Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Synergy of heterogeneous Co/Ni dual atoms enabling selective C-O bond scission of lignin coupling with in-situ N-functionalization
No full textSelective cleavage of Csp2-OCH3 bond in lignin without breaking other types of C-O bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass. Here, a Co/Ni-based dual-atom catalyst CoNiDA@NC prepared by in-situ evaporation and acid-etching of metal species from tailor-made metal-organic frameworks was efficient for reductive upgrading of various lignin-derived phenols to cyclohexanols (88.5%-99.9% yields), which had ca. 4 times higher reaction rate than the single-atom catalyst and was superior to state-of-the-art heterogeneous catalysts. The synergistic catalysis of Co/Ni dual atoms facilitated both hydrogen dissociation and hydrogenolysis steps, and could optimize adsorption configuration of lignin-derived methoxylated phenols to further favor the Csp2-OCH3 cleavage, as elaborated by theoretical calculations. Notably, the CoNiDA@NC catalyst was highly recyclable, and exhibited excellent demethoxylation performance (77.1% yield) in real lignin monomer mixtures. Via in-situ cascade conversion processes assisted by dual-atom catalysis, various high-value N-containing chemicals, including caprolactams and cyclohexylamines, could be produced from lignin. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved
Influence of H<sub>2</sub>O and O<sub>2</sub> on the Homogeneous Conversion of Toluene and the Underlying Reaction Mechanisms
No full textIn this study, the impact of H2O and O-2 on the homogeneous conversion of toluene at various temperatures and concentrations was investigated. Molecular dynamics simulations were performed using the ReaxFF force field to decipher the underlying high-temperature reaction dynamics among toluene, H2O, and O-2. In the presence of both H2O and O-2, the toluene conversion efficiency reached 98%, primarily producing H2 and CO. Toluene conversion and H-2 and CO generation were strengthened under 1-2% O-2 with 5-15% H2O. Conversely, elevated O2 (3%) and H2O (25-35%) hindered the combustible gas yield. Two principal H2 and CO formation pathways were identified: (1) Under high temperatures, H2O and O-2 generate OH radicals, promoting toluene side chain conversion into (CHO) entities, which subsequently break down into H2 and CO. (2) The toluene-benzene ring disintegrates under OH radical activity. The resulting fragments, in the presence of H2O, produce H-2 and CO. The simulation insights were validated by D2O and O-18(2) isotope labeling experiments
Power generation analysis of super-long gravity heat pipe geothermal systems
No full textHighly -efficient and environment -benign heat extraction and utilization technologies are key to large-scale geothermal energy deployment. In recent developments, the innovative super -long gravity heat pipe (SLGHP) geothermal power plant has revolutionized deep geothermal power generation by obviating the need of flash devices or heat exchangers in vapor generation for turbine propulsion. This advancement promises substantial structural simplification, a marked reduction in exergy losses, and significant cost savings. Nevertheless, a comprehensive understanding of the performance of SLGHP power generation systems is still lacking in published research. For a single -well geothermal system, the geothermal gradient assumes critical importance as it serves as a key indicator of resource intrinsic conditions, and the depth of the well emerges as an essential controllable variable in manual drilling. The present investigation seeks to elucidate the impact of these two key parameters on the performance of SLGHP power generation systems. For this purpose, a semi -empirical formula is analytically derived to describe the heat extraction process within the SLGHP system. This formula is integrated with a thermo-economic model to evaluate the performance of the SLGHP power generation system. It is found that adjusting the two parameters can yield simultaneous increases in the heat extraction rate and the energy efficiency, thereby resulting in a significant boost in power generation of SLGHP. Specially, the SLGHP system of a 4000 m deep well and with a 0.045 K/m geothermal gradient can output 35.95 kW electricity, while that of a 5000 m deep well and with a 0.05 K/m geothermal gradient achieves 86.39 kW electricity output. In practical terms, it is found that the optimal strategy for an SLGHP power plant involves drilling multiple wells in a reservoir with a higher geothermal gradient. However, when repurposing abandoned oil/gas wells for power generation, the preference is for deep wells
Alliance of International Science Organizations (ANSO) at the University of Science and Technology of China (USTC)
No full textInterdisciplinary Frontier Next-Generation Researcher Program of the Tokai Higher Education and Research System
No full textGuangdong Special Support Program-Local innovation and entrepreneurship team project[GDME-2022D043]
No full textCrystal structure, Bi<SUP>3+</SUP> yellow luminescence, and high quantum efficiency of Ba<sub>3</sub>SbAl<sub>3</sub>Ge<sub>2</sub>O<sub>14</sub>:Bi<SUP>3+</SUP> phosphor for white light-emitting diodes
No full textBi3+-activated luminescent materials have attracted increasing attention owing to their strong excitation in the near-ultraviolet (NUV) range instead of the visible range. Such a unique feature allows them to avoid reabsorption among phosphors, resulting in their growing popularity in research and applications. However, the majority of Bi3+-doped phosphors suffer from low quantum efficiency, imposing limitations on their practical applications. We hereby present a newly developed phosphor, Ba3SbAl3Ge2O14:Bi3+ (BSAG:Bi3+), which emits a vibrant yellow light when excited by NUV light. Importantly, this phosphor exhibits a high internal quantum efficiency (IQE) of 95.3%, marking a significant advancement in the field. Through charge compensation, BSAG:Bi3+, K+ phosphor achieves a remarkable IQE of 97.2%. The photoluminescence (PL) spectroscopy analysis reveals that this phosphor contains only one Bi3+ luminescent center, which is consistent with the trigonal structure of BSAG. This is supported by the fact that only one Ba site in the structure can accept Bi3+ ions. The critical distance was estimated to be 9.71 & Aring;. The energy transfer mechanism between Bi3+ ions was determined as a dipole-dipole interaction. To explore the application of BSAG:Bi3+ phosphor, pc-WLED devices were fabricated by depositing a blend of this phosphor and one or two commercial phosphors on a 365 nm chip. The final warm pc-WLED device exhibits ideal photoelectric performance with a low CCT of 4229 K and a high Ra of 91.5.<br /
Synergistic Effect of Carbon Nanotubes, Zinc, and Copper Oxides on Rheological Properties of Fracturing Fluid: A Comparative Study
No full textNanomaterials play a beneficial role in enhancing the rheological behavior of fracturing (frac) fluid by reacting with intermolecular structures. The inclusion of these materials into the fluid improves its stability, increases the viscosity of polymers, and enhances its resistance to high temperature and pressure. In this investigation, multi-walled carbon nanotubes (CNTs), nano-zinc oxides (N-ZnO), and nano-copper oxides (N-CuO) have been utilized to ameliorate the rheological properties of water-based fracturing fluid. Different concentrations of these aforementioned nanomaterials were prepared to determine their effects on the rheological behavior of the fluid. The results revealed that the size of nanoparticles ranged from 10 to 500 nm, 300 nm, and 295 nm for CNTs, N-ZnO, and N-CuO, respectively. Moreover, employing CNTs exhibited a resistance of 550 cp at 25 degrees C and reached 360 cp at 50 degrees C with a CNT concentration of 0.5 g/L. In contrast, N-CuO and N-ZnO showed a resistance of 206 cp at 25 degrees C and significantly decreased to 17 cp and 16 cp with higher concentrations of 10 g/L and 1 g/L, respectively. Based on these findings, this study recommends utilizing CNTs to enhance fracking fluid's chemical and physical properties, which need to be highly viscous and stable under reservoir conditions
Role of hydraulic retention time in integration of microalgae and activated sludge process for nutrient recycle from diluted dairy liquid digestate
No full textThe integration of microalgae and activated sludge (MAS) processes presents a promising method for recycling nutrients from animal digestates. However, the effects of operational factors such as hydraulic retention time (HRT) on this process remain unclear. Therefore, this study utilized semi -continuous photobioreactor systems with a working volume of 800 mL to investigate the impact of three different HRTs (4 d, 6 d, and 8 d) on the performance of MAS processes for nutrient recycling from diluted dairy liquid digestate (DLD). Results indicated that the 8 d HRT yielded the highest biomass concentration, ranging from 2.20 to 2.52 g/L. However, extending the HRT beyond 6 d decreased biomass productivity. The growth of MAS biomass favoured nutrient removal, with C. vulgaris the primary contributor. Longer HRTs improved nutrient removal, with the 8 d HRT achieved the highest total nitrogen (TN) removal of 87.68 +/- 4.57 % and complete phosphorus elimination. Complete total ammonia nitrogen (TAN) removal occurred when HRT >= 6 d. All systems exhibited poor COD removal due to the poor biodegradability of DLD and the algal organic matter (AOM) produced by microalgae, with the highest COD removal of 16.43 +/- 3.65 % (8 d HRT). Metagenomic analysis revealed that HRTs affected bacterial communities significantly, with the highest richness and diversity occurring at a 6 d HRT. Dominant phyla in all three systems were Proteobacteria and Bacteroidetes. Longer HRTs enhanced lipid accumulation and reduced carbohydrate contents but had minimal effect on higher heating value (HHV), which ranged from 20.63 to 21.72 MJ kg- 1. These findings have significant implications for developing efficient and sustainable MAS-based treatment systems
Experimental Study on the Effective Thermal Conductivity of Methane Hydrate-Bearing Sediments Using a Steady-State Method
No full textThe thermal conductivity of hydrate-bearing sediments is a key parameter used to evaluate the heat characteristics relevant to phase transformations during gas production. In this study, considering the dynamic evolution of hydrate saturation, a high-pressure experimental apparatus was designed, and the steady-state method was used to measure the effective thermal conductivity of hydrate-bearing sediments. The reliability of the experimental apparatus was verified through the effective thermal conductivity measurement using pure ice and agar gel as standard materials, and optimization of the experimental parameters was carried out. The effective thermal conductivity of hydrate-bearing sediments with the initial water saturation range of 20-60% and the hydrate saturation range of 7.43-48.74% was measured. The results reveal that the effective thermal conductivity of hydrate-bearing sediments increases with increasing hydrate saturation and shows a maximum value in the hydrate saturation range of 25-36%. Moreover, the effective thermal conductivity of the hydrate-bearing sediment is also strongly dependent on the hydrate occurrence patterns and growth habits. In sediments with a low water saturation (30%), gas is the initial main continuous phase, and the maximum difference in thermal conductivity between the sediment with and without hydrates is 40.15%. For a high water saturation in sediments (60%), water is the initial main continuous phase, and the maximum difference in thermal conductivity between the sediment with and without hydrates is 10.59%, indicating that the positive contribution of hydrate formation on effective thermal conductivity is decreased. In addition, a developed fitting model, considering the influence of hydrate saturation in sediments, was proposed. The calculated results of the model are in good agreement with the experimental data for different samples
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