Effect of Inert Gas Pressure on Reversible Solid-State Decomposition

Abstract

This work explores the effect of an inert gas pressure on the kinetics of reversible thermal decomposition of solids. The nature of this effect is diffusional. Theoretical analysis of the effect suggests that the process rate should decelerate with increasing inert gas pressure and that the deceleration should occur at the expense of a decrease in the pre-exponential factor. The effect is illustrated by applying high-pressure differential scanning calorimetry to the process of the thermal dehydration of lithium sulfate monohydrate (Li2SO4·H2O). An increase in nitrogen pressure from 0.1 to 7 MPa shifts the reaction to higher temperature by more than 10 °C. Kinetic analysis by means of the Kissinger and advanced isoconversional methods indicates that the activation energy remains practically unchanged by changing pressure. The pre-exponential factor has been found to decrease in proportion to an increase in pressure.

Upcycling poly(ethylene terephthalate) wastes by solvent extraction: Thermal stability and kinetics studies of the recovered PET

“…For many cases estimation of E a and its changes can explain a change in the reaction rate. For some simultaneous reactions, the rate changes can only be explained by the values of A and/or f ( α ) 33,34 . The most common single‐ and pseudo‐single TGA rate obtained at a constant β showed a sigmoidal shape with a one inflection point and its derivative should be a single‐bell‐shaped peak with no inflection point as was observed for PET‐R (Figures 2(b), (c) and 3(b)).…”

“…Another possible reason is that, at higher heating rates, the true sample temperature lags behind that recorded by the instrument. The origin of this lag in temperature is due to the low thermal conductivity of PET, the heat capacity of the sample, and the heat transfer rates, as well as the association time of the reacting materials in the TGA pan before vaporization 22,34 …”

“…The reaction models are of three major types: accelerating (A), decelerating (D) and sigmoidal ( σ ) or autocatalytic, as shown in Figure 2(a) 28,33–39 . By comparison of the figures, and the reaction rate data, we conclude that the complete thermal decomposition of PET‐R took place in three steps: sublimation of the adsorbed volatile chemicals including moisture (VOCs) at lower temperatures as shown in Figure 2(b), and the decomposition of PET‐R (Figure 2(c)) at higher temperatures.…”

Thermal Dehydration of Lithium Sulfate Monohydrate Revisited with Universal Kinetic Description over Different Temperatures and Atmospheric Water Vapor Pressures

“…7with (a, b) = (0, 1) is equivalent to one of those conventionally used as the AF for describing the influence of the partial pressure of the product gas on the overall kinetics of the thermal decomposition of solids. 50,[74][75][76][77][78][79][80][81][82] The Arrhenius plot for the IP, modified by introducing the AF, is generally expressed by Eq. (8).…”

Determining Preexponential Factor in Model-Free Kinetic Methods: How and Why?

“…The curve with squares ( E = 120 kJ mol −1 and A = 10 11 min −1 ) demonstrates that deceleration and a shift to higher temperature can occur at the expense of a decrease in A without any changes in E . While uncommon, such a case has been observed experimentally in a study of the effect of inert gas pressure on the kinetics of reversible decomposition [ 30 ]. Furthermore, as seen from the curve with stars ( E = 110 kJ mol −1 and A = 10 10 min −1 ), deceleration and a shift to higher temperature can happen even when E decreases if A undergoes a significant decrease as well.…”