## 4 Conclusions  
The molecular structure characteristics of the experimental coal samples of DX 1#, DX 2#, HY 1#, and HY 2# were characterized through proximate and ultimate analysis, XRD experiments, Raman spectroscopy experiments, and FTIR spectroscopy experiments, and the main conclusions obtained are as follows:  
1. Based on the proximate analysis, it is evident that the thermal evolution caused by magmatic activity leads to an increase in coal ash content while reducing the moisture and volatile content. The results obtained from the ultimate analysis indicate that the magmatic thermal evolution coal sample exhibits a high aromaticity rate.
2. X-ray diffraction experiments revealed that magmatic thermal evolution possesses the capability to elevate the aromatization of low-rank coals and foster the advancement of their microcrystalline structure. Moreover, the magmatic thermal evolution coal samples exhibited reduced d002 values, approaching the aromatic interlayer spacing observed in graphite crystals. This implies that the magmatic thermal evolution process promotes the coalification or carbonization of low-rank coal.
3. The Raman spectroscopy experiments show that magmatic thermal evolution promotes the generation of ordered structures in low-rank coals. The \(\rm{I_{D1}}/\rm{I_{G}}\) and \(\rm{F_{D1}}/\rm{F_{G}}\) values of magmatic thermal evolution coal samples are smaller than those of normal coal samples, which indicates that there are less disordered structures and more ordered structures in magmatic thermal evolution coal samples affected by magma intrusion compared with normal coal samples.
4. FTIR spectroscopy analysis demonstrates that magmatic thermal evolution possesses the ability to deoxygenate the coal samples and augment their carbon content. Additionally, the thermally evolved coal samples display higher \(\rm{A(CH_{2})}/\rm{A(CH_{3})}\) values when compared to the normal coal samples, signifying a reduction in the degree of branching attributed to magmatic thermal evolution.
5. It is necessary to recognize the limitations of this study; the microstructures of the two groups of coal samples were analyzed and investigated through the test results, but  
Figure 8: Proportion of different functional groups.  
only approximate relationships could be obtained due to the limited number of coal samples selected. The next step will be to increase the number of test coal samples for studying.  
Conceptualization, J.J.; methodology, W.Z.; validation, W.Z., J.J., Y.H., F.Z., and W.H.; formal analysis, W.Z.; investigation, F.Z. and W.H.; resources, J.J.; data curation, F.Z. and W.H.; writing--original draft preparation, W.Z. and Y.H.; writing--review and editing, J.J. and W.Z.; visualization, F.Z.; supervision, J.J.; project administration, J.J. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, grant number 52174217.  
The study did not require ethical approval.  
The study did not involve humans.  
Readers can email the corresponding author to request data.  
Author [PERSON] was employed by Henan Longyu Power Co. Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.