Study onevolutionary rules of molecular structure changes in coalification jump based on thermal simulation experiments
LI Pengpeng
WANG Anmin
FENG Yiyi
WANG Shengjian
HE Wenting
ZENG Peilin
FENG Sijin
BAO Zhengyu
BIN Xiangshen
CHU Yiran
Abstract：To reveal the characteristics of coalification jumps at the molecular level,low-rank coal samples from Xin-jiang's Yili region were used as experimental subjects.Thermal simulation experiments were conducted within a temperature range of 250～600℃.Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)techniques were employed to systematically analyze the evolution characteristics of the coal molecular structure before and after the thermal simulation experiments.The results indicate that the first three coalification jumps were simula-ted in this study.The first jump occurs near Ro≈0.6%,characterized by a decrease in the length of aliphatic side chains(CH2/CH3),an increase in the proportion of various oxygen-containing functional groups(aromatic ether C—O—C,phenolic ether C—O,ester C—O—C,aliphatic ether C—O—C,and alcoholic C—O),and a signifi-cant decrease in hydroxyl(—OH)and carbonyl(C＝O)content.Concurrently,the interlayer spacing of aromatic sheets(d002),lateral extension(La),stacking height(Lc),and average stacking number(Nave)all decreased to varying degrees,reflecting the thermal degradation and detachment of a large number of aliphatic side chains and un-stable oxygen-containing groups.This drives coal into the first coalification jump stage,consistent with the onset of hydrocarbon generation.The second jump occurs around Ro≈1.4%.During this stage,the content of oxygen-contai-ning functional groups increases,while hydroxy(—OH),carbonyl(C＝O),as well as aliphatic CH2 and CH3 continue to decrease.Correspondingly,d002 decreases significantly,while La and Lc steadily increase,indicating that aromatization reactions begin to dominate,accelerating the conversion of aliphatic structures to aromatic structures.The third jump is located near Ro≈2.3%,characterized by a decrease in the content of various oxygen-containing functional groups,while the percentage of—OH,carboxyl/carbonyl C ＝O,and aliphatic CH2 and CH3 content relatively increase.Simultaneously,d002,La,Lc,and Nave all decrease.This stage reflects the advanced evolution stage of coalification,dominated by condensation reactions.
Keywords：coalification jumpmolecular structurejump nodethermal simulationoxygen-containing functional groups
Publication Date：2026-01-31
Pages：8( 12-19 )