Study On The Process Safety Of Nucleophilic Substitution Reaction Of Triphosgene

Triphosgene is often used in chemical production as the safe substitute of phosgene,and more common in the form of nucleophilic substitution reaction.In recent years,the poisoning accidents of it have aroused people’s concern about the safety of triphosgene.In this paper,the physical and chemical properties,safety standards and detection methods of triphosgene and phosgene were compared.Taking the "nucleophilic substitution" reaction process of triphosgene as the research object,the high-risk links in the process were systematically analyzed.By the experiments of thermal decomposition and DSC,the thermal stability of the triphosgene was researched and the safe condition for dissolution of it was determined.And based on the equations of mass balance,the mathematical model of semi-batch reactor was established,the kinetic parameters were calculated by the least squares.Besides,the reaction risk of the process was evaluated by runaway scenario method.And based on the conservation of mass and energy,a dimensionless semi-bath heterogeneous reaction mathematical model was established,and the possibility of thermal runaway was evaluated by the divergence criterion,the influence of operating conditions was discussed.At last,the concentration and composition of toxic gas in the reaction process were analyzed by means of toxic gas detector.Studies have shown that triphosgene would decompose over 130℃,and the concentration of toxic gas from the sublimation of solids and the volatile of the dissolved liquid was over 100 ppm.During the dissolution process,the purity of triphosgene,the water of solvent and the control of nucleophilic impurities in the dissolution reactor would have a lot influence on the stability of triphosgene.The results of the reaction kinetic indicated that there was phosgene in the process of nucleophilic substitution reaction,and the reaction rate of the triphosgene was limited by the phase interface area.The risk of thermal runaway of the reaction process was evaluated as the third level by runaway scenario method.Meanwhile,the results of the divergence criterion showed that the divergence value was less than 0,which indicated the whole process of the reaction was safe,but the deviation of initial operating conditions such as the feeding rate might cause thermal runaway.