Efficient separation of pyridine compounds from coal-based crude phenol via acidic deep eutectic solvents: experimental and theoretical insights

Abstract

Pyridine (PY) compounds in crude phenol generated during the primary processing of coal-based crude oils reduce the quality of phenolic products. Conventional acid washing produces large amounts of acidic wastewater, resulting in secondary environmental pollution and equipment corrosion. Therefore, developing an efficient and environmentally friendly process for PY removal is essential. Deep eutectic solvents (DESs) were screened using the COSMO-RS model and experimentally validated. In the model oil system, a DES composed of citric acid (CA) and glycerol (GLY) achieved the best extraction performance, with a PY extraction efficiency of over 99%. The DES also exhibited good recyclability. For actual coal-based crude phenol, the DES achieved an extraction efficiency of 99.9% for PY compounds and reduced the content of PY compounds in the purified crude phenol to below 0.1%, enabling the purified crude phenol to meet quality requirements. Quantum chemical calculations revealed that PY separation was driven by the synergistic effects of electrostatic and orbital interactions. This study provides a promising strategy for the efficient removal of nitrogen-containing heterocyclic compounds from complex systems.

Graphical abstract

Keywords

pyridine compounds / coal-based crude phenol / mechanistic analysis / acidic deep eutectic solvents

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