Research On Crystallization Process Of 2,4,6-trimethylbenzoyl-diphenylphosphine Oxide

2,4,6-trimethylbenzoyl-diphenylphosphine oxide(TPO)is a widely used photoinitiator in the market,which is capable of undergoing polymerase chain reaction with active monomers in illumination.Light curing materials are obtained by this method.Although the photoinitiator only takes 3% of the whole system,polymerase chain reaction can't be carried out in the absence of photoinitiator.Therefore,TPO,which has excellent low-yellowing property and high curing efficiency,has become the keystone of research.At present,in order to purify crude TPO,multiple washing,distillation and other purification methods were adopted.It is a pity that these methods not only can't ensure the quality of the product,but also generate a large amount of wastewater,so the purification process needs to be improved.In this context,the new crystallization process in the purification stage was systematically studied.First of all,TPO toluene solvate was prepared,which was characterized by various methods.Subsequently,the single crystals of TPO and toluene solvate were cultivated and analyzed.Meanwhile,the crystal habit of TPO was predicted by BFDH model and AE model based on the single crystal data.At the same time,the desolvation and solvent-mediated transformation process of toluene solvate were studied.Secondly,the solubility of TPO in six pure solvents and two binary solvent mixtures was measured.Four mathematical models of modified Apelblat,?h,NRTL and CNIBS/RK were employed to correlate the experimental data,and the solubility curves were obtained,which provided data for the design of new process.Apart from this,the thermodynamic properties of the dissolution process were calculated by NRTL model.Besides,the induction time of TPO in four solvents were measured and correlated by probability distribution equation.The nucleation rate of TPO under different conditions was obtained by this way.Moreover,the interfacial energy and surface entropy factor were calculated based on the frontal data.Thus,the speed and difficult degree of nucleation process were found.At last,the new crystallization process was designed based on the theoretical research mentioned above.Six factors including initial concentration,cooling rate and seed crystal addition were investigated.When the process was running with optimal operating parameters,the yield and purity of product were 74.2% and 99.4%,respectively.Furthermore,the product obtained from new technology has narrow particle size distribution and beautiful crystal habit,which meets market requirements.