Kinetic study of the nonthermal effect of the esterification of octenyl succinic anhydride modified starch treated by microwave radiation

Abstract

With cassava starch as a raw material and octenyl succinic anhydride as an esterifying agent, octenyl succinic anhydride modified starch (OSA–starch) was prepared in an aqueous medium and treated by water‐bath heating and microwave radiation at a certain temperature, respectively. The reaction kinetics of esterification were studied. The structural analysis and synthesis mechanism of OSA–starch were investigated by means of scanning electron microscopy and Fourier transform infrared spectroscopy. The differences in the esterification reaction kinetics between starches treated with water‐bath heating and microwave radiation were observed. Under the condition of water‐bath heating, the apparent activation energy of the esterification reaction was 52.22 ± 1.21 kJ/mol, and the pre‐exponential factor was 9018.20/min−1. Under the condition of microwave radiation, the apparent activation energy of the esterification reaction was 50.13 ± 1.16 kJ/mol, and the pre‐exponential factor was 4510.21/min−1. We found that microwave radiation could reduce both the activation energy of the reaction and the pre‐exponential factor. The lowering effect of the apparent activation energy was greater than that of the pre‐exponential factor under the condition of microwave radiation, and this resulted in increased reaction rates. The change in the esterification reaction kinetics was a nonthermal effect of microwave radiation on the esterification of cassava starch. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43909.

Synthesis of Jet Fuel from Glycerol and tert-Butyl Alcohol under Microwave Irradiation

“…63,64 In addition, the oscillating electromagnetic field of microwave made the molecules of glycerol and TBA trend in the same direction of the electric field, which could explain the decrease in the pre-exponential factor under microwave irradiation. 65 Thus, these data further confirmed that microwave irradiation can accelerate this reaction greatly, and similar kinetics phenomena were also detected over commercial Amberlyst-45 catalyst (see Figures S12−S14 and Table S2).…”

“…It was found that the activation energy under microwave irradiation was 88.6 kJ/mol, which is lower than that under conventional heating (105.0 kJ/mol). These results could be attributed to the “nonthermal effect” of microwave irradiation, where the rapid energy transfer and absorption bring a nonequilibrium distribution of energy of the activation centers (formation of more centers with high energy) in the reaction mixture under microwave conditions. , In addition, the oscillating electromagnetic field of microwave made the molecules of glycerol and TBA trend in the same direction of the electric field, which could explain the decrease in the pre-exponential factor under microwave irradiation . Thus, these data further confirmed that microwave irradiation can accelerate this reaction greatly, and similar kinetics phenomena were also detected over commercial Amberlyst-45 catalyst (see Figures S12–S14 and Table S2).…”

Extraction, Modification, and Chemical, Thermal and Morphological Characterization of Starch From the Agro‐Industrial Residue of Mango (Mangifera indica L) var. Ubá

“…The amylose chains are linear and responsible for the amorphous character, while the chains of amylopectin form double helices that rearrange into crystalline domains. The ratio of amylopectin/amylose depends on the botanical origin of the starch; thus, crystallinity also depends on that …”

Temperature evolution, atomistic hot‐spot effects and thermal runaway during microwave heating of polyacrylonitrile: A ReaxFF molecular dynamics simulation

“…They found that the cross-linking time using a microwave was about one-eighth of that with the conventional (hot-air oven) approach, however, the obtained materials with the two methods had the same water absorption, tensile strength, and thermal stability. Shi et al [8] prepared octenyl succinic anhydride-modified starch by microwave irradiation in an aqueous medium and found that microwave irradiation could reduce both the activation energy of the reaction and the pre-exponential factor. More recently, researchers have been encouraging the application of microwaves in organic synthesis and flow chemistry.…”