¹H NMR and ¹³C NMR characterization of n-heptane extraction of low-temperature coal tar reacted with formaldehyde

ABSTRACT

The optimum conditions of toluene insoluble-quinoline soluble fraction (TI-QS) obtained by n-heptane Soxhlet extraction residue of low-temperature coal tar (H-CT) reacted with formaldehyde were determined. And ¹H NMR and ¹³C NMR were employed to analyze the structure of H-CT and its reaction products (P-H-CT). The results show that the yield of TI-QS is the largest at the reaction conditions as follows: reaction temperature 90°C, reaction time 3 h and with 3 wt% addition of catalyst. The contents of aliphatic carbon and aromatic carbon bonded to oxygen are higher in H-CT. The contents of aliphatic CH₃ carbon and aromatic CH₃ carbon are higher in P-H-CT. The content of methylene decreases and the content of methane increases, but the decrease of methylene is larger than the increase of methane; therefore, CH/CH₂ carbon decreases slightly. The content of H_γ is 0.10 wt%, and the contents of H_α and H_β are all 0.25 wt% in P-H-CT. The H_γ, H_α and H_β ratios of P-H-CT to H-CT are small, displaying a lower branched degree of P-H-CT.

KEYWORDS:

• Low temperature coal tar
• n-heptane extraction
• formaldehyde
• ¹H NMR
• ¹³C NMR

Additional information

Funding

This work was financed by the project supported by the National Natural Science Foundation of China (21536009, 21776229), the Joint Funds of National Key R&D Program of China (2018YFB0604603), the Science and Technology Plan Projects of Shaanxi Province, China (2017ZDCXL-GY-10-03, 2018ZDXM-GY-167) and the Young Science and Technology Star Project of Shaanxi Province, China (2017KJXX-62).