158 results on '"Evgeny V. Rebrov"'
Search Results
2. Rational design for the microplasma synthesis from vitamin B9 to N-doped carbon quantum dots towards selected applications
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Quoc Hue Pho, LiangLiang Lin, Nam Nghiep Tran, Tung T. Tran, An Hoa Nguyen, Dusan Losic, Evgeny V. Rebrov, and Volker Hessel
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General Materials Science ,General Chemistry - Published
- 2022
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3. Au/TiO2 coatings for photocatalytic reduction of 4-nitrophenol to 4-aminophenol with green light
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Joseph W. Gregory, Yuyan Gong, Yisong Han, Steven Huband, Richard I. Walton, Volker Hessel, Evgeny V. Rebrov, Micro Flow Chemistry and Synthetic Meth., EIRES Chem. for Sustainable Energy Systems, EIRES Systems for Sustainable Heat, Sustainable Process Engineering, and Energy Intensified Chemical Reaction Eng.
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Au/TiO ,Gold nanoparticle ,Langmuir-Hinshelwood kinetics ,General Chemistry ,Green light ,Thin film ,Photocatalysis ,Combustion-evaporation ,Catalysis - Abstract
Au/TiO2 catalytic coatings have been developed onto the inner surface of a quartz tube for photocatalytic applications. Gold nanoparticles with diameter 3–5 nm were synthesised using the citrate method, with sodium borohydride as a reducing agent. The nanoparticles were characterised by UV–vis spectroscopy, small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The photocatalytic activity of gold nanoparticles and Au/TiO2 catalytic coatings was studied in the reduction of 4-nitrophenol (4-NP) with green LEDs. The reaction rate follows Langmuir-Hinshelwood kinetics and increases with the light intensity until a plateau at 3 mW cm−2. The photocatalytic activity of gold nanoparticles was fully preserved in the Au/TiO2 coatings.
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- 2023
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4. Effect of temperature on the CO2 splitting rate in a DBD microreactor
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Deema Khunda, Sirui Li, Nikolay Cherkasov, Mohamed Z. M. Rishard, Alan L. Chaffee, and Evgeny V. Rebrov
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Fluid Flow and Transfer Processes ,Chemistry (miscellaneous) ,Process Chemistry and Technology ,Chemical Engineering (miscellaneous) ,Catalysis - Abstract
Ground electrode cooling improved CO2 conversion in a DBD microreactor. A maximum in CO2 conversion of 10.6% was observed at a gas temperature of 363 K.
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- 2023
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5. Study of plasma parameters and gas heating in the voltage range of nondischarge to full-discharge in a methane-fed dielectric barrier discharge
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Nima Pourali, Khuetian Lai, Joe Gregory, Yuyan Gong, Volker Hessel, Evgeny V. Rebrov, Sustainable Process Engineering, EIRES Systems for Sustainable Heat, EIRES Chem. for Sustainable Energy Systems, and Energy Intensified Chemical Reaction Eng.
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OES ,Polymers and Plastics ,electrical modeling ,methane ,QD ,DBD ,Condensed Matter Physics ,electrical measurement - Abstract
Experimental data are used in theoretical models to study the effects of input voltage and gas flow rate on plasma and background gas parameters in a voltage range where the transition from nondischarge to full-discharge happens. To this end, a specific methane-fed dielectric barrier discharge is used as a plasma reactor, and electrical modeling, the Boltzmann equation method, and emission spectrum analysis are employed to calculate plasma parameters and gas heating. The output of this study proves that a uniform plasma with a controllable background gas heating is achievable by the adjustment of input parameters such as voltage and gas flow rate in a well-designed dielectric barrier discharge.
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- 2023
6. Economic Optimization of Local Australian Ammonia Production Using Plasma Technologies with Green/Turquoise Hydrogen
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Gregory Dean Butler, Jose Luis Osorio Osorio Tejada, Mahdieh Razi Asrami, Volker Hessel, Marian Mihailescu, Nam Nghiep Tran, Ambar Laad, Vy Thi Tuong Lai, André Nathan Costa, Phuc Nguyen Ky Phan, Animesh Srivastava, and Evgeny V. Rebrov
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HD ,TP ,2. Zero hunger ,Economic optimization ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,General Chemical Engineering ,Supply chain ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,7. Clean energy ,01 natural sciences ,0104 chemical sciences ,Ammonia production ,chemistry ,13. Climate action ,Environmental protection ,Environmental Chemistry ,QD ,Business ,0210 nano-technology - Abstract
Growing concern about the supply of goods under the COVID pandemic due to border restrictions and community lockdown has made us aware of the limitations of the global supply chain. Fertilisers are pivotal for the growth and welfare of humankind and there is more than a century history in industrial technology. Ammonia is the key platform chemical here which can be chemically diversified to all kinds of fertilisers. This paper puts a perspective on production technologies that can enable a supply of ammonia locally and on-demand in Australia, for the farmers to produce resilient and self-sustained fertilisers. To assess the validity of such a new business model, multi-objective optimisation has to be undergone, and computing is the solution to rank the millions of possible solutions. In this lieu, an economic optimisation framework for the Australian ammonia supply chain is presented. The model seeks to address the economic potential of distributed ammonia plants across Australia. Different techniques for hydrogen and related ammonia production such as thermal plasma, non-thermal plasma, and electrolysis (all typifying technology-disruption), and mini Haber-Bosch (typifying scale-disruption) are benchmarked to the central mega plant on a world-scale using conventional technology; verifying that ‘Moore’s Law’1 of growing bigger and bigger is not the only path to sustainable agriculture. Results show that ammonia can be produced at $317/ton at a regional scale using thermal plasma hydrogen generation which could be competitive to the conventional production model, if credit in terms of lead time and carbon footprint could be taken into account.
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- 2021
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7. Enhanced Alkaline Oxygen Evolution Using Spin Polarization and Magnetic Heating Effects under an AC Magnetic Field
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Hang-bo Zheng, Yuan-li Wang, Jia-wei Xie, Peng-zhao Gao, Dong-yun Li, Evgeny V Rebrov, Hang Qin, Xiao-pan Liu, and Han-ning Xiao
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General Materials Science - Abstract
Renewable electricity from splitting water to produce hydrogen is a favorable technology to achieve carbon neutrality, but slow anodic oxygen evolution reaction (OER) kinetics limits its large-scale commercialization. Electron spin polarization and increasing the reaction temperature are considered as potential ways to promote alkaline OER. Here, it is reported that in the alkaline OER process under an AC magnetic field, a ferromagnetic ordered electrocatalyst can simultaneously act as a heater and a spin polarizer to achieve significant OER enhancement at a low current density. Moreover, its effect obviously precedes antiferromagnetic, ferrimagnetic, and diamagnetic electrocatalysts. In particular, the noncorrected overpotential of the ferromagnetic electrocatalyst Co at 10 mA cm
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- 2022
8. Development of a microkinetic model for non-oxidative coupling of methane over a Cu catalyst in a non-thermal plasma reactor
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Nima Pourali, Maksim Vasilev, Rufat Abiev, and Evgeny V Rebrov
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TP ,Acoustics and Ultrasonics ,QD ,Condensed Matter Physics ,QC ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
A surface microkinetic plasma model for non-oxidative coupling of methane into H2 and higher hydrocarbons was developed over a Cu catalytic film. Twenty key plasma species including electron, ions, radicals, and neutrals were considered in respective chemical reactions leading to the formation of C2 hydrocarbons onto the catalyst surface. The kinetic model was coupled with a global plasma model to describe the performance of a non-thermal plasma reactor. In the reactor model, the reactant gas flows between the two coaxial cylindrical metal electrodes with a length of 50 mm and a diameter of 2 mm (inner) and 6 mm (outer electrode) coated with a Cu film. The effect of discharge power, initial CH4 concentration, and inlet flow rate on methane conversion was investigated. The surface model shows that the CH4 conversion of 47% is obtained at a discharge power of 70 W with a selectivity of C2H2 (49%). Increase in power increased the conversion of methane while increase in pressure and/or inlet gas flow rate decreased it. Also, the results of the plasma-catalyst model were compared with those of plasma alone (without catalyst). It showed that presence of the catalyst inside the plasma increases the selectivity and yield of acetylene, while it deceases the selectivity and yield of hydrogen. Also, the density of radical CH3 in the plasma phase increased in the presence of catalyst, while CH2 and CH densities decreased with that.
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- 2022
9. Process Intensification for Gram-Scale Synthesis of N-Doped Carbon Quantum Dots Immersing a Microplasma Jet in a Gas-Liquid Reactor
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Quoc Hue Pho, LiangLiang Lin, Evgeny V. Rebrov, Mohammad Mohsen Sarafraz, Thanh Tung Tran, Nam Nghiep Tran, Dusan Losic, and Volker Hessel
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General Chemical Engineering ,Environmental Chemistry ,General Chemistry ,Industrial and Manufacturing Engineering - Published
- 2022
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10. Correction to 'Enhanced Alkaline Oxygen Evolution Using Spin Polarization and Magnetic Heating Effect under AC Magnetic Field'
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Hang-bo Zheng, Yuan-li Wang, Jia-wei Xie, Peng-zhao Gao, Dong-yun Li, Evgeny V Rebrov, Hang Qin, Xiao-pan Liu, and Han-ning Xiao
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General Materials Science - Published
- 2022
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11. Process intensification in photocatalytic decomposition of formic acid over a tio2 catalyst by forced periodic modulation of concentration, temperature, flowrate and light intensity
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Petr Denissenko, Rufat Sh. Abiev, Thomas Ellwood, Luka A. Živković, Menka Petkovska, Evgeny V. Rebrov, Sustainable Process Engineering, Energy Intensified Chemical Reaction Eng., and EIRES Systems for Sustainable Heat
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TP ,Materials science ,Formic acid ,Analytical chemistry ,Continuous stirred-tank reactor ,Bioengineering ,TP1-1185 ,Mole fraction ,Catalysis ,chemistry.chemical_compound ,Desorption ,TiO ,Forced periodic modulation ,Chemical Engineering (miscellaneous) ,Formic acid decomposition ,QD1-999 ,Chemical technology ,Process Chemistry and Technology ,technology, industry, and agriculture ,Decomposition ,Chemistry ,Light intensity ,Non-stationary CSTR ,TA ,chemistry ,Process intensification ,Photocatalysis ,TiO2 - Abstract
The effect of forced periodic modulation of several input parameters on the rate of pho-tocatalytic decomposition of formic acid over a TiO2 thin film catalyst has been investigated in a continuously stirred tank reactor. The kinetic model was adopted based on the literature and it includes acid adsorption, desorption steps, the formation of photocatalytic active sites and decomposition of the adsorbed species over the active titania sites. A reactor model was developed that describes mass balances of reactive species. The analysis of the reactor was performed with a computer-aided nonlinear frequency response method. Initially, the effect of amplitude and frequency of four input parameters (flowrate, acid concentration, temperature and light intensity) were studied. All single inputs provided only a minor improvement, which did not exceed 4%. However, a modulation of two input parameters, inlet flowrate and the acid molar fraction, considerably im-proved the acid conversion from 80 to 96%. This is equivalent to a factor of two increase in residence time at steady-state operation at the same temperature and acid concentration.
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- 2021
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12. Magnetic enrichment behavior of monodispersed MFe2O4 nanoferrites (M= Mg, Ca, Ni, Co, and Cu)
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Evgeny V. Rebrov, Pengzhao Gao, Xiao-pan Liu, Hang-bo Zheng, Zhi-bo Huang, and Jin Wen
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010302 applied physics ,Materials science ,Ferrite nanoparticles ,Process Chemistry and Technology ,Analytical chemistry ,Nanoparticle ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Finite element analysis software ,Adsorption ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Ferrite (magnet) ,Freundlich equation ,0210 nano-technology - Abstract
The magnetic enrichment behavior of monodispersed MFe2O4 (M = Mg, Ca, Ni, Co, and Cu) ferrite nanoparticles with different size (10–130 nm) on the surface of a 15 mm o.d. NdFeB-N40 magnetic rod has been investigated. The materials were synthesized by a modified sol-gel method. They were characterized by XRD, TEM, and VSM. The magnetic field of the rod was modelled numerically using a finite element analysis software to obtain the input data for the magnitude of magnetic force. Three adsorption models can be used to describe the enrichment mechanism of ferrite nanoparticle depending on the magnetic permeability: (i) Freundlich adsorption model at low magnetic permeability ( 100 μemu/Oe) leading to the enrichment percentage above 90%.
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- 2019
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13. Simulation study of a pulsed DBD with an electrode containing charge injector parts
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Evgeny V. Rebrov, N. Pourali, Mohammad Mohsen Sarafraz, Volker Hessel, Micro Flow Chemistry and Synthetic Meth., Chemical Reactor Engineering, and EIRES Systems for Sustainable Heat
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Physics ,Electron density ,Plasma parameters ,TK ,Plasma ,Nanosecond ,Condensed Matter Physics ,7. Clean energy ,01 natural sciences ,010305 fluids & plasmas ,Pulse (physics) ,Fall time ,Physics::Plasma Physics ,Electric field ,0103 physical sciences ,Atomic physics ,010306 general physics ,QC ,Voltage - Abstract
By using a multispecies fluid model, the tunability and controllability of plasma parameters such as distributions of electron density, electron energy, ion density, and electric field in a microdielectric barrier discharge (DBD) with a charge injector electrode and driven by negatively polarized nanosecond pulsed voltage superimposed on a positive DC bias voltage are investigated. To this end, the effects of changing features of pulsed voltage like pulse rise time (10-20 ns), pulse peak width (10-15 ns), and pulse fall time (20-30 ns) on characteristics of argon plasma formed inside the reactor are studied. The results show that with the increase in pulse width and pulse rise time, the density of electron and ion increases, while fall time change does not significantly affect the plasma parameters. Generally, the results of this study explicitly prove the possibility of controlling plasma formed inside DBD reactors driven by negative pulse voltage combined with a positive DC voltage, which is very important in waste gas conversion applications.
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- 2021
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14. Survey of Synthesis Processes for N-Doped Carbon Dots Assessed by Green Chemistry and Circular and EcoScale Metrics
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Marc Escribà-Gelonch, Nam Nghiep Tran, Quoc Hue Pho, Dusan Losic, Evgeny V. Rebrov, and Volker Hessel
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Green chemistry ,TP ,Materials science ,Process (engineering) ,General Chemical Engineering ,chemistry.chemical_element ,02 engineering and technology ,Reuse ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,12. Responsible consumption ,Environmental Chemistry ,QD ,Process engineering ,Renewable Energy, Sustainability and the Environment ,business.industry ,Doped carbon ,General Chemistry ,Energy consumption ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,TA ,Sustainability ,0210 nano-technology ,business ,Carbon ,Efficient energy use - Abstract
Six of the most promising lab-scale synthesis process methodologies for N-doped carbon dots (NCDs) are selected and compared in terms of green chemistry and circular and EcoScale/Good-Manufacturing-Practice metrics. We compare a new innovative route, the low-temperature plasma-enabled synthesis of carbon dots, e.g., from citric acid and monoethanolamine, to more-established literature processes, such as thermochemical processes, from the same or other materials. Along with this study, the advantages and disadvantages of each method are depicted in manifold sustainability facets. It is shown how recycling/reuse of nonconverted starting materials and solvents can improve the sustainability profile. In addition, safety constraints, cost analysis, and energy consumption are considered. The analysis showed that the thermal process from citric acid and monoethanolamine gives the best performance with regard to the sustainability assessment chosen here. It has a material circularity indicator of 0.971, with an EcoScale factor of 56% and an E-factor of 5.56. In continuation of those results, the paper shows how the low-temperature plasma using the same materials and the same recycling strategy can be improved to come closer to the performance of its thermal counterpart. It has the best energy efficiency, while lacking so far in mass efficiency. From this study, we learned more about which of these methods are most promising for scaling-up and industrial manufacturing of N-doped carbon dots.
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- 2021
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15. Fabrication of magnetic superstructure NiFe2O4@MOF-74 and its derivative for electrocatalytic hydrogen evolution with AC magnetic field
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Yuan-li Wang, Xiao-pan Liu, Evgeny V. Rebrov, Hui-hui Chen, Pengzhao Gao, and Hang-bo Zheng
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TP ,Materials science ,Fabrication ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Magnetic field ,Catalysis ,chemistry.chemical_compound ,chemistry ,TA ,General Materials Science ,Hydrogen evolution ,QD ,0210 nano-technology ,Superstructure (condensed matter) ,Derivative (chemistry) ,Hydrogen production - Abstract
As an ideal hydrogen production route, electrolyzed water still faces the challenges of high cost of noble-metal electrocatalysts and low performance of non-noble-metal catalysts in scalable applications. Recently, introduction of external fields (such as magnetic fields, light fields, etc.) to improve the electrocatalytic water splitting performance of non-noble-metal catalysts has attracted great attention due to their simplicity. Here, a simple method for preparing magnetic superstructure (NiFe2O4@MOF-74) is described, and the hydrogen evolution reaction (HER) behavior of its carbonized derivative, a ferromagnetic superstructure, is revealed in a wide range of applied voltage under an AC magnetic field. The overpotential (@10 mA cm–2) required for the HER of the obtained ferromagnetic superstructure in 1 M KOH was reduced by 31 mV (7.7%) when a much small AC magnetic field (only 2.3 mT) is applied. Surprisingly, the promotion effect of the AC magnetic field is not monotonically increasing with the increase of the applied voltage or the strength of AC magnetic field, but increasing first, then weakening. This unusual behavior is believed to be mainly caused by the enhanced induced electromotive force and the additional energy by the applied AC magnetic field. This discovery provides a new idea for adjusting the performance of electrocatalytic reactions.\ud \ud
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- 2020
16. Fabrication of Magnetic Superstructure NiFe
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Hang-Bo, Zheng, Hui-Hui, Chen, Yuan-Li, Wang, Peng-Zhao, Gao, Xiao-Pan, Liu, and Evgeny V, Rebrov
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As an ideal hydrogen production route, electrolyzed water still faces the challenges of high cost of noble-metal electrocatalysts and low performance of non-noble-metal catalysts in scalable applications. Recently, introduction of external fields (such as magnetic fields, light fields, etc.) to improve the electrocatalytic water splitting performance of non-noble-metal catalysts has attracted great attention due to their simplicity. Here, a simple method for preparing magnetic superstructure (NiFe
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- 2020
17. Counting bubbles: precision process control of gas–liquid reactions in flow with an optical inline sensor
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A.J. Expósito, Nikolay Cherkasov, Evgeny V. Rebrov, and Yang Bai
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Fluid Flow and Transfer Processes ,Materials science ,010405 organic chemistry ,business.industry ,Process Chemistry and Technology ,Process analytical technology ,Flow (psychology) ,Process (computing) ,PID controller ,Fraction (chemistry) ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Chemistry (miscellaneous) ,Calibration ,Chemical Engineering (miscellaneous) ,Process control ,QD ,Process engineering ,business ,QC - Abstract
Quality by Design encouraged by the US Food and Drug Administration (FDA) in the continuous flow synthesis requires tight monitoring of all the reaction input and output parameters to improve reproducibility and eliminate the process rejects. The reaction monitoring, however, relies on costly (above 10,000$) process analytical technology (PAT) – one of the factors that prevents a wider utilisation of continuous processes. In the work, we show that gas-liquid reactions can be monitored using low-cost (10$) hardware – optical liquid inline sensors – that allows instantaneous analysis of gas fraction in the moving stream. We discuss the application of the sensor for various gas-liquid reactions. The gas-consuming reactions such as hydrogenation are the easiest to implement because the sensor without calibration provides accurate readings close to complete consumption of the gas. The gas-evolving reactions can be monitored but require sensor calibration to determine the gas fraction accurately. Operation of the sensor was demonstrated for various hydrogenation reactions self-optimised using a proportional-integral (PID) algorithm which adjusted the substrate concentration to provide high (but not full) pre-defined hydrogen consumption. The optimised hydrogen consumption agreed with the product analysis for a range of the substrates hydrogenated under various pressures and with different selectivities. The optical sensor was also proven to be an efficient tool in adapting the reaction condition to the catalyst deactivation in the reaction of 2-methyl-3-butyn-2-ol semi-hydrogenation – the autonomous reactor allowed reaching a turn-over number (TON) of 2.7·106 with the value of 1.5·107 expected till a twofold decrease in the catalyst activity. The TON values demonstrated are significantly higher than those observed in batch reactors (~103) even in case of catalyst re-use (105) demonstrating a substantial improvement of process sustainability operating with the process control.\ud \ud
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- 2019
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18. Thermodynamic potential of a novel plasma-assisted sustainable process for co-production of ammonia and hydrogen with liquid metals
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Evgeny V. Rebrov, Mohammad Mohsen Sarafraz, Nam Nghiep Tran, Volker Hessel, N. Pourali, Chemical Reactor Engineering, and EIRES Systems for Sustainable Heat
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TP ,Zero carbon process ,Materials science ,Hydrogen ,020209 energy ,Analytical chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,7. Clean energy ,Ammonia production ,Ammonia ,chemistry.chemical_compound ,symbols.namesake ,020401 chemical engineering ,Nitrogen fixation ,Plasma-assisted chemical looping ,0202 electrical engineering, electronic engineering, information engineering ,QD ,SDG 7 - Affordable and Clean Energy ,0204 chemical engineering ,Gallium ,Hydrogen production ,Plasma reactor ,Renewable Energy, Sustainability and the Environment ,Nitrogen ,6. Clean water ,Gibbs free energy ,Fuel Technology ,Nuclear Energy and Engineering ,chemistry ,TA ,Sustainability ,symbols ,Chemical looping combustion ,SDG 7 – Betaalbare en schone energie - Abstract
In the present article, the thermodynamic potential of a sustainable plasma-assisted nitrogen fixation process for co-production of ammonia and hydrogen is investigated. The developed process takes advantage of chemical looping system by using a liquid metal such as gallium to drive nitrogen fixation reaction using three reactors including reactor R1 to produce gallium nitride from gallium and nitrogen, reactor R2 to produce ammonia and hydrogen from gallium nitride, and plasma reactor R3 to convert gallium oxide to pure gallium. The results of the thermodynamic assessments showed that the proposed reactions are spontaneous and feasible to occur in the reactors. Likewise, the first two reactions are exothermic with ΔH=-230[Formula presented] and ΔH=-239[Formula presented] in the reactors R1 and R2, respectively with an equilibrium chemical conversion of 100%. The plasma reactor requires thermal energy to drive an endothermic reaction of gallium oxide dissociation withΔH=+870[Formula presented]. Thermochemical equilibrium analysis showed that the molar ratio of steam to GaN, as well as the operating pressure and temperature of reactor R2 are the main operating parameters identifying the product composition in the reactor such that by increasing the temperature, the molar ratio of hydrogen to ammonia increases. However, by increasing the molar ratio of steam/GaN (φ value) from 0.1 to 1, the hydrogen content of the reactor increases from 45% to 70% at 400 °C. For φ > 1.0, the hydrogen content decreases while more hydrogen participate in the formation of NH3 thereby increasing the mole fraction of ammonia in the reactor. The equilibrium chemical conversion of all three reactors is expected to reach the completion point (χ = 100%) due to the highly negative Gibbs free energy of the liquid metal-based reactions together with a large thermal driving force supported by thermal plasma reactor. Finally, a scalability study points at a possible use of the new disruptive process design at small scale, and possible industrial transformation scenarios for a distributed production at a local site of consumption are depicted.
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- 2020
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19. Influence of ceramic substrate porosity and glass phase content on the microstructure and mechanical properties of metallized ceramics via an activated Mo-Mn method
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Xiao-pan Liu, Pengzhao Gao, Evgeny V. Rebrov, Ling Wang, and Wen-tao Kang
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TP ,Materials science ,02 engineering and technology ,01 natural sciences ,Flexural strength ,Phase (matter) ,0103 physical sciences ,Ultimate tensile strength ,Materials Chemistry ,Ceramic ,Composite material ,Porosity ,010302 applied physics ,Process Chemistry and Technology ,021001 nanoscience & nanotechnology ,Microstructure ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,TA ,visual_art ,Ceramics and Composites ,visual_art.visual_art_medium ,Metallizing ,TJ ,0210 nano-technology ,Layer (electronics) - Abstract
With the development of power electronics, metallizing of ceramics has been developed and employed in many industrial applications. This paper describes the effect of porosity, mean pore size and glass phase content of Al2O3 substrate on the microstructure evolution and mechanical properties of metallized ceramics obtained by an activated Mo–Mn method. The interface reaction as well as the joining strength between Al2O3 ceramic and Mo–Mn layer were investigated systematically using X-ray diffraction, SEM, energy dispersive X-ray analysis et al. The overall porosity affects the ‘absorptivity’ of the substrate towards the glass phase in the metallized layer, while the glass phase content affects the diffusion depth of the Mn-containing phase. The results show that the distribution of the Mn-containing glass phase in the alumina substrate determined the failure characteristics of specimens under bending and tension conditions. The mean pore size determines the magnitude of capillary force responsible for the diffusion of Mn-containing glass phase into the ceramic substrate. The thickness of the Mo–Mn layer reduced and the thickness of the transition region increased at high alumina porosity. This resulted in a decrease of tensile strength, and an increase of flexural strength growth rate GR for specimens after metallization. The tensile strength of metallized specimens monotonously increased with the glass phase content, while the flexural strength first increased and then decreased. A tensile strength of 1990 ± 75 N, a flexural strength of 9499 ± 346 N and a He leakage rate of 3.5 × 10−11 Pa m3 s−1 were obtained in the optimized specimens after metallization.
- Published
- 2020
20. Temperature dependence of the magnetic properties of mono-dispersed Co0.5Zn0.5Fe2O4 microtubes derived from different templates
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Evgeny V. Rebrov, Hang-bo Zheng, Zhi-bo Huang, Pengzhao Gao, Jin Wen, and Xiao-pan Liu
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010302 applied physics ,Materials science ,Magnetic moment ,Condensed matter physics ,Spinel ,engineering.material ,Coercivity ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Grain size ,Electronic, Optical and Magnetic Materials ,Crystal ,Ferromagnetism ,0103 physical sciences ,engineering ,Curie temperature ,Electrical and Electronic Engineering - Abstract
In this work, the Co0.5Zn0.5Fe2O4 microtube was prepared via a template-assembled sol–gel method, where three kinds of natural fiber worked as template. Effect of template types on morphology, specific area, and magnetic properties under different temperatures of ferrites microtube was investigated. XRD results confirm the formation of pure spinel Co0.5Zn0.5Fe2O4; SEM results proves that the CZF-microtubes is mono-dispersed and exactly copies the morphology of the corresponding template. It possesses excellent magnetic properties (Ms, 62.62 emu g−1) and higher specific area (51.11 m2 g−1), respectively, the former is mainly due to the net-liked microstructure and distribution of higher magnetic magneton cation in crystal cell, and the latter is attributed to not only the smaller grain size, but also the stack manner of nanoparticles. Below Curie temperature, coercivity of CZF-microtubes decreases with an increased temperatures in accordance with the ferromagnetism theory as the degree of atomic thermal vibration increases; Above Curie temperature, the unique variety of coercivity is attributable to not only the competition between the 2nd and 4th order crystal field terms derived from the d electrons of Fe3+ and Co2+ in crystal cell, but also the easy magnetized direction switches from basal plane to c axis via a preferred orientation of the magnetic moments in microtubes structure; The high Hc value of CZF-microtube above Blocking temperature TB (450.19 K) results from the existence of interparticle interaction as nanoparticles of it aggregate to produce a microtube structure, and resulting in a deviation from normal Kneller’s law.
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- 2018
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21. Zeolite minilith: A unique structured catalyst for the methanol to gasoline process
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Dmitry B. Lukyanov, Nikolay Cherkasov, Toyin Omojola, Semali Perera, and Evgeny V. Rebrov
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TP ,Micromonolith ,Materials science ,Chemistry(all) ,General Chemical Engineering ,Energy Engineering and Power Technology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Industrial and Manufacturing Engineering ,Catalysis ,chemistry.chemical_compound ,Structured reactor ,Methanol-to-gasoline ,Zeolite ,Packed bed ,Methanol-to-olefin ,Microchannel ,Methanol ,Process Chemistry and Technology ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Chemical engineering ,Yield (chemistry) ,Chemical Engineering(all) ,Minilith ,ZSM-5 ,0210 nano-technology ,Gasoline ,Space velocity - Abstract
Structured microchannel H-ZSM-5 catalysts containing up to 80 wt% zeolite (balance bentonite) were fabricated by unit operations of paste preparation, extrusion, drying and firing. The structured catalysts, called miniliths due to their micrometre-range dimensions, were composed of parallel cylindrical channels with a wall thickness of 200–300 μm, density of 2.1 channels/mm2 and a channel diameter of 300 μm. These miniliths were characterised by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, N2 physisorption and thermogravimetric analysis. For the first time, these miniliths were tested for the conversion of methanol to gasoline at 370 °C, 3 bar and a weight hourly space velocity (WHSV) of up to 1170 h−1. A gasoline product yield of 53% was obtained at a methanol conversion of 74% over the ZSM-5 miniliths. The pressure drop at the same conversion over a packed-bed reactor of equal ZSM-5 content was 2 orders of magnitude higher than that of the minilith. Reducing the amount of ZSM-5 catalyst in the packed bed, to obtain similar inlet pressure as the ZSM-5 minilith gave the same product yield at a much higher conversion (81%) demonstrating the potential of these structured microchannel reactors.
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- 2018
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22. Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts
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Toyin Omojola, Dmitry B. Lukyanov, Andrew I. McNab, Nikolay Cherkasov, James A. Anderson, Evgeny V. Rebrov, and Andre C. van Veen
- Subjects
Inorganic chemistry ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Adsorption ,chemistry ,Physisorption ,Desorption ,QD ,Dimethyl ether ,Methanol ,0210 nano-technology ,Plug flow reactor model ,Temporal analysis of products - Abstract
The desorption of methanol and dimethyl ether has been studied over fresh and hydrocarbon-occluded ZSM-5 catalysts with Si/Al ratios of 25, 36 and 135 using a Temporal Analysis of Products (TAP) reactor. The catalysts were characterized by XRD, SEM, N2 physisorption and pyridine FT-IR. The crystal size increases with Si/Al ratio from 0.10 to 0.78 µm. The kinetic parameters were obtained using the Redhead method and a plug flow reactor model with coupled convection, adsorption and desorption steps. ZSM-5 catalysts with Si/Al ratios of 25 and 36 exhibit three adsorption sites (low, medium, and high temperature sites), while there is no difference between medium and high temperature sites at a Si/Al ratio of 135. Molecular adsorption on the low temperature site and dissociative adsorption on the medium and high temperature sites give a good match between experiment and the plug flow reactor model. The DME desorption activation energy was systematically higher than that of methanol. Adsorption stoichiometry shows that methanol and DME form clusters onto the binding sites. When non-activated re-adsorption is accounted for, a local equilibrium is reached only on the low and medium temperature binding sites. No differences were observed, other than in site densities, when extracting the kinetic parameters for fresh and activated ZSM-5 catalysts at full coverage.
- Published
- 2017
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23. Hydrogenation of bio-oil into higher alcohols over Ru/Fe3O4-SiO2 catalysts
- Author
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Nikolay Cherkasov, Yaroslav Losovyj, Evgeny V. Rebrov, Joshua Mann, Lyudmila M. Bronstein, Vishal Jadvani, and Zinaida B. Shifrina
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TP ,010405 organic chemistry ,Chemistry ,General Chemical Engineering ,Cyclohexanol ,Energy Engineering and Power Technology ,Atmospheric temperature range ,010402 general chemistry ,Furfural ,01 natural sciences ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Acetic acid ,Fuel Technology ,Cyclopentanol ,Hydrogenolysis ,Organic chemistry ,Phenol - Abstract
Liquid-phase hydrogenation of a solution of furfural, phenol and acetic acid has been studied in the 50–235 °C range over magnetic Ru/Fe 3 O 4 -SiO 2 catalyst targeting the renewable production of second generation biofuels with minimum hydrogen consumption. Phenol was fully hydrogenated to cyclohexanol in the entire temperature range. Below 150 °C, furfural was mainly hydrogenated to tetrahydrofurfuryl alcohol while hydrogenolysis to cyclopentanol was the main reaction pathway above 200 °C. The hydrogenation rate was doubled in an acidic solution (pH = 3) as compared to that at a pH 6. The spent catalyst was regenerated and reused in subsequent catalytic runs.
- Published
- 2017
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24. Thermal Behavior of a Catalytic Packed-Bed Milli-reactor Operated under Radio Frequency Heating
- Author
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Valentin Yu. Doluda, Valentina G. Matveeva, Sourav Chatterjee, V.P. Molchanov, Thomas K. Houlding, and Evgeny V. Rebrov
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Convection ,Packed bed ,010405 organic chemistry ,Chemistry ,TK ,General Chemical Engineering ,Thermodynamics ,General Chemistry ,010402 general chemistry ,Thermal conduction ,7. Clean energy ,01 natural sciences ,Temperature measurement ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Volumetric flow rate ,Temperature gradient ,Thermal ,Dielectric heating ,QD - Abstract
An approach for analysis of thermal gradients in a catalytic packed bed milli-reactor operated under radio frequency (RF) heating has been presented. A single-point temperature measurement would cause the misinterpretation of the catalytic activity in an RF-heated reactor, because of the presence of a temperature gradient. For reliable data interpretation, the temperature should be measured at three positions along the reactor length. The temperature profile can be accurately estimated with the exact analytical solution of a one-dimensional (1D) convection and conduction heat-transfer model, and it can also be approximated with a second-order polynomial function. The results revealed that the position of maximum temperature in the catalytic bed shifts toward a downstream location as the flow rate increases. The relative contribution of conduction and convection to the overall heat transport has been discussed. The design criteria for a near-isothermal milli-reactor have been suggested.\ud \ud
- Published
- 2017
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25. Hydrogenation of levulinic acid using Ru-containing catalysts based on hypercrosslinked polystyrene
- Author
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I. I. Protsenko, Alexey V. Bykov, Linda Zh. Nikoshvili, Esther M. Sulman, Valentina G. Matveeva, Evgeny V. Rebrov, and Alexandrina Sulman
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010405 organic chemistry ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Health, Toxicology and Mutagenesis ,General Chemical Engineering ,ruthenium nanoparticles ,gamma-valerolactone ,levulinic acid ,010402 general chemistry ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Catalysis ,gamma-Valerolactone ,chemistry.chemical_compound ,Fuel Technology ,hypercrosslinked polystyrene ,Polymer chemistry ,Levulinic acid ,Environmental Chemistry ,Organic chemistry ,Polystyrene ,hydrogenation ,QD1-999 - Abstract
This work is devoted to the investigation of the possibility of the use of Ru-containing catalysts on the basis of polymeric matrix of hypercrosslinked polystyrene (HPS) in the hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL). HPS-based Ru-containing catalysts were synthesized at variation of HPS type (MN100 bearing amino groups or MN270 without functional groups) and metal content. Catalyst 5%-Ru/MN100 was shown to compete with commercial 5%-Ru/C and to allow carrying out the hydrogenation of LA in aqueous medium with high yields of GVL (more than 99%).
- Published
- 2017
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26. Gas-liquid hydrogenation in continuous flow – The effect of mass transfer and residence time in powder packed-bed and catalyst-coated reactors
- Author
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Evgeny V. Rebrov, Shrirang Deshmukh, Petr Denissenko, and Nikolay Cherkasov
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Packed bed ,Pressure drop ,chemistry.chemical_classification ,TP ,Materials science ,Alkene ,General Chemical Engineering ,Drop (liquid) ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Catalysis ,Reaction rate ,Chemical kinetics ,chemistry ,Chemical engineering ,Mass transfer ,Environmental Chemistry ,QD ,0210 nano-technology - Abstract
Catalyst-coated tube reactors have been compared with the reactors packed with catalyst powder in alkyne semi-hydrogenation over a 5 wt% Pd/ZnO catalyst and cinnamic ester full hydrogenation over a 2.4 wt% Pd/C catalyst. The “powder packed-bed” reactors (packing with catalyst powder below 30 μm) showed irreproducible performance in time due to mobility of the catalyst layer in the bed which altered the fluidic path and therefore affected the mean liquid residence time and the dispersion. The catalyst-coated tube reactors demonstrated an ideal plug-flow behaviour (Peclet number > 120), while the powder packed-bed showed a considerable back-mixing (Peclet ~ 25). Under all conditions studied, the reaction rate in the powder packed-bed was limited by external mass transfer, while in the coated tube – by the intrinsic kinetics. The coated tubes demonstrated a much lower pressure drop, an improved alkene selectivity, and a 5 times higher throughput compared to the powder packed-bed. The dilution of the catalyst bed with glass beads improved the throughput 4-fold at the expense of 4-fold increase in the pressure drop. In full hydrogenation reaction, the catalyst-coated tube showed a 14 times higher throughput than in the powder packed-bed at the full alkyne conversion. A reactor model for the catalyst-coated tube has been proposed that takes into account the change in the fluid velocity during the reaction. The model described the reaction kinetics demonstrating that the catalyst-coated tubes can be used as a tool to obtain kinetic data in gas-liquid reactions in flow.
- Published
- 2020
27. Miniaturization of Heterogeneous Catalytic Reactors: Prospects for New Developments in Catalysis and Process Engineering
- Author
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Jaap C. Schouten, Evgeny V. Rebrov, and Mart H.J.M. de Croon
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Catalytic coating ,Integrated microreactor/heat-exchanger ,Micro fuel processing ,Micro reaction systems ,Process intensification ,Chemistry ,QD1-999 - Abstract
This paper gives an overview of the research done since 1999 at Eindhoven University of Technology in the Netherlands in the field of miniaturization of heterogeneous catalytic reactors. It is described that different incentives exist for the development of these microstructured reaction systems. These include the need for efficient research instruments in catalyst development and screening, the need for small-scale reactor devices for hydrogen production for low-power electricity generation with fuel cells, and the recent quest for intensified processing equipment and novel process architectures (as in the fine chemicals sector). It is demonstrated that also in microreaction engineering, catalytic engineering and reactor design go hand-in-hand. This is illustrated by the design of an integrated microreactor and heat-exchanger for optimum performance of a highly exothermic catalytic reaction, viz. ammonia oxidation. It is argued that future developments in catalytic microreaction technology will depend on the availability of very active catalysts (and catalyst coating techniques) for which microreactors may become the natural housing.
- Published
- 2002
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28. Process intensification of continuous-flow imine hydrogenation in catalyst-coated tube reactors
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Nikolay Cherkasov, A.J. Expósito, Yang Bai, Evgeny V. Rebrov, and Kirill Tchabanenko
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TP ,Chemistry ,General Chemical Engineering ,Catalyst support ,Inorganic chemistry ,Imine ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Toluene ,Industrial and Manufacturing Engineering ,Catalysis ,Solvent ,chemistry.chemical_compound ,020401 chemical engineering ,Degradation (geology) ,Amine gas treating ,0204 chemical engineering ,0210 nano-technology ,Tetrahydrofuran - Abstract
Hydrogenation of an imine (N-Cyclohexyl(benzylidene)imine) into a secondary amine (N-Benzylcyclohexylamine) was studied in catalyst-coated tube reactors to utilize the advantages of continuous-flow processes. Tetrahydrofuran (THF) was found to be an optimal solvent providing high reaction and low catalyst deactivation rates compared to toluene and isopropanol. Even in THF, however, the deactivation was noticeable, with a decrease in the imine hydrogenation rate of 80 and 47% during 20 h on stream over the Pd/C and Pd/SiO2 catalyst-coated tubes, respectively. After comparing various regeneration methods, we found that washing with isopropanol recovered the catalyst activity. The catalyst support affected regeneration: the Pd/SiO2 catalyst suffered from a permanent degradation, whereas the Pd/C was stable over multiple reaction-regeneration cycles. Process intensification study at a range of reaction temperatures allowed to establish the optimal secondary amine production temperature of 110 °C. The long-term stability test under the optimized conditions allowed reaching a turnover number (TON) of 150 000, an unprecedented value in heterogeneous imine hydrogenation. A reductive amination cascade reaction (aldehyde and amine condensation simultaneously with imine hydrogenation) showed the byproduct yield below 3%. The cascade reaction, however, decreased the reaction throughput by 45% compared to the direct imine hydrogenation still allowing for a throughput of 0.75 kg of product per day in a single 5 m catalyst-coated reactor opening a way for a multikilogram synthesis.\ud \ud
- Published
- 2019
29. Hydrolytic hydrogenation of cellulose in subcritical water with the use of the Ru-containing polymeric catalysts
- Author
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Valentin Yu. Doluda, Oleg V. Manaenkov, Anastasia E. Filatova, Alexander I. Sidorov, Evgeny V. Rebrov, Esther M. Sulman, Olga V. Kislitza, Mikhail G. Sulman, and Valentina G. Matveeva
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010405 organic chemistry ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Hydrolysis ,chemistry ,Chemical engineering ,Yield (chemistry) ,medicine ,Organic chemistry ,Sorbitol ,Polystyrene ,Mannitol ,Cellulose ,Carbon ,medicine.drug - Abstract
The study presents the results of cellulose hydrolytic hydrogenation process in subcritical water in the presence of Ru-containing catalysts based on hypercrosslinked polystyrene (HPS) MN-270 and its functionalized analogues: NH2-HPS (MN-100) and SO3H-HPS (MN-500). It was shown that the replacement of the traditional support (carbon) by HPS increases the yield of the main cellulose conversion products – polyols – important intermediates for the chemical industry. The catalysts were characterized using transmission electron microscopy (TEM), high resolution TEM, and porosity measurements. Catalytic studies demonstrated that the catalyst containing 1.0% Ru and based on MN-270 is the most active. The total yield of sorbitol and mannitol was 50% on the average at 85% cellulose conversion.
- Published
- 2017
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30. Magnetic zeolites: novel nanoreactors through radiofrequency heating
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Pengzhao Gao, Evgeny V. Rebrov, Javier Fernandez-Garcia, Martin R. Lees, Ángel Berenguer-Murcia, Diego Cazorla-Amorós, Jaime García-Aguilar, Universidad de Alicante. Departamento de Química Inorgánica, Universidad de Alicante. Instituto Universitario de Materiales, and Materiales Carbonosos y Medio Ambiente
- Subjects
Nanotechnology ,02 engineering and technology ,Nanoreactor ,010402 general chemistry ,01 natural sciences ,Nanoreactors ,Catalysis ,chemistry.chemical_compound ,Materials Chemistry ,Radiofrequency heating ,QD ,Zeolite ,Química Inorgánica ,Catalysts ,Chemistry ,Metals and Alloys ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Magnetic zeolites ,Chemical engineering ,Citronellal ,Ceramics and Composites ,0210 nano-technology ,Isomerization - Abstract
Many catalytic applications use conventional heating to increase the temperature to allow the desired reaction. A novel methodology is presented for the preparation of magnetic zeolite-based catalysts, allowing more efficient radiofrequency heating. These nanoreactors are tested in the isomerisation of citronellal with successful results and without any apparent deactivation. We thank the MINECO, GV, and FEDER (Projects CTQ2015-66080-R MINECO/FEDER, BES-2013-063678 and PROMETEOII/2014/010) for financial support. Moreover, the financial support provided by the European Research Council (ERC), project 279867, and Russian Science Foundation (project 15-13-20015) is gratefully acknowledged.
- Published
- 2017
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31. Magnetic actuation of catalytic microparticles for the enhancement of mass transfer rate in a flow reactor
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Philip Lisk, Robert M. Bowman, Volkan Degirmenci, Taifur Rahman, Evgeny V. Rebrov, Erell Bonnot, and Robert Pollard
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TP ,Mass transfer coefficient ,Chemistry ,General Chemical Engineering ,Laminar flow ,02 engineering and technology ,General Chemistry ,Mechanics ,Magnetic particle inspection ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Classical mechanics ,Thermal velocity ,13. Climate action ,Mass transfer ,Environmental Chemistry ,Particle ,Particle velocity ,0210 nano-technology ,Magnetosphere particle motion - Abstract
The effect of periodic changes in particle velocity on mass transfer to the reacting surface of a magnetic particle with a diameter 225 μm in laminar flow has been investigated in a microfluidic reactor. The periodic particle motion in a fluid was investigated under a sinusoidal magnetic field generated by a quadrupole arrangement of electromagnets around the reactor. The effect of operating frequency of the rotating magnetic field, intensity of the magnetic field, and phase shift between the two sets of magnets on particle dynamics has been studied. Three particle motion modes have been observed depending on the frequency of the applied field. The mass transfer rate was estimated under steady velocity and variable velocity of the particle using a mass transfer correlation by Feng and Michaelides (2001). The validity of this correlation for the case of variable particle velocity has been confirmed with a 2D numerical model, describing actual hydrodynamics and mass transfer towards the particle surface. The mass transfer coefficient depends both on the mean particle velocity and the deviation of velocity from the mean value. The periodic movement with variable particle velocity reduces the mass transfer coefficient by 7.6% as compared to steady state motion with the same mean velocity.\ud \ud
- Published
- 2016
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32. Scale up study of capillary microreactors in solvent-free semihydrogenation of 2‐methyl‐3‐butyn‐2‐ol
- Author
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Nikolay Cherkasov, Alex O. Ibhadon, Evgeny V. Rebrov, Ma’moun Al-Rawashdeh, and Chemical Engineering and Chemistry
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TP ,Materials science ,Capillary action ,Batch reactor ,Catalytic coatings ,Analytical chemistry ,chemistry.chemical_element ,010402 general chemistry ,complex mixtures ,01 natural sciences ,7. Clean energy ,Catalysis ,chemistry.chemical_compound ,Semihydrogenation ,Mass transfer ,Acetylene ,010405 organic chemistry ,Alkynol ,technology, industry, and agriculture ,General Chemistry ,equipment and supplies ,0104 chemical sciences ,Microreactor ,chemistry ,Chemical engineering ,Selectivity ,Palladium - Abstract
A 2.5 wt.% Pd/ZnO catalytic coating has been deposited onto the inner wall of capillary reactors with a diameter of 0.53 and 1.6 mm. The coatings were characterised by XRD, SEM, TEM and elemental analysis. The performance of catalytic reactors was studied in solvent-free hydrogenation of 2-methyl-3-butyn-2-ol. No mass transfer limitations was observed in the reactor with a diameter of 0.53 mm up to a catalyst loading of 1.0 kg(Pd) m−3. The activity and selectivity of the catalysts has been studied in a batch reactor to develop a kinetic model. The kinetic model was combined with the reactor model to describe the obtained data in a wide range of reaction conditions. The model was applied to calculate the range of reaction conditions to reach a production rate of liquid product of 10–50 kg a day in a single catalytic capillary reactor.
- Published
- 2016
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33. Controllable synthesis of one-dimensional isolated Ni 0.5 Zn 0.5 Fe 2 O 4 microtubes for application as catalyst support in RF heated reactors
- Author
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Rui-xue Ma, Zhou-li Lu, Jia Xu, Pengzhao Gao, Evgeny V. Rebrov, and Hua-nan Lv
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Materials science ,TK ,Catalyst support ,02 engineering and technology ,7. Clean energy ,01 natural sciences ,law.invention ,Adsorption ,Nuclear magnetic resonance ,law ,Specific surface area ,0103 physical sciences ,Dielectric heating ,Materials Chemistry ,Calcination ,Porosity ,QC ,010302 applied physics ,Process Chemistry and Technology ,Coercivity ,021001 nanoscience & nanotechnology ,Grain size ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Chemical engineering ,Ceramics and Composites ,0210 nano-technology - Abstract
One-dimensional isolated Ni0.5Zn0.5Fe2O4 microtubes have been prepared via a template assisted sol–gel method. Temperature dependence of the structural and magnetic properties was studied via XRD, N2 adsorption, SEM, TEM, and VSM. An increase in calcination temperature from 873 to 1273 K caused a decrease in the specific surface area from 80.7 to 17.0 m2/g due to an increase of the grain size from 25.3 to 112 nm. All samples demonstrated anomalous coercivity behavior due to mechanical stresses acting on their domain walls. The porous microtubes calcined at 1073 K have a mean external diameter of 3.7 μm with a length-to-diameter ratio exceeding 12. The microtubes calcined at 973 K have the highest coercivity of 88.1 Oe and demonstrated the largest specific heating rate of 4.36 W/g in a radiofrequency field at 295 kHz.
- Published
- 2016
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34. Non-Thermal Plasma for Process and Energy Intensification in Dry Reforming of Methane
- Author
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Dmitry A. Sladkovskiy, Kirill V. Semikin, Rufat Sh. Abiev, Evgeny V. Rebrov, and Dmitry Yu. Murzin
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Ferroelectrics ,Post-plasma catalysis ,TP ,Materials science ,020209 energy ,Dielectric barrier discharge ,02 engineering and technology ,Nonthermal plasma ,lcsh:Chemical technology ,Catalysis ,Methane ,lcsh:Chemistry ,chemistry.chemical_compound ,0202 electrical engineering, electronic engineering, information engineering ,lcsh:TP1-1185 ,QD ,SDG 7 - Affordable and Clean Energy ,Physical and Theoretical Chemistry ,Tunable diode laser absorption spectroscopy ,Dry reforming of methane ,Carbon dioxide reforming ,business.industry ,Non-thermal plasma ,Photocatalyst ,Syngas ,021001 nanoscience & nanotechnology ,Renewable energy ,Energy efficiency ,lcsh:QD1-999 ,Pulsed plasma jet ,TA ,Chemical engineering ,chemistry ,Plasma jet reactor ,Optical emission spectroscopy ,Photocatalysis ,TJ ,0210 nano-technology ,business - Abstract
Plasma-assisted dry reforming of methane (DRM) is considered as a potential way to convert natural gas into fuels and chemicals under near ambient temperature and pressure; particularly for distributed processes based on renewable energy. Both catalytic and photocatalytic technologies have been applied for DRM to investigate the CH4 conversion and the energy efficiency of the process. For conventional catalysis; metaldoped Ni-based catalysts are proposed as a leading vector for further development. However; coke deposition leads to fast deactivation of catalysts which limits the catalyst lifetime. Photocatalysis in combination with non-thermal plasma (NTP), on the other hand; is an enabling technology to convert CH4 to more reactive intermediates. Placing the catalyst directly in the plasma zone or using post-plasma photocatalysis could generate a synergistic effect to increase the formation of the desired products. In this review; the recent progress in the area of NTP-(photo)catalysis applications for DRM has been described; with an in-depth discussion of novel plasma reactor types and operational conditions including employment of ferroelectric materials and nanosecond-pulse discharges. Finally, recent developments in the area of optical diagnostic tools for NTP, such as optical emission spectroscopy (OES), in-situ FTIR, and tunable diode laser absorption spectroscopy (TDLAS), are reviewed.
- Published
- 2020
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35. One-step synthesis of ZIF-8/ZnO composites based on coordination defect strategy and its derivatives for photocatalysis
- Author
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Xiao-pan Liu, Evgeny V. Rebrov, Wei Liu, Jin Wen, Hang-bo Zheng, Yuan-li Wang, Pengzhao Gao, and Di Wu
- Subjects
Materials science ,Oxide ,One-Step ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,Metal ,Dodecahedron ,chemistry.chemical_compound ,law ,Materials Chemistry ,Methyl orange ,Calcination ,Composite material ,Mechanical Engineering ,Metals and Alloys ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,visual_art ,visual_art.visual_art_medium ,Photocatalysis ,0210 nano-technology ,Visible spectrum - Abstract
A new approach was proposed for the preparation of metal–organic framework/metal oxide composites in one step using only metal salts. Here, crystalline rhombohedral dodecahedron ZIF-8, hollow ZnO microsphere, and ZIF-8/ZnO composites were obtained in different one-pot solvothermal processes where the growth toward individual ZIF-8 and ZnO phases and toward ZIF-8/ZnO composites was controlled by adjusting the ratio of metal salts to 2-methylimidazole. Subsequently, a series of derived (C and/or N)-doped ZnO nanoparticles was obtained by a two-step calcination process. The absorption kinetics and photocatalytic activity in methyl orange degradation under visible light were investigated. ZIF-8-derived ZnO could maintain their original morphology and displayed excellent photocatalytic activity 10 times higher than that of the original ZIF-8.
- Published
- 2020
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36. Development of Novel Multiphase Microreactors: Recent Developments and Future Challenges
- Author
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Evgeny V. Rebrov
- Subjects
Materials science ,Sustainability ,Systems engineering ,Microreactor - Published
- 2019
- Full Text
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37. A highly active and synergistic Pt/Mo 2 C/Al 2 O 3 catalyst for water-gas shift reaction
- Author
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Nikolay Cherkasov, Javier Fernandez-Garcia, Richard I. Walton, David Rooney, David Walker, Evgeny V. Rebrov, Jehad K. Abu-Dahrieh, and Ahmed I. Osman
- Subjects
Materials science ,Scanning electron microscope ,Process Chemistry and Technology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,Water-gas shift reaction ,0104 chemical sciences ,Metal ,X-ray photoelectron spectroscopy ,Elemental analysis ,visual_art ,visual_art.visual_art_medium ,Composition (visual arts) ,QD ,Physical and Theoretical Chemistry ,0210 nano-technology ,Nuclear chemistry ,Space velocity - Abstract
Catalysts consisting of Pt and Cu supported on Mo2C/η-Al2O3, Mo2C/γ-Al2O3 or Mo2C were prepared and used for the low-temperature water gas shift reaction (WGSR). The catalysts were characterized by elemental analysis, powder X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The catalysts were studied in water gas shift reaction with a reaction mixture containing 11% CO, 43% H2, 6% CO2, 21% H2O (real feed composition mixture from the reformer) and balance He, with a reaction temperature range of 180–300 °C at a space velocity (SV) of 125,000 h−1. Catalyst supports (η-Al2O3 and γ-Al2O3), led to different synergetic effect between the two most active phases of Pt metal and Mo2C. Pt/Mo2C/η-Al2O3 is a promising catalyst (44% conversion at 180 °C) due to the close interaction between Pt and Mo2C phases on the surface of the catalyst. The 4 wt% Pt-Mo2C showed the highest activity where the temperature at which 50% conversion observed was at only 180 °C with SV of 125,000 h−1 and constant stability over 85 h.
- Published
- 2018
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38. Metal oxide–zeolite composites in transformation of methanol to hydrocarbons: do iron oxide and nickel oxide matter?
- Author
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Zinaida B. Shifrina, Esther M. Sulman, Yaroslav Losovyj, Nikolay Cherkasov, Sergey S. Bukalov, Maren Pink, Zachary D. Harms, Valentin Yu. Doluda, Joshua Mann, David Gene Morgan, Clara Leonard, Barry D. Stein, Lyudmila M. Bronstein, and Evgeny V. Rebrov
- Subjects
General Chemical Engineering ,Nickel oxide ,Inorganic chemistry ,Oxide ,Iron oxide ,02 engineering and technology ,General Chemistry ,Coke ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,chemistry ,13. Climate action ,QD ,Methanol ,0210 nano-technology ,Zeolite ,Magnetite - Abstract
The methanol-to-hydrocarbon (MTH) reaction has received considerable attention as utilizing renewable sources of both value-added chemicals and fuels becomes a number one priority for society. Here, for the first time we report the development of hierarchical zeolites (ZSM-5) containing both iron oxide and nickel oxide nanoparticles. By modifying the iron oxide (magnetite, Fe3O4) amounts, we are able to control the catalyst activity and the product distribution in the MTH process. At the medium Fe3O4 loading, the major fraction is composed of C9–C11 hydrocarbons (gasoline fraction). At the higher Fe3O4 loading, C1–C4 hydrocarbons prevail in the reaction mixture, while at the lowest magnetite loading the major component is the C5–C8 hydrocarbons. Addition of Ni species to Fe3O4–ZSM-5 leads to the formation of mixed Ni oxides (NiO/Ni2O3) positioned either on top of or next to Fe3O4 nanoparticles. This modification allowed us to significantly improve the catalyst stability due to diminishing coke formation and disordering of the coke formed. The incorporation of Ni oxide species also leads to a higher catalyst activity (up to 9.3 g(methanol)/(g(ZSM-5) × h)) and an improved selectivity (11.3% of the C5–C8 hydrocarbons and 23.6% of the C9–C11 hydrocarbons), making these zeolites highly promising for industrial applications.
- Published
- 2016
- Full Text
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39. Direct amide synthesis over core–shell TiO2@NiFe2O4 catalysts in a continuous flow radiofrequency-heated reactor
- Author
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Evgeny V. Rebrov, Yawen Liu, Pengzhao Gao, and Nikolay Cherkasov
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Anatase ,Materials science ,General Chemical Engineering ,Inorganic chemistry ,Sintering ,02 engineering and technology ,General Chemistry ,Rate equation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,0104 chemical sciences ,law.invention ,Catalysis ,Reaction rate ,chemistry.chemical_compound ,chemistry ,law ,Dielectric heating ,QD ,Calcination ,0210 nano-technology ,Hydrogen peroxide - Abstract
Core-shell composite magnetic catalysts TiO2@NiFe2O4 with a titania loading of 9–32 wt. % have been synthesised by sol-gel method for direct amide synthesis in a radiofrequency (RF)-heated continuous flow reactor. The catalyst calcination temperature was optimised in the range of 350-500 ºC and the highest activity was observed for the catalyst calcined at 500 ºC due to conversion of titania into catalytically active anatase phase. No reaction between the magnetic core and the titania shell was observed up to the calcination temperature of 1000 ºC and no sintering of titania shell was observed after calcination at 500 ºC. The comparison of direct amide synthesis in a continuous flow fixed bed reactor under conventional and RF heating demonstrated that the RF heating mode increased the apparent reaction rate by 60 % and decreased the deactivation rate due to a better temperature uniformity. The titania weight normalised reaction rate in the RF-heated reactor was constant for titania loadings above 17 wt. %, while it decreased by a factor of 3 at lower titania loadings because of interactions between the ferrite core on the thin layer of the catalyst. The catalyst deactivation study showed that the deactivation rate could be accurately described by a first order kinetics and that the main reason of deactivation was coking. The catalyst regeneration via calcination at 400 ºC resulted in the catalyst sintering, while a treatment with a hydrogen peroxide solution at 90 ºC fully recovered catalytic activity.
- Published
- 2016
- Full Text
- View/download PDF
40. Design and operation of a radio-frequency heated micro-trickle bed reactor for consecutive catalytic reactions
- Author
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Evgeny V. Rebrov, Sourav Chatterjee, and Volkan Degirmenci
- Subjects
geography ,geography.geographical_feature_category ,Chemistry ,General Chemical Engineering ,Analytical chemistry ,General Chemistry ,Trickle-bed reactor ,Inlet ,Industrial and Manufacturing Engineering ,Catalysis ,Yield (chemistry) ,Heat transfer ,Dielectric heating ,Thermal ,Environmental Chemistry ,Radio frequency - Abstract
A radiofrequency heated micro-trickle bed reactor with two adjacent thermal zones was designed. In the first thermal zone, citronellal is converted to isopulegol over a H-ZSM-5 catalyst at 80 °C. This is followed by the second thermal zone where hydrogenation isopulegol to menthol occurs over a Pd/TiO 2 catalyst at 70 °C. The two catalytic zones are separated by heating zones made of nickel ferrite particles that produce heat under radiofrequency field at 180 kHz. The position of the catalytic zones was determined based on a one dimensional heat transfer model, in which the actual flow pattern was approximated. Such configuration allows achieving desired temperatures in the catalyst beds whereas the inlet and outlet gas temperatures are close to ambient temperature which increases energy efficiency of the system. The overall product yield was increased by 9 times as compared with a single thermal zone configuration.
- Published
- 2015
- Full Text
- View/download PDF
41. Scale-up of an RF heated micro trickle bed reactor to a kg/day production scale
- Author
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Evgeny V. Rebrov, Javier Fernández, Sourav Chatterjee, and Volkan Degirmenci
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Convection ,scale-up ,magnetic nanoparticles ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Health, Toxicology and Mutagenesis ,General Chemical Engineering ,Trickle-bed reactor ,Thermal conduction ,fine chemicals ,7. Clean energy ,Industrial and Manufacturing Engineering ,Fuel Technology ,radiofrequency ,trickle bed ,SCALE-UP ,Environmental Chemistry ,Magnetic nanoparticles ,Composite material ,Microreactor ,micro reactor ,QD1-999 ,Order of magnitude ,Radiofrequency coil - Abstract
The scale-up of a radiofrequency (RF) heated micro trickle bed reactor for hydrogenation of 2-methyl-3-butyne-2-ol (MBY) over a Pd/TiO2 catalyst has been performed. The axial and radial temperature profiles were calculated using a 2D convection and conduction heat transfer model. The effect of the reactor length, tube diameter and number of parallel tubes on the temperature non-uniformity parameter has been studied. The axial scale-up was achieved by repeating a single periodic unit consisting of one heating and one catalytic zone along the reactor length. The catalyst loading can be increased by an order of magnitude following this approach. A radial temperature difference of 2 K was developed in a reactor with an inner diameter of 15 mm. The scale-up by numbering up allows the accommodation of seven parallel tubes inside a single RF coil. It creates a 7 K difference in the average temperature between the central and the outer tubes which results in a 5% difference in MBY conversion. An overall scale-up factor of near 700 is achieved which corresponds to a production rate of 0.5 kg of product/day.
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- 2015
42. Mechanochemical synthesis of TiO2/NiFe2O4 magnetic catalysts for operation under RF field
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Volkan Degirmenci, Pengzhao Gao, Thomas K. Houlding, Kirill Tchabanenko, and Evgeny V. Rebrov
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Materials science ,010405 organic chemistry ,Mechanical Engineering ,Catalyst support ,Condensation ,Composite number ,Inorganic chemistry ,Nanoparticle ,Continuous stirred-tank reactor ,010402 general chemistry ,Condensed Matter Physics ,7. Clean energy ,01 natural sciences ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,Aniline ,chemistry ,Mechanics of Materials ,Yield (chemistry) ,General Materials Science - Abstract
Composite NiFe2O4–TiO2 magnetic catalysts were prepared by mechanochemical synthesis from a mixture of titania supported nickel ferrite nanoparticles and P25 titania (Evonic). The former provides fast and efficient heating under radiofrequency field, while the latter serves as an active catalyst or catalyst support. The highest heating rate was observed over a catalyst prepared for a milling time of 30 min. The catalytic activity was measured over the sulfated composite catalysts in the condensation of aniline and 3-phenylbutyric acid in a stirred tank reactor and in a continuous RF heated flow reactor in the 140–170 °C range. The product yield of 47% was obtained over the sulfated P25 titania catalyst in the flow reactor.
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- 2015
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43. KINETICS OF THE CELLULOSE HYDROGENOLYSIS IN SUBCRITICAL WATER
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A. E. Filatova, Oleg V. Manaenkov, A. I. Sidorov, Olga V. Kislitza, Valentina G. Matveeva, E.M. Sulman, Evgeny V. Rebrov, and V. Yu. Doluda
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chemistry.chemical_compound ,chemistry ,Hydrogenolysis ,General Chemical Engineering ,Kinetics ,Organic chemistry ,Cellulose - Published
- 2016
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44. Lignin-containing feedstock hydrogenolysis for biofuel component production
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Elena I. Shimanskaya, Valentina G. Matveeva, Evgeny V. Rebrov, Esther M. Sulman, and Аntonina A. Stepacheva
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TP ,hydrogenolysis ,lignin ,Raw material ,010402 general chemistry ,01 natural sciences ,Catalysis ,chemistry.chemical_compound ,Chemical engineering ,Hydrogenolysis ,Lignin ,Organic chemistry ,Chemical reaction engineering ,010405 organic chemistry ,Process Chemistry and Technology ,Anisole ,0104 chemical sciences ,chemistry ,Biofuel ,visual_art ,visual_art.visual_art_medium ,biofuel ,TP155-156 ,Sawdust ,depolimerization - Abstract
In this paper, the commercial 5%Pd/C and 5%Pt/C catalysts and synthesized 5%Pt/MN-270 and 5%Pd/MN-270 were used in the hydrogenolysis of lignocellulosic material (softwood sawdust) to obtain liquid fuels in the form of hydrocarbons. As lignin has a very complex structure, anisole was used as a model compound. It was found that the use Pt-containing catalysts based on hypercrosslinked polystyrene in both processes of anisole and lignin-containing feedstock conversion allowed obtaining the highest yield of oxygen-free hydrocarbons (up to 96 wt. %). Besides, the polymer based catalysts showed high stability in hydrogenolysis process in comparison with the commercial carbon based catalysts. Copyright © 2018 BCREC Group. All rights reservedReceived: 3rd March 2017; Revised: 18th August 2017; Accepted: 21st August 2017; Available online: 22nd January 2018; Published regularly: 2nd April 2018How to Cite: Shimanskaya, E.I., Stepacheva, A.A., Sulman, E.M., Rebrov, E.V., Matveeva, V.G. (2018). Lignin-containing Feedstock Hydrogenolysis for Biofuel Component Production. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (1): 74-81 (doi:10.9767/bcrec.13.1.969.74-81)
- Published
- 2018
45. Highly Selective Continuous Flow Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol in a Pt/SiO2 Coated Tube Reactor
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David Walker, Nikolay Cherkasov, Richard I. Walton, Steven Huband, Evgeny V. Rebrov, and Yang Bai
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TP ,flow chemistry ,catalyst-coated ,Alcohol ,02 engineering and technology ,010402 general chemistry ,unsaturated aldehyde ,lcsh:Chemical technology ,7. Clean energy ,01 natural sciences ,Aldehyde ,Catalysis ,Cinnamaldehyde ,Reaction rate ,lcsh:Chemistry ,chemistry.chemical_compound ,lcsh:TP1-1185 ,platinum ,Physical and Theoretical Chemistry ,chemistry.chemical_classification ,Cinnamyl alcohol ,alcohol ,hydrogenation ,tube reactor ,selectivity ,stability ,Flow chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,lcsh:QD1-999 ,0210 nano-technology ,Selectivity ,Nuclear chemistry - Abstract
A novel continuous flow process for selective hydrogenation of α, β-unsaturated aldehyde (cinnamaldehyde, CAL) to the unsaturated alcohol (cinnamyl alcohol, COL) has been reported in a tube reactor coated with a Pt/SiO2 catalyst. A 90% selectivity towards the unsaturated alcohol was obtained at the aldehyde conversion of 98.8%. This is a six-fold improvement in the selectivity compared to a batch process where acetals were the main reaction products. The increased selectivity in the tube reactor was caused by the suppression of acid sites responsible for the acetal formation after a short period on stream in the continuous process. In a fixed bed reactor, it had a similar acetal suppression phenomenon but showed lower product selectivity of about 47–72% due to mass transfer limitations. A minor change in selectivity and conversion caused by product inhibition was observed during the 110 h on stream with a turnover number (TON) reaching 3000 and an alcohol production throughput of 0.36 kg gPt−1 day−1 in the single tube reactor. The catalysts performance after eight reaction cycles was fully restored by calcination in air at 400 °C. The tube reactors provide an opportunity for process intensification by increasing the reaction rates by a factor of 2.5 at the reaction temperature of 150 °C compared to 90 °C with no detrimental effects on catalyst stability or product selectivity.
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- 2018
46. Performance of novel CaO-based sorbents in high temperature CO2 capture under RF heating
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Alexey G. Okunev, Javier Fernández, Ekaterina V. Parkhomchuk, Vladimir S. Derevschikov, Guannan Hu, Victoria S. Semeykina, Maria V. Sotenko, A.I. Lysikov, and Evgeny V. Rebrov
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Sorbent ,Materials science ,business.industry ,020209 energy ,Process Chemistry and Technology ,General Chemical Engineering ,TK ,Analytical chemistry ,Energy Engineering and Power Technology ,Sintering ,02 engineering and technology ,General Chemistry ,Template synthesis ,021001 nanoscience & nanotechnology ,Electrical grid ,Medium scale ,Industrial and Manufacturing Engineering ,Desorption ,Dielectric heating ,0202 electrical engineering, electronic engineering, information engineering ,Radiofrequency heating ,0210 nano-technology ,Process engineering ,business ,TD - Abstract
The problem of CO2 mitigation on a small and medium scale can be resolved by developing a combined system of CO2 capture and its consecutive conversion into valuable products. The first stage of CO2 looping, however, should be reliable, effective and easy to control and radiofrequency heating, as a new advanced technology, can be used to improve the process. CO2 absorption and desorption RF units can be installed within power plants and powered during the periods of low energy demand thus stabilizing the electrical grid. In this work, a CaO sorbent produced by template synthesis was studied as a sorbent for a CO2 looping system under RF heating which offers short start-up times, highly controlled operation, high degree of robustness and low price. The sorbent reached its stable CO2 capacity of 15.4 wt.% already after 10 temperature cycles (650/850 °C) under RF heating. Higher CO2 desorption rate and lower degree of the sorbent sintering was observed under RF heating as compared to conventional heating.\ud \ud
- Published
- 2017
47. The enhancement of direct amide synthesis reaction rate over TiO 2 @SiO 2 @NiFe 2 O 4 magnetic catalysts in the continuous flow under radiofrequency heating
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Martin R. Lees, Evgeny V. Rebrov, Pengzhao Gao, Nikolay Cherkasov, Yawen Liu, and Javier Fernández
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Inorganic chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Reaction rate ,Absorbance ,chemistry.chemical_compound ,Aniline ,chemistry ,Physisorption ,Chemical engineering ,Amide ,QD ,Lewis acids and bases ,Physical and Theoretical Chemistry ,0210 nano-technology ,Sol-gel - Abstract
A series of TiO2@SiO2@NiFe2O4 composite magnetic catalyst with a core-double shell structure was synthesized by a sol-gel method. The morphology of the catalysts was studied by XRD, SEM, N2 physisorption and their magnetic properties were examined with magnetometry, and specific absorption rate measurements. The catalytic activity was determined in a direct amide synthesis reaction between aniline and phenylbutyric acid at 150 °C in a fixed bed flow reactor under radiofrequency heating. The intermediate silica layer of the catalyst increased the porosity of the outer titania layer and the specific absorbance rate of the catalyst. The initial reaction rate increased by 61% as compared to a similar core-shell TiO2@NiFe2O4 catalyst showing the detrimental effect of nickel ferrite on titania. The reaction rate was further increased by a factor of 3.5 after a sulfation treatment due to an optimum Lewis acid site strength. The highest specific reaction rate over TiO2@SiO2@NiFe2O4 was observed at a 7.5 wt% sulfate loading which was 2.6 times higher as compared to a mechanical mixture of the same composition. The initial reaction rate decreased by 36% after a period of 55 h on stream. The catalyst activity was restored after a treatment with a H2O2 solution.\ud
- Published
- 2017
48. Nanosized Ce–Zn substituted microwave absorber material for X-band applications
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Evgeny V. Rebrov, Shahzad Naseem, Irshad Ali, Imran Sadiq, M.U. Rana, and M. Naeem Ashiq
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Nuclear magnetic resonance ,Materials science ,Dopant ,Electrical resistivity and conductivity ,Doping ,Reflection loss ,Analytical chemistry ,Crystallite ,Coercivity ,Condensed Matter Physics ,High-resolution transmission electron microscopy ,Grain size ,Electronic, Optical and Magnetic Materials - Abstract
The sol–gel autocombustion method has been used to synthesize the Ce–Zn substituted with composition Sr2−xCexNi2Fe28−yZnyO46 (x=0.02, 0.04, 0.06, 0.08, 0.010 and y=0.1, 0.2, 0.3, 0.4, 0.5) X-type hexagonal ferrites. The XRD analysis confirms the single phase of the material. The variation in lattice parameters can be observed with addition of Ce–Zn dopant. The ferrites substituted with Ce–Zn contents have low value of grain size than the unsubstituted ferrites. The crystallite size measured from TEM and HRTEM analysis was found in the range of 40–45 nm which is in good agreement with the theoretically measured by Scherer formula. The room temperature electrical resistivity lies in the range of ~109 Ω-cm, so the investigated sample can be considered good material for reducing the eddy current losses. The enhancement in magnetic properties (saturation magnetization, retentivity and coercivity) has been observed with the substitution of Ce–Zn contents in pure ferrites. The increment in resistivity and magnetic properties with the substitution of Ce–Zn dopant makes it important candidate to be used in the formation of multilayer chip inductors (MLCIs). The maximum reflection loss of −23.4 dB at 12.858 GHz is obtained by Ce–Zn doped ferrites and attenuation constant agrees well with the reflection loss. The microwave absorption properties of this substituted material reflect its applications in super high frequency (SHF) devices.
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- 2014
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49. Microreactors for Gold Nanoparticles Synthesis: From Faraday to Flow
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Evgeny V. Rebrov and Md. Taifur Rahman
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scale-up ,Materials science ,Process Chemistry and Technology ,Microfluidics ,microfluidics ,Bioengineering ,Nanotechnology ,lcsh:Chemical technology ,law.invention ,Core shell ,lcsh:Chemistry ,Narrow channel ,core-shell ,lcsh:QD1-999 ,Colloidal gold ,law ,gold nanoparticles ,Chemical Engineering (miscellaneous) ,Nanorod ,lcsh:TP1-1185 ,Microreactor ,Faraday cage ,nanorods - Abstract
The seminal work of Michael Faraday in 1850s transmuted the “Alchemy of gold” into a fascinating scientific endeavor over the millennia, particularly in the past half century. Gold nanoparticles (GNPs) arguably hold the central position of nanosciences due to their intriguing size-and-shape dependent physicochemical properties, non-toxicity, and ease of functionalization and potential for wide range of applications. The core chemistry involved in the syntheses is essentially not very different from what Michael Faraday resorted to: transforming ions into metallic gold using mild reducing agents. However, the process of such reduction and outcome (shapes and sizes) are intricately dependent on basic operational parameters such as sequence of addition and efficiency of mixing of the reagents. Hence, irreproducibility in synthesis and maintaining batch-to-batch quality are major obstacles in this seemingly straightforward process, which poses challenges in scaling-up. Microreactors, by the virtue of excellent control over reagent mixing in space and time within narrow channel networks, opened a new horizon of possibilities to tackle such problems to produce GNPs in more reliable, reproducible and scalable ways. In this review, we will delineate the state-of-the-art of GNPs synthesis using microreactors and will discuss in length how such “flask-to-chip” paradigm shift may revolutionize the very concept of nanosyntheses.
- Published
- 2014
50. Microwave assisted flow synthesis : coupling of electromagnetic and hydrodynamic phenomena
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Evgeny V. Rebrov, N.G. Patil, L.A. Hulshof, Erik D. C. Esveld, J Jan Meuldijk, F. Benaskar, Volker Hessel, JC Jaap Schouten, Chemical Reactor Engineering, Macromolecular and Organic Chemistry, and Micro Flow Chemistry and Synthetic Meth.
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heat-transfer ,Environmental Engineering ,catalysis ,Chemistry ,General Chemical Engineering ,dry-media reactor ,Analytical chemistry ,Dissipation ,field ,Catalysis ,Coolant ,organic-synthesis macos ,Physics::Fluid Dynamics ,efficiency ,Electric field ,thin-films ,Heat transfer ,Dielectric heating ,Food Technology ,Thin film ,Microwave ,Library Systems & Metadata ,Biotechnology - Abstract
This article describes the results of a modeling study performed to understand the microwave heating process in continuous-flow reactors. It demonstrates the influence of liquid velocity profiles on temperature and microwave energy dissipation in a microwave integrated milli reactor-heat exchanger. Horizontal cocurrent flow of a strong microwave absorbing reaction mixture (ethanol + acetic acid, molar ratio 5:1) and a microwave transparent coolant (toluene) was established in a Teflon supported quartz tube (i.d.: 3 × 10−3 m and o.d.: 4 × 10−3 m) and shell (i.d.: 7 × 10−3 m and o.d.: 9 × 10−3 m), respectively. Modeling showed that the temperature rise of the highly microwave absorbing reaction mixture was up to four times higher in the almost stagnant liquid at the reactor walls than in the bulk liquid. The coolant flow was ineffective in controlling the outlet reaction mixture temperature. However, at high flow rates it limits the overheating of the stagnant liquid film of the reaction mixture at the reactor walls. It was also found that the stagnant layer around a fiber optic temperature probe, when inserted from the direction of the flow, resulted in much higher temperatures than the bulk liquid. This was not the case when the probe was inserted from the opposite direction. The experimental validations of these modeling results proved that the temperature profiles depend more on the reaction mixture velocity profiles than on the microwave energy dissipation/electric field intensity. Thus, in flow synthesis, particularly where a focused microwave field is applied over a small tubular flow reactor, it is very important to understand the large (direct/indirect) influence of reactor internals on the microwave heating process. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3824–3832, 2014
- Published
- 2014
- Full Text
- View/download PDF
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