Extraction of Organonitrogen Compounds from Five Chinese Coals with Methanol

Extraction of Organonitrogen Compounds from Five Chinese Coals with Methano

Characterization of the Oxygenated Chemicals Produced from Supercritical Methanolysis of Modified Lignites

Lignites are promising as feedstocks for producing value-added oxygenated chemicals (OCs) due to their high contents of oxygen-containing organic species. Two modified lignites were produced from Xiaolongtan lignite and Shengli lignite via sequential ultrasonic extraction and subsequent supercritical methanolysis to produce OCs. Solid-state ¹³C nuclear magnetic resonance analysis reveals the differences in carbon skeleton structures and oxygen-functional groups between the two modified lignites. The molecular compositions of OCs from the methanolysis were characterized with Fourier transform infrared spectrometer (FTIRS), gas chromatograph/mass spectrometer (GC/MS), and negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FTICRMS). Six types of hydrogen bonds and distribution of >CO groups in the OCs were analyzed with FTIRS. Alkylphenols with C₁−C₆ in alkyl group(s) dominate in the GC/MS-detectable organic species and methyl is the major alkyl group. The analysis with high-resolution negative-ion ESI FTICRMS reveals higher-molecular, less volatile, and polar OCs, which are assigned to <i>O</i>₁–<i>O</i>₇ class species, detection of which is difficult with GC/MS. Among the <i>O</i>₁–<i>O</i>₇ class species, <i>O</i>₁–<i>O</i>₃ classes are predominant with double bond equivalent values of 1–17 and carbon numbers of 10–38. They could be acidic OCs, such as arenols, arenediols, alkoxyarenols, and/or arenecarboxylic acids with 1–5 aromatic rings and different alkyl groups, as well as some aliphatic acids. The combination of various advanced analytical techniques should be an ideal approach for characterizing valuable OCs in complex coal-derived liquids

Effect of Ethanolysis on the Structure and Pyrolytic Reactivity of Zhaotong Lignite

Lignite ethanolysis is one of the efficient conversion processes. In our previous study, Zhaotong lignite (ZL) from Southwest China was subjected to ethanolysis to afford an ethanol-soluble portion and ethanolyzed residue (ER). The structural features of ZL and ER were investigated by ruthenium-ion-catalyzed oxidation (RICO) and Fourier transform infrared spectrometry. The pyrolytic reactivities of ZL and ER were examined with a thermogravimetric analyzer and Curie-point pyrolyzer–gas chromatograph/mass spectrometer. The results show that both ZL and ER are rich in −CH₂CH₂– and −CH₂CH₂CH₂– bridged linkages connecting aromatic rings. In comparison to the RICO of ZL, the RICO of ER produced much less long-chain alkanoic and alkanedioic acids, suggesting that long alkylene bridges and alkyl side chains in ZL were largely cleaved via ethanolysis. Interestingly, ZL has a higher condensation degree than ER, which was confirmed by RICO and solid-state ¹³C nuclear magnetic resonance analysis. The result was explained by ethanolysis simulation of lignite-related model compounds using density functional theory. Thermogravimetric analysis of ZL and ER exhibits their different pyrolytic reactivities. According to analysis with a Curie-point pyrolyzer–gas chromatograph/mass spectrometer, significant differences in the distributions of the volatile species from the pyrolyses of ZL and ER were observed. Guaiacols and carbazoles are the most abundant group components from the pyrolyses of ZL and ER, respectively. ZL pyrolysis released much more alkanes and phenolic compounds than ER pyrolysis. The cleavage of C_ar–O bonds significantly proceeded during ZL ethanolysis

Nitrogen Evolution during Fast Pyrolysis of Sewage Sludge under Inert and Reductive Atmospheres

The influence of atmospheres on the product distribution and behaviors of nitrogen evolution during fast pyrolysis of sewage sludge (SS) was investigated in a drop-tube quartz reactor. The results indicated that H₂ improved the formation of gas products and gave a relatively low tar yield in comparison to an inert atmosphere. The char N yield obtained under a H₂ atmosphere is lower than that under an Ar atmosphere. Above 500 °C, H₂ further promoted the conversion of nitrogenous compounds to NH₃. The HCN yield was low under all conditions. The decomposition of nitrogenous substances in SS produced more amine N, nitrile N, and heterocyclic N under a H₂ atmosphere. The synergistic effect of a reductive atmosphere and high temperature promoted the thermal decomposition of more difficult-to-cleave N-containing heterocycles, such as piperidines, pyrroles, and pyridines. This study provides a better and deep understanding of the nitrogen transformations during fast pyrolysis of SS under a reductive atmosphere, which would benefit the environmental protection and sustainable clean use of SS

Characterization of Biomarkers and Structural Features of Condensed Aromatics in Xianfeng Lignite

Xianfeng lignite (XL) was sequentially extracted under ultrasonication at room temperature with petroleum ether, carbon disulfide (CDS), methanol, acetone, and isometric CDS/acetone mixed solvent to afford extracts 1–5, respectively. The mixed solvent-inextractable portion was sequentially extracted with cyclohexane, benzene, 1-methylnaphthalene, methanol, and ethanol at 320 °C to afford extracts 6–10, respectively. The extracts were analyzed with a gas chromatography/mass spectrometer (GC/MS) to characterize biomarkers in XL. The biomarkers were significantly enriched in extracts 1 and 6. They can be classified into a series of <i>n</i>-alkanes, isoprenoid alkanes, terpenoids, <i>n</i>-alkenes, methyl alkanones, <i>n</i>-alkylbenzenes, <i>n</i>-alkyltoluenes, and <i>n</i>-alkyl-<i>p</i>-xylenes. The biomarker distributions provided important information on the main origin of organic matter in XL. Related mechanisms for the formation of biomarkers during coalification were discussed. The residue from sequential thermal extraction was subjected to ruthenium-ion-catalyzed oxidation along with subsequent product analyses with GC/MS and direct analysis in a real-time ionization source coupled to a time-of-flight mass spectrometer (DARTIS/TOFMS) to understand its structural features. The results show that the residue is rich in condensed aromatics (CAs) and methyl is the dominant alkyl side chain on aromatic rings. The aromatic rings in the residue are mainly connected by −(CH₂)₃– and −CHCH₃(CH₂)₂–. DARTIS/TOFMS analysis suggests that CAs with alkyl-substituted biphenyl and alkyl-substituted phenylbiphenyl skeletons also exist in the residue. This investigation provides an effective approach for understanding biomarkers and the structural features of the macromolecular network in XL

Poplar Liquefaction in Water/Methanol Cosolvents

Poplar liquefaction (PL) in methanol, water, or water/methanol cosolvents (WMCSs) was investigated at 240–320 °C for 0–90 min. The results show that the yields of bio-oils (BOs) obtained from PL in WMCSs are higher than those in either methanol or water, indicating that methanol has a synergic effect with water on PL. The maximum BO yield of 44.2% was obtained at 270 °C for 15 min in a WMCS containing 70 vol % water. The BOs were analyzed with a gas chromatograph/mass spectrometer (GC/MS) and Fourier transform infrared (FTIR) spectrometer. Poplar and its residues were analyzed with the FTIR spectrometer and a scanning electron microscope (SEM). The fiber structure of poplar was significantly destroyed during PL in WMCS based on the SEM observation. According to GC/MS analysis, the BOs mainly consist of hydrocarbons, phenols, furans, other ethers, aldehydes, ketones, carboxylic acids, esters, and nitrogen-containing organic compounds. Among of them, phenols, ketones, and esters are the main group components. To investigate the liquefaction mechanism, the three major components in biomass, i.e., cellulose, hemicellulose, and lignin, were subjected to degradation in the same solvents. The results suggest that WMCS exhibits better synergic effects for cellulose and hemicellulose than for lignin. Further investigations are needed for a detailed mechanism on synergic effects

Isolation and Identification of Two Novel Condensed Aromatic Lactones from Zhundong Subbituminous Coal

Zhundong subbituminous coal was extracted with isometric carbon disulfide (CDS) and acetone mixed solvent (IMCDSAMS) to obtain the extract (E_M). E_M was fractionated with petroleum ether (PE), CDS, methanol, acetone, IMCDSAMS, and tetrahydrofuran to obtain the sub-extracts 1–6 (E_S1–E_S6), respectively. E_S2 was sequentially eluted with PE and 30, 50, and 70% CDS/PE mixed solvents through a silica-gel-packed column to obtain eluted fractions 1–4 (EF₁–EF₄). A series of condensed aromatic lactones (CALs) were detected in EF₄. Among them, 5<i>H</i>-phenanthro­[1,10,9-<i>cde</i>]­chromen-5-one and 4<i>H</i>-benzo­[5,10]­anthra­[1,9,8-<i>cdef</i>]­chromen-4-one were further isolated as nearly pure compounds by gelatin column chromatography and identified by gas chromatography/mass spectrometry, atmospheric solid analysis probe/time-of-flight mass spectrometry, Fourier transform infrared spectrometry, ¹H nuclear magnetic resonance spectrometry, and ¹H–¹H correlation spectrometry. Main fragmental ions in the mass spectrum of each CAL are formed by successive losses of <i>m</i>/<i>z</i> 28 (CO) and 29 (−CHO) from the molecular ion. An effective way to isolate CALs from low-rank coals was provided in this paper

Enhancement of Aromatic Products from Catalytic Fast Pyrolysis of Lignite over Hierarchical HZSM‑5 by Piperidine-Assisted Desilication

HZSM-5 was post-treated by piperidine-assisted desilication (PAD) and metallic Co and/or Zr modification to introduce the meso-/microporous system and metal active sites to enhance the activity for catalytic fast pyrolysis (CFP) of lignite for aromatic products. CFP was conducted over parent and hierarchical HZSM-5 in a drop tube reactor at 600 °C and a gas residence time of 1.5 s. The results showed that assisted desilication with piperidine (PI) concentration of 0.3 mol/L (AT_0.2–PI_0.3), retained the morphology of HZSM-5, and avoided severe alkaline corrosion. This was due to the shield of the zeolite crystals from extensive dissolving of NaOH by organic amines. It not only decreased the deactivation rate of the catalyst, but also enhanced the mass transfer in the catalyst. The selectivity of light aromatics (LAs) such as benzene, toluene, ethylbenzene, xylene, and naphthalene remarkably increased to 24.9% over AT_0.2–PI_0.3 in comparison to the HZSM-5. In addition, introducing bimetallic Zr–Co facilitated the hydrogen transfer of pyrolysis fragments at the metal sites and sped up the cracking reaction and deoxygenation step of the cascade reactions. 5Zr/Co–AT_0.2–PI_0.3 with Zr loading of 5% exhibited an excellent activity for upgrading of pyrolysis vapors, and its LA selectivity further increased to 30.5%. Meanwhile, the organic oxygen species and macromolecular compound (C₁₄⁺ and C₁₈⁺) contents were decreased gradually. This work provides a potential approach for directional production of LAs from lignite

Structural Characterization of Typical Organic Species in Jincheng No. 15 Anthracite

The structures of typical organic species in Jincheng No. 15 anthracite (J15A) were characterized by solid-state ¹³C nuclear magnetic resonance, X-ray photoelectron spectrometry, X-ray diffraction, and Fourier transform infrared spectrometry in combination with gas chromatography/mass spectrometry and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry analyses of the resulting soluble organic species from ruthenium-ion-catalyzed oxidation (RICO) of J15A. The results show that the typical organic species in J15A are condensed aromatics, along with small amounts of methyl group as the dominant side chain on the condensed aromatic rings (CARs) and methylene linkage connecting the CARs. Every aromatic cluster contains five rings on average, and the substituted degree of each aromatic ring is very low. In addition, J15A is rich in <i>peri</i>-condensed aromatics but poor in <i>cata</i>-condensed aromatics and polyaryls. The oxygen functional groups in J15A include C–O and >CO groups. Pyrrolic nitrogen species and arylthiophenes are the main organic nitrogen and sulfur species in J15A, respectively

Selective Hydrogen Transfer to Anthracene and Its Derivatives over an Activated Carbon

Hydrogenation reactions of three polycyclic arenes (PCAs), that is, anthracene, 9-phenylanthracene (PA), and 9,10-diphenylanthracene (DPA) were carried out under an initial hydrogen pressure of 5 MPa at 300 °C. An activated carbon (AC, a metal-free catalyst), was employed to catalyze the PCA hydroconversions. The results show that the AC can split gaseous hydrogen into atomic form and catalyze monatomic hydrogen transfer to aromatic rings. Interestingly, the AC selectively catalyzed the hydrogenation of the anthracene ring, and prevented the benzene ring from hydrogenation and the C−C linkage from cleavage. The reactivity of the PCAs toward hydrogenation over the AC decreased in the order of anthracene > PA > DPA. The hydrogen-accepting ability and steric hindrance effect are demonstrated to be responsible for the difference in reactivity