scholarly journals Sonochemical and Sonoelectrochemical Production of Energy Materials

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 284
Author(s):  
Faranak Foroughi ◽  
Jacob J. Lamb ◽  
Odne S. Burheim ◽  
Bruno G. Pollet
Keyword(s):  
Reaction Rates ◽  
Surface Cleaning ◽  
Energy Materials ◽  
Fast Reaction ◽  
Ultrasound Frequency ◽  
Production Of Hydrogen ◽  
Scientists And Engineers ◽  
Electrocatalyst Materials ◽  
Made In ◽  
Semiconductor Photocatalyst

Sonoelectrochemistry is the combination of ultrasound and electrochemistry which provides many advantages in electrochemistry, such as fast reaction rates, surface cleaning and activation, and increased mass transport at an electrode. Due to the advantages, some efforts have been made in order to benefit sonoelectrochemistry in the field of energy and environmental engineering. This review paper highlights the developed progress of the application of sonoelectrochemistry in the production of hydrogen, electrocatalyst materials and electrodes for fuel cells and semiconductor photocatalyst materials. This review also provides the experimental methods that are utilized in several sonoelectrochemical techniques, such as different set-ups generally used for the synthesis of energy-related materials. Different key parameters in the operation of sonoelectrochemical synthesis including ultrasonication time, ultrasound frequency and operation current have been also discussed. There are not many research articles on the sonoelectrochemical production of materials for supercapacitors and water electrolyzers which play crucial roles in the renewable energy industry. Therefore, at the end of this review, some articles which have reported the use of ultrasound for the production of electrocatalysts for supercapacitors and electrolyzers have been reviewed. The current review might be helpful for scientists and engineers who are interested in and working on sonoelectrochemistry and electrocatalyst synthesis for energy storage and energy conversion.

scholarly journals Fast Reaction Limits via $$\Gamma $$-Convergence of the Flux Rate Functional

2021 ◽  
Author(s):  
Mark A. Peletier ◽  
D. R. Michiel Renger
Keyword(s):  
Evolution Equations ◽  
Detailed Balance ◽  
Approximate Solutions ◽  
Reaction Rates ◽  
Convergence Result ◽  
Rate Function ◽  
Jump Processes ◽  
Kolmogorov Equations ◽  
Markov Jump ◽  
Fast Reaction

AbstractWe study the convergence of a sequence of evolution equations for measures supported on the nodes of a graph. The evolution equations themselves can be interpreted as the forward Kolmogorov equations of Markov jump processes, or equivalently as the equations for the concentrations in a network of linear reactions. The jump rates or reaction rates are divided in two classes; ‘slow’ rates are constant, and ‘fast’ rates are scaled as $$1/\epsilon $$ 1 / ϵ , and we prove the convergence in the fast-reaction limit $$\epsilon \rightarrow 0$$ ϵ → 0 . We establish a $$\Gamma $$ Γ -convergence result for the rate functional in terms of both the concentration at each node and the flux over each edge (the level-2.5 rate function). The limiting system is again described by a functional, and characterises both fast and slow fluxes in the system. This method of proof has three advantages. First, no condition of detailed balance is required. Secondly, the formulation in terms of concentration and flux leads to a short and simple proof of the $$\Gamma $$ Γ -convergence; the price to pay is a more involved compactness proof. Finally, the method of proof deals with approximate solutions, for which the functional is not zero but small, without any changes.

scholarly journals Effects of Synthetic Procedures and Postsynthesis Incubation pH on Size, Shape, and Antibacterial Activity of Copper (I) Oxide Nanoparticles

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Vinh Tien Nguyen ◽  
Khanh Son Trinh
Keyword(s):  
Antibacterial Activity ◽  
High Surface ◽  
Size Variation ◽  
Reaction Rates ◽  
Bacterial Suspension ◽  
Oxide Nanoparticles ◽  
Surface Charges ◽  
Fast Reaction ◽  
Sem Images ◽  
Etching Effect

Copper (I) oxide nanoparticles (Cu2O NP) were synthesized by reducing CuSO4 with glucose in the presence of polyvinyl alcohol as a capping agent. We used three different synthetic procedures with a fast reaction (procedure 1p), a fast-then-slow reaction (procedure 2p), and a slow-then-fast reaction (procedure 3p). The reaction rates were controlled by changing the temperature and the speed of adding reagents. The synthesized Cu2O NP were subsequently incubated for 24 h in a pH 6 solution (Cu2O NP6) or a pH 8 solution (Cu2O NP8) at 5°C. XRD and SEM images analysis revealed that the 1p procedure produced smaller NP, while the 2p procedure produced larger but more uniform NP. The 3p procedure produced the largest NP with a higher size variation. The 24-hour acidic postsynthesis incubation resulted in an etching effect, which reduced the size and size variation of Cu2O NP6. To evaluate the antibacterial activity, E. coli suspensions were mixed with the obtained Cu2O NP (32, 96, or 160 ppm) for different time intervals (1 or 24 h) and then grown on Petri dishes at 37°C for 24 h. Higher doses, smaller sizes of Cu2O NP, and longer contact times with the bacterial suspension resulted in higher inactivation efficiencies. Cu2O NP6 showed higher antibacterial effects at low doses, possibly due to the etching effect and the positive surface charge. Increasing the Cu2O doses from 32 to 96 and 160 ppm noticeably increased the antibacterial effect of the Cu2O NP8, but not significantly for Cu2O NP6. We suggested that the Cu2O NP6 suffered from agglomeration at high doses due to their high surface activity and low surface charges.

Novel process and catalytic materials for converting CO2 and H2 containing mixtures to liquid fuels and chemicals

2015 ◽  
Vol 183 ◽  
pp. 197-215 ◽  
Author(s):  
Nora Meiri ◽  
Yakov Dinburg ◽  
Meital Amoyal ◽  
Viatcheslav Koukouliev ◽  
Roxana Vidruk Nehemya ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
High Performance ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Reactor System ◽  
Liquid Fuels ◽  
High Productivity ◽  
Carbide Phases ◽  
Production Of Hydrogen ◽  
Higher Hydrocarbons

Carbon dioxide and water are renewable and the most abundant feedstocks for the production of chemicals and fungible fuels. However, the current technologies for production of hydrogen from water are not competitive. Therefore, reacting carbon dioxide with hydrogen is not economically viable in the near future. Other alternatives include natural gas, biogas or biomass for the production of carbon dioxide, hydrogen and carbon monoxide mixtures that react to yield chemicals and fungible fuels. The latter process requires a high performance catalyst that enhances the reverse water-gas-shift (RWGS) reaction and Fischer–Tropsch synthesis (FTS) to higher hydrocarbons combined with an optimal reactor system. Important aspects of a novel catalyst, based on a Fe spinel and three-reactor system developed for this purpose published in our recent paper and patent, were investigated in this study. Potassium was found to be a key promoter that improves the reaction rates of the RWGS and FTS and increases the selectivity of higher hydrocarbons while producing mostly olefins. It changed the texture of the catalyst, stabilized the Fe–Al–O spinel, thus preventing decomposition into Fe3O4 and Al2O3. Potassium also increased the content of Fe5C2 while shifting Fe in the oxide and carbide phases to a more reduced state. In addition, it increased the relative exposure of carbide iron on the catalysts surface, the CO2 adsorption and the adsorption strength. A detailed kinetic model of the RWGS, FTS and methanation reactions was developed for the Fe spinel catalyst based on extensive experimental data measured over a range of operating conditions. Significant oligomerization activity of the catalyst was found. Testing the pelletized catalyst with CO2, CO and H2 mixtures over a range of operating conditions demonstrated its high productivity to higher hydrocarbons. The composition of the liquid (C5+) was found to be a function of the potassium content and the composition of the feedstock.

Steam-Reheat Option for SCWRs

2009 ◽  
Author(s):  
Eugene Saltanov ◽  
Romson Monichan ◽  
Elina Tchernyavskaya ◽  
Igor Pioro
Keyword(s):  
Thermal Efficiency ◽  
Power Plants ◽  
Nuclear Reactors ◽  
Low Cost ◽  
Thermal Power ◽  
Reaction Rates ◽  
Pressure Tube ◽  
Outlet Temperature ◽  
Chemical Production ◽  
Production Of Hydrogen

Concepts of nuclear reactors cooled with water at supercritical pressures were studied as early as the 1950s and 1960s in the USA and Russia. After a 30-year break, the idea of developing nuclear reactors cooled with SuperCritical Water (SCW) became attractive again as the ultimate development path for water cooling. The main objectives of using SCW in nuclear reactors are: 1) to increase the thermal efficiency of modern Nuclear Power Plants (NPPs) from 30 – 35% to about 45 – 48%, and 2) to decrease capital and operational costs and hence decrease electrical energy costs. SCW NPPs will have much higher operating parameters compared to modern NPPs (pressure about 25 MPa and outlet temperature up to 625°C), and a simplified flow circuit, in which steam generators, steam dryers, steam separators, etc., can be eliminated. Also, higher SCW temperatures allow direct thermo-chemical production of hydrogen at low cost, due to increased reaction rates. To achieve higher thermal efficiency a nuclear steam reheat has to be introduced inside a reactor. Currently, all supercritical turbines at thermal power plants have a steam-reheat option. In the 60’s and 70’s, Russia, USA and some other countries have developed and implemented the nuclear steam reheat at subcritical-pressure in experimental reactors. There are some papers, mainly published in the open Russian literature, devoted to this important experience. Pressure-tube or pressure-channel SCW nuclear-reactor concepts are being developed in Canada and Russia for some time. It is obvious that implementation of the nuclear steam reheat at subcritical pressures in pressure-tube reactors is easier task than that in pressure-vessel reactors. Some design features related to the nuclear steam reheat are discussed in this paper. The main conclusion is that the development of SCW pressure-tube nuclear reactors with the nuclear steam reheat is feasible and significant benefits can be expected over other thermal-energy systems.

Steam-Reheat Options for Pressure-Tube SCWRs

2010 ◽  
Author(s):  
Eugene Saltanov ◽  
Wargha Peiman ◽  
Amjad Farah ◽  
Krysten King ◽  
Maria Naidin ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Power Plants ◽  
Nuclear Reactors ◽  
Thermal Power ◽  
Reaction Rates ◽  
Pressure Tube ◽  
Outlet Temperature ◽  
Chemical Production ◽  
Production Of Hydrogen ◽  
The Usa

Concepts of nuclear reactors cooled with water at supercritical pressures were studied as early as the 1950s and 1960s in the USA and Russia. After a 40-year break, the idea of developing nuclear reactors cooled with SuperCritical Water (SCW) became attractive again as the ultimate development path for water cooling. The main objectives of using SCW in nuclear reactors are: 1) to increase the thermal efficiency of modern Nuclear Power Plants (NPPs) from 30–35% to about 45–48%, and 2) to decrease capital and operational costs and hence decrease electrical energy costs. SCW NPPs will have much higher operating parameters compared to modern NPPs (pressure about 25 MPa and outlet temperature up to 625°C), and a simplified flow circuit, in which steam generators, steam dryers, steam separators, etc., can be eliminated. Also, higher SCW temperatures allow direct thermo-chemical production of hydrogen at low cost, due to increased reaction rates. To achieve higher thermal efficiency Nuclear Steam Reheat (NSR) has to be introduced inside a reactor. Currently, all supercritical turbines at thermal power plants have a steam-reheat option. In the 60’s and 70’s, Russia, the USA and some other countries have developed and implemented the nuclear steam reheat at subcritical-pressure experimental boiling reactors. There are some papers, mainly published in the open Russian literature, devoted to this important experience. Pressure-tube or pressure-channel SCW nuclear reactor concepts are being developed in Canada and Russia for some time. It is obvious that implementation of the nuclear steam reheat at subcritical pressures in pressure-tube reactors is easier task than that in pressure-vessel reactors. Some design features related to the NSR are discussed in this paper. The main conclusion is that the development of SCW pressure-tube nuclear reactors with the nuclear steam reheat is feasible and significant benefits can be expected over other thermal-energy systems.

Solar Gasification of Biomass: Kinetics of Pyrolysis and Steam Gasification in Molten Salt

2010 ◽  
Author(s):  
Brandon J. Hathaway ◽  
Jane H. Davidson ◽  
David B. Kittelson
Keyword(s):  
Molten Salt ◽  
Average Rate ◽  
Reaction Rates ◽  
Steam Gasification ◽  
Reactivity Index ◽  
Concentrated Solar Energy ◽  
Production Of Hydrogen ◽  
Order Of Magnitude ◽  
Carbonate Salts ◽  
Kinetics Of

The use of concentrated solar energy for pyrolysis and gasification of biomass is an efficient means for production of hydrogen rich synthesis gas. Utilizing molten alkali-carbonate salts as a reaction and heat transfer media offers enhanced stability and higher reaction rates to these solar processes. To establish the reaction kinetics, experiments were carried out in an electrically heated molten salt reactor. Cellulose or activated charcoal were pyrolyzed or gasified with steam from 1124 K to 1235 K with and without salt. Arrhenius rate expressions are derived from the data supported by a numerical model of heat and mass transfer. The average rate of the reactions in molten salt, as measured by their reactivity index, is increased by 70% for pyrolysis and by an order of magnitude for steam gasification.

Thiol Michael-Type Reactions of Optically Active Mercapto-Acids in Aqueous Medium

MRS Advances ◽  
2019 ◽  
Vol 4 (46-47) ◽  
pp. 2515-2525 ◽  
Author(s):  
Makafui Y. Folikumah ◽  
Axel T. Neffe ◽  
Marc Behl ◽  
Andreas Lendlein
Keyword(s):  
Chemical Reactivity ◽  
Aqueous Media ◽  
Phenyl Group ◽  
Reaction Rates ◽  
Fast Reaction ◽  
Bioorthogonal Reaction ◽  
Click Reactions ◽  
Naoh Solution ◽  
The Individual

AbstractDefined chemical reactions in a physiological environment are a prerequisite for the in situ synthesis of implant materials potentially serving as matrix for drug delivery systems, tissue fillers or surgical glues. ‘Click’ reactions like thiol Michael-type reactions have been successfully employed as bioorthogonal reaction. However, due to the individual stereo-electronic and physical properties of specific substrates, an exact understanding their chemical reactivity is required if they are to be used for in-situ biomaterial synthesis. The chiral (S)-2-mercapto-carboxylic acid analogues of L-phenylalanine (SH-Phe) and L-leucine (SH-Leu) which are subunits of certain collagenase sensitive synthetic peptides, were explored for their potential for in-situ biomaterial formation via the thiol Michael-type reaction.In model reactions were investigated the kinetics, the specificity and influence of stereochemistry of this reaction. We could show that only reactions involving SH-Leu yielded the expected thiol-Michael product. The inability of SH-Phe to react was attributed to the steric hindrance of the bulky phenyl group. In aqueous media, successful reaction using SH-Leu is thought to proceed via the sodium salt formed in-situ by the addition of NaOH solution, which was intented to aid the solubility of the mercapto-acid in water. Fast reaction rates and complete acrylate/maleimide conversion were only realized at pH 7.2 or higher suggesting the possible use of SH-Leu under physiological conditions for thiol Michael-type reactions. This method of in-situ formed alkali salts could be used as a fast approach to screen mercapto-acids for thio Michael-type reactions without the synthesis of their corresponding esters.

Recent Advances in On-Water Multicomponent Synthesis of Coumarin Derivatives

2020 ◽  
Vol 24 (22) ◽  
pp. 2601-2611
Author(s):  
Komal Chandrakar ◽  
Jeevan Lal Patel ◽  
S. P. Mahapatra ◽  
Santhosh Penta
Keyword(s):  
Aqueous Medium ◽  
Biological Activities ◽  
Reaction Rates ◽  
Synthetic Methods ◽  
Sustainable Chemistry ◽  
Multicomponent Synthesis ◽  
Biologically Relevant ◽  
Naturally Occurring ◽  
Recent Developments ◽  
Made In

Coumarin-linked heterocycles represent privileged structural subunits and are welldistributed in naturally occurring compounds with immense biological activities. Multicomponent reactions (MCRs) are becoming a valuable tool for synthesizing structurally diverse molecular entities. On the other hand, the last year has seen a tremendous outburst in modifying chemical processes to make them sustainable for the betterment of our environment. The application of aqueous medium in organic synthesis is fulfilling some of the goals of ‘green and sustainable chemistry’ as it has some advantages over the traditional synthetic methods in terms of reaction rates, yields, purity of the products, product selectivity, etc. Hence, significant progress has been made in recent years. In the present review, we provide an overview of the recent developments of multicomponent synthesis of biologically relevant coumarin linked and fused heterocyclic compounds carried out from 2015 till today in an aqueous medium.

scholarly journals AN INVESTIGATION OF THE DENSITY OF A VAPOR IN EQUILIBRIUM WITH A LIQUID NEAR THE CRITICAL TEMPERATURE

1933 ◽  
Vol 9 (3) ◽  
pp. 217-239 ◽  
Author(s):  
J. S. Tapp ◽  
E. W. R. Steacie ◽  
O. Maass
Keyword(s):  
Critical Temperature ◽  
Critical Phenomena ◽  
Gaseous Phase ◽  
Reaction Rates ◽  
Short Time ◽  
Work Done ◽  
Outstanding Work ◽  
Considerable Doubt ◽  
Good Agreement ◽  
Made In

An account is given of the outstanding work done and theories developed in connection with the critical phenomena during the last century. It was because of certain observations made in this laboratory a short time ago upon reaction rates at the critical temperature that the present investigation was begun with a view to providing more definite data concerning the density of both the liquid and gas in the region of the critical point.Experimental conditions have been kept under the most rigid supervision and previous errors eliminated or evaluated. A distinctly new technique has been developed, utilizing quartz spirals, for determining the density of both the liquid and gaseous phase almost simultaneously, up to, and past, the point where the meniscus vanishes. The results have been compiled from a great many observations taken over a period of two years upon eight separate units. In general, good agreement has been obtained in all but one case, and a probable solution has been advanced for the exception. Primarily, the paper is an experimental one designed to fill an important gap in previously recorded data.Extensive theoretical deductions have been purposely omitted because of the radical nature of the findings; and it would be necessary to proceed further with the work before anything really definite might be concluded. Briefly, it might be stated that the results cast considerable doubt upon Van der Waals' classical theory of the continuity of state.

Photoelectrolytic Production of Hydrogen: Annex-14 of the IEA Hydrogen R&D Program

Solar Energy ◽  
2005 ◽  
Author(s):  
Andreas Luzzi
Keyword(s):  
Water Splitting ◽  
Research Progress ◽  
Research Groups ◽  
Redox Systems ◽  
Two Photon ◽  
Production Of Hydrogen ◽  
Significant Research ◽  
Photoactive Materials ◽  
Dual Bed ◽  
Made In

Nine research groups from four countries have been collaborating for 4.5 years under Annex-14 with the aim to advance the science underlying photoelectrolytic hydrogen production from water-splitting. Significant research progress has been made in the areas of material science (semiconductor photoelectrodes, light absorption, photocatalyst stability and charge transfer) and systems development (monolithic multijunction systems, two-photon tandem systems, dual-bed redox systems and monomaterial two-step systems), resulting in the synthesis as well as development of new photoactive materials and the demonstration of various photoelectrochemical (PEC) water-splitting prototype devices, limited to typical laboratory-size miniature scales.

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