Multiple step thermal decomposition

Status reviews on multiple step cycles have been presented,46,47 and include the leading candidates GA s 3-step cycle based on the thermal decomposition of H2SO4 at 1130 K,48 and the UT3 s 4 step cycle based on the hydrolysis of CaBn and FeBn at 1020 and 870 K 49 This process involving two Ca and two Fe compounds has received some attention.4 The process is operated in a cyclic manner in which the solids remain in their reaction vessels and the flow of gases is switched when the desired reaction extent is reached ... 

Kinetics models of gas-solid non-catalytic reaction include uniform conversion model (UCN), multiple fine particle model (GPM), crack core model (CCM), phase-change model (PCM), change void model (CVM), thermal decomposition model (TDM), shrinking core model with multi-step reactions, and multi-step reaction model of formation porous structure in reaction etc. Among these models, the shrinking core model (SCM) is the most important and most widely used. For conversion of solid it is also the most simple and practical model. Commonly it is suitable for experimental data. However, it can only be used in some reactions of many solid reactions. A more complex model must be used in other cases. 

As shown by Eq. (8), the kineties governing a thermal decomposition event depend on time, temperature, and rate of decomposition. TG experiments performed at a constant heating rate allow temperature and time to be interehanged in the ease of first order kinetics and one-step decompositions. ] Hi-Res TGA allows the determination of kinetic parameters such as activation energy and reaction order for each step in multiple component materials using four different TG approaches I constant heating rate, constant reaction rate, dynamic heating rate, and stepwise isothermal. 

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