravimetric method from 268.15 K to 303.15 K.The results illustrated that the solubility of BTA in N,N-dimethylacetamide is the highest while that in 1,2-dichloroethane is the lowest in all the tested solvents.And the values of solubility increase with the increasing of temperature.Secondly,the effect of microwave and ultrasound on metastable zone width(MSZW)of benzotriazole(BTA)was investigated in cooling crystallization.It was found that narrower MSZW was obtained by applying microwave and ultrasound.The lower power 30 W of microwave and ultrasound with frequency(41 KHz)will result in narrowest MSZW.The MSZW increased when the cooling rates(0.2℃/min,0.3℃/min and 0.4℃/min)were increasing.Finally,the effect of microwave and ultrasound on crystal structure and habit was investigated from cooling crystallization.It was found that the solid obtained from cooling crystallization process under microwave,ultrasound,without microwave,and ultrasound condition exhibited same needle shape and agglomerated morphology with a size dimension of 50m.From XRPD data,it was found that crystals obtained from different conditions have the same XRPD patterns,indicating that the crystal form of BTA was not change by microwave and ultrasound.DSC results shown that the melting process of crystals are around 98.14-98.50℃ and enthalpy of fusion is 12.25-12.63KJ/mol.