scholarly journals High efficiency extractions of V, Cr, Ti, Fe and Mn from vanadium slag by microwave heating

2021 ◽  
pp. 23-23
Author(s):  
B. Tan ◽  
S. Wu ◽  
L.-J. Wang ◽  
K.-C. Chou
Keyword(s):  
High Temperature ◽  
Reaction Time ◽  
Diffusion Process ◽  
Microwave Heating ◽  
High Efficiency ◽  
Conventional Heating ◽  
Vanadium Slag ◽  
Reduction Processes ◽  
Fe And Mn ◽  
Speed Up

The vanadium slag (V-slag) is generated from smelting vanadium titanomagnetite ore, which contains valuable elements, such as V, Ti, Cr, Fe and Mn. The traditional methods were mainly focused on the extractions of V and Cr by oxidation or reduction processes. In the present work, chlorination method was adopted to keep the valence state of each elements as original state. In order to speed up the diffusion of elements and reduce volatility of molten salt, microwave heating has been examined in the current paper. The results indicated that it only took 30 min to chlorinate V-slag at 800 ?C, and the chlorination ratios of V, Cr, Mn, Fe and Ti could reach to 82.67%, 75.82%, 92.96%, 91.66% and 63.14%, respectively. Compared with the results by conventional heating for 8 h, this extraction rate by microwave heating shows greater advantages. In addition, microwave heating can reduce effectively volatilization of AlCl3 by shortening the reaction time. The volatilization ratio of AlCl3 in this microwave heating was 3.92% instead of 8.97% in conventional heating (1h). The mechanism of efficient chlorination can be summarized as the enhancement of ions diffusion process and enhanced chemical reaction due to local high temperature.

Preparation of WC-TiC-Ni3Al-CaF2 functionally graded self-lubricating tool material by microwave sintering and its cutting performance

2020 ◽  
Vol 39 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Siwen Tang ◽  
Rui Wang ◽  
Pengfei Liu ◽  
Qiulin Niu ◽  
Guoqing Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Microwave Heating ◽  
Cutting Performance ◽  
Conventional Heating ◽  
Hard Alloys ◽  
Dry Cutting ◽  
Temperature Oxidation ◽  
Lubricating Material ◽  
Heating Technology

AbstractWith the concern of the environment, green dry cutting technology is getting more and more attention and self-lubricating tool technology plays an important role in dry cutting. Due to the demand for high temperature performance of tools during dry cutting process, cemented carbide with Ni3Al as the binder phase has received extensive attention due to its excellent high temperature strength and high temperature oxidation resistance. In this paper, WC-TiC-Ni3Al-CaF2 graded self-lubricating material and tools were prepared by microwave heating method, and its microstructure, mechanical properties and cutting performance were studied. Results show that gradient self-lubricating material can be quickly prepared by microwave heating technology, and the strength is equivalent to that of conventional heating technology. CaF2 not only plays a role in self-lubrication, but also refines the grain of the material. A reasonable gradient design can improve the mechanical properties of the material. When the gradient distribution exponent is n1 = 2, the material has high mechanical properties. Cutting experiments show that the WC-TiC-Ni3Al-CaF2 functional gradient self-lubricating tool has better cutting performance than the homogeneous WC-TiC-Ni3Al hard alloys.

A high-yield microwave heating method for the preparation of (phthalocyaninato)bis(chloro)silicon(IV)

2001 ◽  
Vol 05 (04) ◽  
pp. 376-380 ◽  
Author(s):  
DOMINIC A. DAVIES ◽  
CHRISTINA SCHNIK ◽  
JACK SILVER ◽  
JOSE L. SOSA-SANCHEZ ◽  
PHILIP G. RIBY
Keyword(s):  
Reaction Time ◽  
Microwave Heating ◽  
Silicon Tetrachloride ◽  
Conventional Heating ◽  
High Yield ◽  
Thermal Heating ◽  
Heating Method ◽  
Purification Time

The microwave heating synthesis of (phthalocyaninato)bis(chloro)silicon(IV) prepared from diiminoisoindolene and silicon tetrachloride in quinoline has been shown to be rapid (5 min reaction time compared to 30 min with thermal heating) and results in a high yield (91% compared to 71% using thermal heating). A modified microwave ashing furnace was used to heat the reaction mixture. The high yield has led to a reduction in the purification time to 1 h (compared to 4 h or more using conventional heating).

Synthesis of anti-inflammatory 2,3-unsaturated O-glycosides using conventional and microwave heating techniques

2017 ◽  
Vol 23 (3) ◽  
pp. 205-211
Author(s):  
Adriana Cristina N. de Melo ◽  
Ronaldo N. de Oliveira ◽  
João R. de Freitas Filho ◽  
Teresinha G. da Silva ◽  
Rajendra M. Srivastava
Keyword(s):  
Reaction Time ◽  
Microwave Irradiation ◽  
Microwave Heating ◽  
Acid Catalyst ◽  
Conventional Heating ◽  
Microwave Exposure ◽  
Ferrier Rearrangement ◽  
Acetyl Group ◽  
Anti Inflammatory

AbstractThe preparation of eight 2,3-unsaturated O-glycosides from D-glycals and alcohols, using montmorillonite K-10 as an acid catalyst, is described. The Ferrier rearrangement products were obtained in good yields using conventional heating and microwave irradiation but the reaction time was substantially reduced employing the latter procedure. The yields were slightly lower under microwave exposure. Five of the di-O-acetylated products were deacetylated to the glycosides in excellent yields. The acetylated products possess good anti-inflammatory property suggesting that the acetyl group plays an important role in reducing the inflammation. Among the compounds tested, glycosides containing thiophene as an aglycone present much better inflammation reducing characteristics than the analogues without this function.

Microwave-assisted Al-substituted Tobermorite Synthesis

2000 ◽  
Vol 15 (4) ◽  
pp. 850-853 ◽  
Author(s):  
Michihiro Miyake ◽  
Shigeto Niiya ◽  
Motohide Matsuda
Keyword(s):  
Reaction Time ◽  
Hydrothermal Synthesis ◽  
Microwave Heating ◽  
Conventional Heating ◽  
Crystallization Time ◽  
Short Reaction Time ◽  
Microwave Assisted

The effect of microwave heating on the hydrothermal synthesis of Al-substituted tobermorite and the removal characteristics of resulting materials were examined and compared with the effect of conventional heating. The microwave heating reduced the crystallization time of Al-substituted tobermorite—i.e., Al-substituted tobermorite was synthesized within 80 min at around 140 °C—and produced smaller crystallites than the conventional heating. The minute crystallites were found to promote the removal characteristics for Cs+ ions in short reaction time.

scholarly journals Intensification and optimization of biodiesel production using microwave-assisted acid-organo catalyzed transesterification process

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Moina Athar ◽  
Sadaf Zaidi ◽  
Saeikh Zaffar Hassan
Keyword(s):  
Reaction Time ◽  
Organic Acid ◽  
Microwave Heating ◽  
Low Cost ◽  
Acid Catalyst ◽  
Operating Conditions ◽  
Biodiesel Production ◽  
Conventional Heating ◽  
Molar Ratio ◽  
Inorganic Acid

AbstractTo produce biodiesel cost-effective, low-cost, high free fatty acid (FFA) oil feedstock is desirable. But high FFA creates difficulty during the base-catalyzed transesterification process by yield loss due to the formation of soap. However, these problems are overcome by the use of an acid catalyst. The acid catalysts can directly convert both triglycerides and FFAs into biodiesel without the formation of soaps or emulsions. The shortcomings of mostly used inorganic acids are that they work well for esterification of FFA present in low-cost oil, but their kinetics for transesterification of triglycerides present in oils is considerably slower. Corrosion of equipment is another major problem associated with an inorganic acid catalyst. The usage of an organic acid catalyst of the alkyl benzene sulfonic type, like 4-dodecyl benzene sulfonic acid (DBSA) minimizes these disadvantages of inorganic acid-catalyzed transesterification. The aim of the present investigation was to reduce the reaction time of transesterification of triglycerides further by using microwaves as a heating source in the presence of DBSA catalyst to achieve higher conversions under mild operating conditions. To optimize the transesterification variables for the higher conversion of biodiesel, the response surface methodology was employed to design the experiment. By using the DBSA catalyst under microwave heating at a temperature of 76 °C, conversion close to 100% in only 30 min of reaction time was obtained using a 0.09 molar ratio of catalyst to oil and 9.0 molar ratio of methanol to oil. A modified polynomial model was developed and was adequately fitted with the experimental data and could be used for understanding the effect of various process parameters. The catalyst to oil molar ratio and reaction temperature created a stronger effect on the biodiesel production than that exhibited by the methanol to oil molar ratio. It was observed that the microwave heating process outperformed conventional heating, providing a rapid, easy method for biodiesel synthesis from triglycerides in the presence of DBSA, an organic acid catalyst. The produced biodiesel was of good quality, as all the properties were within the prescribed limits of the ASTM D6751 standard.

scholarly journals Microwave Heating Improvement: Permittivity Characterization of Water–Ethanol and Water–NaCl Binary Mixtures

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4861
Author(s):  
Fabio Fanari ◽  
Giacomo Muntoni ◽  
Chiara Dachena ◽  
Renzo Carta ◽  
Francesco Desogus
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Reaction Time ◽  
Microwave Heating ◽  
Scientific Literature ◽  
Conventional Heating ◽  
Impedance Measurements ◽  
Positive Effects ◽  
Wide Range

Microwave heating offers a lot of advantages compared to conventional heating methods in the chemical reactions field due to its positive effects on reaction time and selectivity. Dielectric properties, and in particular permittivity, of substances and mixtures, are important for the optimization of microwave heating processes; notwithstanding this, specific databases are poor and far from being complete, and in the scientific literature very little data regarding these properties can be found. In this work, impedance measurements were carried out using a specially designed system to get the real and imaginary parts of the dielectric constant. The apparatus was tested in the estimation of permittivity of water–ethanol and water–NaCl mixtures, varying their composition to obtain a wide range of permittivity values. The results were compared to literature data and fitted with available literature models to verify the correspondence between them, finding that permittivity dependence on mixture composition can be effectively described by the models.

scholarly journals Microwave-Assisted Synthesis of Isopropylβ-(3,4-Dihydroxyphenyl)-α-hydroxypropanoate

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Qun-Zheng Zhang ◽  
Xue-Feng Tian ◽  
Guan-Le Du ◽  
Qing Pan ◽  
Yi Wang ◽  
...  
Keyword(s):  
Reaction Time ◽  
Microwave Heating ◽  
Orthogonal Design ◽  
Power Level ◽  
Conventional Heating ◽  
Microwave Assisted Synthesis ◽  
Reaction Conditions ◽  
Microwave Assisted ◽  
Clemmensen Reduction ◽  
Microwave Power Level

Using microwave irradiation heating, isopropylβ-(3,4-dihydroxyphenyl)-α-hydroxypropanoate was synthesised from 3,4-dihydroxybenzaldehyde and acetylglycine through the formation of 2-methyl-4-(3,4-acetoxybenzylene)oxazol-5-ones,α-acetylamino-β-(3,4-diacetoxyphenyl)acrylic acid, andβ-(3,4-dihydroxyphenyl)pyruvic acid followed by Clemmensen reduction and esterification. The reaction conditions in terms of operating parameters were optimised by using an orthogonal design of experiment (ODOE) approach, including reaction temperature, reaction time, and microwave power level. Compared with conventional heating, the reaction time was significantly reduced for all reactions and the product yields were increased (except for the third-step reaction) under microwave heating conditions. The most remarkable microwave enhancement was found in the step of isopropylβ-(3,4-dihydroxyphenyl)-α-hydroxypropanoate production where the reaction time was reduced from 10 hrs (conventional heating) to 25 mins (microwave heating) whilst the yield was increased from 75.6% to 87.1%, respectively.

The Potential of Photoelectrochemical Carbon Sinks

2018 ◽  
Author(s):  
Matthias May ◽  
Kira Rehfeld
Keyword(s):  
Global Warming ◽  
High Temperature ◽  
Greenhouse Gas ◽  
Large Scale ◽  
High Efficiency ◽  
Carbon Sink ◽  
Solar Fuels ◽  
Negative Emissions ◽  
Viable Approach ◽  
Low Sensitivity

Greenhouse gas emissions must be cut to limit global warming to 1.5-2C above preindustrial levels. Yet the rate of decarbonisation is currently too low to achieve this. Policy-relevant scenarios therefore rely on the permanent removal of CO<sub>2</sub> from the atmosphere. However, none of the envisaged technologies has demonstrated scalability to the decarbonization targets for the year 2050. In this analysis, we show that artificial photosynthesis for CO<sub>2</sub> reduction may deliver an efficient large-scale carbon sink. This technology is mainly developed towards solar fuels and its potential for negative emissions has been largely overlooked. With high efficiency and low sensitivity to high temperature and illumination conditions, it could, if developed towards a mature technology, present a viable approach to fill the gap in the negative emissions budget.<br>

The Potential of Photoelectrochemical Carbon Sinks

2018 ◽  
Author(s):  
Matthias May ◽  
Kira Rehfeld
Keyword(s):  
Global Warming ◽  
High Temperature ◽  
Greenhouse Gas ◽  
Large Scale ◽  
High Efficiency ◽  
Carbon Sink ◽  
Solar Fuels ◽  
Negative Emissions ◽  
Viable Approach ◽  
Low Sensitivity

Greenhouse gas emissions must be cut to limit global warming to 1.5-2C above preindustrial levels. Yet the rate of decarbonisation is currently too low to achieve this. Policy-relevant scenarios therefore rely on the permanent removal of CO<sub>2</sub> from the atmosphere. However, none of the envisaged technologies has demonstrated scalability to the decarbonization targets for the year 2050. In this analysis, we show that artificial photosynthesis for CO<sub>2</sub> reduction may deliver an efficient large-scale carbon sink. This technology is mainly developed towards solar fuels and its potential for negative emissions has been largely overlooked. With high efficiency and low sensitivity to high temperature and illumination conditions, it could, if developed towards a mature technology, present a viable approach to fill the gap in the negative emissions budget.<br>

scholarly journals Microwaves and Heterogeneous Catalysis: A Review on Selected Catalytic Processes

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 246 ◽  
Author(s):  
Vincenzo Palma ◽  
Daniela Barba ◽  
Marta Cortese ◽  
Marco Martino ◽  
Simona Renda ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Energy Saving ◽  
Microwave Heating ◽  
Microwave Radiation ◽  
Heterogeneous Catalysts ◽  
Conventional Heating ◽  
Specific Effects ◽  
Natural Choice ◽  
Future Challenges ◽  
Catalyzed Reactions

Since the late 1980s, the scientific community has been attracted to microwave energy as an alternative method of heating, due to the advantages that this technology offers over conventional heating technologies. In fact, differently from these, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy embodied in the microwaves. Application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. The synthesis and sintering of materials by means of microwave radiation has been used for more than 20 years, while, future challenges will be, among others, the development of processes that achieve lower greenhouse gas (e.g., CO2) emissions and discover novel energy-saving catalyzed reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this review is to give an overview of microwave applications in the heterogeneous catalysis, including the preparation of catalysts, as well as explore some selected microwave assisted catalytic reactions. The review is divided into three principal topics: (i) introduction to microwave chemistry and microwave materials processing; (ii) description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) applications of microwaves in some selected chemical processes, including the preparation of heterogeneous catalysts.

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