Construction of Macromolecules of Depolymerized Lignite

Area of Science:

• Chemical Engineering
• Organic Chemistry
• Materials Science

Background:

• Lignite utilization is key for energy, but its high ash content poses challenges.
• Converting lignite into chemicals offers a promising avenue for value addition.
• Ash-less coal preparation is an efficient strategy for lignite upgrading.

Purpose of the Study:

• To depolymerize lignite and prepare ash-less coal (SDP).
• To separate SDP into hexane-soluble (HS), toluene-soluble (TS), and tetrahydrofuran-soluble (THFS) fractions.
• To characterize the structural properties of SDP and its subfractions for chemical conversion.

Main Methods:

• Depolymerization of lignite.
• Fractionation of ash-less coal into HS, TS, and THFS.
• Characterization using elemental analysis, GPC, FTIR, SFS, 1H-NMR, and 13C-NMR.

Main Results:

• SDP is an aromatic derivative mixture with alkyl and oxygen-containing functional groups.
• Molecular weight, aromaticity, and oxygen functional groups increase in the order HS < TS < THFS.
• THFS macromolecules feature significant ring systems (9.2 aromatic, 6.6 naphthenic) and hydroxyl/carboxyl groups, with ether linkage breakage as the dominant depolymerization reaction.

Conclusions:

• The structural characterization provides insights into lignite's chemical makeup for targeted conversion.
• The fractionation strategy effectively separates lignite components based on polarity and molecular size.
• This research supports the efficient utilization of lignite for producing valuable chemicals.