*Article* **Analysis of Outburst Coal Structure Characteristics in Sanjia Coal Mine Based on FTIR and XRD**

**Anjun Jiao 1, Shixiang Tian 1,2,\* and Huaying Lin <sup>1</sup>**


**Abstract:** In order to reveal the distribution characteristics of functional groups and the difference of microcrystalline structure parameters between outburst coal and primary coal, the coal samples inside and outside the outburst holes of the Sanjia coal mine were examined. The functional groups and microcrystalline structure parameters of outburst coal and primary coal in the Sanjia coal mine were studied by infrared spectroscopy, X-ray diffraction (XRD) experiment and peak-splitting fitting method. The results showed that the substitution mode of the benzene ring in an aromatic structure was mainly benzene ring tri-substituted, with primary coal of 32.71% and outburst coal of 31.6%. The primary coal contained more functional groups, from which hydrogen bonds can easily be formed, meaning that gas is not easily adsorbed by coal. The aromatic hydrogen rate (*fHa*) of the outburst coal was 0.271, the aromatic carbon rate (*ƒC*) was 0.986, the aromaticity *I*<sup>1</sup> was 0.477, *I*<sup>2</sup> was 0.373 and the length of the aliphatic branched chain (*ACH*2/*ACH*3) was 0.850. Compared with the primary coal, the aromatic hydrogen rate, aromatic carbon rate and the aromaticity of the outburst coal were higher, indicating that the hydrogen and carbon elements in the aromatic functional groups of outburst coal were higher and that the aliphatic functional group was higher than the aromatic structural functional group. *ACH*2/*ACH*<sup>3</sup> and maturity (*Csd*) were slightly lower than those of primary coal, indicating that the coal has more straight chains than side chains, while aliphatic hydrocarbons are mostly short chains and have high branched degree. There were obvious 002 and 100 peaks in the XRD pattern. The *d*<sup>002</sup> and *d*<sup>100</sup> of outburst coal were 3.570 and 2.114, respectively, while the number of effective stacking aromatics was 3.089, which was lower than that of primary coal, indicating that the structure of the dense ring in the coal saw certain changes.

**Keywords:** outburst coal; primary coal; structural parameters; infrared spectrum; XRD
