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Synthesis of Tunable-Acidity Vanadium Phosphorus Oxide CatalystsModified by Layered Double Oxide for the Selective Oxidation ofn-Butane br
No full textA series of tunable-acidity vanadium phosphorus oxide (VPO) catalysts modified by layered double oxide (LDO)werefirst fabricated by a mechanical milling approach. The optimum Zn2Mg1Al1O-VPO sample achieved 63.2% yield of maleicanhydride (MA), which is 8.9% higher than that of Blank-VPO. Various characterizations were used to explore the relationshipbetween the surface properties such as the crystal structure, surface P/V ratio, surface acidity, and catalytic performance. The NH3-TPD and pyridine IR analysis demonstrated that the appropriate surface acidity could significantly improve the performance of theVPO catalyst. A synergistic catalysis mechanism between the Lewis and Bronsted acid sites is tentatively proposed to enhance thecatalytic performance of VPO. The Lewis acid sites accelerate the C-H bond activation and cleavage, thereby increasing theconversion ofn-butane. Moreover, the Bronsted acid sites can stabilize the reaction intermediates and facilitate the desorption ofMA, consequently improving the selectivity of MA
A facial synthesis of nitrogen-doped reduced graphene oxide quantum dot and its application in aqueous organics degradation
No full textN-doped reduced graphene oxide quantum dots (N-rGQDs) have attracted more and more attention in efficient catalytic degradation of aqueous organic pollutants. However, the synthesis of N-rGQDs is generally a complex and high energy required process for the reduction and N-doping steps. In this study, a facile and green fabrication approach of N-rGQDs is established, based on a metal-free Fenton reaction without additional energy-input. The N structures of N-rGQDs play a significant role in the promotion of their catalytic performance. The N-rGQDs with relatively high percentage of aromatic nitrogen (N-Ar-rGQDs) perform excellent catalytic activities, with which the degradation efficiency of pollutant is enhanced by 25 times. Density functional theory (DFT) calculation also indicates aromatic nitrogen structures with electron-rich sites are prone to transfer electron, presenting a key role in the catalytic reaction. This metal-free Fenton process provides a green and cost-effective strategy for one-step fabrication of N-rGQDs with controllable features and potential environmental catalytic applications. (C) 2020 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd
A novel process to prepare high-purity vanadyl sulfate electrolyte from leach liquor of sodium-roasted vanadium slag
No full textThe leach liquor of sodium-roasted vanadium slag in vanadium industry is an alkaline solution containing vanadium, sodium, chromium, and other impurities, and preparing high-purity vanadyl sulfate electrolyte (used in vanadium redox flow battery) directly from this solution is challenging but cost-effective. A novel process consisting of selective reduction-precipitation of chromium and solvent extraction of vanadium was proposed and optimized in this study. Approximately 90% of Cr(VI) in the solution was reduced to Cr(III) and precipitated after adding sodium sulfite at a pH of 5.77 and 25?, while V(V) remained in this process and needed a further reduction to V(IV) prior to extraction. More than 99.9% of V(IV) remained in the solution was extracted by two stage extraction using the "P507 + TBP + kerosene " extractant system at a pH of 2.00 and an organic-to-aqueous phase ratio of 1.5:1. Sodium entrained in the organic phase was washed off through three-stage scrubbing. A high-purity vanadyl sulfate solution of 2.1 mol L-1 was prepared by two-stage stripping using 5.5 mol L-1 sulfuric acid. According to the slope analysis and infrared spectra, the extraction of V(IV) by P507 follow the cation exchange mechanism. This study provides a feasible way to remove chromium and recover vanadium in the form of vanadyl sulfate from the industrial leach liquor of sodium-roasted vanadium slag
Novel approach to energy-efficient flexible job-shop scheduling problems
No full textIn this work, we develop a novel mathematical formulation for the energy-efficient flexible job-shop scheduling problem using the improved unit-specific event-based time representation. The flexible job-shop is represented using the state-task network. It is shown that the proposed model is superior to the existing models with the same or better solutions by up to 13.5 % energy savings in less computational time. Furthermore, it can generate feasible solutions for large-scale instances that the existing models fail to solve. To efficiently solve large-scale problems, a grouping-based decomposition approach is proposed to divide the entire problem into smaller subproblems. It is demonstrated that the proposed decomposition approach can generate good feasible solutions with reduced energy consumption for large-scale examples in significantly less computational time (within 10 min). It can achieve up to 43.1 % less energy consumption in comparison to the existing gene-expression programming-based algorithm. (c) 2021 Elsevier Ltd. All rights reserved
