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A novel pathway for the preparation of Mg metal from magnesia
No full textHigh-purity anhydrous magnesium chloride was prepared from magnesia and ammonium chloride. The chlorination process was analyzed and then the critical stages affecting the purity of anhydrous magnesium chloride were pinpointed. The effect of sample dimension on the above critical stages was investigated respectively. The purity guarantee mechanism of anhydrous magnesium chloride was proposed. After that, magnesium metal was obtained via electrolyzing the anhydrous magnesium chloride-containing molten salt. The new process for the continuous production of magnesium metal from magnesia was proposed and discussed. The incomplete chlorination reaction and the hydrolysis of anhydrous magnesium chloride are the two critical stages affecting the purity of the anhydrous magnesium chloride. The dimension of the sample can influence reaction process and reaction mechanism, and thus the problems of incomplete chlorination reaction and hydrolysis can be solved together. The magnesia content in anhydrous magnesium chloride was below 0.1 wt.% when the ratio of height to diameter of the sample was over 2.43. The content of impurities in the magnesium metal obtained met the specifications of the product Mg9980. The current efficiency was (94.7卤1.8)% and the electricity consumption was (9107卤97) kW h/t. 漏 202
High performance ozone decomposition spinel (Mn,Co)3O4 catalyst accelerating the rate-determining step
No full textAt present, it is still a challenge to develop ozone decomposition catalysts with high efficiency and high humidity resistance. Herein, a series of spinel (Mn,Co)3O4 catalysts are synthesized by coprecipitation method. Compared with the Mn3O4 and Co3O4 analogues, the obtained (Mn,Co)3O4 has CoCoIIIII脳 acceptor-defect and MnMnIIIII脳 donor-defect, which could contribute to the electron transfer between catalyst and ozone, accelerating ozone decomposition. Importantly, the in-situ Raman spectra of Mn3O4 shows the accumulation of peroxide species (O22-) inferring that the decomposition of O22- is the rate-determining step. On the other side, the reaction of the atomic oxygen with ozone would be rate-determining for Co3O4, as revealed by the low efficiency but no O22- signal. However, the synergy of Mn and Co in (Mn,Co)3O4 accelerates both the rate-determining steps obtaining high efficiency, which provides a new idea to develop catalysts in ozone elimination. 漏 202
Relationship of particle size, reaction and sticking behavior of iron ore fines toward efficient fluidized bed reduction
No full textThe relationship of particle size, reaction and sticking behavior of iron ore fines toward efficient fluidized bed hydrogen reduction were systematically investigated at 600鈥?00 掳C in a laboratory fluidized bed. First, the reduction kinetics were studied, and the results showed that hydrogen reduction of granulated iron ore was controlled by reduction reaction, and the activation energy was approximately 88.4 kJ/mol. The reduction rate of granulated iron ore with a diameter of 200 渭m could be increased by 10 times as the reduction temperature rose from 600 to 800 掳C. Then, a modified force balance model was established to distinguish the critical sticking point of granulated iron ore during high temperature fluidized bed hydrogen reduction, and it indicated that the defluidization temperature could be raised from 630 to 790 掳C as the particle size was enlarged from 100 to 200 渭m with a fluidization number of 10. Eventually, coupling the kinetic model and modified force balance model, the maximum gas utilization rate of fluidized bed hydrogen reduction was estimated, and it indicated that at reduction temperatures of 650鈥?50 掳C with particle sizes of 200鈥?00 渭m, the optimal gas utilization rate could be achieved, which was consistent with the experimental results. Contradictory to traditional understandings of chemical reaction engineering, due to the interaction of reduction performance and sticking behavior, too high of a reduction temperature or too small of a particle size might not be preferable for fluidized bed hydrogen reduction, and this study provided valuable references for industrial operation. 漏 2022 Elsevier B.V
Preparation and Photo-Fenton Catalytic Properties of High-Purity Hercynite
No full textTo develop novel environmental-friendly photo-Fenton catalysts, hercynite (FeAl2O4) was prepared via reaction sintering. The catalytic performance in photo-Fenton and the degradation of hercynite for rhodamine B dye was investigated. The results show that the phase composition in the samples is a high-purity hercynite with Fe2+ and Fe3+ complex valence states. The optimal degradation efficiency and TOC removal efficiency are 90.71% and 76.46%, respectively at pH value of 3.14, FeAl2O4 of 1.0g/L and H2O2 of 2% (in volume fraction). After four cycles, hercynite still maintains a good stability. The synthesized hercynite as an optical photo-Fenton catalyst can be recycled and reused for times, The synthesized hercynite which has a potential application prospect in dye wastewater treatment. 漏 2022, Editorial Department of Journal of the Chinese Ceramic Society. All right reserved
Supergravity-enhanced liquation crystallization for metal recovery from waste printed circuit boards
No full textWaste printed circuit boards (WPCBs) present serious threats to the environment but also the opportunity to recover the valuable metals, motivating a search for processes to allow their cost-effective recycling. In this regard, the advantages afforded by liquation crystallization and supergravity technology were combined herein to develop a new supergravity-enhanced liquation crystallization process for recovering metals from WPCBs. The WPCB particles were fully smelted to obtain WPCB alloy. Fe-rich, Cu鈥揨n, Cu鈥揝n, and Pb-rich phases were progressively precipitated from the alloy melt as the temperature decreased and subsequently stratified from top to bottom after supergravity-induced enrichment owing to their different densities. Fe-rich, Cu鈥揨n, Cu鈥揝n, and Pb-rich alloys were obtained via supergravity-assisted separation at 1100, 850, and 500 掳C, respectively. The mass fractions of Fe in the Fe-rich alloy, (Cu + Zn) in the Cu鈥揨n alloy, (Cu + Sn) in the Cu鈥揝n alloy, and Pb in the Pb-rich alloy reached 81.8 wt.%, 92.9 wt.%, 91.2 wt.%, and 94.6 wt.%, respectively, in the three separation steps. The final recoveries of Fe, Cu, Zn, Sn, and Pb after three supergravity-assisted separation stages reached 98.8%, 97.8%, 94.1%, 96.9%, and 97.4%, respectively. This study demonstrates an efficient method for separating metals from WPCBs and improving the grade of the separated metals. 漏 202
Synthesis and characterization of form-stable carbonate/steel slag composite materials for thermal energy storage
No full textIt is of practical importance to develop form stable composite phase change materials (FSPCMs) for high temperature thermal energy storage. Carbonates are promising candidates as the phase change material and steel slag is a promising economical skeleton material. However, the molten carbonates (Na2CO3 and K2CO3) react with steel slag (SS) at high temperature. Here, a two-step process was developed to overcome this problem. Firstly, the modified steel slag (MSS) was obtained by activation of the two carbonates, and secondly, FSPCMs were synthesized by mix-sintering method. The obtained K2CO3/KMSS FSPCMs kept better shape than that of Na2CO3/NMSS FSPCMs after the thermal cycles. Further test showed that K2CO3 had good chemical compatibility with KMSS and was uniformly distributed. With the increased K2CO3 content, the latent heat of K2CO3/KMSS FSPCMs gradually increases, and the measured latent heat was consistent with the calculated values. With mass ratio 4:6 (40K2CO3/60KMSS), the developed FSPCM showed the best thermal stability, the latent heat attenuation was 7.08%, and the mass loss was 6.56% after 200 thermal cycles. 漏 2022 Elsevier Lt
Fabrication of asymmetric bilayer solid-state electrolyte with boosted ion transport enabled by charge-rich space charge layer for 20~70掳C lithium metal battery
No full textLi6.4La3Zr1.4Ta0.6O12 (LLZTO), a typical oxidizing ceramic solid electrolyte of excellent lithium-ion conductivity, is considered as a promising candidate for next-generation high-energy-density solid-state lithium metal batteries (SSLMBs). However, great challenges, such as the unexpected growth of lithium dendrites and the excessive resistance of electrolyte/electrode interface, need to be well addressed through their commercialization. Here, a local conjugated polymer solid-state electrolytes nanolayer was formed onto ceramic oxide particles via selective adsorption through an in-situ polymerization process. Li solid NMR spectra and TEM (ex-situ and in-situ) characterizations suggest that optimized layer provided effective pathways for Li+ conduction between SSEs and ceramic oxide. Consequently, this composite electrolyte possesses a high ionic conductivity of 0.69 mS cm鈭? at 25 掳C. Lithium symmetrical batteries exhibit a reduced charge voltage polarization and the critical current density could be increased up to 2.4 mA cm鈭?. Moreover, lithium metal batteries based on CPE show an excellent cycle stability over a broad temperature range from 鈭?0 to 70 掳C, and super-long cycling performance (> 600 cycles) at 0.5 C under 0 掳C. This new strategy creates a new route to resolve the LLZTO/electrode interface issue by constructing rich-large space charge layer and promoting Li+ conduction, it will be helpful for the commercialization and application of wide-temperatures SSLMBs. 漏 202
From fundamentals to chemical engineering on oxidative coupling of methane for ethylene production: A review
No full textA comprehensive overview is presented to summarize the research works since 1982 on oxidative coupling of methane (OCM), a complex reaction network combining heterogeneous and homogeneous reaction steps. Fundamentals on reaction mechanisms and thermodynamics have revealed that the OCM process is highly exothermic and its C2+ selectivity and yield is critical in evaluating its commercial viability. Catalytic strategies have been put to enhance C2+ selectivity, improve C2+ yield and lower reaction temperature. The catalyst Mn-Na2WO4/SiO2 enables methane activation at a temperature of 800 掳C and simultaneously a high C2+ selectivity of 70鈥?0%, while the nanowire and La2O3-based catalysts enable to lower the reaction temperature to 200鈥?00 掳C and 500 掳C, respectively. Reaction engineering aspects have also been dealt in many investigations in order to make the process technically feasible. Particularly, research works on reaction kinetics, reactor selection and reactor operating mode choice have been addressed. Intermediate cooling and distributed oxygen feed have been integrated into a multi-stage adiabatic fixed-bed reactor system to suppress the side oxidation reactions and improve the performance of the catalysts towards CH4 conversion and C2+ yield. This review paper proposes employing a circulating reactor system coupled with catalyst fine particles but having little internal diffusion resistance to maximize one-pass C2+ selectivity and yield of the OCM reaction and evaluate its industrial application potential. 漏 202
Highly Zn2+-conductive and robust modified montmorillonite protective layer of electrodes toward high-performance rechargeable zinc-ion batteries
No full textThe corrosion, parasitic side-reaction and dendrite of Zn anode as well as the dissolution of MnO2 cathode limit the commercial application of zinc-ion batteries (ZIBs). Herein, a novel coating layer on Zn anode and MnO2 cathode of rechargeable ZIBs is rationally designed by mixing hexadecyl trimethyl ammonium bromide(CTAB)-pillared organic montmorillonite with ZnSO4/MnSO4 solution (ZnOMMT). ZnOMMT can serve as the protective layer to alleviate Zn corrosion and MnO2 dissolution while the unique interlayer structure of ZnOMMT can also offer a selective pathway for fast Zn2+ transfer and uniform Zn2+ diffusion to inhibit the side-reaction and Zn dendrite generation. Notably, by the powerful pillaring of CTAB cations, the expanded and robust nanoscale interlayer tunnels of ZnOMMT for Zn2+ diffusion are constructed to guarantee outstanding ionic conductivity (6.52 mS cm鈭?), high Zn2+ transference number (t+=0.66) and outstanding cyclic stability during deep cycles. Therefore, ZIBs with ZnOMMT coating layer deliver a steady long-term reversible capacity (267 mAh g鈭? until 300 cycles at 0.5 A g鈭?, 205 mAh g鈭? until 700 cycles at 1.0 A g鈭?). The rational design of CTAB-pillared montmorillonite protective layer brings a brand-new opportunity to the realization of high-performance rechargeable ZIBs. 漏 2022 Elsevier B.V
Effect of Co on the pre-reduction process of WO3-Co3O4 and carbonization performance of its product
No full textIn order to avoid the formation of 畏 phase (Co6W6C or Co3W3C) that adversely affect the sintering process and its products in the preparation process ultra-fine WC-Co powder, we propose a technical route of pre-reduction of WO3-Co3O4 to WO2-Co and then deep reduction carbonization to WC-Co. The influence of Co content and cobalt source particle size on the pre-reduction process of WO3-Co3O4 was investigated at 600 H2-C2H4-Ar atmosphere in a fluidized-bed reactor, and the deep reduction and carbonization properties of the pre-reduced products were tested. The results show that the presence of Co can catalyze the splitting of C2H4to separate H2and C, significantly accelerate the pre-reduction rate of WO3, and the pre-reduction rate increases significantly with the increase of Co content. The carbon evolution rate and carbon evolution amount of ethylene also increase with the increase of Co content. Cobalt source particle size has a significant effect on the pre-reduction rate of WO3 and carbon evolution rate of C2H4. In this experimental system, the carbon evolution rate of C2H4 in nano cobalt source system is about twice that of micron cobalt source system. Meanwhile, WO3 in nano cobalt source system also has faster reduction rate. The pre-reduced product was calcined with methane partial pressure of 1.25% at 950 for 60 min, and fine WC-Co composite powder without 畏 could be obtained. 漏 2022 Chemical Industry Press. All rights reserved