Study On The Reaction Path And Inhibition Mechanism Of Coal Oxidation Of Hydroxyl Radicals At Low Temperature

Coal is the major energy of China.Spontaneous combustion of coal(CSC)is common in the coal mining process,which can cause huge property losses and casualties.With the deep research of the mechanism of CSC,researchers have discovered that hydroxyl radicals(·OH)is an important factor leading to CSC.In order to deeply proclaim the reaction mechanism of·OH and propose a kind of inhibitor,a variety of researches have been put into practice.The quantum chemical calculation method is applied to discuss the reaction dynamics of·OH in the low-temperature oxidation of coal,and the reaction mechanism of hydroxytyrosol(HTY)to remove·OH is discussed.ESP,MOs and NBO population analysis are combined to determine the active site.The quantum chemical method was used to optimize the molecular structure,and the transition state calculation The thermodynamic data analysis and IRC verification were carried out on the reaction path of·OH and the reaction of HTY scavenging·OH.Our results indicate that·OH is mainly formed through the decomposition of·OOH or ROO·.The bond dissociation energy of·OOH is 317.69 k J/mol,and the hydrogen transfer within ROO·needs to surmount an barrier height of 86.64 k J/mol.Therefore,·OH is primarily produced from ROO·in the initial stage,but the decomposition of·OOH gradually becomes the main pathway with increasing temperature.H in hydrocarbons and oxygen-containing groups is abstracted by·OH to form C·,-C(OH)·,-C(O)·,-CO(O)·radicals and H₂O.The C·radicals then adsorb O₂ to generate ROO·,which can decompose to produce·OH.Therefore,the whole process of coal oxidation is a cyclic oxidation reaction.The reactions of hydrocarbons and hydroxyl groups with·OH need to surmount energy barriers of 39.38 and 23.63 k J/mol,with corresponding heat releases of 18.38 and154.90 k J/mol,respectively.H abstractions from aldehyde and carboxyl groups need to overcome energy barriers of 68.26 and 73.51 k J/mol and absorb heats of 97.14 and49.88 k J/mol,respectively.The O18-H19 bond in HTY can eliminate·OH after overcoming a barrier of 36.75 k J/mol,with a heat release of 23.63 k J/mol,and the rate constant for which is 1.60×10⁹s^-1M^-1.After H19 in HTY is extracted,a semiquinone structure is formed.The?E of O19-H20 scavenging·OH is 181.16k J/mol,and the reaction rate constant k is 2.71×10^-18 s^-1M^-1.In this paper,through XPS full-spectrum scanning analysis,compared with the raw coal sample,the reduction range of C-C/C-H of the HTY coal sample is smaller,The increased range of the oxygen-containing structure content is also smaller.Based on the EPR experiment,the inhibitory effect of HTY on CSC was studied.According to the spectrum,it is found that the amount of radicals in the HTY coal sample is lower;and the g-value of the both coal samples are in the range of 2.034-2.0039,indicating the content of radicals containing oxygen and heteroatoms centered on carbon is the highest;the g value and the line width value of the HTY coal sample is lower,indicating that the number of heteroatoms and oxygen-containing free radicals is reduced.The specific surface and pore size analyzer is applied to discuss the oxygen adsorption.Under normal pressure,as the temperature increases the oxygen adsorption capacity also increases.At the same temperature,the oxygen adsorption of HTY coal samples has been significantly reduced,and this phenomenon is most obvious around 90-110?.