Thermal Safety Of Phenol Hydroxylation Under Different Catalytic Systems

In recent years,various chemical production accidents have occurred frequently at home and abroad,and the safety of the chemical industry has also received a lot of attention.One of the root causes of chemical accidents is that they are not familiar enough with the heat release and kinetics of these reactions,so they cannot Achieving a perfect process design leads to a series of problems in production,which ultimately leads to accidents.As an important chemical intermediate,benzenediol has a wide range of functions and is used in the fields of dyes and polymers.A common synthetic process is the synthesis of benzenediol by the reaction of phenol and hydrogen peroxide using a catalyst.In order to facilitate experimental research and guide industrial production,the thermal stability analysis of hydrogen peroxide and phenol was carried out by differential scanning calorimetry（DSC）.The results show that hydrogen peroxide is highly prone to self-decomposition.The substance,adiabatic accelerated calorimeter（ARC）experiment,measured when the hydrogen peroxide was in adiabatic state,the temperature will reach 42.04℃ will decompose,the extrapolation method to obtain hydrogen peroxide T_D24 is only 35℃.Phenol is relatively stable,only the melting peak,the liberated heat is almost negligible,safer,almost no danger.Then,the thermodynamic study of the phenol hydroxylation reaction process under different catalytic systems was carried out by using a calorimeter（RC1e）,and the products after the reaction were analyzed for thermal stability.According to the experimental results,the risk matrix method and risk were used.The reaction was evaluated by grading.Under the action of iron-based catalyst: when the reaction temperature of phenol hydroxylation is 50℃ and 60℃,the reaction has a induction period of 55 min.When the induction period is over,the reaction will release a large amount of heat in an instant.The heat is large.When the reaction temperature was 80℃,the induction period was almost no,the exotherm of the process was 82.27 k J,and the MTSR was 84.20℃.Combined with the thermal stability of the initial materials and products,the risk matrix method evaluates the result as “measures must be taken to reduce the risk”.The risk grading assessment results are: T_p<MTSR<T_D24<MTT,which is a level 2 risk.Under the action of copper-based catalyst: the reaction induction period is relatively short,only about 3min.When the reaction temperature is 80℃,the exotherm of the process is 76.18 k J,and the MTSR is 82.95℃.Combined with the thermal stability of the initial materials and products,the risk matrix method evaluates the result as “measures must be taken to reduce the risk”.The risk grading assessment results are: T_p<MTSR<T_D24<MTT,which is a level 2 risk.Under the action of iron-copper composite catalyst: copper ions preferentially play a catalytic role,and the catalytic reaction proceeds.When the reaction is carried out for a period of time,the iron ions begin to catalyze,thus avoiding the accumulation of heat during the single iron ion catalysis.The phenomenon occurs.When the reaction temperature was 80℃,the exotherm of the process was 92.45 k J and the MTSR was 85.29℃.Combined with the thermal stability of the initial materials and products,the risk matrix method evaluates the result as “measures must be taken to reduce the risk”.The risk grading assessment results are: T_p<MTSR<T_D24<MTT,which is a level 2 risk.