| Spontaneous combustion of vegetable oil is a special combustion phenomenon with strong concealment and uncertainty.Its continuous oxidation in the air will generate heat.If there is a suitable carrier,the heat released by the reaction will easily accumulate,and the risk of fire will be greatly increased.In order to effectively prevent the spontaneous combustion of vegetable oil,this paper takes the oxidation process as the starting point,and uses microcalorimetry and synchronous thermal analysis to analyze the heat flow changes in the low temperature oxidation process,and the thermal weight loss and heat changes in the programmed temperature process.Macroscopic data analysis,and then taking vegetable oil oxidized at different temperatures as an example,the oxidation mechanism of vegetable oil was deduced and analyzed by Raman spectroscopy and gas chromatography-mass spectrometry according to the changes of functional groups and main components during the oxidation process.During the low temperature oxidation process,the three typical vegetable oils began to undergo obvious oxidation at about 78℃,and their main exothermic peaks appeared at about102℃,and reached their maximum exothermic rates at the same time.Comparing its exothermic characteristic parameters,it can be seen that linseed oil is more prone to spontaneous combustion at low temperature,and the risk of spontaneous combustion is higher.Considering the temperature and calorific value parameters comprehensively,the order of spontaneous combustion tendency of the three typical vegetable oils is linseed oil>perilla seed oil>safflower seed oil.The activation energy of each sample in the low-temperature oxidation stage is about33.79k J/mol,indicating that vegetable oil is extremely easy to react at low temperature（<200°C）,and the risk of spontaneous combustion is high.In the low-temperature oxidation stage,the order of spontaneous combustion tendency of typical vegetable oils is linseed oil>perilla seed oil>safflower oil,and the order of spontaneous combustion tendency of common vegetable oils is sunflower oil>tung oil>sorghum oil>soybean oil,the order of the spontaneous combustion tendency of the medium is cotton yarn>cotton cloth.The strongest Raman characteristic peaks of typical vegetable oils all appear at 1662 cm-1,which are attributed to the stretching vibration of carbon-carbon double bonds（C=C）,which meant that the content of unsaturated double bond functional groups in vegetable oil was the most.The Raman spectra of vegetable oil before and after oxidation show significant changes in both spectral type and intensity.The change in peak shape mainly indicates that the vegetable oil is undergoing different degrees of oxidation reaction at different temperatures,and the peak intensity is higher.The change is mainly due to the change of the content of various functional groups in the oxidation process of vegetable oil.Vegetable oils contain a certain amount of unsaturated fatty acid glycerides.What they have in common is the carbon-carbon double bond（C=C）,and the carbon-carbon double bond is unstable in the air and easily reacts with oxygen to cause spontaneous combustion.Among them,linseed oil is dominated by linolenic acid,followed by oleic acid,linoleic acid,and stearic acid;perilla seed oil is dominated by linolenic acid,followed by linoleic acid,oleic acid,palmitic acid,and stearic acid;red Flower seed oil is dominated by linoleic acid,followed by linolenic acid.Taking carbon-carbon double bond（C=C）as the basic unit structure of unsaturated fatty acids,the oxidation pathways of two vegetable oils were deduced,and the oxidative spontaneous combustion mechanism of typical vegetable oils was discussed. |
