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

Facile Fabrication of Ultralow Density and Ultrahigh Solar Absorption Monolithic Phenolic Carbon Aerogel from Lignite for Solar Vapor Generation

Solar vapor generation has been recognized as one of the most sustainable desalination methods due to its high energy efficiency and zero carbon emissions. However, it is often limited by poor mechanical properties, a complex preparation process, and/or the high density of photothermal materials. Here, we present a simple and effective method for preparing high-strength lignite-based phenolic carbon aerogels (LPCAs) for seawater desalination. LPCAs were prepared using an ethanol-soluble portion (ESP) from lignite as the raw material and melamine as the skeleton by polymerization/gelation, vacuum-drying, and carbonization, avoiding the energy-intensive freeze-drying step. Due to the abundant alkyl side chains and condensed aromatics in the ESP, LPCA has an ultralow density (42 mg·cm–3) and ultrahigh light absorbance (97.3%) without the need of additional expensive photothermal materials. Moreover, LPCA can regulate the intermediate water content and absorb energy from the environment. Based on these advantages, the evaporation rate of the LPCA evaporator can reach up to 2.40 kg·m–2·h–1 under 1 sun with an energy efficiency of 93.5%. Additionally, LPCAs with high strength (4.48 MPa under 90% strain), self-floating, good salt resistance, and applicability under harsh conditions facilitate practical application for producing clean water

Facile Fabrication of Ultralow Density and Ultrahigh Solar Absorption Monolithic Phenolic Carbon Aerogel from Lignite for Solar Vapor Generation

Solar vapor generation has been recognized as one of the most sustainable desalination methods due to its high energy efficiency and zero carbon emissions. However, it is often limited by poor mechanical properties, a complex preparation process, and/or the high density of photothermal materials. Here, we present a simple and effective method for preparing high-strength lignite-based phenolic carbon aerogels (LPCAs) for seawater desalination. LPCAs were prepared using an ethanol-soluble portion (ESP) from lignite as the raw material and melamine as the skeleton by polymerization/gelation, vacuum-drying, and carbonization, avoiding the energy-intensive freeze-drying step. Due to the abundant alkyl side chains and condensed aromatics in the ESP, LPCA has an ultralow density (42 mg·cm–3) and ultrahigh light absorbance (97.3%) without the need of additional expensive photothermal materials. Moreover, LPCA can regulate the intermediate water content and absorb energy from the environment. Based on these advantages, the evaporation rate of the LPCA evaporator can reach up to 2.40 kg·m–2·h–1 under 1 sun with an energy efficiency of 93.5%. Additionally, LPCAs with high strength (4.48 MPa under 90% strain), self-floating, good salt resistance, and applicability under harsh conditions facilitate practical application for producing clean water

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

Insight into the Chemical Complexity of Soluble Portions from Cornstalk Methanolysis

Cornstalk was subjected to methanolysis in the presence of NaOH at 220–320 °C to afford soluble portions (SPs) 1–5 (SP₁–SP₅) and an inextractable portion (IEP). The maximum total yield (ca. 51%) of SPs was acquired at 300 °C with the same mass of NaOH and cornstalk. Under the same conditions, SP₁ has the highest yield, followed by SP₅ and SP₂. The relatively volatile and less polar species in the resulting SPs and IEP were identified with a gas chromatograph/mass spectrometer (GC/MS). The polar species in SP₁, SP₂, and SP₅ were further analyzed with a negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS). The analysis with GC/MS shows that phenolic compounds and alcohols are the dominant group components in SP₁ and SP₂, respectively, while the predominant compounds in esterified SP₃–SP₅ and IEP are esters. According to analysis with FTICRMS, thousands of compounds were detected in SP₁, SP₂, and SP₅. Most of the compounds are <i>O</i>_<i>n</i> (<i>n</i> = 1–10) class species with double bond equivalent (DBE) values of 1–14 and carbon atom numbers of 5–35. The most abundant class species in SP₁, SP₂, and SP₅ are <i>O</i>₃, <i>O</i>₃, and <i>O</i>₈, respectively. SP₁ and SP₂ are rich in <i>O</i>₂–<i>O</i>₄ class species with DBE values of 5–8, which may be attributed to lignin-derived compounds. Different from SP₁ and SP₂, SP₅ has relatively high contents of <i>O</i>₅–<i>O</i>₁₀ class species, corresponding to various acidic species. In addition, <i>N</i>₁<i>O</i>_<i>n</i> (<i>n</i> = 0–8) class species with DBE values of 3–14 were also identified, which should contain a pyrrole ring as the parent structure

Structural Features of Extraction Residues from Supercritical Methanolysis of Two Chinese Lignites

The methanol-insoluble portions from supercritical methanolysis of Shengli lignite (SL) and Huolinguole lignite (HL) were extracted with an isometric carbon disulfide/acetone mixed solvent under ultrasonic irradiation to afford extracts and extraction residues (ERs). The ERs were subjected to ruthenium-ion-catalyzed oxidation, and soluble portions were separated from the reaction mixture and esterified. The resulting products were analyzed with a gas chromatography/mass spectrometer and atmospheric solids analysis probe/time-of-flight mass spectrometer to reveal structural features of heavy species in the two lignites. The results show that the ER from SL is richer in highly condensed aromatic species than that from HL, while both ERs have the same carbon number range (C₉–C₂₄) of alkyl groups with the highest content at C₁₅ on aromatic rings and the same distribution of alkylene bridges (C₂–C₂₀) connecting aromatic rings with a higher abundance of shorter linkages than that of longer linkages