Separation and structural characterization of the value-added chemicals from mild degradation of lignites: A review
Maohong Fan and
Applied Energy, 2016, vol. 170, issue C, 415-436
Lignite utilizations are limited due to the disadvantages of lignites such as high moisture content, high ash yield, and low calorific value. Direct combustion and other conventional utilization processes of lignites emit a huge amount of CO2, leading to catastrophic global warming. Accordingly, mild and eco-friendly utilization technologies should be paid attention to overcome the disadvantages. Separation and structural characterization of organic species in degraded lignites are crucial for producing clean liquid fuels and value-added chemicals. Several molecular and network structural models for lignites have been proposed since 1976 based on the characteristics of the organic species from lignites. Since then, great progress has been achieved in this area, while reviews on the advances have rarely reported. This review focuses on mild (<400°C) and low-CO2-emission chemical degradation methods for separating and characterizing value-added chemicals (VACs) from lignites, including low-temperature extraction (LTE), thermal dissolution (TD), extraction in ionic liquids (ILs), and mild oxidation. LTE gives low extract yields for lignites due to strong noncovalent interactions between the soluble organic species (SOSs) and macromolecular network in lignites. Such interactions can be significantly disrupted by TD around 300°C, leading to dissolving much more SOSs (almost ash-free) which can be used as clean fuels for gas turbines or valuable precursors for chemicals and carbon materials. ILs could be promising green solvents for separating valuable SOSs from lignites. Mild oxidation also proved to be an effective approach for understanding macromolecular structures of lignites and simultaneously producing VACs such as short-chain aliphatic acids and benzenepolycarboxylic acids. Special attention has also been paid to the application of advanced analytical techniques for characterizing the VACs from mild degradation of lignites. Important information on functional groups, carbon and hydrogen forms, molecular mass distributions, and molecular compositions of the VACs can be characterized by using different analytical techniques presented in the review.
Keywords: Lignite; Value-added chemicals; Separation; Analytical techniques (search for similar items in EconPapers)
References: View references in EconPapers View complete reference list from CitEc
Citations View citations in EconPapers (1) Track citations by RSS feed
Downloads: (external link)
Full text for ScienceDirect subscribers only
This item may be available elsewhere in EconPapers: Search for items with the same title.
Export reference: BibTeX
RIS (EndNote, ProCite, RefMan)
Persistent link: https://EconPapers.repec.org/RePEc:eee:appene:v:170:y:2016:i:c:p:415-436
Ordering information: This journal article can be ordered from
http://www.elsevier. ... 405891/bibliographic
Access Statistics for this article
Applied Energy is currently edited by J. Yan
More articles in Applied Energy from Elsevier
Series data maintained by Dana Niculescu ().