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
Long-term thermal behaviour of silver and graphene nanoparticle-enhanced phase change materials under accelerated thermal stress
No full textLong-term performance of a nano enhanced phase change material (NePCM) plays a crucial role in its application for thermal-related application. PCMs often encounter challenges related to their stability and reliability in maintaining effective thermal regulation. Over time, they tend to degrade and lose their storage capability due to prolonged exposure to the ambient environment and repeated melting/freezing cycles. Therefore, it is essential to assess the cycle test stability of PCMs to ensure their long-term durability before integrating them into thermal systems. However, relevant long-term stability assessment of the NePCMs has been rarely reported. This study, therefore, investigate the stability and durability of the RT50 (a commercial PCM) based NePCM, with silver (Ag) and graphene (Gr) NPs as nano-additives. Accelerated thermal cycling method with up to 3000 cycles was adopted to evaluate the durability PCM (RT50) and its NePCM (0.8%Ag/RT50 & 0.6%Gr/RT50). Moreover, their key properties including the microstructure, chemical stability, optical absorbance, thermal reliability and energy storage ability are examined at regular interval. The results show that NePCMs possess excellent thermal chemical stability even after 3000 thermal cycles, and latent heat (slight reduction approximately 10 %). It is worth noting that owing to the stronger intermolecular force between RT50 and Gr, the energy storage capacity of Gr/RT50 NePCM is observed to display an increasing trend with thermal cycling. Overall, the prepared NePCM has validated the long-term reliability, and pave ways for its thermal regulation application
Kinetic Formation Process of Carbon Dioxide Hydrate in Porous Sands under 274.15-280.15 K Reaction Temperature and 20-70% Initial Water Saturation
No full textUsing gas hydrates to store CO2 is currently considered a promising technology for carbon capture, utilization, and storage with great industrial application prospects. Three groups of phase equilibrium experiments with 72 groups of environmental conditions were arranged to conduct the reaction kinetics of CO2 hydrate in natural sands. The effects of 20-70% initial water saturation, 274.15-280.15 K reaction temperature, and 0.025-0.2 mm natural sands on the reaction process were analyzed. From test results, the final gas storage of a porous media system is proved to depend largely on the initial water saturation and has a linear relationship with it. The reaction temperature has an insignificant promotion effect on the final gas storage, and the porous sands with a particle size of 0.025-0.055 mm consistently operate at the lowest level in 93.05% of the working conditions. The results reveal that the classic fugacity model has a good fitting effect at lower reaction temperatures (274.15-278.15 K), while the fitting effect will be reduced in other conditions. After inserting the capillary pressure of the van Genuchten style into the modified fugacity kinetic model, the applicability scope and accuracy of the model can be excellently improved
Effect of Ionic Composition on Methane Hydrate Formation Kinetics in Natural and Artificial Deep-Sea Seawater
No full textOn the cold seep seafloor, methane hydrate is an important form of carbon storage. The stability of methane hydrates and mechanisms of ionic effects on hydrates are closely related to seafloor methane release and carbon cycling. Cold seeps are endowed with abundant and high-quality hydrate resources under the environmental conditions of low temperatures and high pressures. Methane hydrates are seen as a potential source of renewable energy and a possible form of energy storage, as the global demand for clean energy increases. Although studies have focused on the formation and dissociation processes of methane hydrates, the influence of seawater ions on the kinetics of hydrate formation is still unclear. In this study, we studied the formation kinetics of methane hydrate in ion systems, analyzed the effects of various main ions, and compared them with in situ seawater composition. The phase equilibrium point of methane hydrate in the in situ seawater system was experimentally determined by us to better understand the stability. The degree of inhibition on the methane hydrate formation kinetics in natural seawater is more closely to that of CaCl2, MgCl2, and SrCl2, as indicated by gas consumption during methane hydrate formation. However, NaCl exhibits a greater inhibition effect than that of CaCl2, MgCl2, and SrCl2. The thermodynamic behavior of in situ seawater is consistent with the inhibition degree of SrCl2 on methane hydrate formation. In addition, morphological characteristics of hydrates possessed dense powdery particles and ice particles on the surface of the seawater-methane system, which combined with both hydrate morphologies, the pure water-methane system (ice particles), and the saline ions-methane system (powdery particles). The findings of this study may provide a reference for further exploration of methane hydrate formation in cold seep environments and provide a basis for an in-depth understanding of submarine methane release and carbon cycling
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
International Science and Technology Innovation Cooperation Program of the National Key Research and Development Plan of China[22408365]
No full textExperimental research on a novel OWC with two chambers separated by a buoyancy module
No full textThe reciprocating motion of waves poses significant challenges in improving overall conversion efficiency. In this study, the concept of a single floating oscillating water column (OWC) with two chambers separated by a buoyancy module was proposed based on the diffraction and focusing characteristics of wave propagation. Experimental investigations were conducted in a wave flume and tank to validate this concept. The results of small-scale model tests in a narrow wave flume revealed a peak Capture Width Ratio (CWR) of 197.8% under regular wave and 84.3% under irregular waves. In large-scale model tests conducted in a wide wave tank, the peak CWR reached 252.6%, accompanied by a peak wave-to-battery efficiency of 77.1% in regular wave cases. The results suggest that this technology offers simplicity, a shallow draft, low material cost, and high conversion efficiency. Research results provide the effective reference for OWC operation at open sea. Further research is warranted to address the three major challenges wave energy technologies face: high cost, poor reliability, and low conversion efficiency
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