Molecular composition of extracts obtained by hydrothermal extraction of brown coal

a b s t r a c tWith no use of hydrogen or a hydrogen donor, a novel process is proposed for the production of aromatic hydrocarbons from brown coal in water medium, which consists of hydrothermal oxidation at 240°C and Cu 2 O-catalysed hydrothermal decarboxylation at 350°C. Using this hydrothermal oxidation and catalytic hydrothermal decarboxylation method, aromatic carboxylic acids were formed from brown coal by an oxidation process, and then decarboxylated to the corresponding aromatic hydrocarbons. The validity of the decarboxylation method was examined using several aromatic carboxylic acids as model compounds for the acid products after hydrothermal oxidation of brown coal, including o-phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, 1-naphthoic acid, 2-naphthoic acid, and 2,6-naphthalic acid. Use of Cu 2 O catalyst increased the decarboxylation yields of all the aromatic carboxylic acids. Especially for benzene carboxylic acids, all decarboxylation yields were above 90% with 100% selectivity. The Cu 2 O-catalysed hydrothermal method was proven to be effective, not only for the decarboxylation reactions from monocarboxylic acids to hydrocarbons, but also for the decarboxylation reactions from tricarboxylic acids to dicarboxylic acids and from dicarboxylic acids to monocarboxylic acids. In the presence of alkali and oxygen during the oxidation process, various valuable aromatic hydrocarbons and heterocyclic compounds, especially benzene, were obtained from Loy Yang coal using the hydrothermal oxidation and catalytic decarboxylation process. Based on analyses of aromatic carboxylic acids or ions before and after the decarboxylation process, it was found that decarboxylation reactions were the major reactions and the use of Cu 2 O was effective not only for the decarboxylation from monocarboxylic acids but also from polycarboxylic acids to monocarboxylic acids, consistent with the results for the model aromatic carboxylic acids. Additionally, it was found that a Cu 2 O catalyst was also effective for the conversion of 'heavy' compounds in oxidised coal to 'light' compounds.

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“…From our past research, it has been shown that LDI-MS is an important tool in the characterisation of heavy compounds [31]. Fig.…”

Section: Hydrothermal Oxidation and Hydrothermal Decarboxylation Of Lymentioning

confidence: 99%

A novel process for the production of aromatic hydrocarbons from brown coal in water medium by hydrothermal oxidation and catalytic hydrothermal decarboxylation

Zheng

Morimoto

Takanohashi

2016

Fuel

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“…Solvent extraction is an effective method to obtain low-weight molecules from coal. 8 , 9 During solvent extraction, organic solvents can destroy interaction forces such as hydrogen bonds and van der Waals forces and obtain organic components embedded in the macromolecular network structure. 10 Among many solvent extraction methods (the extraction temperature is higher than 300 °C), microwave-assisted extraction (MAE) can extract efficiently organic components in coal at low temperatures (below 200 °C).…”

Section: Introductionmentioning

confidence: 99%

“…Low molecular weight compounds are uniformly dispersed and embedded in the structure and affect the properties. Solvent extraction is an effective method to obtain low-weight molecules from coal. , During solvent extraction, organic solvents can destroy interaction forces such as hydrogen bonds and van der Waals forces and obtain organic components embedded in the macromolecular network structure . Among many solvent extraction methods (the extraction temperature is higher than 300 °C), microwave-assisted extraction (MAE) can extract efficiently organic components in coal at low temperatures (below 200 °C). − Mahat et al found that the extraction rate of MAE for 20 min is 30–40% higher than that of Soxhlet extraction for 72 h. A higher extraction rate also provides greater structural information.…”

Section: Introductionmentioning

confidence: 99%

Insights into a Low-Rank Naomaohu Coal Structural Information by Multistage Fractions Coupled with LIAD-VUVPI-TOFMS

Liu

Deng

et al. 2022

ACS Omega

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In-depth insights into the chemical composition and structural information of coal are an effective way to improve the efficiency of coal utilization. Laser-induced acoustic desorption coupling with vacuum ultraviolet photoionization time-of-flight mass spectrometry (LIAD-VUVPI-TOFMS) was applied to structural characterization of cyclohexane extracts of low-rank Naomaohu coal. The characterization of four types (12 model compounds) of mixed coal model compounds (three compounds per category)—saturated hydrocarbons, substitute aromatic hydrocarbons, aromatic hydrocarbons, and aromatic heteroatom rings—demonstrated that the approach can provide intact molecular weight information. The cyclohexanone extract ( E CYC ) was obtained by microwave-assisted extraction and separated into four group components (F1–4) by column chromatography to achieve component classification and simplify analysis. The molecular weight and structure were obtained by LIAD-VUVPI-TOFMS and synchronous fluorescence spectroscopy, combined with microwave-assisted extraction and column chromatography to separate product characteristics. Chemical components of a total of 248 species were observed, of which 46 are derived from aliphatic hydrocarbons embedded in the coal skeleton structure, 132 species are derived from aromatic hydrocarbons embedded in the coal skeleton structure, 61 are derived from possible coal skeleton units (compounds have obvious stacking and bonding effects), and 9 could not be determined (aromatic hydrocarbons or a possible coal skeleton structure unit).

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“…In recent years, the effective use of fossil fuels and diversification of fuels have become important concerns due to problems such as depletion of fossil fuels, global warming, and the nuclear accident during the Great East Japan Earthquake. Extensive global research has been conducted to expand the use of low-grade fuels such as brown coal − and carbon-neutral fuels, such as biomass − and biofuels. − Among these next-generation fuels, biogas has received particular interest. − Biogas is a carbon-neutral fuel produced by methane fermentation of food waste, livestock manure, sewage sludge, etc., and CO 2 generated by biogas combustion is not counted as a greenhouse gas. However, the flame stability of biogas is low because biogas is composed of ∼60% CH 4 and ∼40% CO 2 , and its calorific value is very low.…”

Section: Introductionmentioning

confidence: 99%

Influence of Nozzle Shape on Partial Oxidation Reforming of Biogas Using Microwave Plasma

et al. 2021

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Biogas, composed of ∼60% CH 4 and ∼40% CO 2 , is a carbon-neutral fuel but suffers from low flame stability. Thus, for effective utilization, the combustion reaction must be enhanced or biogas must be upgraded. Herein, microwave plasma-assisted combustion was utilized for partial oxidation reforming of biogas to enhance the reforming reaction and to upgrade biogas. The characteristics of the biogas reforming process and effects of the nozzle shape were investigated using four different nozzles. The small thin nozzle suppressed microwave attenuation to the greatest extent and thus most effectively promoted the reforming reaction. Microwave plasma not only reformed CH 4 into H 2 and CO but also decomposed CO 2 (which does not have any calorific value) into CO (which has calorific value); thus, the maximum cold gas efficiency achieved with the small thin nozzle was 112.7%, and the biogas was upgraded. Biogas reforming using O 2 as an oxidizer was also evaluated to improve the cold gas efficiency, but the cold gas efficiency undesirably decreased in this reaction relative to that using air with N 2 as the oxidizer because the reforming reactions are enhanced by increasing the active radicals like H and OH in the latter.

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Molecular composition of extracts obtained by hydrothermal extraction of brown coal

Cited by 18 publications

References 21 publications

A novel process for the production of aromatic hydrocarbons from brown coal in water medium by hydrothermal oxidation and catalytic hydrothermal decarboxylation

A novel process for the production of aromatic hydrocarbons from brown coal in water medium by hydrothermal oxidation and catalytic hydrothermal decarboxylation

Insights into a Low-Rank Naomaohu Coal Structural Information by Multistage Fractions Coupled with LIAD-VUVPI-TOFMS

Influence of Nozzle Shape on Partial Oxidation Reforming of Biogas Using Microwave Plasma

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