Microwave heating in heterogeneous catalysis: Modelling and design of rectangular traveling-wave microwave reactor

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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Sonochemical preparation of alumina-spheres loaded with Pd nanoparticles for 2-butyne-1,4-diol semi-hydrogenation in a continuous flow microwave reactor

RSC Advances ◽

10.1039/c8ra00331a ◽

2018 ◽

Vol 8 (13) ◽

pp. 7029-7039 ◽

Cited By ~ 7

Author(s):

Emanuela Calcio Gaudino ◽

Maela Manzoli ◽

Diego Carnaroglio ◽

Zhilin Wu ◽

Giorgio Grillo ◽

...

Keyword(s):

Heterogeneous Catalysis ◽

Continuous Flow ◽

Flow Reactor ◽

Pd Nanoparticles ◽

Microwave Assisted ◽

Continuous Flow Reactor ◽

Microwave Reactor

A novel protocol for microwave-assisted alkyne semi-hydrogenation under heterogeneous catalysis in a continuous flow reactor is reported herein.

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Numerical Simulation of the Processes of Microwave Heating of Dielectrics in Traveling Wave Chambers

2019 International Conference on Electrotechnical Complexes and Systems (ICOECS) ◽

10.1109/icoecs46375.2019.8949964 ◽

2019 ◽

Author(s):

Vadim S. Alekseev ◽

Vadim V. Zakharov ◽

Ivan I. Artyukhov ◽

Sergey V. Trigorly

Keyword(s):

Numerical Simulation ◽

Microwave Heating ◽

Traveling Wave

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Comparison of Conventional and Microwave Heating for Evaluation of Microwave Effects

Australian Journal of Chemistry ◽

10.1071/ch16017 ◽

2016 ◽

Vol 69 (8) ◽

pp. 865 ◽

Cited By ~ 5

Author(s):

Péter Bana ◽

István Greiner

Keyword(s):

Temperature Measurement ◽

Microwave Heating ◽

Organic Synthesis ◽

Convenient Method ◽

Thermal Effects ◽

Fibre Optic ◽

Organic Transformations ◽

Microwave Assisted ◽

Microwave Reactor ◽

Microwave Effects

In microwave-assisted organic synthesis, the question of microwave effects is still debated. Proper examination of these hypothesized phenomena is encumbered by some specific features of microwave heating. We devise a convenient method to eliminate most of the irreproducibility observed in microwave-heated organic transformations by thermal conditioning of the microwave reactor cavity. To show the utility of this approach, we investigated a reaction of 2-chloropyridine, in which microwave conditions were shown to be beneficial by previous studies. Using our method to ensure proper reproducibility together with fibre optic temperature measurement, the observed differences were traced back to large hidden thermal differences, while non-thermal effects could not be detected in the comparison experiments.

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CH4 Decomposition over Pyrolysis Residue of Sewage Sludge under Microwave Heating

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.953-954.935 ◽

2014 ◽

Vol 953-954 ◽

pp. 935-938

Author(s):

Wen Yi Deng ◽

Shu Gang Liu ◽

Ya Xin Su

Keyword(s):

Sewage Sludge ◽

Microwave Heating ◽

Low Cost ◽

Methane Decomposition ◽

Initial Activity ◽

Microwave Assisted ◽

Microwave Reactor ◽

Pyrolysis Residue

The microwave-assisted CH4decomposition over a pyrolysis residue of sewage sludge (PRSS), which acted as a microwave receptor and a low-cost catalyst without further activation, was investigated in a multimode microwave reactor. The results indicated that the microwave heating of PRSS is heavily influenced by atmosphere. The PRSS temperature in CH4, N2and H2atmosphere follow the sequence ofTCH4<TH2<TN2. PRSS shows excellent initial activity for methane decomposition, but it deactivated very quickly. It was inferred that the fast deactivation of PRSS was mainly caused by temperature falling in CH4atmosphere.

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Catalyst Heating Characteristics in the Traveling-Wave Microwave Reactor

Catalysts ◽

10.3390/catal11030369 ◽

2021 ◽

Vol 11 (3) ◽

pp. 369

Author(s):

Alberto Martínez González ◽

Andrzej Stankiewicz ◽

Hakan Nigar

Keyword(s):

Traveling Wave ◽

Scale Up ◽

Experimental Studies ◽

Packed Bed ◽

Microwave Cavity ◽

Average Deviation ◽

Heterogeneous Catalytic ◽

Microwave Reactor ◽

Bed Temperature ◽

Process Scale Up

Traveling-Wave Microwave Reactor (TMR) presents a novel heterogeneous catalytic reactor concept based on a coaxial waveguide structure. In the current paper, both modeling and experimental studies of catalyst heating in the TMR are presented. The developed 3D multiphysics model was validated from the electromagnetic and heat transfer points of view. Extrudes of silicon carbide (SiC) were selected as catalyst supports and microwave absorbing media in a packed-bed configuration. The packed-bed temperature evolution was in good agreement with experimental data, with an average deviation of less than 10%. Both experimental and simulation results show that the homogeneous temperature distribution is possible in the TMR system. It is envisioned that the TMR concept may facilitate process scale-up while providing temperature homogeneity beyond the intrinsic restrictions of microwave cavity systems.

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Multi-physical simulation of stirring effect on heating uniformity in a microwave reactor with interlayer

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4050787 ◽

2021 ◽

pp. 1-46

Author(s):

Pengcheng Zou ◽

Guangyuan Jin ◽

Guoyu Nie ◽

Chunfang Song ◽

Zhengwei Cui

Keyword(s):

Heat Transfer ◽

Power Consumption ◽

Microwave Heating ◽

Optimization Model ◽

Physical Simulation ◽

Nonuniform Heating ◽

Microwave Reactor ◽

Stirring Effect ◽

Microwave Reactors ◽

Heating Uniformity

Abstract Due to the exhaustion of fossil fuels and environmental degradation, biodiesel has attracted much attention as a new energy source. Currently, microwave reactors are used extensively for producing biodiesel. However, nonuniform heating of producing biodiesel in microwave reactors is a major problem. In order to solve the problem, a microwave reactor with an interlayer which can obviously improve the uniformity of microwave heating was designed. In this work, the heating efficiency and heating uniformity of the reactor were discussed from two aspects of waveguide position and interlayer thickness by means of multi-physical coupling calculation. According to the calculation results, the optimization model of a microwave reactor with an interlayer was obtained. Then, based on the above optimization model of a microwave reactor with an interlayer, a stirrer that can improve the heat transfer of the fluid material was introduced. The Maxwell equation, heat transfer equation and flow equation were coupled by multi-physical field simulation method to explore the influence of different factors of stirrer on power consumption and heating uniformity. Through response surface analysis, it was found that the primary and secondary order of stirring factors affecting microwave heating uniformity was stirring speed > impeller diameter > bottom clearance, and there was an interaction between different factors. From the two aspects of stirring power consumption and heating uniformity, the best stirring effect was obtained.

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