Search

Methanolysis of the three biomass components was conducted to afford soluble portions (SPs) and residues. Cellulose has the highest SP yield, followed by hemicellulose and lignin. The relatively volatile or less polar species in the SPs were analyzed with a gas chromatograph/mass spectrometer (GC/MS) and the polar species were identified with a negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS). According to analysis with GC/MS, sugars, esters, and phenols are the predominant compounds in cellulose- and hemicellulose-, and lignin-derived SPs, respectively. The analysis with FTICRMS shows that the molecular masses in the SPs range from 100 to 500 u and those in cellulose-/hemicellulose-derived SPs dominate from 250 to 300 u but in lignin-derived SP concentrates from 300 to 350 u. The identified compounds were assigned to On class species with double bond equivalent (DBE) values of 1–14 and carbon atom numbers of 5–35. The most abundant class species in cellulose-, hemicellulose-, and lignin-derived SPs are O5, O5, and O2, respectively. The van Krevelen diagrams of On class species suggest that primary species in lignin-derived SP are mainly located in a relatively narrow region with atomic ratio of O/C 0.0–0.3 and atomic ratio of H/C 1.0–1.3, while those in cellulose- and hemicellulose-derived SPs are principally located in a wider region with atomic ratio of O/C 0.2–0.8 and atomic ratio of H/C 0.8–1.5. The oxygen atom numbers of O4−O10 class species was negatively correlated with the average DBE value, which indicates a cyclic structure or double bond will be generated (opened or saturated) with the removal (addition) of oxygen atoms.

Knowledge about the rate of coal pyrolysis is of great importance because it exerts remarkable effect on its thermal conversions such as combustion, gasification and liquefaction. Different approaches can be used to obtain the kinetics of coal pyrolysis, the simplest are empirical and global kinetics, where Arrhenius expression is used to correlate the mass loss with temperature. This work conducted pyrolysis of a lignite and a bituminite at various heating rates with a thermo-gravimetric analyzer (TGA). Thermogravimetry coupled with mass spectroscopy (TG-MS), solid state 13C Cross Polarization/ Magic Angle Spinning nuclear magnetic resonance (13C CP/MAS NMR) and Raman analyses were also conducted to correlate the structural characteristics and pyrolysis behavior of the coals. Kinetic analysis was performed by using three model-free methods including Distributed Activation Energy model (DAEM), Ozawa-Flynn-Wall (OFW) and Friedman method. Kinetic modeling was also performed based on the DAEM model with multiple Gaussian sub-distributions of activation energy. The results show that DAEM, OFW and Friedman methods are almost equally effective for analyzing activation energy, which gradually increases with the extent of pyrolysis. Pyrolysis of both the coals can be divided into three stages corresponding to the reactions of various covalent bonds. Three-Gaussian distributed activation energy model (DAEM-G3) is applicable to describing pyrolysis of both coals. The well-matched modeling results with the experimental data over the entire temperature range indicate the validity of DAEM-G3 model in studying and understanding the reaction mechanism of coal pyrolysis.

The improvement of organonitrogen compounds (ONCs) in methanol-soluble portions (MSPs) obtained from supercritical methanolysis of raw and pretreated rice straw (RS) with Trichoderma sp. AH was investigated. According to detailed analysis with positive-ion ESI FT-ICR MS and GC/MS, the molecular masses (MMs) of ONCs in MSPs of raw and pretreated RS range from 100 to 500 u and dominate from 300 to 450 u . The relative abundance of ONCs with MMs from 300 to 350 u in MSP of pretreated RS is higher than those in MSP of raw RS. Most of detected ONCs in MSPs of raw and pretreated RS are N 2 O n (n = 1–9) species with double bond equivalent values of 2–25 and carbon atom numbers of 4–35. The most abundant ONCs in MSP of pretreated RS are N 2 O 4 , while those in MSP of raw RS are N 2 O 5 . These results facilitate understanding the effect of pretreatment with Trichoderma sp. AH on the conversion and specificity of ONCs in methanolysis of RS and the application of MSP on production of transportation fuel.

Ethanolysis is an efficient approach for converting lignites into chemicals under mild conditions. However, yield of soluble portion from lignite ethanolysis is limited and product distribution cannot be well regulated. In this paper, a series of catalysts (MMgAlOx, M = Cu, Zn, Co, Ni) were prepared by a coprecipitation method. The catalysts were characterized by X-ray powder diffraction, high resolution transmission electron microscope, N2 physisorption, and CO2- and NH3-temperature-programed desorption. The results show that the catalysts have layered and mesoporous structures with tunable acidity/basicity. Catalytic ethanolysis of Xilinguole lignite was performed and the resulting ethanol-soluble portions (ESPs) were analyzed with a Fourier transform infrared spectrometer, thermogravimetric analyzer, and gas chromatograph/mass spectrometer. The results suggest that except NiMgAlOx, other catalysts significantly increased the yields of the ESPs, especially CuMgAlOx and ZnMgAlOx, which is probably related to the amount of H2 produced from ethanol. Four major platform chemicals, i.e., arenes, phenols, alcohols, and esters, can be produced via the catalytic ethanolysis. The catalysts have high ethanolysis activity and low hydrogenation ability and therefore aromatic rings can be reserved. Distribution of the platform chemicals could be tuned by altering the catalysts. In addition, possible pathways on the catalytic ethanolysis were proposed.

Piliqing subbituminous coal (PSBC) was exhaustively extracted with isometric acetone/carbon disulfide mixed solvent under ultrasonic irradiation to afford extractable portion (EP) and extraction residue (R E ). Then R E was subjected to sequential thermal dissolution (TD) in ethanol at 200, 240, 280, and 320 °C and TD at each temperature was conducted for 2 h. The sequential TD provided soluble portions (SPs) 1–4 (SP 1 –SP 4 ) and residue 4 (R 4 ). EP and the SPs were analyzed with a gas chromatograph/mass spectrometer and Fourier transform infrared (FTIR) spectrometer, while PSBC, R E , and R 4 were characterized with a solid-state 13 C nuclear magnetic resonance (SS 13 C NMR), FTIR, and X-ray photoelectron spectrometer (XPS). In total, ca. 36 wt% of organic matter was released from PSBC by the ultrasonic extraction and sequential TD. EP is rich in normal alkanes and arenes, while dialkoxyalkanes are predominant in SP 1 and esters are the main compounds in SP 2 –SP 4 . No significant difference in the distribution of functional groups was observed in FTIR spectra of PSBC and R E , while the distribution of functional groups in R 4 is significantly different from that in either PSBC or R E . According to analysis with XPS, the content of oxygen-containing species in R 4 is relatively low. PSBC consists of 32.6% aliphatic carbon atoms, 63.0% aromatic carbon atoms, and 4.4% carbonyl carbon atoms, while the content (2.0%) of carbonyl carbon atoms in R 4 is significantly lower than that (4.4%) in PSBC based on analysis with SS 13 C NMR.

Ethanolysis of an ethanolyzed residue (ER) from Zhaotong lignite with NaOH was conducted to afford extracts 1–4 (E 1 –E 4 ). The yields of E 1 –E 4 are 47.1%, 10.6%, 3.0%, and 10.0%, respectively. All the extracts were analyzed with a negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FTICRMS). In addition, carbon skeleton structures in the ER were determined using a solid-state 13 C nuclear magnetic resonance spectrometer. The results suggest that the carbon types in the ER mainly consist of aliphatic (52.3%) and aromatic (42.0%) carbons. C H 3 – and – C H 2 – are the major aliphatic carbons. Each aromatic cluster contains one or two aromatic rings on average. According to analysis with FTICRMS, thousands of compounds were detected in the extracts, mainly being oxygen-containing ( O x , x = 1–8) class species with double bond equivalent (DBE) values of 1–18 and carbon numbers of 7–37. The most abundant class species in E 1 –E 4 are O 2 , O 2 , O 3 , and O 4 , respectively. E 4 contains low relative contents of O 2 – O 3 class species but high relative contents of O 4 – O 6 class species. The identified O x class species are mainly ascribed to fatty acids, areneols, and arenecarboxylic acids. Furthermore, nitrogen-containing multiheteroatomic ( N 1 O x and N 2 O x , x = 1–8) class species with DBE values of 3–17 and carbon numbers of 13–34 were also identified in the extracts.

Organonitrogen and organooxygen compounds (ONCs and OOCs) in the extraction residue (ER) from Buliangou subbituminous coal were characterized with an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FTICRMS). Pyrrolic and hydroxy are the most abundant nitrogen and oxygen moieties on the ER surface according to analysis with an X-ray photoelectron spectrometer. The m / z values of ONCs and OOCs detected by FTICRMS mainly range in 200–450. The main basic ONCs detected are N 1 O x ( x = 0–1) class species with double bond equivalent (DBE) values of 4–20 and carbon numbers (CNs) of 12–32. The core moieties in most of the basic N 1 O x ( x = 0–1) class species are aromatic rings (ARs), including benzene, pyridine, quinoline, and acridine rings. O x ( x = 1–4) class species are the main OOCs in the soluble portions from thermal dissolution of the ER. In acidic O 2 class, the most abundant species with DBE = 1, 2, 9, and 12 and CNs of 13–21 can be observed. The main acidic O 1 class species are alkylarenols with 1–6 ARs, while most of the acidic O 3 class species contain an AR, such as a naphthalene, dihydroanthracene, or anthracene ring, with at least a hydroxy or carboxy group.

Buliangou subbituminous coal (BSBC) was sequentially extracted with carbon disulfide, methanol, and acetone under ultrasonic irradiation to afford extracts 1–3 (E 1 –E 3 ). All the extracts were analyzed with a positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). In total, 11.11% of organic matter in BSBC was extracted with the three solvents. According to analysis with positive-ion ESI FT-ICR MS, the molecular masses of basic nitrogen compounds (BNCs) in E 1 –E 3 range from 200 to 600 u and dominate from 250 to 450 u . The BNCs detected are mainly N 1 O x ( x = 0–2) and N 2 O y ( y = 0 and 1) with 4–25 of double bond equivalent (DBE) values and 12–38 of carbon numbers (CNs). The BNCs in E 2 have lower DBE values (4–16) and CNs (14–28). According to DBE distributions, molecular core structures of most N 1 O x classes should be aromatic rings, including benzene, pyridine, quinoline, and acridine rings. Moreover, core structures of most N 1 O x moieties connected with an amino group or condensed with a pyrrole ring are characteristic structures for N 2 O y classes in E 1 –E 3 . In addition, a small amount of amines (DBE

Bio-oils (BOs) obtained from sweet sorghum stalk (SSS) methanolysis (BO m ) and ethanolysis (BO e ) at 300 °C for 30 min were analyzed with an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FT-ICR MS). In negative-ion mode, the predominant compounds in BO m and BO e are O n ( n = 1–10) class species with double bond equivalent (DBE) values of 1–14 and carbon atom numbers (CANs) of 5–35. The most abundant class species in BO m and BO e are O 4 and O 3 , respectively. According to the distribution of O n class species and the van Krevelen diagram, lignin-derived compounds are the main acidic species in the BOs. In addition, N 1 O n ( n = 0–10) class species with DBE values of 1–14 and CANs of 7–35 were also identified. In positive-ion mode, most of detected compounds in BO m and BO e are N 2 O n ( n = 1–6) class species with DBE values of 1–19 and CANs of 10–40, in which N 2 O 2 –N 2 O 4 class species with DBE = 8–12 and CAN = 19–28 are the most abundant. These results facilitate understanding thermochemical behavior of SSS.

The chemical structures of Zhaotong lignite (ZL) were characterized with multiple direct tools, including solid-state 13C nuclear magnetic resonance (NMR), X-ray photoelectron spectrometer (XPS), Fourier transform infrared (FTIR) spectrometer, and thermogravimetric (TG) analyzer, combined with ZL ethanolysis and subsequent electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FT-ICR MS) analysis of the resulting ethanol-soluble portion (ESP). According to 13C NMR analysis, ZL mainly consists of aliphatic (52.3%) and aromatic (42.2%) carbons. Methylene is the most abundant among the aliphatic carbons. Each aromatic cluster contains 2 rings on average and the number of substituents on each aromatic ring is 3 or 4. XPS analysis suggests that oxygen atoms mainly exist in C O moieties, which is consistent with 13C NMR and FTIR analyses, and pyrrolic nitrogen species are the main nitrogen form in ZL. Based on TG analysis, cleavage of Cal O and Cal Cal bonds should be the major reactions during ZL ethanolysis. A series of neutral nitrogen compounds (NNCs, i.e., pyrrolic nitrogen) in the ESP were detected by negative-ion ESI FT-ICR MS analysis. The identified NNCs are N1Ox (x = 0–5) class species with 3–13 double bond equivalent (DBE) values and 10–31 carbon numbers, in which N1O2 class species are predominant NNCs. According to DBE distributions of NNCs, pyrroles, indoles, and carbazoles account for most of the neutral nitrogen occurrences in ZL. Such multiple characterizations proved to be an effective method for fully understanding the chemical structures of coals, especially lignites.

A deep understanding of coal pyrolysis behaviors is essential for the clean and efficient coal utilization. Detailed structural characterization and kinetic analysis could provide valuable information about coal pyrolysis. This work deals with structural analysis and pyrolysis kinetics of four low-medium rank coals with the distributed activation energy model (DAEM). The carbon structures, pyrolysis characteristic and kinetic parameters were correlated to gain some updated insights into coal pyrolysis. The results show that aliphatic carbons gradually convert into aromatic ones, and the aromatic clusters grow in both size and weight with the rise of coal rank. The side-chains of aromatic clusters are shortened and eliminated thus aromaticity is increased. Characteristic temperatures of pyrolysis are closely related to coal properties and carbon types. Both initial and peak temperatures increase with FC ar and C daf while decrease with VM ar and H / C . Meanwhile, the initial temperature is related to the aliphatic carbon ( f al ) and aliphatic carbon bonded oxygen ( f al o ) due to their low bonding energies, while the peak temperature is linked to the aromatic carbon ( f a ) and aromatic bridgehead carbon ( f a B ) because of their higher bonding energy. DAEM model is reliable for analyzing pyrolysis kinetics of bituminous coals. The range of activation energy gradually narrows down with the increase of coal rank, corresponding to the concentrating distribution of different carbon types. Moreover, DAEM could accurately predict the pyrolysis behavior of bituminous coals at very high heating rates, but the effectiveness of DAEM in modeling and predicting pyrolysis of lignite is less satisfying.

Ethanol-soluble portion (ESP) from Zhaotong lignite ethanolysis at 305 °C was analyzed with a positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). The range of molecular mass distribution is from m/z 100 to 600 with the center around m/z 330. Assignment of molecular formulae reveals that the main nitrogen-containing species with relative content of 86.4% are most probably basic nitrogen compounds (BNCs) ionized during ESI in positive-ion mode. The BNCs are N1Ox (x = 0–5) and N2Oy (y = 0–2) with 0–14 double bond equivalent (DBE) values and 9–39 carbon numbers. According to DBE distributions, pyridines and quinolines should be predominant BNCs in the ESP. In addition, amines (DBE < 4) were also identified in the ESP. The average DBE values are 6–8 for N1Ox class species and 7 and 8 for N2Ox class species, indicating that pyridines (or quinolones) and quinolines with an amino group are characteristic structures for N1Ox and N2Ox classes, respectively. Positive-ion ESI FT-ICR MS proved to be a powerful tool for identifying BNCs in coal-derived liquids.

The products in the water-soluble portion from mild oxidation of Jincheng No. 15 anthracite in aqueous hydrogen peroxide were analyzed with a gas chromatograph/quadrupole time-of-flight-mass spectrometer (GC/QTOF-MS) along with theoretical calculation for the first time. A series of heteroatom(s)-containing components were identified by comparing their mass spectra with NIST11 library data. Moreover, two organosulfur compounds without matched library mass spectra were inferred according to their tandem mass spectra and the formation of their fragmental ions was convincingly explained by energy calculation based on density functional theory. The investigation suggests that GC/QTOF-MS analysis combined with theoretical calculation would be a powerful tool for identifying unknown compounds in complicated mixtures from coals or their derivates.

Wheat straw (WS) was oxidized in a sodium hypochlorite (NaOCl) aqueous solution at 40 °C followed by sequential extraction of the water-soluble fraction (WSF) with petroleum ether, carbon disulfide (CDS), diethyl ether and ethyl acetate (EA). The EA-inextractable solution was acidized and filtrated. The filtration was also sequentially extracted with the same series of solvents. In total, 38 organonitrogen compounds (ONCs) were identified by GC/MS analysis from the extracts. The ONCs can be classified into amides, sulfonamides, amines, an amino acid, nitriles, an isocyanatoethane, chloro(nitro)methanes, an oxime, N-heterocyclic compounds (NHCCs, most of them are pyrrolidones) and a benzohydrazide, indicating the diversity of ONCs in WS. NHCCs, amides and nitriles are the most abundant among the ONCs, implying that these types of species might be main existing forms of nitrogen in the oxidized WS and even in WS itself to some extent. Most of the ONCs, especially amides and pyrrolidones, were enriched in the CDS-extractable fraction from the WSF because of the strong π–π interaction between C S bond in CDS and C O bonds in the ONCs. This investigation provides an effective approach for understanding the modes of ONC occurrences in WS.