Effect of atmospheric water vapor on independent-parallel thermal dehydration of a compacted composite of an inorganic hydrate: sodium carbonate monohydrate grains comprising crystalline particles and a matrix

Abstract

The effect of atmospheric water vapor on the thermal dehydration of sodium carbonate monohydrate (SC-MH), which is characterized as cubic grains of a compacted composite comprising columnar SC-MH crystals and...

Kinetic Insight into the Effect of Self-Generated CO2 on the Thermal Decomposition of Inorganic Carbonates in an Inert Gas Atmosphere: ZnCO3 and CaCO3

“…Therefore, the optimized exponent b can have an arbitrary value. Although the exponents ( a , b ) were set to be independent for analytical purposes in examining the extended Friedman plots presented in Figures and , identical values of a and b have been theoretically justified while deriving the AF based on the multistep chemical process of the interfacial reaction. ,− The identical values of a and b in the AF are derived for the interfacial process controlled by an elementary step of the consumption of interstitial CO 2 defects and formation of the solid product building unit, where the a (= b ) value denotes the coefficient of the defect in the chemical equation of the elementary step. Reexamination of the extended Friedman plots with the restriction of a = b provided comparable results with the previous examination by assuming independent a and b values, as depicted in Figures S8 and S9 for the thermal decomposition of ZnCO 3 and CaCO 3 , respectively.…”

“…In addition, h ( p (CO 2 ), P eq ( T )) denotes the accommodation function (AF) for describing the change in the reaction rate by p (CO 2 ) and P eq ( T ) values. Various functional forms of AF have been proposed to satisfy the universal kinetic description of the subjected thermal decomposition process. , Recently, an analytical form of AF has been proposed for universally describing the reversible thermal decomposition of solids and has been tested with various reaction systems ,− h false( p ( CO 2 ) , P normaleq ( T ) false) = true( 1 p ( CO 2 ) true) a true[ 1 − ( p false( normalCO 2 false) P eq false( T false) ) b true] where the exponents ( a , b ) are variables and optimized through kinetic calculations to enable a universal kinetic description under various temperature and p (CO 2 ) conditions. The AF in eq has been derived based on the theoretical consideration of the elementary steps of surface and interface reactions by selecting one possible rate-determining step with a steady-state approximation for the other elementary steps. ,,− , When ( a , b ) = (0, 1), eq becomes identical to the traditional and most widely used AF, i.e., h ( p (CO 2 ), P eq ( T )) = 1 – p (CO 2 )/ P eq ( T )...…”

Efflorescence kinetics of sodium carbonate decahydrate: a universal description as a function of temperature, degree of reaction, and water vapor pressure

“…Based on the outcomes from many historical challenges and the reexamination of the surface and interfacial reaction kinetics comprising various elementary steps, we recently proposed an analytical form of the AF with two variable exponents ( a , b ). 4,19–30 where the unit of all pressure terms is in atm. Originally, the exponents ( a , b ) have physico-chemical significance with various combinations of ( a , b ), which may be further extended to unrestricted variables for analytical purposes to achieve the universal kinetic description based on eqn (2).…”

“…Based on the outcomes from many historical challenges and the reexamination of the surface and interfacial reaction kinetics comprising various elementary steps, we recently proposed an analytical form of the AF with two variable exponents (a, b). 4,[19][20][21][22][23][24][25][26][27][28][29][30] h p GP ð Þ;…”

“…Originally, the exponents (a, b) have physico-chemical significance with various combinations of (a, b), which may be further extended to unrestricted variables for analytical purposes to achieve the universal kinetic description based on eqn (2). The kinetic description based on eqn (2) with the AF of eqn (3) has been demonstrated for several reversible thermal decompositions/ dehydration reactions of metal hydroxides, 19,20,[25][26][27] metal carbonates, 23,[26][27][28]30 and salt hydrates, 21,22,29 achieving the universal description of the kinetics at different T and p(GP) values while parameterizing the effect of p(GP) by the exponents (a, b) for each reaction. Further advancement has already been challenged for the thermal decomposition of ZnCO 3 and CaCO 3 : parameterizing the contributions of the self-generated p(GP) and atmospheric p(GP) to the effective p(GP) to be introduced into eqn (3).…”