Experimental And Theoretical Studies On Thermal Runaway Of Cyclohexanone Peroxidation

Peroxide oxidation of cyclohexanone is a typical hazardous chemical process. Theseperoxide reactions are complex heterogeneous liquid-liquid reaction system, which arecontrolled by the combination of heat and mass transfer. Furthermore, these reaction areextreme exothermic, and the decomposition temperature of peroxide products are low. Allabove factors are the reaction of easily initiating thermal runaway reaction of peroxideoxidation process, which results in fires, explosions and major accidents. Therefore,accurately evaluating thermal risk, reducing thermal runaway reaction of the chemicalprocess and optimization operating parameters are the important parts of safe chemicalproduction.This paper made study on the thermal runaway hazard of cyclohexanone peroxidereaction process. Based on the runaway scenario, the thermal hazard class was presented.Furthermore, based on the safety boundary diagram and temperature diagram, thermalsafety operating conditions were established. Combined the experimental data calculation,the reaction path and kinetic parameters were calculated in the theoretical view. Theorycalculation of different thermal behavior in semi-batch reactor was accomplished, inaccompany with the interaction of every operating parameter on the output.1) Reaction Calorimeter (RC1e), Differential Scanning Calorimeter (DSC), andAccelerating Rate Calorimeter (ARC) were used to evaluate thermal hazards of theperoxide oxidation of cyclohexanone. The results showed that during the experimentalrange, higher temperature could accelerate reaction rate, increase the specific heat of thereaction system and activate the side reaction and intermediate reaction; higher stirring ratecould accelerate reaction. Meanwhile, prolonging addition time could remove the reactionheat well, however, it made the reaction rate lower, and the productivity of cyclohexanoneperoxide decreased at the same time. The average activation energy of the peroxide reactionis110kJ·mol-1, and the frequency factor is about4.21×1017s-1, which were simulatedbased on the experiments. To verify the accuracy of simulated reaction activationparameters, the experimental process is compared with the theoretical calculations.2) The thermal hazard evaluation methods of cyclohexanone peroxide oxidation wereput forward, and the criterion of experimental parameters scaled-up to industrial processwas established. According to the runaway scenario, the thermal hazard level of cyclohexanone peroxide reaction is five. However, if the mass of cyclohexanone is reduced,the level is changed to two. Combined safety boundary diagram with temperature diagram,the thermal safe operating conditions and maximum temperature threshold were obtained.Safer operating parameters at the laboratory scale are used for the scale-up to the industrialone, based on the verification of the optimization parameters. In accordance to the aboveanalysis, the value oft D,MIN,ind191.5mincan be easily computed.3) The optimization structure and vibration analysis of all the related stationary pointsare calculated using density functional theory (B3LYP) with6-311++G**basis set.Furthermore, at the same level, the minimum energy paths (MEP) are obtained based on theintrinsic reaction coordinate (IRC) method. The single-point energies are calculated at theCCSD(T)/6-311++G**. Finally, the rate constants are evaluated by CTST method. Thetheory calculated results indicate that the cyclohexanone peroxide oxidation proceeds in athree-step concerted mechanism, and the first step, which produces IM Criegeeintermediate, is rate-determining. The reaction kinetics parameters calculated by the abovemethods is consistent with the results, which were based on thermal experiments.4) The special thermal behavior of a semi-batch reactor is simulated by theory analysis,and local sensitivity calculation methods were put forward on different thermal behaviortype. The simulation methods have carried out for local sensitivity analysis for everyoperating parameter. The results showed that the slope sensitivity curves with operatingparameters equals zero, which is defined as the critical point from no-ignition to thermalrunaway. The other is the local sensitivity index equals to zero on dimensionless timeversus operating parameters. The theory indication of above two parts is verified by theexperiments of cyclohexanone peroxide reaction.5) The global sensitivity analysis method for the related semi-batch process with slowreaction in the continuous phase is developed. Based on the LHS Monte Carlo methodsampling, a scatter plots were first used to obtain a visual identification of the operatingparameters and identify the relationship between the input and output parameters. Theresults showed that the relationship was nonlinear of some operating parameters. Theuncertainty of input parameters was quantified by the EFAST model. The global sensitivityresults wereB＞St＞Da＞θd＞γ＞θ0. The calculating results are much more objective.