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The one-pot catalytic conversion of cellulose into ethylene glycol (EG) is an attractive way of biomass utilization. However, low-cost, efficient, and stable catalysts are the premise and research challenges of industrial applicat...
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The one-pot catalytic conversion of cellulose into ethylene glycol (EG) is an attractive way of biomass utilization. However, low-cost, efficient, and stable catalysts are the premise and research challenges of industrial application. Herein, the magnetic recyclable W-Ni@C catalyst was synthesized by in-situ pyrolysis of Ni-MOFs impregnated with ammonium metatungstate. Compared with the Ni-W bimetallic catalysts prepared by the impregnation method and the sol-gel method, the W-Ni@C catalyst for cellulose hydrogenolysis reaction can achieve a higher ethylene glycol yield (67.1% vs 43.3% and 42.6%) and 100% of cellulose conversion rate. The uniformly dispersed Ni nanoparticles and abundant defective WOx were formed in a reductive atmosphere generated in pyrolysis of Ni-MOFs, which was indispensable for the hydrogenolysis of cellulose into EG. Besides, the hierarchical porous carbon derived from organic ligands in Ni-MOFs reduces the mass transfer resistance while confining Ni nanoparticles and WOx to prevent their leaching, effectively enhancing the stability of the W-Ni@C catalyst. Therefore, the remarkable catalytic performance, the simple and effective recovery method as well as satisfying stability would make W-Ni@C become a promising catalyst for the conversion of cellulose to EG. [GRAPHICS]
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Solar-driven CO2 reduction to solar fuel is an effective way to deal with the greenhouse effect and energy crisis. A one-step hydrothermal method was used to synthesize Bi4Ti3O12/SrTiO3 composite photocatalysts. The heterogeneous ...
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Solar-driven CO2 reduction to solar fuel is an effective way to deal with the greenhouse effect and energy crisis. A one-step hydrothermal method was used to synthesize Bi4Ti3O12/SrTiO3 composite photocatalysts. The heterogeneous structure formed by intimate contact was observed between SrTiO3 (STO) nanoparticles and Bi4Ti3O12 (BTO) nanoplates, achieving an enhanced photocatalytic CO2 reduction yield of CO (13.37 mu mol/g) that was 5.74-fold that of pure STO (2.33 mu mol/g), with a high yield of CH4 (1.55 mu mol/g). Characterizations of phase composition, morphology, and optical/electrochemical properties were applied to prove the heterojunction structure and its role in improving the photocatalytic performance. X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy tests demonstrate that electrons transfer from STO to BTO and result in the generation of an internal electron field between the two phases. Consequently, a direct Z-scheme system was formed: photoelectrons in the conduction band of BTO transferred to the valence band of STO to recombine with the holes thus spatially separated the photogenerated electron-hole pairs while enabling the photocatalyst to achieve the maximum reduction and oxidation capability. The catalyst structure system proposed here may bring new ideas for the development of titanate-based photocatalysts with high CO2 reduction activity. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)
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We report the seed-mediated synthesis of CuS@CdS core-shell heterojunction with diverse morphologies by introducing kinetic control. By using CuS nanoplates as seeds and a collective manipulation of the injection rate of Cd2+ prec...
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We report the seed-mediated synthesis of CuS@CdS core-shell heterojunction with diverse morphologies by introducing kinetic control. By using CuS nanoplates as seeds and a collective manipulation of the injection rate of Cd2+ precursor with a syringe pump and the reaction temperature, two distinctive growth modes, i.e., island and layer-by-layer modes, respectively, could be realized. It is found that the growth is, in principle, determined by the deposition rate relative to the diffusion rate of the CdS growth monomers. Specifically, at a high injection rate and a relatively low reaction temperature, the deposition of CdS monomers on the surface of the CuS nanoplate follows an island growth mode because of the lattice mismatch between CuS and CdS and distinct binding energies of them. We can facilitate surface diffusion of these deposited monomers by reducing the injection rate of Cd2+ and increasing the reaction temperature. In this case, growth can be switched to a layer-by-layer mode. The products are found with tunable and significantly improved photocatalytic performance toward dye degradation and H-2 production from water under visible-light irradiation in comparison to the sole use of either CdS or CuS photocatalyst. This work provides an effective approach to the rational design of heterojunctions.
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A series of transitional metal disubstituted ternary heteropoly quaternary ammonium salts, [TPA](4)H-3[PW7Mo3M2O38(H2O)(2)] (M = Mn, Co, Ni, Cu), were prepared by the reaction of the anion PW6Mo3O34 (9-) and the corresponding salt...
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A series of transitional metal disubstituted ternary heteropoly quaternary ammonium salts, [TPA](4)H-3[PW7Mo3M2O38(H2O)(2)] (M = Mn, Co, Ni, Cu), were prepared by the reaction of the anion PW6Mo3O34 (9-) and the corresponding salts of the transitional metal in water, characterized by FI-IR, UV-Vis, XRD and TGA spectra, and appied to the epoxidation of 1-butene to 1,2-butene oxide (BO). The influences of temperature, reaction time, H2O2 concentration and catalyst concentration on the epoxidation of 1-butene were studied in the acetonitrile/hydrogen peroxide catalytic system. The variation ranges of these parameters ensuring a high H2O2 conversion and high selectivity of BO were established. It can be observed that the catalytic activity decreases in the order PWMoMn > PWMoCo > PWMoNi > PWMoCu. The best conversion of H2O2 and selectivity toward BO were achieved under optimized conditions: reaction time = 2 h, reaction temperature = 50 A degrees C, H2O2 concentration = 0.5 mol/L and a catalyst concentration of 2.5 g/L. In particular, the catalyst PWMoMn is the most active one for epoxidation of 1-butene to BO (selectivity of BO up to 97.6 %).
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Background: The combination of flow chemistry and microreactor technology is emerging in the modern chemical industry. It can link chemical engineering, organic synthesis, and green chemistry, which provides a safety guarantee for...
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Background: The combination of flow chemistry and microreactor technology is emerging in the modern chemical industry. It can link chemical engineering, organic synthesis, and green chemistry, which provides a safety guarantee for dangerous chemical processes.Method: In view of the advantages of continuous flow synthesis, a more efficient method for the synthesis of 3,5,5-trimethylhexanoyl chloride from triphosgene and 3,5,5-trimethylhexanoic acid catalyzed by N, N-dimethylformamide was obtained by using silicon carbide microreactor, which was reported for the first time. Computational fluid dynamics (CFD) simulation of single-phase flow in an advanced microreactor was carried out with OpenFOAM software. The flow lines, lag zone, velocity distribution, pressure field, and residence time distribution (RTD) were obtained at different flow rates (5-100 mL/min).Significant findings: A continuous flow process for the 3,5,5-trimethylhexanoyl chloride with a 91% isolated yield has been reported. Triphosgene and 3,5,5-trimethylhexanoic acid were used as starting materials to achieve excellent results in the silicon carbide flow reactor, which could tolerate the corrosion of chloride ions at 55 celcius and 0.8 MPa. In the continuous flow process, based upon the cyclic feed reaction method, the product was obtained with sufficiently high 3,5,5-trimethylhexanoic acid conversion (> 99%) and product 3,5,5-trimethylhexanoyl chloride selectivity (95%). The throughput reached 0.35 kg/h, and the purity of the final product was greater than 90% by distillation, which was in accordance with the needs of production. This new process using more polar tetrahydrofuran as the solvent was time- and cost-effective, and the obtained product had a higher yield, brighter color, and less impurity. With the increase of the flow velocity, the stagnation area and the swirling intensity increased slightly, but the velocity and pressure distribution in each mixing unit were relatively uniform. Additionally, the reactor had symmetric RTDs at all flow rates. Due to the larger flow rate, the Peclet number was increased and the axial dispersion was reduced, with the result of a narrower RTD curve.
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Considering that CO2 is a harmful greenhouse gas, the effective conversion of this compound to high-value hydrocarbons is highly desirable, but also challenging. Herein, we synthesize a series of Cu- and Ag-modified TiO2 (B phase)...
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Considering that CO2 is a harmful greenhouse gas, the effective conversion of this compound to high-value hydrocarbons is highly desirable, but also challenging. Herein, we synthesize a series of Cu- and Ag-modified TiO2 (B phase) photocatalysts, and we analyze their efficiency in catalyzing the photoreduction of CO2 in the presence of H2O and simulated solar irradiation. The obtained results show that the TiO2(B) catalyst modified with 1% Ag and 0.5% Cu has the best photoreduction performance, with CO and CH4 yields of 860 and 410 mu mol/g, respectively, after for 3 h of reaction. Based on CO2-TPD testing, Cu enhances the photocatalytic activity of TiO2(B) by adsorbing and activating CO2. Meanwhile, the Ag nanoparticles increase the absorption of visible light through surface plasmonic resonance effect (SPR), and they transfer electrons to the TiO2(B) nanosheets. The transferred electrons migrate to the Cu particles where they reduce the adsorbed and activated CO2. This study provides an effective method for improving the photocatalytic CO2 reduction performance of TiO2(B)-based catalysts.
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Graphitic carbon nitride is considered as one of the promising photocatalysts for pollution elimination from wastewater. Manipulating the microstructure of carbon nitride remains a challengeable task, which is essential for improv...
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Graphitic carbon nitride is considered as one of the promising photocatalysts for pollution elimination from wastewater. Manipulating the microstructure of carbon nitride remains a challengeable task, which is essential for improving light absorption, separating photogenerated carrier and creating reactive sites. Herein, a carbon vacancy modified hierarchical carbon nitride microrod (CN1.5) has been prepared templated from a melamine-NH2OH center dot HCl complex. The hierarchical microrods are demonstrated to be comprised of interconnected nanosheets with rich carbon vacancies, which endows it with high specific surface area, enhanced light utilization efficiency, available reactive sites, improved charge carrier separation and numerous mass-transport channels. The resultant photocatalyst CN1.5 exhibits an excellent photodegradation efficiency of 87.9% towards tetracycline under visible light irradiation. The remarkable apparent rate constant of 4.91 x 10(-2) min(-1) is 7.3 times higher than that of bulk CN. In addition, the degradation pathways are deduced base on the observation of degradation intermediates generating in the photocatalytic process. Mechanism investigation indicates that the major contribution for photodegradation is attributed to center dot O-2(-), O-1(2) and H2O2 species. This work provides new insights into advancing carbon nitride's microstructure to improve photocatalytic degradation performance for highly efficient antibiotic removal and environment remediation.
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A series of HfxZr1-xP/SiO2 catalysts were prepared for the catalytic conversion of cellulose to HMF in a two-phase solution system. Metal phosphate supported on mesoporous SiO2 microspheres had improved stability owing to the meta...
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A series of HfxZr1-xP/SiO2 catalysts were prepared for the catalytic conversion of cellulose to HMF in a two-phase solution system. Metal phosphate supported on mesoporous SiO2 microspheres had improved stability owing to the metal phosphate-O-Si chemical bonds, and used less active metals than conventional catalysts. The effect of the reaction conditions on the preparation of HMF was studied. Hf0.7Zr0.3P/SiO2 reacted at 463 K for 4 h, the cellulose conversion rate reached 86.2%, and the HMF yield was 62.03%. The structures and physicochemical properties of the catalysts were characterized using various techniques. The catalysts haves both Lewis acid and Bronsted acid active sites, which can facilitate the hydrolysis of cellulose, the isomerization of glucose and the dehydration of fructose to obtain HMF. A suitable Bronsted acid to Lewis acid ratio was obtained by adjusting the Hf/Zr/Si content ratio to produce Hf0.7Zr0.3P/SiO2. This helped improve the HMF yield. The catalyst retained more than 90% of its performance after five test cycles.
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Nanosized semiconductors with hierarchical structures are attractive for use as catalysts. Development of high porous structures, to this end, has received intense interest. By using a well-defined titanium-based metal-organic fra...
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Nanosized semiconductors with hierarchical structures are attractive for use as catalysts. Development of high porous structures, to this end, has received intense interest. By using a well-defined titanium-based metal-organic framework, i.e., MIL-125(Ti), as a template, we report the synthesis of Ni-doped mesoporous TiO2 nanocrystals with tablet morphologies. While the obtained Ni-TiO2 composites could be used for photoreduction of CO2 in the presence of water vapor, this photocatalytic property could be largely improved by further deposition of Ag nanoparticles. In principle, Ni species in the lattice matrix lead to the formation of impurity levels in the bandgap of TiO2, promoting both light absorption and charge separation. On the other hand, Ag, as a cocatalyst, can trap electrons and simultaneously activate the C=O bonds from the adsorbed CO2. Our results demonstrate that 1.0% Ag/0.5% Ni-TiO2 photo-catalyst exhibits the highest activity. The yields of CO and CH4 reach 14.31 and 279.07 mu mol/g, respectively, for a 3-h reaction. We believe the strategy based upon the synergy of Ni doping and Ag loading can be extended to other photocatalytic systems. (C) 2019 Society of Photo Optical Instrumentation Engineers (SPIE)
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The perovskite-type LaFeO3 serves as a promising photo-Fenton-like catalyst, but its low adsorption ability and catalytic activity inhibit the effective removal of ofloxacin. Herein, the LaFeO3 and lignin-biochar composites were f...
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The perovskite-type LaFeO3 serves as a promising photo-Fenton-like catalyst, but its low adsorption ability and catalytic activity inhibit the effective removal of ofloxacin. Herein, the LaFeO3 and lignin-biochar composites were fabricated by a facile sol-gel pyrolysis route. As compared with LaFeO3 nanoparticles, the LaFeO3/lignin-biochar composites showed better adsorption and degradation ability due to the synergistic effect between LaFeO3 nanoparticles and lignin-biochar. Compared with LaFeO3, the adsorption capacity of LaFeO3/lignin-biochar for ofloxacin increased from 0.72 to 30.4 mg.g(-1). Importantly, this catalyst exhibited the improved degradation efficiency of ofloxacin during 75 min (95.6 % for LaFeO3/lignin-biochar Vs 53.4 % for LaFeO3) as the adsorption process was combined with the photo-Fenton-like process. Notably, the lignin-biochar in the LaFeO3/lignin-biochar composites decreased the bandgap of LaFeO3 nanoparticles from 2.10 eV to 1.79 eV due to the interface interaction between LaFeO3 and lignin-biochar, facilitating the enhanced photo-Fenton-like activity. The hydroxyl radicals that were generated in the photo-Fenton-like process effectively induced the oxidative degradation of ofloxacin, which was confirmed by free radical capture experiments and ESR characterization. Moreover, the photo-Fenton-like degradation pathway of ofloxacin was proposed according to LC-MS analyses, and the toxicity analysis of degradation intermediates was further carried out. Hence, the LaFeO3/lignin-biochar composite was a promising photo-Fenton-like catalyst to eliminate ofloxacin via coupling of adsorption and photo-Fenton-like processes.
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