Construction of a bituminous coal molecular model and its pyrolysis mechanism based on reactive molecular dynamics

doi:10.16265/j.cnki.issn1003-3033.2026.07.1961

Abstract

Abstract:

To reveal the molecular structure evolution and product generation characteristics during bituminous coal pyrolysis, Pingdingshan bituminous coal was selected as the research object. A method combining experimental characterization and ReaxFF-MD simulations was adopted. Structural parameters of the coal sample were obtained using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance spectroscopy (¹³C NMR). A coal molecular model was constructed and validated based on density functional theory (DFT). Subsequently, the product distribution and structural evolution during bituminous coal pyrolysis were investigated using ReaxFF-MD simulation. The simulation results were further compared with macroscopic pyrolysis characteristics. The results show that the carbon skeleton of bituminous coal is consisted of 71.23% aromatic carbon and 28.77% aliphatic carbon. The aromatic structures are mainly composed of benzene and naphthalene rings. The constructed coal molecular formula is C₁₃₀H₈₂O₁₈N₆S. The molecular vibrational frequencies calculated by DFT are consistent with the broad peaks in the experimental FTIR spectra within the ranges of 1 500~1 000 cm^-1 and 3 700~2 800 cm^-1. During coal molecular pyrolysis, oxygen-containing functional groups are removed. Aromatic structures are gradually condensed. Gaseous products including CH₄, CO, CO₂, H₂, and H₂O, are generated simultaneously. Their total yield decreases with increasing heating rate. A lower heating rates is more favorable for secondary recombination reactions. The mass residual ratio, characteristic peak temperature shift trend, and gaseous product types of bituminous coal pyrolysis are consistent with the simulation results. The corresponding deviations in mass residual ratio are all less than 5%. The bituminous coal molecular model can well reflect the structural evolution and product generation behaviors during bituminous coal pyrolysis.

Key words: reactive force field molecular dynamics (ReaxFF-MD), bituminous coal, molecular model, pyrolysis, oxygen-containing functional groups

CLC Number:

X936

Li Jingjing, Jiang Bingyou, Xu Po, Su Mingqing, Lu Kunlun, Yu Changfei. Construction of a bituminous coal molecular model and its pyrolysis mechanism based on reactive molecular dynamics[J]. China Safety Science Journal, 2026, 36(7): 153-163.

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工业分析				元素分析
M_ad	A_ad	V_ad	FC_ad	C	H	O	S	N
0.7	7.9	27.5	63.9	77.7	4.1	13.9	0.3	4.0

元素峰	官能团	结合能/eV	相对含量/%
C 1s	COOH	290.28	5. 169 63
	C-O-C	285.72	32. 977 81
	C-C/C=C	284.80	61. 852 57
O 1s	C=O	533.59	51. 620 22
O 1s	C-O	532.62	48. 379 78
N 1s	N-X	401.23	18. 247 73
	N-Q	400.64	16. 611 68
	N-5	399.91	42. 775 53
	N-6	398.53	22. 365 06
S 2p	砜	170.45	13. 897 43
	亚砜	166.60	16. 257 78
	噻吩	165.24	19. 142 05
	噻吩	164.02	50. 702 74

波数范围/ cm^-1	波数/ cm^-1	峰面积	官能团	相对含量/%	波数范围/ cm^-1	波数/ cm^-1	峰面积	官能团	相对含量/%
900~700	872.2	0. 850 10	五取代苯	22.57		1 097.8	2. 152 65	C-OH拉伸振动	3.12
	853.1	0. 201 05	五取代苯	22.57		1 029.4	6. 991 23	C-O-C拉伸振动	10.15
	814.3	0. 885 18	四取代苯	19.01	3 000~2 800	2 953.7	3. 052 24	CH₃不对称拉伸振动	18.64
	793.4	0. 776 29	三取代苯	58.42		2 925.1	4. 415 97	CH₂不对称拉伸振动	26.97
	751.8	1. 944 53	三取代苯	58.42		2 905.4	2. 849 96	CH拉伸振动	17.40
1 800~ 1 000	1 719	1. 113 30	C=O拉伸振动	9.31		2 882.7	2. 078 29	CH₃对称拉伸振动	12.69
	1 653.4	5. 302 16	C=O拉伸振动	9.31		2 856.7	2. 871 38	CH₂对称拉伸振动	24.30
	1 615.7	10. 642 89	C=C拉伸振动	28.73		2 834.2	1. 107 36	CH₂对称拉伸振动	24.30
	1 585.5	7. 433 99			3 600~3 000	3 545.5	2. 792 15	OH…π	37.14
	1 550.8	1. 716 26				3 503.7	4. 363 83
	1 492.2	2. 769 61	CH₃变形振动	29.39		3 459.1	6. 190 90
	1 449.5	8. 566 95				3 417.2	6. 630 59	OH…OH	44.61
	1 415.5	4. 423 83				3 374.8	5. 747 91
	1 375.3	4. 488 36				3 329	3. 651 45
	1 333.6	3. 330 70	Ar-O-C拉伸振动	13.63		3 279.3	2. 455 88	OH…OR	11.63
	1 297.7	2. 735 69				3 230.8	1. 723 99	OH…OR	11.63
	1 260.1	3. 320 63				3 182	0. 993 59	环形OH	2.77
	1 221.6	2. 317 16	C-O拉伸振动	5.67		3 036	1. 382 72	C-H拉伸振动	3.85
	1 181.5	1. 586 09	C-O拉伸振动	5.67		3 036	1. 382 72	C-H拉伸振动	3.85

化学位移/10^-6	相对含量/%	归属
174.73	0.71	C=O
161.82	1.19	Ar-O
152.44	4.77	Ar-O
143.13	6.30	Ar-C
136.79	12.56	C-C
127.39	27.00	Ar-H
120.33	13.74	Ar-H
111.86	4.27	Ar-H
102.14	1.08	Ar-H
62.34	1.36	O-CH₃
50.39	3.11	O-CH₃
40.38	6.23	C, CH
31.97	8.73	CH₂
20.71	7.32	Ar-CH₃
15.13	1.64	R-CH₃

类型	芳香单元结构	数量
苯		1
萘		4
吡咯		4
吡啶		2
噻吩		1