Study On The Oxidation Characteristics,Kinetics And Products Of 1,3-Butadiene(BD) By MCPVT

1,3-butadiene（BD）is one of the basic raw materials of petrochemical industry,which is widely used in rubber industry and fine chemical industry.BD produces explosive peroxides in contact with oxygen during production,use and storage.However,the thermal stability of BD at low temperature has not received enough attention,it is necessary to investigate the reaction characteristics of BD under oxygen conditions.The main research contents and results were as follows:（1）The thermal stability and oxidation characteristics of BDAccording to the mini closed pressure vessel test（MCPVT）,which can accurately determine the temperature and pressure change characteristics of the chemical reaction process,the temperature and pressure behavior of BD in the oxidation process under the conditions of nitrogen and oxygen was tracked by MCPVT to investigate the thermal stability and oxidation reaction characteristics of BD.The experiment results show that there is no polymerization reaction occurred of BD when the temperature is lower than 388.15 K under nitrogen conditions.Under the condition of oxygen,the chemical reaction has been observed at 323.15 K,and the higher the temperature is,the more obvious the oxidation reaction is,with the increase of the reaction temperatures,the total amount of reaction increases.The oxidation reaction is divided into three stages:the first stage is the initial stage of oxidation;The second stage is rapid oxidation stage;The third stage is the polymerization stage.（2）Kinetics of initial oxidation of BDThe pressure change with time（P-t）of BD under oxygen atmosphere was measured by mini closed pressure vessel test（MCPVT）,and the kinetics of initial oxidation of BD was calculated by P-t plot.The experiment results show that the initial oxidation reaction of BD and oxygen is the kinetic second order,the kinetic equation is,and activation energy is 30.5 k J/mol.The initial oxidation of oxygen excessive and 1,3-butadiene excessive in two special cases is a pseudo first-order reaction,the kinetic equation is lnk_p2=-3018×（1/T）+3.433,activation energy is 25.1k J/mol,,activation energy is 26.6k J/mol.（3）Products and possible reaction pathway of BD oxidation reactionThe gas products of BD oxidation reaction were analyzed by gas chromatography-mass spectrometry（GC-MS）.Headspace（injection）-gas chromatography-mass spectrometry（HS-GC-MS）was used to analyze the solid products.The experiment results show that the main oxidation products of BD are acrolein and furan.According to the reaction products,the possible oxidation pathway is proposed as follows:firstly,BD reactes with oxygen to form BD peroxides,and then the peroxides decompose to generates free radicals,which reacte with BD to form acrolein,furan and other oxides,and then undergoe polymerization.（4）Analysis of peroxides formed by BD oxidation and their thermal decomposition propertiesThe peroxides generated by the initial oxidation reaction of BD were analyzed by iodimetry,the relationship between the content of peroxides and the reaction temperature,reaction time were investigated,and the thermal decomposition properties of peroxides were determined by differential scanning calorimeter（DSC）.The experiment results show that the peroxide content increases first and then decreases with the temperature and time.When the reaction temperature is 65℃and the time is 26 h,the content of peroxides reaches the maximum.The content of peroxides increases with the increase of oxygen.When the content of BD peroxides is 33.6 mmol/kg,the initial decomposition temperature T₀of DSC is 62℃,the self-decomposition temperature T_onset is94.37℃,the maximum thermal decomposition rate T_p is 134.14℃,and the decomposition heat Q_DSC is 1887 J/g.