The chemical looping pyrolysis (CLP) of cellulose over NiFe2O4 was probed to elucidate the kinetic and thermodynamic mechanisms and compensation effects. The incorporation of oxygen carrier NiFe2O4 induced additional decomposition peaks, indicative of altered reaction pathways. Thermogravimetric/Fourier transform infrared spectroscopy (TG-FTIR) and thermogravimetry/gas chromatography-mass spectrometry (TG-GC/MS) analyses revealed a shift in major products from D-glucose in cellulose to furan derivatives and acetic acid in the cellulose/NiFe2O4 blend, demonstrating catalytic promotion of secondary conversion pathways. Model-free kinetic analyses showed a decrease in the apparent activation energies from 147.90 kJ mol(-)(1) to 93.99 kJ mol(-)(1) . Master-plots analysis indicated the dominant R3 reaction mechanism, with deviations toward the A2 model at alpha> 0.60. Thermodynamic parameters revealed a decrease in the enthalpy change from 142.66 kJ mol(-)(1) to 88.50 kJ mol(-)(1) and negative entropy change (-0.088 kJ mol(-)(1)K(-)(1)) for the blend, while Gibbs free energy change remained nearly constant (similar to 143.5 kJ mol(-)(1)). Kinetic and enthalpy-entropy compensation effects were confirmed, with isokinetic temperatures of 596.50 K and 880.07 K for cellulose and the blend, and corresponding free energy of compensation of 143.81 and 140.05 kJ mol(-)(1) . These findings demonstrated that NiFe2O4 lowered energy barriers, reorganized transition states, and enhanced cellulose reactivity, providing a quantitative basis for optimizing CLP processes.
To address the issues of low thermal efficiency, poor product quality, and low value associated with conventional pyrolysis of waste tires, this study comparatively investigated the mechanisms influencing product characteristics under three pyrolysis methods: conventional electric heating (EP), low-power microwave (MP-L), and high-power microwave (MP-H). Using multiple characterization techniques including thermogravimetry, chromatography, Raman spectroscopy, X-ray photoelectron spectroscopy, and nitrogen adsorption, the composition, structure, and properties of the gaseous, liquid, and solid pyrolysis products were systematically analyzed. Results indicate that microwave heating (especially MP-H) significantly promotes the formation of light products (increased gas yield with higher H2, CH4, and light oil content); while EP yields gas with higher calorific value due to its greater C2-C6 hydrocarbon content. MP-H promotes carbon black ordering and surface purification at low temperatures (400 degrees C) but causes pore sintering and decreased specific surface area at high temperatures (800 degrees C). The carbon black obtained from EP exhibits higher porosity and surface functional group content. This study elucidates the regulatory mechanism of energy input rate on pyrolysis pathways and product characteristics, providing crucial theoretical foundations and practical references for achieving high-value and directed pyrolytic conversion of waste tires.
Efficient extraction of proto-lignin without compromising the carbohydrate value by a mild biorefinery has encountered challenges. Herein, an alkaline deep eutectic solvent (Tetramethylammonium hydroxide/urea peroxide, TMAH/UP) was tailored to fractionate lignocellulose into proto-lignin and carbohydrate-rich substrate for downstream value-added conversion. The fractionation efficiency of TMAH/UP with diverse concentrations (5 %-40 %) at room temperature was investigated. Higher solvent concentrations increased lignin extraction efficiency but also led to greater carbohydrate loss. High monosaccharide conversion (100 % glucose yield and >50 % xylose yield) was achieved from the carbohydrate-rich substrates with high accessibility. The extracted lignin was equipped with abundant beta-O-4 bond content and high molecular weight, which exhibited excellent potential for aromatic monomer conversion. The proto-lignin extraction mechanism of targeted cleavage of lignin-carbohydrate esters was verified by the model compound studies. A life cycle assessment (LCA) revealed that the room-temperature fractionation substantially lowered CO2 emissions and energy consumption relative to the prior scalable biorefinery. In this work, the proposed TMAH/UP process realized a breakthrough toward proto-lignin extraction and carbohydrate value upgrading, highlighting the sustainable biorefinery future for biomass value maximization.
Polyvinyl chloride (PVC) is one of the most widely used halogenated polymers, but its chlorine content and inherent chemical stability pose major problems for re-use and disposal. We assessed the ability of purified lignin peroxidase (LiP) from the white-rot fungus Phanerochaete chrysosporium to degrade additive‑free PVC and three types of post‑consumer PVC waste. The enzyme production process was optimized by response surface methodology (RSM). Enzymatic degradation was monitored by mass loss, gel permeation chromatography (GPC), chloride ion release and various surface and chemical analyses. The work also critically examined the substrate preparation, pointing out the practical issues with energy‑consuming cryogenic milling. Characterization of the real‑world waste streams was conducted by thermogravimetric analysis and density functional theory (DFT) was used to quantify the initial hydrogen‑abstraction reaction. The results have been compared with recent progress in biological degradation of PVC. LiP yield was optimized using the RSM to 0.482 ± 0.02 U·mL⁻¹, constrained by the low productivity of shake‑flask cultivation. Following 120 h of incubation, the additive‑free PVC exhibited 4.7 ± 0.3 % mass loss, a 12 % decrease in number‑average molecular weight, and 18.5 ± 1.2 µmol Cl⁻ per mg polymer. Chlorine release was significantly different among commercial samples (3.5-16.8 µmol Cl⁻·mg⁻1 PVC). The activity correlated closely with the product's formulation: flexible film was the most active; materials containing high inorganic filler levels (pipe and cable sheathing) were significantly inhibited. Surface microscopy and spectroscopy revealed material degradation, Cl⁻ depletion, and the presence of oxidized and unsaturated functional groups. The initiation - hydrogen‑atom abstraction - was thermodynamically supported (ΔG = -18.3 kJ·mol⁻¹). Overall, fungal LiP is capable of oxidative dechlorination and partial depolymerization of PVC, but it is strongly influenced by additive chemistry; depolymerization efficiency is low only in terms of polymer alone (versus some bacterial systems), and feedstock preparation poses some non‑negligible challenges.
Rechargeable magnesium-sulfur (Mg & horbar;S) batteries are considered promising next-generation energy storage solutions because of their high volumetric energy density. However, they often suffer from severe performance degradation due to the well-known polysulfide shuttle effect and sluggish reaction kinetics. Defective materials are widely employed in metal-sulfur battery systems due to their unique adsorptive and catalytic properties, which effectively address the challenges of polysulfide shuttle and sluggish conversion kinetics during charge-discharge processes. Nevertheless, studies systematically correlating defect concentration with the adsorptive-catalytic properties of electrodes remain scarce. In this study, MoxV1-xSe2 (x = 0-0.1) with tunable selenium-vacancy concentrations is employed as a model system to modulate its electronic structure and enhance catalytic performance. A quantitative correlation is further established between selenium-vacancy concentration and adsorption-catalytic properties to regulate sulfur redox kinetics. Experimental and theoretical findings indicate that a higher density of selenium vacancies effectively provides additional active sites and promotes electron accumulation, leading to reduced energy barriers for MgS nucleation/decomposition as well as faster kinetics in polysulfide conversion reactions. Thus, the Mo0.075V0.925Se2 with abundant selenium vacancies concentrations exhibits exceptional performance as a sulfur host, delivering the highest reversible capacity (1127 mAh g-1) and remarkable cycling stability (200 cycles with similar to 99.7% capacity retention). This study contributes to advancing the practical implementation of defect engineering with quantitative control for application in Mg & horbar;S batteries.
