Thermally induced dehydration reactions of monosodium l-glutamate monohydrate: dehydration of solids accompanied by liquefaction

Abstract

In this study, we investigated the mechanistic features and kinetics of the thermal decomposition of solids accompanied by liquefaction as exemplified by the thermal dehydration reactions of monosodium L-glutamate monohydrate...

Physico-geometrical Kinetic Aspects of the Thermal Dehydration of Trehalose Dihydrate

“…m n (10) The acceleration and deceleration stages with a rate behavior depicted by upswept peak shape and sharp peak top were well described by ePT(1, 0, q) and ePT(0, 1, q), respectively. 25,26,30 However, the present reaction exhibited the rate behavior at a constant temperature with a bell-like peak shape and a dull peak top different from previously studied thermal decomposition processes accompanied by liquefaction (Figure 9b). Therefore, the previous approach based on Bawn's model was not particularly successful in an application to the present reaction (Figure S15).…”

“…Reaction kinetics with progressive liquefication under isothermal conditions may be characterized by a conjunction of two kinetic models for the process until complete liquefication and the subsequent process in the liquid state, as has been formalized by Bawn . The similar kinetic procedure may be applicable to the reaction under linearly increasing temperature conditions by combining two empirical kinetic models, such as the extended Prout–Tompkins (ePT) model, , as recently reported by the present authors. ,, Further complex kinetic behaviors are expected when reactions in the solid and liquid states occur successively, because of the special distributions of the solid product and the solid reactant to be liquefied during the reaction.…”

“…The physicochemical features of the thermal dehydration of TH-DH accompanied by liquefaction is fundamentally different from the previously studied reactions, that is, thermal decompositions of 3,4,5-trinitropyrazole ammonium salt 26,30 and monosodium L-glutamate. 25 Notably, the previously studied reactions accompanied by liquefaction were controlled by the chemical process of the intermolecular decomposition ; however, contact with the neighboring particles was observed at temperatures below the mass-loss initiation (Figure 10a). This observation implies that the partial liquefaction of the outer surface layer of the sample particles occurred before the mass-loss process initiates, which may occur through the interaction of the particle surfaces with the atmospheric water vapor and the inhabitation of the evaporation of the water vapor generated by the thermal dehydration at particle surfaces due to the high p(H 2 O) in the atmosphere.…”

“…The basic kinetic modeling for such process under isothermal conditions is originated from Bawn’s approach, which describes the overall process by a conjunction of individual kinetic expressions for each stage that switch at a specific α value ( α *). The similar can be applied to the reactions under any temperature conditions based on the experimental master plot. normald α normald θ = A 1 f 1 ( α ) + A 2 f 2 ( α ) Previously, we derived the formal kinetic description of the thermal decomposition/dehydration of solids accompanied by liquefaction under linearly increasing temperature conditions using an ePT( m , n , q ) model for both reaction stages. ,, normale normalP normalT ( m , n , q ): f ( α ) = false[ 1 − q ( 1 − α ) false] m false( 1 − α false) n The acceleration and deceleration stages with a rate behavior depicted by upswept peak shape and sharp peak top were well described by ePT(1, 0, q ) and ePT(0, 1, q ), respectively. ,, However, the present reaction exhibited the rate behavior at a constant temperature with a bell-like peak shape and a dull peak top different from previously studied thermal decomposition processes accompanied by liquefaction (Figure b). Therefore, the previous approach based on Bawn’s model was not particularly successful in an application to the present reaction (Figure S15).…”

“…Alternatively, the reactions can occur below the boiling point of water; therefore, liquid water can develop by condensing water vapor (the gaseous product), contributing to the thermal dehydration process. − In addition, the reactant can melt and gelate midway through the thermal dehydration, − which can similarly occur for the solid product. Besides the physico-geometrical constraints of thermal dehydration in a solid–gas system, contribution of liquid phase to the reaction dramatically alters the reaction conditions and physico-geometrical constraints for the reaction, resulting in complex kinetic behaviors. − The kinetic approach to the thermal dehydration/decomposition of solids accompanied by liquefaction is a current challenge. Reaction kinetics with progressive liquefication under isothermal conditions may be characterized by a conjunction of two kinetic models for the process until complete liquefication and the subsequent process in the liquid state, as has been formalized by Bawn .…”