Characterization of coal structure by CP/MAS carbon-13 NMR spectrometry

Yoshida, Tadashi; Maekawa, Yosuke

doi:10.1016/0378-3820(87)90060-9

Cited by 33 publications

(15 citation statements)

References 20 publications

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“…Prior to deconvolution, the 13 C-NMR spectrum was adjusted using the Nuts Software. Then, the PFM module of the Origin Software was used to subtract the baseline, add peaks manually according to the spectrum shape and assignment of NMR structure The chemical shifts and assignment for the 13 C-NMR spectra of coal and its precursor have been summarized in previous studies [57][58][59][60][79][80][81][82][83][84][85], and the reported chemical shifts are mostly identical with only minor differences. The 13 C-NMR structure parameters and assignment used in the present study are given in Table 2 [84,[86][87][88].…”

Section: Samples and Analytical Methodsmentioning

confidence: 99%

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Wei

Tang

2018

Minerals

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Abstract:The structure evolution characteristics of high-organic-sulfur (HOS) coals with a wide range of ranks from typical Chinese areas were investigated using 13 C-CP/MAS NMR. The results indicate that the structure parameters that are relevant to coal rank include CH 3 carbon (f al *), quaternary carbon, CH/CH 2 carbon + quaternary carbon (f al H ), aliphatic carbon (f al C ), protonated aromatic carbon (f a H ), protonated aromatic carbon + aromatic bridgehead carbon (f a H+B ), aromaticity (f a CP ), and aromatic carbon (f ar C ). The coal structure changed dramatically in the first two coalification jumps, especially the first one. A large number of aromatic structures condensed, and aliphatic structures rapidly developed at the initial stage of bituminous coal accompanied by remarkable decarboxylation. Compared to ordinary coals, the structure evolution characteristics of HOS coals manifest in three ways: First, the aromatic CH 3 carbon, alkylated aromatic carbon (f a S ), aromatic bridgehead carbon (f a B ), and phenolic ether (f a P ) are barely relevant to rank, and abundant organic sulfur has an impact on the normal evolution process of coal. Second, the average aromatic cluster sizes of some super-high-organic-sulfur (SHOS) coals are not large, and the extensive development of cross bonds and/or bridged bonds form closer connections among the aromatic fringes. Moreover, sulfur-containing functional groups are probably significant components in these linkages. Third, a considerable portion of "oxygen-containing functional groups" in SHOS coals determined by 13 C-NMR are actually sulfur-containing groups, which results in the anomaly that the oxygen-containing structures increase with coal rank.

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Section: Samples and Analytical Methodsmentioning

confidence: 99%

13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Wei

Tang

2018

Minerals

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“…The chemical shifts for different CTs in the ER and their assignments were referred to previous literature. 47,48 As demonstrated in Figure 1, SS 13 C NMR spectrum of the ER can be clearly divided into aliphatic carbon (0−90 ppm), aromatic carbon (90−170 ppm), and carbonyl carbon (170−220 ppm) bands. Using curve-fitting software, the spectrum was further separated into 15 peaks, which represent different CTs.…”

Section: Resultsmentioning

confidence: 99%

Characterization of Oxygen-Containing Species in Methanolysis Products of the Extraction Residue from Xianfeng Lignite with Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

et al. 2014

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Methanolysis of an extraction residue (ER) from Xianfeng lignite was carried out to obtain extracts 1−4 (E 1 −E 4 ). The molecular compositions (MCs) of oxygen-containing species (OCSs) in E 1 −E 4 were characterized using negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). In addition, solid-state 13 C nuclear magnetic resonance and X-ray photoelectron spectrometry were used to analyze the carbon types and oxygen functional groups (OFGs) in the ER. The results show that the carbon skeleton structures in the ER are dominated by aliphatic (50.2%) and aromatic (44.9%) carbons. Methylene and methoxy carbons are the most abundant among the aliphatic carbons. Each aromatic cluster contains three rings on average with two substituent groups on each ring. The OFGs in the ER include hydroxy, ether, carbonyl, and carboxyl groups, among which the hydroxy group is the most abundant. The ESI FT-ICR MS analysis shows that the molecular mass distributions of E 1 −E 4 range from 150 to 500 u. The O n (n = 1−6) class species are the predominant OCSs in E 1 −E 4 , with 0−14 double bond equivalent (DBE) values and 9−34 carbon numbers (CNs). The most abundant O n class species in E 1 −E 4 are O 2 , O 2 , O 2 −O 3 , and O 3 , respectively. The OCSs in E 4 contain low abundances of O 1 and O 2 class species but relatively high abundances of O 4 −O 6 class species. In addition, the O n class species in E 4 have narrower ranges of DBE values and CNs than those in E 1 −E 3 . A series of acidic species with different DBE values and CNs are assigned to alkanoic acids, alkanedioic acids, alkanetricarboxylic acids, alkylarenols, alkylarenediols, alkylarenetriols, and alkylarenoic acids. With high resolving power and mass accuracy, ESI FT-ICR MS is an effective technique for characterizing MC of the soluble portion from lignites, which will facilitate producing important chemicals from lignites.

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“…As low rank coals contain relatively high levels of oxygen in oxygen functional groups attached to the carbon skeletal structure, it is desirable to obtain structural information of samples free from the effect of these polar groups, especially when comparing samples with different levels of oxygen content. A method to calculate the aromaticity as the fraction of aromatic carbon in total carbon minus oxygen bonded carbon, similar to that used by Yoshida and Maekawa [24], is adopted. The modified aromaticity f ar 0 is calculated using Eq.…”

Section: Ss 13 C Nmrmentioning

confidence: 99%

“…The fact that the spectra of all the residues (not shown) are almost identical to those of the corresponding untreated coals, showing no discrete CAN and methyl CAH peaks, is evidence that the effect of any residual DIMCARB is minimal. The non-exclusive assignments to some of the intense resonances in the spectra of the coals and their solubilisation products, mostly based on studies of brown coals [22][23][24][25][26] and lignin [27], are summarised in Table 4.…”

Section: Ss 13 C Nmrmentioning

confidence: 99%