Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Development of Robust CuNi Bimetallic Catalysts for Selective Hydrogenation of Furfural to Furfuryl Alcohol under Mild Conditions
No full textFurfuryl alcohol represents a pivotal intermediate in the high-value utilization of renewable furfural, derived from agricultural residues. The industrial-scale hydrogenation of furfural to furfuryl alcohol typically employs Cu-based catalysts, but their limited catalytic activity necessitates high-temperature and high-pressure conditions. Here, we develop robust CuNi bimetallic catalysts through direct calcination of dried sol-gel precursors under H2 atmosphere, enabling the complete conversion of furfural to furfuryl alcohol under mild conditions. By adjusting the calcination atmosphere and introducing small amounts of Ni, we achieve the formation of highly dispersed, ultrasmall Cu nanoparticles, resulting in a significant enhancement of the catalytic activity. The optimized 0.5%Ni-10%Cu/SiO2-CA(H2) catalyst demonstrates superior catalytic performance, achieving 99.4% of furfural conversion and 99.9% of furfuryl alcohol selectivity, respectively, at 55 degrees C under 2 MPa H2, outperforming previously reported Cu-based catalysts. The excellent performance of CuNi bimetallic catalysts can be attributed to the highly dispersed Cu nanoparticles and the synergistic effect between Cu and Ni for H2 activation. This research contributes to the rational design of Cu-based catalysts for the selective hydrogenation of furfural
Entropy generation in radiative motion of tangent hyperbolic nanofluid in the presence of gyrotactic microorganisms and activation energy
No full textIn this work, entropy generation is optimized through the application of the second law of thermodynamics. The slip mechanisms, Brownian diffusions, and thermophoresis are elaborated using the tangent hyperbolic nanomaterial model. Magnetohydrodynamic (MHD) fluid is taken into consideration. To characterize the impact of activation energy, a unique model involving the binary chemical reaction is deployed. The effects of mixed convection that is nonlinear in nature, bioconvection, and Joule effect are all taken into consideration. The key partial differential equations (PDEs) are reduced into ordinary differential equations (ODEs) by utilizing appropriate similarity transformations and then solved numerically with the help of a built-in 'bvp4c' technique of MATLAB software. Varied flow parameters' impacts on the nanoparticle volume concentration, entropy number, microorganism concentration, temperature, and velocity fields are analyzed using graphs. Various flow variables are taken into consideration to calculate the total rate of entropy generation. The obtained results show that concentration irreversibility, Joule effect irreversibility, viscous dissipation, and heat irreversibility all influence the entropy. The numerical outcomes were observed by fixing the physical parameters as 0.1 < alpha < 4.0 , 0.1 < M < 1.2 , 0.1 < N r < 2.2 , 0.1 < L e < 2.2 , 0.1 < N b < 0.4 , 0.1 < N t < 1.0 , 2.0 < Pr < 5.0 , and 0.1 < L b < 2.0 , as well as their impact on the momentum, thermal, concentration, and microorganism density profiles. From results, an increasing estimate of the variable representing chemical reaction indicates a decline in the concentration. The higher the chemical reaction variable, Hartmann number, and Weissenberg number, the higher the entropy number, while the Bejan number has a contrary behavior. Subsequently, all the outcomes are plotted in graphs and discussed in detail, when subjected to the involving physical quantities
Entropy generation in radiative motion of tangent hyperbolic nanofluid in the presence of gyrotactic microorganisms and activation energy
No full textIn this work, entropy generation is optimized through the application of the second law of thermodynamics. The slip mechanisms, Brownian diffusions, and thermophoresis are elaborated using the tangent hyperbolic nanomaterial model. Magnetohydrodynamic (MHD) fluid is taken into consideration. To characterize the impact of activation energy, a unique model involving the binary chemical reaction is deployed. The effects of mixed convection that is nonlinear in nature, bioconvection, and Joule effect are all taken into consideration. The key partial differential equations (PDEs) are reduced into ordinary differential equations (ODEs) by utilizing appropriate similarity transformations and then solved numerically with the help of a built-in 'bvp4c' technique of MATLAB software. Varied flow parameters' impacts on the nanoparticle volume concentration, entropy number, microorganism concentration, temperature, and velocity fields are analyzed using graphs. Various flow variables are taken into consideration to calculate the total rate of entropy generation. The obtained results show that concentration irreversibility, Joule effect irreversibility, viscous dissipation, and heat irreversibility all influence the entropy. The numerical outcomes were observed by fixing the physical parameters as 0.1 < alpha < 4.0 , 0.1 < M < 1.2 , 0.1 < N r < 2.2 , 0.1 < L e < 2.2 , 0.1 < N b < 0.4 , 0.1 < N t < 1.0 , 2.0 < Pr < 5.0 , and 0.1 < L b < 2.0 , as well as their impact on the momentum, thermal, concentration, and microorganism density profiles. From results, an increasing estimate of the variable representing chemical reaction indicates a decline in the concentration. The higher the chemical reaction variable, Hartmann number, and Weissenberg number, the higher the entropy number, while the Bejan number has a contrary behavior. Subsequently, all the outcomes are plotted in graphs and discussed in detail, when subjected to the involving physical quantities
Synthesis of Trisiloxane with the Dioxaborolane Group as a Cathode Film-Forming Electrolyte Additive for High-Temperature LiMn<sub>2</sub>O<sub>4</sub>/Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> Batteries
No full textLiMn2O4 batteries have been widely applied as various portable electronic devices and electric vehicles owing to the merits of low cost, high operating voltage, excellent rate capability, and environmental friendliness. However, the poor performance at elevated temperatures remains a serious technical challenge in terms of commercial application purposes. A borate-containing trisiloxane compound of TSMBO is designed and synthesized as a cathode film-forming electrolyte additive to improve the electrochemical performances of LiMn2O4/Li4Ti5O12 batteries, especially at high temperatures of 55 degrees C. Atomic force microscopy measurement confirms that the trisiloxane moiety in TSMBO can construct a cathode electrolyte interface (CEI) with higher mechanical strength and better flatness compared to the disiloxane moiety in the TSMBO analogue with a similar chemical structure. The robust CEI film on the surface of the LiMn2O4 cathode and the inhibited hydrolysis of LiPF6 in the electrolyte significantly suppress the dissolution of Mn from the LiMn2O4 cathode and maintain the structural integrity of the LiMn2O4 lattice over cycling. Thus, the LiMn2O4/Li4Ti5O12 coin cell using the TSMBO-containing electrolyte with an optimized addition level of 0.5 wt % exhibits a higher capacity retention of 49.3% compared with 34.3% for the baseline electrolyte after 300 cycles under 1C rate at 55 degrees C. The LiMn2O4/Li4Ti5O12 pouch cell tests show excellent high-temperature and cycling performance at 55 degrees C and a higher capacity retention of 90.4% after 500 cycles at 2C compared to 79.7% for that with the baseline electrolyte after 430 cycles at 2C. This work demonstrates that TSMBO is a promising electrolyte additive for practical use to improve the cycling stability of LiMn2O4/Li4Ti5O12 batteries at elevated temperatures
Parametric Analysis of a Novel Array-Type Hydrogen Storage Reactor with External Water-Cooled Jacket Heat Exchange
No full textHydrogen energy is a green and environmentally friendly energy source, as well as an excellent energy carrier. Hydrogen storage technology is a key factor in its commercial development. Solid hydrogen storage methods represented by using metal hydride (MH) materials have good application prospects, but there are still problems of higher heat transfer resistance and slower hydrogen absorption and release rate as the material is applied to reactors. This study innovatively proposed an array-type MH hydrogen storage reactor based on external water-cooled jacket heat exchange, aiming to improve the heat transfer efficiency and absorption reaction performance, and optimize the absorption kinetics encountered in practical applications of LaNi5 hydrogen storage material in reactors. A mathematical model was built to compare the hydrogen absorption processes of the novel array-type and traditional reactors. The results showed that, with the same water-cooled jacket, the hydrogen absorption rate of the array-type reactor can be accelerated by 2.78 times compared to the traditional reactor. Because of the existence of heat transfer enhancement limits, the increase in the number of array elements and the flow rate of heat transfer fluid (HTF) has a limited impact on the absorption rate improvement of the array-type reactor. To break the limits, the hydrogen absorption pressure, as a direct driving force, can be increased. In addition, the increased pressure also increases the heat transfer temperature difference, thereby further improving heat transfer and absorption rate. For instance, at 3 MPa, the hydrogen absorption time can be shortened to 147 s
Molecular dynamics study of waste tire pyrolysis: Focus on intermediate product evolution and sulfur migration law
No full textWith the rapid development of the automotive industry, the large number of waste tires poses significant environmental and health pressures. Pyrolysis technology offers a way to resourcefully utilize waste tires by converting them into pyrolysis oil, pyrolysis gas, and pyrolysis char, which has promising application prospects. However, there are still considerable challenges in the application of this technology, such as unclear reaction mechanisms and the high sulfur content of the products, which limit its practical implementation. Although some research has elucidated the pyrolysis mechanisms, there remain significant gaps in understanding the evolution paths of key intermediate and final products, as well as the detailed migration and transformation patterns of sulfur. This study uses reactive molecular dynamics simulation to investigate the pyrolysis process of tires. A three-dimensional polymer molecular model was constructed to study the pyrolysis process of waste tires at different temperatures, focusing on the evolution of key products, intermediate products, and sulfur-containing components. The results indicate that CH4 and & sdot;CH3 radicals collide with unsaturated hydrocarbons through carbon-hydrogen transfer reactions and radical chain reactions, leading to polymerization. During the initial stage of pyrolysis, sulfur primarily exists in the form of sulfur-containing hydrocarbons (CHS). As pyrolysis progresses, the quantity of CHS decreases. With increasing pyrolysis temperature, the proportion of sulfur in the S form far exceeds that of CHS. At a pyrolysis temperature of 3000 K, the proportion of S is 64 %, while the proportion of CHS is 23 %
Impact of the NH<sub>4</sub><SUP>+</SUP>/NO<sub>3</sub><SUP>-</SUP> ratio on growth of oil-rich filamentous microalgae <i>Tribonema minus</i> in simulated nitrogen-rich wastewater
No full textThis study delves into the impact of varying NH4+-N: NO3--N ratios in simulated nitrogen-rich wastewater on the physiological and biochemical responses of the Xanthophyceae Tribonema minus. Our findings revealed intriguing patterns: the maximum biomass observed was 5 g/L, which occurred in treatments containing NH4+-N at a concentration of 60 mg/L and NO3--N at a concentration of 180 mg/L (mass concentration ratio of 1:3). Due to the excessive concentration of NH4+-N, the photosynthetic apparatus is damaged. When NH4+-N exceeds 120 mg/L (ratio 1:1 of NH4+-N: NO3--N), growth is seriously hindered. However, increased NH4+-N levels foster lipid accumulation. Notably, NH4+-N removal was high across all NH4+-N treatments, ranging from 78 %-90 %. Nitrate, ammonium, and total phosphorus removal declined with increasing NH4+-N proportions due to limited growth of Tribonema minus. When NH4+-N was 120 mg/L (ratio 1:1 of NH4+-N: NO3--N), the lipid content accounted for 50 % of the biochemical components, surpassing the control group without ammonium addition by 15 %. The lipid composition of T. minus primarily comprises palmitoleic acid, constituting around 50 % of total fatty acids, with its concentration rising at higher NH4+-N supply. Increasing NH4+-N also improved fatty acid profiles and biodiesel properties according to international standards. Overall, this work adds knowledge to stimulate microalgal lipid production. Not only should absolute amounts of nutrients be considered, but also the NH4+-N: NO3--N ratio to optimize biomass yields with high lipid content
Hazelnut shell-based activated carbon/carbon nanotubes/palmityl alcohol as new form-stable phase change material with enhanced energy storage capacity and thermal conductivity
No full textRecently, high thermal properties of phase change materials (PCMs) with low costs, and low density have been highly recommended for solar thermal energy storage (STES) in residential buildings. However, they suffer from leakage issues and must be encapsulated within porous materials. Among the porous materials used, biomassbased activated carbon is the most suitable. This study used waste hazelnut shells from the agricultural industry as biomass materials to produce activated carbon. The hazelnut shell-derived activated carbon (HSAC), incorporating carbon nanotubes (CNTs) and palmityl alcohol (PAl), was used in various ratios to manufacture form-stable PCMs (FSPCMs) with enhanced thermal properties. Several tests, such as XRD, FTIR, DSC, and IR thermal camera, were used to measure the chemical stability, thermal storage properties, the change in surface temperature of the proposed FSPCMs, and thermal reliability before and after the thermal cycling process (1000th cycle). The designed FSPCMs' TC values, enhanced by CNT, were carefully assessed. The results show that the inclusion of the PCMs into HSAC and CNT hybrid matrix, HSAC/PAl (43 %), HSAC/CNTs (4 %)/PAl (52 %), and HSAC/CNTs (8 %)/PAl (65 %) resulted in improved final values to 0.29, 0.57, and 0.86 W/m center dot K, respectively, compared to 0.17 W/m center dot K obtained with pure PAl. The 8 wt% CNT additive also boosted the energy storage capacity of the composite from 121.82 J/g to 184.92 J/g due to the increased impregnation ratio of PAl into the hybrid supporting matrix from 43 wt% to 65 wt%. Furthermore, utilizing HSAC in PCM production brings several environmental advantages, such as reducing landfill and carbon dioxide emissions, and can contribute to cleaner production of green construction elements for STES buildings implementations
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