Influences of exchangeable metallic species on solvent extraction of Xiaolongtan lignite and characterization of the separated portions

Li, Xiao; Bai, Zongqing; Bai, Jin; Yong, Han; Li, Pei; Lv, Dongmei; Xu, Junli; Dai, Xin; Kong, Lingxue; Li, Wen

doi:10.1016/j.fuproc.2015.05.014

Cited by 12 publications

(5 citation statements)

References 35 publications

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“…Detailed functional group changes of raw coal during thermal treatment can be obtained from FTIR spectra. As shown in Figure 2, the band intensity at 1600 cm −1 (C═C stretching vibration of arene) of all the treated samples is similar to that of ZDC, indicating that skeletal structures of raw coal are not influenced during thermal treatment 33 . The band intensity at 1260 cm −1 is clearly observed for both ZDC and the treated samples.…”

Section: Resultsmentioning

confidence: 67%

“…As shown in Figure 2, the band intensity at 1600 cm À1 (C═C stretching vibration of arene) of all the treated samples is similar to that of ZDC, indicating that skeletal structures of raw coal are not influenced during thermal treatment. 33 The band intensity at 1260 cm À1 is clearly observed for both ZDC and the treated samples. It implies that the amount of COO À does not change obviously during thermal treatment.…”

Section: Gas Release and Functional Group Changesmentioning

confidence: 90%

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Structural changes of Zhundong coal matrix induced by thermal treatment and its effects on oil yield in direct coal liquefaction

Han

2021

Intl J of Energy Research

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Sodium-rich coals are suitable raw materials for direct coal liquefaction (DCL).However, sodium species in coals, especially exchangeable ones, can significantly reduce oil yield. In this work, to increase oil yield in direct liquefaction of sodium-rich coals, a feasible method using organic solvents to pretreat sodium-rich coals is proposed. Initially, sodium-rich coal was thermally treated with tetralin or 1-methylnaphtalene. Then, raw coal and all the treated coals were liquefied under the same conditions to evaluate the effects of thermal treatment on structural changes of coal molecules and oil yield. The results show that surface areas of the treated coals increased to 7.86 m 2 /g at most, which was favorable for combination between hydrogen and coal molecules during the DCL process. More importantly, the content of hydrogen in the treated coals was 0.95 wt% higher than that of raw coal on average, suggesting that treated coals could be later liquefied at mild conditions. Raman spectra demonstrated that during thermal treatment with tetralin, small aromatic ring systems in raw coal were prehydrogenated and transformed into nonaromatic systems. The pre-hydrogenation of the coal matrix definitely contributes to the increase in oil yield. In view of sodium species distribution in the treated coals, it is proved that tetralin can promote the transformation of exchangeable sodium species into other chemical forms more easily than 1-methylnaphtalene, which implies that tetralin has more positive effects on the increase of oil yield. Compared with that of raw coal, oil yields in direct liquefaction of the samples treated by tetralin increase by 14.0 to 15.1 wt% (daf).

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Section: Resultsmentioning

confidence: 67%

Section: Gas Release and Functional Group Changesmentioning

confidence: 90%

Structural changes of Zhundong coal matrix induced by thermal treatment and its effects on oil yield in direct coal liquefaction

Han

2021

Intl J of Energy Research

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“…On the contrary, flat shoulders are reflected in the spectra of DCLR 2 (Figure B). The peaks between 1100 and 1300 cm –1 are assigned to the oxygen-containing or other heteroatomic compounds. , In light of this, it could be speculated that more heteroatoms were released from coals at high temperatures. The peaks at 750 and 870 cm –1 are attributed to the presence of C–H stretching in phenyl groups and condensed aromatics with two or more rings, respectively.…”

Section: Resultsmentioning

confidence: 99%

Insight into the Effects of Sodium Species with Different Occurrence Modes on the Structural Features of Residues Derived from Direct Liquefaction of Zhundong Coal by Multiple Techniques

Xiao

Bai

et al. 2015

Energy Fuels

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In this work, to better understand the characteristics of the direct coal liquefaction residue (DCLR) derived from the sodium-rich Zhundong coal, effects of sodium species with different occurrence modes on the structural features of the DCLR were investigated. Multiple techniques, including the element determination, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and solid-state 13C nuclear magnetic resonance (SS-NMR), were jointly used to characterize the structural features of the coal samples and DCLR. The results show that the coalescence of the high-molecular-weight substances in coals could be obviously intensified in liquefaction, and high temperatures are found to significantly enhance the cross-link structure of the DCLR. In the meantime, the DCLR derived from samples with different sodium species were observed to show different weight losses in pyrolysis. According to the amount of total sulfur content in residues, the sulfur retention ability of ammonium-acetate-soluble sodium species (AS-Na) is verified to be stronger than that of water-soluble sodium species (WS-Na). Moreover, AS-Na could also facilitate the cross-link reactions more easily than WS-Na, and the DCLR derived from Na-9.0, which was prepared by ion exchanging the demineralized sample with sodium acetate solution, contains ca. six more aromatic carbons than that from Im-Na obtained by immersing the demineralized sample with sodium chloride solution.

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“…In order to examine the transformations and roles of sodium species with different occurrence modes in direct ZDC liquefaction, raw coal was initially demineralized with 2 mol/L hydrochloric acid in accordance with our previous work. 35 In each experiment, 400 mL of hydrochloric acid was added to 50 g of raw coal and the mixtures were magnetically stirred at 60 °C for 4 h in a beaker. After that, the slurries were cooled to room temperature, followed by filtering and washing with adequate distilled water.…”

Section: Methodsmentioning

confidence: 99%

Transformations and Roles of Sodium Species with Different Occurrence Modes in Direct Liquefaction of Zhundong Coal from Xinjiang, Northwestern China

Xiao

Bai

et al. 2015

Energy Fuels

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In this work, to better understand the thermal behavior of sodium species in the utilization of Zhundong coal (ZDC) from Xinjiang, northwestern China, the transformations of sodium species in direct liquefaction of ZDC were investigated in a bench-scale autoclave. The effects of sodium species with different occurrence modes on the product distributions in ZDC liquefaction were also examined. The results show that the transformations of sodium species strongly depend on the occurrence modes and the liquefaction temperatures. Below 370°C, ammonium acetate-soluble sodium species (AS-Na) could be partly transformed into water-soluble ones (WS-Na). However, when the temperatures further increased, the reactions between AS-Na and silicates to form hydrochloric acid-insoluble sodium species (HIS-Na) predominated and the residue formed in this process was firmly adhered to the bottom of the autoclave. The retention ratios of sodium species over all temperature ranges are significantly higher (>89 wt %) than those in ZDC pyrolysis, which implies a significant enrichment of sodium species in liquefaction residues. Besides, both WS-Na and AS-Na are verified to be the detrimental species in ZDC liquefaction; especially, the oil generation could be more severely inhibited by AS-Na, and this negative effect could be mitigated by demineralization with hydrochloric acid.

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Influences of exchangeable metallic species on solvent extraction of Xiaolongtan lignite and characterization of the separated portions

Cited by 12 publications

References 35 publications

Structural changes of Zhundong coal matrix induced by thermal treatment and its effects on oil yield in direct coal liquefaction

Structural changes of Zhundong coal matrix induced by thermal treatment and its effects on oil yield in direct coal liquefaction

Insight into the Effects of Sodium Species with Different Occurrence Modes on the Structural Features of Residues Derived from Direct Liquefaction of Zhundong Coal by Multiple Techniques

Transformations and Roles of Sodium Species with Different Occurrence Modes in Direct Liquefaction of Zhundong Coal from Xinjiang, Northwestern China

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