In a detailed investigation into the thermal decomposition of oil shale, Fajun Zhao, Zian Yang, Lei Zhang, Changjiang Zhang, Tianyu Wang, and Hong Zhang have published their findings in Scientific Reports. Their study systematically explores how temperature influences the distribution and reaction mechanisms of gas, liquid, and solid products during oil shale pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, providing crucial insights for optimizing energy resource utilization.

The research categorizes the oil shale pyrolysis process into three distinct temperature stages. The low-temperature stage (below 200°C) is primarily characterized by water evaporation and minimal changes in mass. The mid-temperature stage, ranging from 400°C to 650°C, is identified as the main phase for organic matter decomposition, where significant mass loss occurs. Finally, the high-temperature stage (above 650°C) is marked by the secondary cracking of heavy components and the decomposition of mineral residues.

Temperature proves to be a critical factor in determining the product yields. The total gas yield, for instance, increases significantly under high-temperature conditions, with hydrogen (H₂) and methane (CH₄) becoming the dominant gaseous products. Specifically, H₂ content reached nearly 70% at 650°C, indicating intensified organic matter pyrolysis. Conversely, carbon dioxide (CO₂) is predominantly released at lower temperatures, around 450°C, and then gradually decreases. For liquid products, particularly shale oil, the yield peaks in the mid-temperature range of 400-500°C. However, at temperatures exceeding 550°C, the shale oil yield begins to decrease due to secondary cracking reactions that convert liquid hydrocarbons into gaseous products and solid carbonaceous residues. Analysis of shale oil composition showed that at 400°C, heavy components (C21+) were relatively high, but as the temperature increased to 650°C, light components.

Regarding solid products, the study found that the fixed carbon content of the semi-coke decreases with increasing temperature. Furthermore, at high temperatures, the mineral components decompose into porous oxides, which can enhance the porous structure of the residue, making it potentially suitable for use in construction materials. The semi-coke yield progressively decreased from 88% at 400°C to 78% at 650°C, reflecting the intensified pyrolysis of organic matter and further cracking of carbonaceous material.

Kinetic analysis, using both model-free (FWO and KAS) and multi-step models, provided a deeper understanding of the reaction pathways. The analysis indicated that primary reactions, characterized by lower activation energies, drive the mid-temperature pyrolysis, making it ideal for shale oil production. In contrast, secondary reactions, which require higher activation energies, become dominant at high temperatures, leading to enhanced gas production.

This comprehensive study by Zhao et al. elucidates the regulatory mechanisms of temperature on oil shale pyrolysis, offering valuable guidance for the targeted optimization of specific products—whether it’s maximizing shale oil yield at 400-500°C or prioritizing hydrogen and methane gas production at temperatures above 650°C. These findings serve as critical scientific and technical references for improving the efficient utilization of unconventional energy resources.

Source: Zhao, F., Yang, Z., Zhang, L., Zhang, C., Wang, T., & Zhang, H. (2025). The effect of temperature on pyrolysis products during oil shale thermal decomposition.Scientific Reports, 15(1), 26135.