# Study on the Combustion Behavior and Kinetic Characteristics of Semi-Coke from Oil Shale
## 3 Results and Discussion
### Characterization of Combustion Residues Analysis
#### 3.3.3 Infrared Spectroscopy (IR) Characterization  
Figure 8 presents the infrared spectroscopy analysis of oil shale and combustion semi-coke. As shown in Figure 8, the wavenumber range of 3700-3625 cm\({}^{-1}\) (OH/NH) corresponds to the stretching vibration peaks of hydrogen bonds (OH or NH), indicating the presence of moisture and amino or hydroxyl functional groups in the sample. The intensity of the stretching vibration peak in semi-coke is lower than that in oil shale, suggesting that some moisture and amino groups are removed during combustion. The absorption peaks at 2928 cm\({}^{-1}\) and 2850 cm\({}^{-1}\) (C-H) represent the typical stretching vibrations of C-H bonds, indicating the presence of hydrocarbons such as methane and alkanes. These peaks generally reflect the existence of hydrocarbon groups in organic matter. The absorption peak intensity in semi-coke is lower than that in oil shale, suggesting a reduction in alkanes due to hydrocarbon cracking or volatilization during combustion.  
Figure 7: XRD patterns of oil shale and semi-coke samples. Note: C—calcite, M—dolomite, P—pyrite, Q—quartz. (**a**) XRD pattern of oil shale sample; (**b**) XRD pattern of semi-coke sample.  
The 1604 cm\({}^{-1}\) (C=C) peak represents the characteristic absorption of C=C double bonds, reflecting the presence of aromatic compounds or incompletely cracked organic matter in oil shale. This peak is still observed in semi-coke, indicating that aromatic compounds and unbroken organic structures remain in the semi-coke.  
The 1400 cm\({}^{-1}\) (C-H) absorption peak suggests the presence of certain alkyl substances in semi-coke, possibly low-molecular-weight organic compounds or incompletely cracked structures.  
The absorption peaks at 910 cm\({}^{-1}\) and 500 cm\({}^{-1}\) (C-H) are related to C-H vibrations, typically indicating the presence of benzene rings or aliphatic hydrocarbons in organic matter. A comparison between oil shale and semi-coke highlights the differences in organic composition and chemical bond transformations. Oil shale contains more moisture and hydrocarbons, whereas semi-coke exhibits reduced moisture content and decreased volatile components. Hydrocarbons are significantly reduced, while aromatic compounds and other stable structures remain intact.  
While this study provides a detailed understanding of the combustion behavior and kinetics of oil shale semi-coke, its practical relevance is of particular importance. In regions where oil shale is an abundant resource, such as in the Middle East, China, and the United States, oil shale semi-coke can be considered a potential alternative fuel for industrial applications, including power generation and cement production. By optimizing combustion processes and improving energy efficiency, oil shale semi-coke could help reduce the reliance on traditional fossil fuels and contribute to more sustainable energy solutions [28]. Future studies will need to explore the feasibility of using oil shale semi-coke in real-world combustion systems to assess its performance in industrial-scale applications.