Extraction of coal-tar pitch using NMP/ILs mixed solvents

Abstract

Coal-tar pitch (CP) is a promising carbon raw material for producing needle coke, carbon fiber etc. During processing, the H/C ratio, ash content, and quinoline insoluble (QI) in the CP are the key factors that influence the material preparation. In this study, NMP was selected to extract CP first; then [BMIM]Cl/NMP mixed solvent was used; and finally a series of ionic liquids (ILs) mixtures with NMP were developed for the extraction of CP to obtain the refined pitch. The extracts were analyzed via elemental analysis, TGA, FT-IR, and 13C-NMR. Results indicate that different NMP/IL mass ratios or different kinds of ILs have impact on the extraction yield. The relationship of the hydrogen to carbon (H/C) ratio changed with different solvents and QI extracts were obtained. Results showed that the H/C ratios changed little between NMP extracts and could be adjusted by changing the NMP/ILs mass ratio or using different ILs. The extracts are suitable for preparation mesophase pitch because of no ash content, low QI, and appropriate H/C ratios. As a result, NMP can be used to refine pitch. In addition, [BMIM]Cl is good mixed with NMP for CP extraction, because it can obtain a relatively high yield under the same extraction conditions.