Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Oxidative Catalytic Fractionation of Lignocellulose Enhanced by Copper-Manganese-Doped CeO<sub>2</sub>
No full textOxidative catalytic fractionation (OCF) represents an efficient approach to valorize lignocellulose for coproduction of monophenols and cellulose. To achieve an adequate monophenol yield, lignin oxidation, typically, requires high O2 pressure and an excess of Cu catalysts (the Cu dosage is approximately 3-5 mol equiv relative to the aromatic units in lignin). However, these conditions are relatively harsh for cellulose, resulting in severe decomposition to aliphatic acids. To address the trade-off between the monophenol yield and cellulose production, we develop an enhanced OCF using a CuMnCeO2 solid solution as the catalyst. Under relatively mild conditions (specifically, 0.1 MPa O2), 28.7 wt % monophenols were released from birch, using catalytic amounts of Cu (the Cu dosage was about 0.03 mol equiv relative to the aromatic units in lignin). Meanwhile, up to 83.9% of cellulose was collected as a solid pulp. The synergistic effect between doped metals (Cu and Mn) and oxygen vacancies was found to be crucial for enhanced lignin oxidation under mild conditions with minimized cellulose loss. The abundant surface oxygen vacancies facilitated oxygen activation by well-dispersed Cu and Mn species, while the strong interaction between these metals enhanced the catalyst's reducibility. Key intermediates such as beta-vinyl aryl ethers and byproduct glycolic acid were identified by model experiments, confirming that lignin oxidation primarily followed a 1,2-dioxetane homolysis mechanism. Overall, this enhanced OCF demonstrates the potential viability of lignin oxidation in practical biorefinery applications
An investigation on synergistic effects and kinetic characteristics of pyrolysis of kitchen waste components: Starch, protein and lipid
No full textThe large volume and complex composition of kitchen waste necessitate environmentally sound treatment methods. Pyrolysis emerges as a promising way in treatment and utilization of kitchen waste. However, due to the complex composition and structure of kitchen waste, its pyrolysis characteristics remain unclear. Herein, thermogravimetric analysis was used to compare the pyrolysis characteristics of starch, protein, and lipid in kitchen waste as well as their synergistic interactions at various heating rates. Activation energy and reaction mechanisms were explored using the model-free and model methods. Evolved vapors were analyzed with thermogravimetric-mass spectrometry. The results showed that the presence of lipid slowed down the escape of volatile fractions when co-pyrolyzing with starch, protein or their mixtures (250-420 degrees C), but promoted the overall conversion with lower solid residual rates (Delta W > 1.6 wt%) and higher generation of gaseous products (mainly C2H4/CO and H2O). The increased activation energies led by lipid addition during co-pyrolysis were mainly because of the liquid phase formation over starch and protein, thereby preventing the deep degradation of organics. Contrary to the pyrolysis of starch, protein and lipid, distinct reaction mechanisms were revealed during the co-pyrolysis, with starch/lipid, starch/protein, protein/lipid and starch/protein/lipid following reaction models of F1.5, R1, ZH and F2, respectively. This study provides theoretical support for the development of advanced pyrolysis-based technologies for kitchen waste treatment
Electrocatalytic activities of iron-supported N-doped porous carbon towards the oxygen/hydrogen evolution reaction
No full textRed mud (RM) disposal has been highly apprehensive due to its environmental impact. The aluminum industry produces large amounts of red mud waste annually, and turning it into a value-added product is a key component of sustainable development. This study combines RM with an N-doped porous carbon (biomass precursor) as an effective electrocatalyst for oxygen evolution and hydrogen evolution reactions (OER and HER). One significant obstacle to anion-exchange membrane (AEM) electrolyzer applications is the development of electrocatalysts that do not require noble metals and are both efficient and effective at HER and OER. The synthesized ironsupported (RM-derived) N-doped porous carbon (RMNPC) exhibits excellent catalytic activities with 276 and 191 mV overpotentials at 10 mA cm-2 for OER and HER, respectively. A two-electrode cell system is designed with an RMNPC/NF electrode as anode and cathode, and it necessitates just 1.82 V to realize 10 mA cm- 2 and shows outstanding durability. This study presents a low-cost but effective electrocatalyst for water splitting for renewable hydrogen production, achieving the goal of RM recycling and highlighting the potential of porous carbon electrocatalysts
Selective Hydrogenation of Furfural Under Mild Conditions Over Single-Atom Pd<sub>1</sub>/α-MoC Catalyst
No full textThe selective activation of C=O bonds was the key challenge in the field of biomass utilization. Researchers worked on this purpose by developing high-active and high-selective catalysts. In this study, a Pd1/alpha-MoC single-atom catalyst was synthesized and applied in selective hydrogenation of biomass-derived furfural with 96.7 % conversion and 92.4 % selectivity under a near-room temperature. With various characterizations, the formation of Pd single-atom sites over the surface of alpha-MoC was confirmed. Then, the dominant structure of Pd single-atom site and the reaction pathway were proposed with experimental and Density Functional Theory (DFT) studies. Compared with undecorated alpha-MoC, the introduction of Pd single-atom species significantly altered the reaction mechanism from Meerwein-Ponndorf-Verley (MPV) process. Moreover, the Pd single-atoms loading on alpha-MoC(111) surface notably reduced the energy barriers of H2 activation and C=O bond hydrogenation, which may lead to the improving catalytic performance of alpha-MoC based catalyst. Hence, this investigation could provide a new strategy and understanding for the development of high-active and low-cost catalysts
Temporal asynchrony analysis for dynamic operation of hydraulic-thermal-electricity multiple energy networks based on holomorphic embedding method
No full textAnalyzing the operational states of multiple energy networks (MEN) in multi-energy systems is crucial for ensuring system stability. The dynamic operational characteristics of different energy flows pose challenges for computational analysis. Traditional steady-state methods are inadequate for addressing the dynamics of MEN, especially when dealing with temporal discrepancies between hydraulic and thermal flows in thermal networks (TN) and the heterogeneity between TN and electrical networks. Therefore, this paper proposes a novel holomorphic embedding method (HEM) based on multi-stage decomposition method. The developed HEM constructs a time coefficient matrix and utilize inner-outer loop recursion to handle the time lag between thermal flow and hydraulic flow in the TN. Additionally, we reconstruct a holomorphic matrix, integrating hydraulic flow to bridge thermal and electric power flows, thereby improving the operational heterogeneity among different networks. Real-case simulations show that when the Taylor expansion order in HEM is equal to 4, the proposed method achieves a mere 1 % discrepancy from actual operational data, enhancing computational efficiency by 60 % compared to the Newton-Raphson method. Moreover, in this real-case scenario, the TN exhibits a maximum delay response time of 180 seconds compared to electrical networks. Exploiting this delay time effectively increases renewable energy generation within multi-energy systems by 961.58 kW per day
Effect of cellulase-assisted cold isostatic pressure extraction on the characteristics and functional properties of polyphenol extracts from camellia sinensis seeds
No full textIn this experiment, polyphenolic substances were extracted from Camellia sinensis seeds (CSS) using a synergistic treatment of cold isostatic pressure (CIP) and cellulase. The effects of pressure, treatment time, and cellulase addition on the experiment were investigated. And the optimal extraction conditions were established by single factor experiment and Box-benhken experiments: the pressure applied by CIP was 408.649 MPa, the treatment time was 10.995 min, and the cellulase addition was 4.098 %. The polyphenols in the extract were characterized and quantified using LC-MS/MS. By comparing the different treatments, it was found that the synergistic treatment of CIP and cellulase resulted in a higher extraction yield. FTIR, XRD and SEM mapping showed that CIP synergistic pretreatment with cellulase was able to disrupt the microstructure of the plant and promote the influx of the active ingredients into solution. Finally, the activity of the extracts was detected by using in vitro antioxidant experiments and RAW264.7 cellular anti-inflammatory experiments, which indicated that CIP and cellulase synergistically treated polyphenol extracts had high antioxidant and anti-inflammatory capacity. This experiment provides a new pretreatment method for extracting active substances from CSS
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