To improve catalytic performance of metal active sites in hydrodeoxygenation and hydrocracking conversion of methyl palmitate into high-quality jet biofuel, Ni-1,3,5-benzenetricarboxylate (Ni-BTC) ...metal-organic framework loaded on MCM-41(Mobil Composition of Matter No. 41) was prepared to enhance the accessibility of Ni active sites, facilitating hydrodeoxygenation to increase alkane yield with suitable arene content. The distance (0.98 nm) between Ni active sites within Ni-BTC structure, which was much larger than that (0.20 nm) within Ni nanoparticles, enabled methyl palmitate with maximum molecule width of 0.68 nm to go through Ni-BTC crystalline plane and get access to Ni active sites more easily. Ni-BTC nanosheets newly assembled in pore channels of MCM-41 were beneficial to effectively screen chain molecules of alkane products. With the largest BET surface area of 1014.2 m2/g, the Ni-BTC@MCM-41 catalyst with 2.5 wt% nickel (2.5Ni-BTC@MCM-41) reduced the nickel metal consumption by 75% comparing to nickel nanoparticle loading (10Ni@MCM-41), but achieved the best catalytic performances through hydrodeoxygenation on Ni active sites and hydrocracking on -SiOH acid sites. The alkane yield increased from 23.3% to 33.9%, while arene yield reduced from 22.4% to 6.5% in jet biofuel products. This resulted in an overall jet biofuel yield of 53.2% with uniform distribution along carbon numbers. The higher heating value of jet biofuel products thus increased to a peak of 45.90 MJ/kg.
Distance between Ni active sites (0.98 nm) in Ni-BTC larger than maximum molecule width of methyl palmitate (0.68 nm) was beneficial for the contact of reactants with Ni active sites and enhanced HDO capacity of Ni-BTC@MCM-41 catalyst, obtaining jet biofuel product with significantly improved alkane yield (33.9%) and reduced arene yield (6.5%). Display omitted
•Ni-BTC loaded on MCM-41 was prepared to enhance the accessibility of Ni active sites.•Distance between Ni in Ni-BTC (0.98 nm) enabled methyl palmitate to go through.•Split d orbital of higher energy level enhanced catalyst hydrodeoxygenation capacity.•Ni-BTC assembled in MCM-41 were beneficial to effectively screen alkane products.•Overall jet biofuel yield of 53.2% with 33.9% alkane and 6.5% arene was obtained.
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•Graphene oxide (GO) catalyzed wet microalgae lipids into fatty acids methyl esters.•GO contained 0.997mmol of SO3H groups per gram and many OH groups.•Hydrophilic GO surfaces ...adsorbed wet microalgal cells.•GO achieved 95.1% lipids conversion efficiency.
In order to produce biodiesel from lipids in wet microalgae with graphene oxide (GO) as solid acid catalyst, the effects on lipids conversion efficiencies of catalyst dosage, transesterification temperature, reaction time, methanol dosage and chloroform dosage were investigated. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis revealed that GO contained 0.997mmol SO3H groups per gram and high amounts of OH groups. Scanning electron microscopy showed that wet microalgae cells were adsorbed on hydrophilic GO surfaces covered with many OH groups. Lipids extracted by chloroform from microalgal cells were transformed into fatty acids methyl esters (FAMEs) through transesterification catalyzed by the acid centers (SO3H groups) in GO catalysts. The lipids conversion efficiency into FAMEs was 95.1% in microwave-assisted transesterification reactions of 5wt.% GO catalyst at 90°C for 40min.
Methyl-mercury (CH3Hg+) and ethyl-mercury (C2H5Hg+) have much higher toxicity than Hg2+ and can be more easily accumulated by organisms to form severe bioamplification. Hence, the specific and ...on-site detection of CH3Hg+ and C2H5Hg+ in seafood is of great significance and a hard challenge. We herein designed two T-rich aptamers (HT5 and HT7) for specifically recognizing CH3Hg+ and the total of CH3Hg+ and C2H5Hg+, respectively. In the presence of all Au3+, Ag+, and T-rich aptamer, CH3Hg+ and C2H5Hg+ specifically and preferentially bind with aptamer and thus induced the formation of alloy Ag–Au nanoparticles after reduction, which led to the color change in solution. This provided a sensing platform for the instrument-free visual discrimination and detection of CH3Hg+ and C2H5Hg+. By using HT5 as probe, the method can be used to detect as low as 5.0 μM (equivalent to 1.0 μg Hg/g) of CH3Hg+ by bare eye observation and 0.5 μM (equivalent to 100 ng Hg/g) of CH3Hg+ by UV–visible spectrometry. By using HT7 as probe, the method can be used to detect the total concentration of CH3Hg+ and C2H5Hg+ with a visual detection limit of 5.0 μM (equivalent to 1.0 μg Hg/g) and a UV–visible spectrometry detection limit of 0.6 μM (equivalent to 120 ng Hg/g). The proposed method has been successfully used to detect CH3Hg+ and C2H5Hg+ in fish muscle samples with a recovery of 101–109% and a RSD (n = 6) < 8%. The success of this study provided a potential method for the specific and on-site detection of CH3Hg+ and C2H5Hg+ in seafood by only bare eye observation.
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•First time use of ultrasound-assisted TEPDA to extract lipids from wet microalgae.•TEPDA dissociated into cations to promote cell disruption and lipid extraction.•Ultrasound-assisted ...TEPDA reduced lipid extraction time of SHS from 24 h to 2 h.•Ultrasound-assisted TEPDA achieved the lipid extraction efficiency of 98.2%
To facilitate the lipid extraction from Nannochloropsis oceanica with thick cell wall using switchable hydrophilicity solvent, ultrasound-assisted N, N, N', N'-tetraethyl-1,3-propanediamine (TEPDA) was used to effectively destruct the cell wall. TEPDA cations were adsorbed on the cells via electrostatic force and formed the electron-donor–acceptor (EDA) complex with the hydroxyl groups in cellulose. This broke the hydrogen-bonding interactions between cellulose chains and stripped them from cell wall, thus reducing the cell wall thickness from 141 nm to 68.6 nm. Moreover, TEPDA cations neutralized the negatively charged phospholipid bilayers, decreasing the cell surface zeta potential from −27.5 eV to −14.1 eV. The local electrostatic equilibrium led to cell membrane leakage. The ultrasound promoted the stripping of the cellulose chains at a power intensity of 0.5 W/mL and frequency of 20 kHz, achieving the lipid extraction efficiency of 98.2% within 2 h at a volume ratio of 1:4 of wet microalgae to TEPDA.
The processes of ignition and combustion of aluminum (Al) under different pressure conditions have received widespread attention. In the present work, experiments were performed in a mixed O
2
/CO
2
...atmosphere and at five different pressures (1 atm, 5 atm, 9 atm, 13 atm and 17 atm) to study the ignition and combustion of aluminum. The microstructure and burning rate of the condensed phase products were determined using scanning electron microscopy and inductively coupled plasma spectrometer. The results showed that, with the increase in pressure, the ignition delay time of the sample shortened, while the combustion temperature, heat release rate, maximum intensity of the emission spectrum and burnout rate gradually increased. Experiments showed that at the pressure of 17 atm, the minimum ignition delay time (36 ms) achieved. At the same time, the combustion temperature and maximum burnout rate arrived at their maximum, which are 1855 °C and 99.53%, respectively. However, under high- and low-pressure conditions, there were two distinct reaction mechanisms. One was the melt-dispersion reaction (rupture of the oxide layer), which occurred under high pressure, while the other was the diffusion reaction (molecular diffusion), which took place under low pressure. In addition, physical models of the Al sample under high- and low-pressure conditions were established. The ignition temperature of Al in O
2
/CO
2
atmosphere at 1 atm was about 930 °C. The spatial distributions of Al and AlO radicals under different pressures were found to be similar. The radicals were more concentrated on the surface of the sample, while free radicals diffused into the gas phase and reacted only under high temperature.
The surface tension of a liquid fuel is an important parameter in the fuel atomization process. B/JP-10 nanofluid fuels with different particle concentrations (5 mass%, 10 mass%, 15 mass% and 20 ...mass%) were prepared by selecting 100 nm, 300 nm and 500 nm B particles by a two-step method, in which Tween-85 was used as a surfactant. The surface tension of the above nanofluid fuels was tested at different temperatures (10–90 ℃) using the platinum plate method to investigate the effects of surfactant, temperature, particle concentration and temperature on the surface tension of B/JP-10 nanofluid fuels. The results show that the addition of surfactants helps to reduce the surface tension of the nanofluid fuel. The surface tension of the nanofluid fuel is higher than that of pure JP-10 and increases with increasing particle concentration and decreases with increasing particle size. The surface tension of the suspended fuel decreases linearly with increasing temperature in a certain temperature range (10–60 °C).
Aluminum (Al) is a promising hydrogen carrier. Continuous reaction of pure Al and water (H2O) cannot proceed smoothly because Al particles are covered with a protective oxide layer. Thus, 20% Mg, Li, ...Zn, Bi, and Sn content were added as additives to Al–H2O reaction at high temperature. Thermogravimetric experiments were conducted to determine the reactivity of pure Al and five other samples with additives in a vapor atmosphere. Experiments indicated that Mg and Li drove the Al–H2O reaction, but Zn, Bi, and Sn had little effect. Thus, Mg and Li were selected as activators in the hydrogen generation of the Al–H2O reaction conducted on a specially designed experimental facility. Hydrogen was monitored in the reaction of Al-based composites with H2O vapor in real time. Among them, Al–20%Li achieved the fastest hydrogen generation rate (309.74 ml s−1 g−1) and the largest hydrogen amount (1038.9 ml g−1). XRD (X-ray diffraction), SEM (scanning electron microscopy), and TEM (transmission electron microscopy) were used for product analyses to identify the influence of adding Mg and Li. This method of Al energy utilization may be used in underwater propulsion systems.
•In this paper, we discussed a way of hydrogen production by the reaction of molten aluminum with water.•20% Mg, Li, Zn, Bi, and Sn content were added as additives to Al–H2O reaction at high temperature.•Al–20%Li achieved the fastest hydrogen generation rate and the largest hydrogen amount.
With high calorific value and the environmental friendly features, hydrogen has been attached much importance. Aluminum–water reactions at medium–high temperature perform well in hydrogen generation ...as well as heat utilization. Active researches of the aluminum–water reactions in recent years can be attributed to the increasing interest of hydrogen generation and energy conversion.
In the basis of aluminum–water reactions, the concept of a novel electricity and heat co-generation system was proposed here and it was primarily composed of a reactor, one or two turbines and generators, heat exchanger for heat user, a fuel cell and a pump. Two layouts were designed and analyzed: the one turbine layout (OTL) and the two turbine layout (TTL).
The effects of key parameters, such as the steam temperature and pressure at turbine inlet, the heat user temperature and fuel cell conversion efficiency were investigated. The co-generation system could generate heat and electricity of about 22.2 MJ/kg (Al) in the OTL design. The system utilization efficiency, the ratio of the output was approximate 70% and the electricity generation efficiency could reach up to 41.52% (OTL) and 49.25% (TTL) in the two cases respectively. The OTL presented a higher heat user utilization efficiency than TTL, because of the higher turbine outlet parameters. The TTL layout with the integration of fuel cell and heat user enhanced electricity output by 45.06% in comparison with the OTL layout. The steam temperature at turbine inlet showed considerable impacts on the system utilization efficiency at the TTL case. Enhancing fuel cell conversion efficiency benefited the system and fuel cell utilization efficiencies, especially at the TTL case.
•A novel electricity and heat co-generation system in the basis of AlH2O reaction.•Two kinds of layouts with one or two turbines were designed and analyzed.•Enhancing fuel cell conversion efficiency benefits the system, especially TTL case.
Particle size and oxygen content are two of the key factors that affect the ignition and combustion properties of aluminum particles. In this study, a laser ignition experimental system and flame ...test system were built to analyze the ignition and combustion characteristics and the flame morphology of aluminum particles. A thermobalance system was used to analyze the thermal oxidation characteristics. In addition, the microstructure of aluminum was analyzed by scanning electron microscopy. It was found that the oxidized products were some of the gas phase products agglomerated. Smaller particle size samples showed better combustion characteristics. The combustion intensity, self-sustaining combustion time and the burn-off rate showed a rising trend with the decrease in the particle size. Increasing the oxygen content in the atmosphere could improve the ignition and combustion characteristics of the samples. Four distinct stages were observed in the process of ignition and combustion. Small particle size samples had a larger flame height and luminance, and the self-sustaining combustion time was much longer.Three distinct stages were observed during the thermal oxidation process. The degree of oxidation for small-sized samples was significantly higher than that for the larger particle size samples.Moreover, it was observed that the higher the oxygen content, the higher the degree of oxidation was.
The utilization of the exhaust gas of a solid oxide fuel cell is important to improve the energy efficiency and control pollutant emission. In this work, the combustion of solid oxide fuel cell ...exhaust gas (H 2 /CO) in a honeycomb ceramic catalytic burner is investigated numerically. A 2D numerical combustion model with 17 channels is built to analyze the influence of channel position on thermal performance and combustion characteristics. The high burnout of H 2 and CO is obtained as 96.75% and 97.75%, respectively. The channels can be divided into three groups from the inside to the outside as follows: part 1, from the 9th channel to the 13th channel; part 2, from the 14th channel to the 16th channel; and part 3, the 17th channel. The channels in the same group presented the same results of flow, temperature, and combustion. Compared with the other channels, the outermost channel shows notable differences in depressing the temperature of the whole channel, moving the maximum temperature downstream, enlarging the temperature bias of the lower and upper walls, and enlarging the combustion zone. H 2 and CO perform different combustion processes in the honeycomb ceramic catalytic burner. Compared with H 2 , the initial position of CO conversion is more affected by channel distribution. In the 17th channel, the CO oxidation rate is controlled mostly by the slower oxygen adsorption and the resulting low O(s) coverage. In the 9th channel, the CO oxidation rate is controlled mostly by the wall temperature and fuel-limited. The burnout rate of H 2 changes from 95% to 99.9% with the channel position, but the burnout of CO varies little. The closer the channel to the outer wall, the higher the proportion of heterogeneous reaction and the more the generated heat. The generated heat by the channel can present a diversity of 4%.
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