Effect of solvent extraction on the composition of coal tar residues and their pyrolysis characteristics

ABSTRACT

A large amount of coal tar residues (CTRs) produced in the coal coking or gasification industry has not been effectively utilized in China. In this study, CTRs are extracted by 12 organic solvents. Detailed investigations are carried out via ultimate analysis, Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG) analyzer. The pyrolysis process of CTRs and their extraction residues (RCTRs) can be accurately fitted by Coast-Redfern integral model. The results indicate that the reaction order (n), apparent activation energy (E_a) and pre-exponential factor (A) were in the range of 2–7, 34.42–60.08 kJ mol⁻¹ and 10²-10⁵ min⁻¹, respectively. Correlations are observed between parameters (H, C, O, H/C, W_T, R_max, n, E_a, and lnA) and the yield of RCTRs, suggesting that the composition and pyrolysis behavior are controlled by the solvent extraction. Specifically, extraction with n-heptane, methanol and ethanol could reduce the E_a and promote CTRs decomposition by disrupting the noncovalent bonds. When extracted with CS₂, DMF, benzene, toluene, acetone, etc. the recovery rate of tar and the yield of pyrolysis products are improved, however, the reactivity decrease due to the increase in activation energy.

KEYWORDS:

• Coal tar residues
• extraction
• structural parameters
• pyrolysis
• kinetics

Nomenclature

Table

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2022.2129881

Additional information

Funding

The work was supported by the Natural Science Foundation of Shanxi Province [20210302123167]; Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering [2021SX-TD006].