A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions

Abstract

The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H2S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea’) decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea’ under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea’ was determined. MW irradiation energy was partially transformed to reduce the Ea’, and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology.

Optimization of N‐alkylation in the Synthesis of Methotrexate and Pteridine‐based Derivatives Under Microwave‐Irradiation

“…Microwave‐assisted organic synthesis has become a particularly attractive way for the preparation of key intermediates and new bioactive molecules due to some advantages including reduction of reaction times, minimization of by‐products and increased yields ,. Since the long reaction time (from 1 day for MTX, up to 7 days for many pteridine derivatives) and the complex procedure of purification in the S N 2 step between Pt−Br and the nucleophilic amine, we explored the use of MW irradiation to reduce reaction time and optimize yield and purity of the desired compounds.…”

Drastic Microwave Heating of Percolated Pt Metal Nanoparticles Supported on Al2O3 Substrate

“…To estimate the extent of the Pt NPs aggregation quantitatively, we calculated an apparent packing fraction of the Pt NPs (Φ) in an assumed model of 5 mm × 5 mm × H nm as the Pt NPs layer, where the H was the thickness of the Pt NPs layer observed in the TEM image. If the model is composed of close-packed Pt atoms with the packing fraction of 74% as Pt bulk metal [45], the Pt amount is calculated as 2.75 × H nmol by the following calculation; the volume of 5 mm × 5 mm × H nm is multiplied by the density of 21.45 g/cm 3 [46] and divided by the molar mass of 195.1 g/mol [47]. As for the 60 s-sputtered Pt/Al 2 O 3 substrate, the Pt NPs amount was estimated as 10.5 nmol by the ICP analysis.…”

“…Microwave (MW) heating processes have been applied to a lot of catalytic reactions [1][2][3][4][5][6][7][8]. In the heterogeneous gas-solid system, solid catalysts are selectively heated due to the interactions of the conduction electrons or the dipoles with MWs [1].…”

Saponificação Assistida Por Micro-Ondas Na Extração De Diterpenos Em Café Arábica Torrado

“…Segundo Zhou et al, 30 reações químicas conduzidas em micro-ondas ocorrem mais rapidamente devido à redução da energia de ativação da reação. Souza et al 45 também descrevem que na saponificação por micro-ondas para obtenção de colesterol e óxidos de colesterol em camarão houve redução do tempo (75%) em relação ao método de saponificação a frio.…”

“…[26][27][28] Entre as vantagens do uso de micro-ondas em reações químicas em relação ao aquecimento convencional destacam-se a redução no tempo e aumento da taxa de reação, o aumento do rendimento e da seletividade e o menor consumo de energia, permitindo realizar transformações mais seguras, com menor produção de resíduos e em um maior número de amostras. 29,30 O emprego de uma reação de saponificação mais eficiente, e em maior escala, poderia viabilizar a extração de diterpenos da matriz de café torrado, permitindo seu posterior uso em produtos de alimentos ou farmacêuticos, ou, após purificação, como padrões analíticos.…”