Hydrolysis of Adenosine Triphosphate by Conventional or Microwave Heating

Jahngen, Edwin; Lentz, Ronald R.; Pesheck, Peter S.; Sackett, Patricia Holt

doi:10.1557/proc-189-469

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…It is well-accepted that chemical kinetic study is a strong and comprehensive tool to reveal quantitatively the impact of MW energy on chemical reactions. Various reactions were reported that show similar kinetics in both the presence and absence of MW at comparable temperatures, suggesting the simple dielectric heating of materials by MW. − ,− There are reports, however, which show a clear reaction rate enhancement in the presence of MW radiation, indicating a specific MW effect other than the well-accepted dielectric heating. − ,, The importance of adequate and accurate temperature control in MW reactor for detecting the MW specific effect by kinetic studies is well-reported. − It has been proposed that temperature should be measured microscopically due to the temperature gradient in the bulk. ,− ,− In recent years, technical developments on temperature, pressure, and power (energy) measurements and process control allowed one to design specialized computer controlled systems that are adapted to chemical synthesis, extending the possibilities of MW-assisted reaction engineering …”

Section: Introductionmentioning

confidence: 99%

Kinetic Approach for Investigating the “Microwave Effect”: Decomposition of Aqueous Potassium Persulfate

Ergan

Bayramoǧlu

2011

Ind. Eng. Chem. Res.

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In this work, the specific effect of microwave (MW) energy on chemical reactions was investigated by online monitoring of the decomposition kinetics of potassium persulfate (K2S2O8). Experiments conducted at constant temperature and constant MW power revealed that the rate constant was about 1.1–1.8 times higher than the rate constant of the thermally heated system at the same temperature, depending on the MW power. To model the dependence of the rate constant on the MW power as k = f(P) exp(−g(P)/T), various functional forms of MW power were envisaged for g(P) (activation energy E a) and for f(P) (preexponential factor k o). Linear, quadratic, and cubic polynomial models were tried for both functions. Nonlinear regression analysis was performed and detailed statistical analysis was applied, and the best results were obtained with quadratic f(P) and cubic g(P) functions, with the highest R 2 adj (0.9975) and the lowest standard deviation (0.94 × 10–5). The mathematical model revealed that both the activation energy and preexponential factor were higher than their thermal counterparts (for P = 0.75 kW dm–3, k o,mw/k o,th = 120, E a,mw/E a,th = 1.12).

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Section: Introductionmentioning

confidence: 99%

Kinetic Approach for Investigating the “Microwave Effect”: Decomposition of Aqueous Potassium Persulfate

Ergan

Bayramoǧlu

2011

Ind. Eng. Chem. Res.

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“…The next year, however, Jahngen (4) , who was one of the authors, conducted the same experiments and concluded that the rate of hydrolysis solely depends on the temperature and not on the method of heating. Mayo et al (5) conducted ring-closing metathesis reactions using microwaves and reported that microwaves accelerated the reaction.…”

Section: Introductionmentioning

confidence: 95%

Isothermal Reactor for Continuous Flow Microwave-Assisted Chemical Reaction

Matsuzawa

Togashi

Hasebe

2012

JTST

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An isothermal reactor in which reaction solutions can be controlled at constant temperature under constant microwave irradiation was developed. This is useful for investigating microwave effects on chemical reactions that are not observed under conventional heating conditions. We devised a structure in which a heat-transfer medium with a low dielectric loss factor, which hardly absorbs any microwaves, flowed outside a spiral reaction tube and designed the basic structure of the reactor using electromagnetic simulation to optimize the energy absorption rate. The conditions for increasing the temperature controlling ability of the reactor were also investigated theoretically and experimentally by taking into consideration the influences of three elements: the velocity of the internal fluid, the material for the tube, and the velocity of the external fluid. The velocity of the external fluid had the greatest influence on temperature controlling ability and the material for the tube had the least influence under the experimental conditions. The overall heat transfer coefficient was about 3.9×10 2 W/(m 2 ·K) when water flowed through the quartz reaction tube at 7.1 mm/s and the external fluid flowed outside the tube at 44 mm/s. We also tested and confirmed that the temperature of water used as internal fluid could be controlled to within ±1.5 K at 309.3 K when microwaves at 26 W were irradiated into the reactor, whereas the temperature of water was over 373 K and boiled without the heat-transfer medium flowing outside the reaction tube using a conventional method of microwave heating. In addition, we investigated microwave effects on Suzuki-Miyaura coupling reaction using the developed isothermal reactor and we confirmed that the temperatures were controlled well in the reactor. The yields obtained by microwave heating were almost the same as that obtained by oil-bath heating.

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“…Other investigators have rejected the theory of specific activation at a controlled temperature in homogeneous media [57][58][59][60][61][62] . A study by Stadler et al 63 on the rate enhancements observed in solid-phase reactions revealed that the significant rate enhancements were a result of direct, rapid 'in-core' heating of the solvent by microwave energy and not a specific non-thermal 'microwave effect' .…”

Section: Mechanisms and Effects Of Microwave Heatingmentioning

confidence: 99%

Scale‐Up of Microwave‐Assisted Organic Synthesis

Roberts

Strauss

2005

Microwave Assisted Organic Synthesis

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In 1986 it was first reported that organic reactions could be conducted by heating in sealed containers in domestic microwave ovens 1,2 . Rate enhancements of up to three orders of magnitude were disclosed 3 . However, temperature and pressure measurement were technically difficult to achieve and in some instances the vessels deformed or exploded 1-3 .From these publications, workers interested in exploring the microwave technique perceived it to be simultaneously beneficial through increased rates, yet hazardous in the presence of flammable organic solvents. Subsequently, a vast body of work was carried out with domestic microwave ovens, but under solvent-free conditions and without recourse to sample mixing or temperature measurement. This continued across a broadening front on the laboratory scale. These and other developments in microwave chemistry have been reviewed extensively in journals, book chapters 4-20 and in a recent monograph 21 .Although relatively inexpensive in terms of purchase price, domestic microwave ovens are not designed to contain chemical explosions or toxic fumes and are incompatible with corrosive and inflammable compounds 13 . Flux densities within the microwave cavity can vary considerably, resulting in 'hot' and 'cold' spots. Mode stirrers and circulation of the vessel within the cavity are sometimes incorporated to assist in overcoming the non-uniformity of the energy distribution, but such measures are usually inadequate. Domestic ovens operate on duty cycles and intervals between zero and full power can be many seconds. This is not always ideal for heating common foods and beverages, let alone for performing delicate chemical manipulations. Intermittent bursts of power afford poor temperature control in chemical reactions. When these matters are considered in conjunction with the initial lack of dedicated pressure vessels for microwave-assisted organic chemistry, it is not surprising that explosions occurred 1-3 and that reactions are not necessarily reproducible in domestic microwave systems 6 .During the decade after 1986, disadvantages of domestic microwave ovens for organic chemistry became apparent to many researchers. Because of the unavailability of specifically designed commercial equipment, however, workers with volatile organic solvents, still found it necessary to adapt domestic units for reflux conditions or for operations under pressure. For reactions at reflux 22-30 , domestic microwave ovens were modified by fitting with a shielded opening to prevent microwave leakage and through which the reaction vessel within the microwave cavity could be connected to an external condenser 22,23,30 . Commercial systems adopting this approach have since appeared. When microwave-transparent coolants (chilled hydrocarbons, ice or solid carbon dioxide) are used, along with the reaction vessel, the condenser can also be located within the microwave cavity, thereby avoiding potential problems with microwave leakage 26,29,31 . 237Microwave Assisted Organic Synthesis Edited by Jason P. T...

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Hydrolysis of Adenosine Triphosphate by Conventional or Microwave Heating

Cited by 3 publications

References 2 publications

Kinetic Approach for Investigating the “Microwave Effect”: Decomposition of Aqueous Potassium Persulfate

Kinetic Approach for Investigating the “Microwave Effect”: Decomposition of Aqueous Potassium Persulfate

Isothermal Reactor for Continuous Flow Microwave-Assisted Chemical Reaction

Scale‐Up of Microwave‐Assisted Organic Synthesis

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