Significance of the kinetics of thermal decomposition of NaHCO3 evaluated by thermal analysis

Tanaka, Haruhiko; Takemoto, Hiroyuki

doi:10.1007/bf01915507

Cited by 14 publications

(15 citation statements)

References 12 publications

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“…On preliminary runs, the following operating conditions were chosen: the heating rate as slow as 1 deg/min, the sample mass as small as ∼7 mg of 53–74 μm solids, and a dry nitrogen flow of 55 cm 3 /min was maintained around the sample to ward off the gaseous products of reaction and to supply needed heat. In light of commonly accepted practice, − it is believed that such operating conditions ensure that relevant, unbiased experimental kinetic data can be amassed. Also, invariant-temperature measurements were carried out under such conditions.…”

Section: Experimental Sectionmentioning

confidence: 99%

Decomposition of Potassium Hydrogen Carbonate: Thermochemistry, Kinetics, and Textural Changes in Solids

Hartman

Svoboda

Čech

et al. 2019

Ind. Eng. Chem. Res.

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To determine unbiased rates of the decomposition of KHCO 3 , slowly increasing-and constant-temperature TGA methods were employed with small, finely ground samples. Such reaction provides a novel, porous, and highly reactive sorbent for noxious and/or malodorous gases. The bicarbonate commences decomposing at 364 K, and the maximum rate of reaction, attained at 421.9 K, amounts to 5.73 × 10 −4 1/s. Taking advantage of the Schlomilch function, an Arrhenius-type relationship is developed by an integral method: the activation energy is as large as 141.3 kJ/mol and the order of reaction amounts to 1.145. While the pore volume made by calcination (0.2309 cm 3 /g) is not affected by temperature at 403−503 K, the mean pore diameter and the grain size augment with increasing temperature. The diagram presented makes it possible to conveniently predict the conditions to attain near-complete conversion of the bicarbonate and minimize undesirable sintering of the nascent carbonate.

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Section: Experimental Sectionmentioning

confidence: 99%

Decomposition of Potassium Hydrogen Carbonate: Thermochemistry, Kinetics, and Textural Changes in Solids

Hartman

Svoboda

Čech

et al. 2019

Ind. Eng. Chem. Res.

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“…In addition to relevant industrial importance in the Solvay process, the thermal decomposition process has the potential for various applications as is seen in the recently published articles of utilizing the reversibility of the thermal decomposition of SHC for the CO 2 separation technology. 3,4 On the basis of the findings accumulated, the thermal decomposition of SHC has also been applied as a kind of test process for developing the new experimental techniques of thermal analyses, 5,6 for testing the techniques and conditions of measuring the kinetic rate data of the solid-state reaction, 7,8 and for evaluating the calculation methods of kinetic analysis. 9À11 The overall process of the thermal decomposition of SHC is characterized by the simultaneous evolutions of CO 2 and water vapor to produce sodium carbonate (SC): 2NaHCO 3 (s) f Na 2 CO 3 (s) + CO 2 (g) + H 2 O (g).…”

Section: Introductionmentioning

confidence: 99%

Phenomenological Kinetics of the Thermal Decomposition of Sodium Hydrogencarbonate

et al. 2011

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Aiming to find rigorous understanding and novel features for their potential applications, the physico-geometrical kinetics of the thermal decomposition of sodium hydrogencarbonate (SHC) was investigated by focusing on the phenomenological events taking place on a single crystalline particle during the course of the reaction. The overall kinetics evaluated by systematic measurements of the kinetic rate data by thermogravimetry under carefully controlled conditions were interpreted in association with the morphological studies on the precursory reaction, mechanism of surface reaction, structure of the surface product layer, diffusion path of evolved gases, crystal growth of the solid product, and so on. The precursory reaction was identified as the decomposition of impurity, taking place at the boundary between the surface of the SHC crystal and the adhesive small SHC particles deposited on the surface. In flowing dry N(2), the thermal decomposition of SHC proceeds by two-dimensional shrinkage of the reaction interface controlled by chemical reaction with the apparent activation energy of about 100 kJ mol(-1), after rapid completion of the surface reaction and formation of porous surface product layer. Atmospheric CO(2) and water vapor influence differently on the overall kinetics of the thermal decomposition of SHC. Added gas phase of CO(2) slightly inhibits the overall rate because of the increasing contribution of the surface reaction. Under higher water vapor pressure, the physico-geometrical mechanism of the surface reaction changes drastically, indicating the preliminary reformation of reactant surface and the formation of needle crystals of solid product on the surface. The mechanistic change and extended contribution of the surface reaction result in the deceleration of the surface reaction and acceleration of the established reaction.

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“…The thermal decomposition of alkali-metal hydrogen carbonates has emerged as a candidate based on the previously reported kinetic behaviors. The thermal decomposition of sodium and potassium hydrogen carbonates (NaHCO 3 and KHCO 3 , respectively) has been studied for preparing MHCO 3 /M 2 CO 3 sorbents for CO 2 and others. − Detailed kinetic analyses of the thermal decomposition of NaHCO 3 have been reported by different groups. − Several studies have reported a sigmoidal shape for the mass-loss curve of the thermal decomposition of NaHCO 3 under isothermal conditions and the empirical fitting of the nucleation and growth-type model known as the Johnson–Mehl–Avrami model (A( m )) − to the experimental kinetic curves under linear nonisothermal conditions. , In contrast, kinetic fitting of the PBR model (R( n )) to the kinetic data recorded under linear nonisothermal and constant-transformation-rate thermal analysis (CRTA) , conditions has also been reported. − However, the contribution of SR in the early stage of the reaction is evidenced by the microscopic observations in different studies. − Therefore, the apparent fitting of the A( m ) model to experimental kinetic curves can be interpreted based on the physico-geometrical consecutive process comprising the initial acceleration period owing to SR and subsequent deceleration period owing to PBR . The fitting of the R( n ) model showed detectable deviations in the initial part of the kinetic curves, which could be explained by the contribution of SR.…”

Section: Introductionmentioning

confidence: 99%

“…25−34 Several studies have reported a sigmoidal shape for the mass-loss curve of the thermal decomposition of NaHCO 3 under isothermal conditions and the empirical fitting of the nucleation and growth-type model known as the Johnson−Mehl−Avrami model (A(m)) 35−38 to the experimental kinetic curves under linear nonisothermal conditions. 25,26 In contrast, kinetic fitting of the PBR model (R(n)) 39 to the kinetic data recorded under linear nonisothermal and constant-transformation-rate thermal analysis (CRTA) 40,41 conditions has also been reported. 27−29 However, the contribution of SR in the early stage of the reaction is evidenced by the microscopic observations in different studies.…”

Section: Introductionmentioning

confidence: 99%

Effects of Particle Size on the Kinetics of Physico-geometrical Consecutive Reactions in Solid–Gas Systems: Thermal Decomposition of Potassium Hydrogen Carbonate

2021

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In this study, we investigated the mechanisms of variations in the overall kinetic behavior of the physico-geometrical consecutive process of the surface reaction (SR) and phase boundary-controlled reaction (PBR) in solid−gas systems with varying particle size of the reactants. Thermal decomposition of potassium hydrogen carbonate (KHCO 3 ) was selected as a suitable model reaction owing to the significant changes in its kinetic behavior with particle size and less sensitivity to experimental conditions for recording kinetic data. The reaction was characterized by an induction period (IP) accompanied by the formation of a gelatinated surface layer. The subsequent mass-loss process was indicated by the consecutive SR and PBR, which was accompanied by the nucleation and growth of solid products in the gelatinated layer and inward advancement of the reaction interface, respectively. Formal kinetic analyses of systematically recorded kinetic data revealed variations in the overall kinetic behaviors with the sample particle size, including changes in the variation trend of isoconversional activation energy values as the reaction progressed and the shape of the experimental master plot. The kinetics of each reaction step in the physico-geometrical consecutive process was investigated using an advanced kinetic approach based on an IP−SR−PBR model. The results revealed variations in the overall kinetic behaviors of the thermal decomposition of KHCO 3 with particle size, owing to changes in the reactivity of the reactant surface in IP, overlapping degree of SR and PBR, and total migration length of the reaction interface in PBR.

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Significance of the kinetics of thermal decomposition of NaHCO3 evaluated by thermal analysis

Cited by 14 publications

References 12 publications

Decomposition of Potassium Hydrogen Carbonate: Thermochemistry, Kinetics, and Textural Changes in Solids

Decomposition of Potassium Hydrogen Carbonate: Thermochemistry, Kinetics, and Textural Changes in Solids

Phenomenological Kinetics of the Thermal Decomposition of Sodium Hydrogencarbonate

Effects of Particle Size on the Kinetics of Physico-geometrical Consecutive Reactions in Solid–Gas Systems: Thermal Decomposition of Potassium Hydrogen Carbonate

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