The Reactivity And Hazard Of 1,3-butadiene And Isoprene

1,3-Butadiene and isoprene are the important monomers for synthetic rubber.They are the major raw materials for the production of polymeric materials such as styrene-butadiene and isoprene-rubber,and they are two simple conjugated dienes of interest to the chemical industry.Due to their active chemical properties,conjugated dienes are prone to various chemical reactions such as polymerization and oxidation reactions.Although 1,3-butadiene and isoprene have been extensively reported in the literature in the field of organic synthesis,and there are some literatures on the hazards of 1,3-butadiene.However,the thermal stability,oxidation hazards,and the reaction pathways and mechanisms of the two conjugated dienes still need to be further investigated.The safety study of these two conjugated dienes has considerable theoretical significance and practical application value for their safe production,storage,transportation,and use.The main research contents and results of this thesis are as follows.（1）Oxidation reactivity and hazard of 1,3-butadieneConsidering that 1,3-butadiene is characterized as a gas at room temperature,a mini closed pressure vessel test（MCPVT）was used to monitor the temperature and pressure behavior of the oxidation reaction of 1,3-butadiene.The effects of two initiators,CHP（cumene hydroperoxide）and AIBN（2,2’-azodiisobutyronitrile）,on the oxidation reaction were investigated.The results show that 1,3-butadiene is stable under a nitrogen atmosphere up to 383.15 K,while it is prone to autoxidation under an oxygen atmosphere.The oxidation reaction can be accelerated when the CHP and AIBN initiators are added to the reaction system.By measuring the kinetics of the autoxidation reaction of 1,3-butadiene,it is found to be a second-order reaction with an activation energy E_a of 20.87 k J·mol^-1.In contrast,the oxidation reactions initiated by initiators CHP and AIBN are first-order reactions with the activation energies E_aof 33.34 k J·mol^-1 and 56.29 k J·mol^-1,respectively.The thermal stability of the peroxide mixtures generated from the initial oxidation of 1,3-butadiene was studied by differential scanning calorimeter（DSC）.The results show that the initial exothermic temperatures T_on of the oxidation products initiated by autoxidation,CHP,and AIBN initiator are 365.59 K,332.39 K,and 337.06 K,respectively.The accelerated decomposition temperature T_DSC are370.71 K,346.13 K,and 355.40 K,respectively.The thermal decomposition exothermic Q_DSC are 113.81 J·g^-1,859.80 J·g^-1,and 1152.8 J·g^-1,respectively.The peroxide mixtures are unstable and hazardous.In addition,the reaction products were analyzed qualitatively and quantitatively by gas chromatography-mass spectrometry（GC-MS）.The main gaseous products are acrolein,furan,and ethyl formate.The liquid products are mainly 1,2-divinylcyclobutane,3-butene-1,2-diol,2（5H）-furanone,4-vinylcyclohexene,and2,6-cyclodiene-1-one.The main volatile components in the solid products are 2（5H）-furanone and 4-vinylcyclohexene.Possible reaction pathways for 1,3-butadiene have been proposed based on the reaction products and the results of thermal analysis.（2）Photolysis reactivity of 1,3-butadieneConjugated diene is prone to a variety of reactions under ultraviolet radiation.The photochemical reaction properties of 1,3-butadiene were investigated using a self-designed micro-photoreaction device.The results show that the activation energy of 1,3-butadiene polymerization is 50.47 k J·mol^-1 without ultraviolet light.Under 254 nm ultraviolet radiation,1,3-butadiene is prone to photolysis reaction.The activation energies decrease significantly and decrease with the increase of ultraviolet intensity（I）.A good linear relationship exists between the activation energy and the logarithm of ultraviolet intensity:E_a=-7.294·ln I+66.15（R²=0.9886）.The reaction products of 1,3-butadiene were analyzed by GC-MS.In the absence of ultraviolet light,the main products are 1,2-divinylcyclobutane and 4-vinylcyclohexane.The reaction products of photolysis reactions include ethylene,acetylene,cyclobutene,and 1-butene.The possible reaction mechanisms for 1,3-butadiene has been proposed based on the reaction products.（3）Reaction characteristics and hazard of isopreneIsoprene is also a diene with a conjugate structure.The polymerization and oxidation reaction characteristics of isoprene were innovated to measure by MCPVT.The hazards of the reaction process were evaluated,and the effects of solid acid and base on the reaction were discussed.The experimental results show that the initial reaction temperature T_on is 352.28 K under a nitrogen atmosphere.The kinetics of the polymerization shows a second-order reaction with an activation energy E_a of29.69±1.11 k J·mol^-1.The initial oxidation temperature T_on under an oxygen atmosphere is 345.65 K.The kinetics of oxidation shows a second-order reaction（a first-order for oxygen and a first-order for isoprene）,and the activation energy E_a is86.88±5.61 k J·mol^-1.The solid base Na OH has no significant effect on the initial reaction temperature,while the solid acid RS300-80 has a certain effect on the initial reaction temperature.The oxidation reaction of isoprene is prone to the thermal runaway with a rapid rise in temperature and pressure.When the molar rate of isoprene/oxygen（C₅H₈/O₂）was 1:2.0 and the temperature increased to 352.15 K,thermal runaway and explosion phenomena had been monitored in the MCPVT experiment.The glass tube in the reactor was blasted into black smoke powder,and the safety sheet（resistant pressure up to 5 MPa）was broken.This result indicates that the oxidation reaction of isoprene is hazardous.（4）Thermal decomposition and hazard of isoprene peroxidesThe thermal decomposition of peroxide mixtures and isoprene hydroxyl peroxide（1,2-ISOPOOH）generated by the oxidation of isoprene were studied by DSC,TG（Thermogravimetric Analysis）,and MCPVT,respectively.This study aims to explore the nature of the explosive risk of isoprene under an oxygen atmosphere.The DSC results show that the initial exothermic temperature T_on of the peroxide mixtures of isoprene is 365.84 K,the accelerated exothermic temperature T_DSC is394.38 K,and the decomposition heat Q_DSC is 991.08 J·g^-1.For the thermal decomposition reaction of 1,2-ISOPOOH,the initial exothermic temperature T_on is324.88 K,the accelerated exothermic temperature T_DSC is 362.99 K,and the decomposition heat Q_DSC is 1915 J·g^-1.The activation energy of 53.46 k J·mol^-1 is obtained from TG kinetic calculation.The mechanism of the first decomposition is consistent with the Mample Power law and the reaction order n is 3/2.The kinetic equation is（?）.The thermal decomposition of 1,2-ISOPOOH measured by MCPVT shows that its thermal decomposition reaction is a rapid thermal decomposition process with an initial thermal decomposition temperature of 351.10 K.The maximum temperature rise rate（d T/dt）_max is 65.57 K·min^-1,and the maximum pressure rise rate（d P/dt）_maxis 48.75 MPa·min^-1.（5）Reaction pathways for the polymerization reaction,oxidation reaction of isoprene,and the decomposition reaction of 1,2-ISOPOOHThe reaction products of the polymerization,the oxidation of isoprene,and the thermal decomposition reaction of 1,2-ISOPOOH were determined by GC-MS.The effects of the solid acid RS300-80 and the solid base Na OH on the polymerization and oxidation products of isoprene were investigated.According to the products,the possible pathways for the polymerization,oxidation of isoprene,and thermal decomposition of 1,2-ISOPOOH has been proposed,respectively.