摘要 :
Micromixers are important components in microfluidic systems and play a pivotal role in chemical processes. In this work, numerical simulation and experimental studies were used to investigate the mixing efficiencies of spiral (S-...
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Micromixers are important components in microfluidic systems and play a pivotal role in chemical processes. In this work, numerical simulation and experimental studies were used to investigate the mixing efficiencies of spiral (S-M) and serpentine (C-S-M) micromixers in a wide Reynolds number (Re) range. We found that the structure of the Dean vortex played a crucial role in the mass transfer of the mixing process. The two structures produced Dean vortices with double vortex structures at the Re of 1 and 300, the mixing efficiency of C-S-M was lower than S-M. A Dean vortex with a four-vortex structure was produced in the two micromixers at the Re of 300 and 500, and the mixing efficiency of C-S-M was higher than S-M. Finally, the running cost (RQ concept was proposed to evaluate the comprehensive efficiencies of the two micromixers, which showed that the RC of S-M was lower at the Re of 50 and 100, and the RC of C-S-M was lower at the Re of 300 and 500. Our research may provide theoretical guidance for the design and application of micromixers.
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Nano-sized SSZ-13 with hierarchical structure were fast synthesized by combining ultrasonic pretreatment and seed induced crystallization.The physicochemical properties of the synthesized catalysts were characterized bv X-ray diff...
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Nano-sized SSZ-13 with hierarchical structure were fast synthesized by combining ultrasonic pretreatment and seed induced crystallization.The physicochemical properties of the synthesized catalysts were characterized bv X-ray diffraction(XRD),scanning electron microscopy(SEM),N2 adsorption-desorption,X-ray fluorescence(XRF),Transmission electron microscopy(TEM),and temperature programmed desorption of ammonia(NH3-TPD)analysis.As verified by XRD and SEM,ultrasonic pretreatment not only remarkably reduced the crystallization time to 7 h but also evidently decreased the zeolite crystals to nano size(ca.650 nm).The N2 adsorption-desorption and TEM resulted revealed that ultrasonic pretreatment created abundant intracrystalline mesopores in the zeolite structures.In comparison to the conventional SM-24 catalyst,both improved catalytic lifetime and selectivity of ethylene and propylene were obtained over the hierarchical nano-sized SN-17 catalyst due to the greatly enhanced mass transport efficiency and decreased coking rate.
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Hierarchical SSZ-13 microspheres, with abundant mesoporous channels, have been successfully synthesized by addition of calcined SSZ-13 crystals in the starting gel in the absence of any organic templates. This strategy not only re...
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Hierarchical SSZ-13 microspheres, with abundant mesoporous channels, have been successfully synthesized by addition of calcined SSZ-13 crystals in the starting gel in the absence of any organic templates. This strategy not only remarkably reduces the production cost and environmental pollution, but also significantly decreases the crystallization time as well as evidently reducing the zeolite crystal sizes in many cases. The synthesized sample was characterized by XRD, BET, ICP, SEM, TEM, TG, and NH_3-TPD, which indicates that the organic template free synthesized SSZ-13 exhibits high crystallinity, textural properties, and acidity. Moreover, the synthesized hierarchical SSZ-13 catalyst shows outstanding performance in the methanol-to-olefin (MTO) reaction, with slightly higher ethylene plus propylene selectivity and prolonged catalyst lifetime as compared to the templated SSZ-13 catalyst.
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Catalytic oxidative desulfurization (Cat-ODS) of benzothiophene (BT) in n-octane has been investigated with hydrogen peroxide (H_2O_2) over catalysts of activated carbon (AC) supported iron oxide under mild conditions. The catalys...
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Catalytic oxidative desulfurization (Cat-ODS) of benzothiophene (BT) in n-octane has been investigated with hydrogen peroxide (H_2O_2) over catalysts of activated carbon (AC) supported iron oxide under mild conditions. The catalyst was characterized by N_2 adsorption, XRD, SEM/EDS, TPR and XPS. Under the best operating condition for the catalytic oxidative desulfurization-temperature 60 ℃, atmospheric pressure, 0.15 g Fe/AC, 18 molar ratio of hydrogen peroxide to sulfur, using acetonitrile as extraction solvent for double extraction-the sulfur content in model diesel fuel (MDF) was reduced from 700 ppmw to 30 ppmw with 95.66% of total sulfur was removed.
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In this paper, synthesis of 1,3-propanediol (1,3-PDO) through coupling of hydroesterification-hydrogenation from ethylene oxide (EO) catalyzed by 1-butyl-3-methylimidazolium cobalt tetracarbonyl [Bmim][Co(CO)_4] functional ionic l...
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In this paper, synthesis of 1,3-propanediol (1,3-PDO) through coupling of hydroesterification-hydrogenation from ethylene oxide (EO) catalyzed by 1-butyl-3-methylimidazolium cobalt tetracarbonyl [Bmim][Co(CO)_4] functional ionic liquid which was prepared by metathesis reaction between [Bmim]Cl and KCo(CO)_4 has been studied. The structure of [Bmim][Co(CO)_4] was characterized by FT-IR and ~1H NMR. Using [Bmim][Co(CO)_4] as catalyst and [Bmim]PF_6 as solvent, 1,3-PDO was prepared for the first time by coupling of hydroesterifaction of EO and hydrogenation of methyl 3-hydroxypropionate (3-HPM). The yield of 3-HPM can reach 90.8%, while the yield of 1,3-PDO up to 82.9%. The catalyst can be separated from the product mixture by extraction with deionized water and recycled several times without significant loss of catalytic efficiency. A possible reaction mechanism has also been proposed.
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The conversion/alloying-type electrode has promising potential in
next-generation large-scale energy storage. However, it is plagued by vast
volume expansion, the sluggish ion transport capability due to the anion
migration and...
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The conversion/alloying-type electrode has promising potential in
next-generation large-scale energy storage. However, it is plagued by vast
volume expansion, the sluggish ion transport capability due to the anion
migration and the deficient geometric conformation. Herein, an ultrastable
Sb_2Se_3 anode is elaborately designed for potassium-ion batteries (PIBs)
through combined strategies of expedited side-chain transport with bulky
polar groups and stable molecular conformations. By rendering flexible
polymer conductor (PC), hyaluronic acid conjugated dopamine, (named as
HD) with a dissociated tetraethylthiuram disulfide (TETD) side chain, i.e.,
THD, via the in situ growth protocol over the hollow nitrogen-doped
polyhedron carbon (NC) confined Mn-Sb_2Se_3 nanospheres
(THD/Mn-Sb_2Se_3@NC) grafting multipolar intramolecular covalent bonds,
the fabricated THD/Mn-Sb_2Se_3@NC displays gloriously enhanced side chain
transport capability along with planarity and rigidity, benefiting from the finely
decoupled segmental motion of the polymer chains and the dislocated 𝝅-𝝅
electrons. Consequently, THD/Mn-Sb_2Se_3@NC exhibits superior
fast-charging behavior with a wider temperature adaptability from −50℃ to
80℃. The findings provide fundamental guidance for developing advanced
electrodes with outstanding side chain transport kinetics that go beyond safe,
high-performance PIBs.
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摘要 :
The catalytic oxidative desulfurization of benzothiophene in n-octane has been investigated with hydrogen peroxide over catalysts of activated carbon (AC) supported iron oxides under mild conditions. The prepared composites, which...
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The catalytic oxidative desulfurization of benzothiophene in n-octane has been investigated with hydrogen peroxide over catalysts of activated carbon (AC) supported iron oxides under mild conditions. The prepared composites, which combine the adsorption features of AC with the magnetic and excellent catalytic properties of γ-Fe2O3 and/or Fe3O4 nanoparticles, were fabricated by a modified deposition-precipitation method using HNO3 as the carbon modifying agent and characterized by N2 adsorption, XRD, SEM/EDS, TPR and XPS. The main results suggest that the hydrogen treatment results in an increase of sulfur removal, probably as a function of more reduced iron species formed with the hydrogen treatment. Using acetonitrile as an extraction solvent, the sulfur content in model diesel fuel reduced from 700 to 38.6 ppmw, and 94.5 % of total sulfur was removed under the operating conditions of room temperature (30 °C) and atmospheric pressure.
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A novel pilot two-level dielectric barrier discharge (DBD) reactor has been proposed and applied for degradation of continuous model wastewater. The two-level DBD reactor was skillfully realized with high space utilization efficie...
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A novel pilot two-level dielectric barrier discharge (DBD) reactor has been proposed and applied for degradation of continuous model wastewater. The two-level DBD reactor was skillfully realized with high space utilization efficiency and large contact area between plasma and wastewater. Various conditions such as applied voltage, initial concentration and initial pH value on methyl orange (MO) model wastewater degradation were investigated. The results showed that the appropriate applied voltage was 13.4 kV; low initial concentration and low initial pH value were conducive for MO degradation. The percentage removal of 4 L MO with concentration of 80 mg/L reached 94.1% after plasma treatment for 80min. Based on ultraviolet spectrum (UV), Infrared spectrum (IR), liquid chromatography-mass spec-trometry (LC-MS) analysis of degradation intermediates and products, insights in the degradation pathway of MO were proposed.
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Reverse atom transfer radical copolymerization of styrene (St) and butyl acrylate was carried out in emulsion under normal emulsion conditions, using CuBr 2/bpy complex as catalyst. The effects of surfactant type, initiator type a...
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Reverse atom transfer radical copolymerization of styrene (St) and butyl acrylate was carried out in emulsion under normal emulsion conditions, using CuBr 2/bpy complex as catalyst. The effects of surfactant type, initiator type and concentration, and CuBr _2 addition on the system livingness, polymer molecular weight control, and latex stability were examined in detail. It was found that the Polysorbate 80 (Tween 80) and azodiisobutyronitrile gave the best exhibition in this system, polymer samples were got with narrow molecular-weight dispersity (M _w/M _n = 1.1-1.2) and linear relationships of molecular weight versus monomer conversion, as well as a relatively low polydispersity index (<0.1). Through the GPC and SEM analysis, the polymerization processes under these conditions showed good living/control characteristics relative to the processes under normal emulsion polymerization, although the latex stability was susceptible to the CuBr _2 catalyst.
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Phosphorus (P) modified boehmite catalysts were prepared with wet impregnation method using phosphoric acid (H_3PO_4) as the P source. The P/boehmite catalysts with different P loadings ranging from 0 to 6.4 wt% were obtained by r...
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Phosphorus (P) modified boehmite catalysts were prepared with wet impregnation method using phosphoric acid (H_3PO_4) as the P source. The P/boehmite catalysts with different P loadings ranging from 0 to 6.4 wt% were obtained by regulating the concentration of H_3PO_4. These catalysts were characterized by BET surface area and FTIR spectroscopy measurements and their catalytic performance for hydrogen generation by methanolysis of sodium borohydride at 0 ℃ was evaluated. The results show that the as-prepared non-metallic P/boehmite catalyst exhibited high catalytic activity toward the methanolysis reaction under the circumstance of low environmental temperature. Appropriate calcination treatment can enhance the catalytic activity of P/boehmite catalyst to some extent. To understand the kinetic behavior of the methanolysis reaction in the presence of these catalysts, the experimental data were fitted to both zero-order and first-order kinetic models using the integral method.
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