High thermochemical decomposition

Westinghouse A proposed thermochemical process for decomposing water to oxygen and hydrogen by electrolysis, coupled with the high-temperature decomposition of sulfuric acid ... 

High-temperature decomposition of sulphuric acid is a major step for sulphur-based thermochemical cycles such as hybrid sulphur and sulphur-iodine. It is generally also the most energy-intensive, so that the overall heat requirement for this step can determine whether a particular decomposition reactor or flow sheet design is practical. 

Sample confinement apparently represents one external boundary condition that directly influences the predominant HMX physical state present during a given energetic process or event this in turn, dictates the rate—controlling mechanistic step. It appears there is a mechanistic correlation with the KDIE-determined rate-controlling steps observed in the ambient pressure, slow thermochemical decomposition process with both the rapid pyrolytic decomposition/deflagration process and the thermal explosion event. TUs causes one to wonder if a correlation exists between the high pressure combustion event and the ambient pressure thermochemical decomposition process. 

The first mechanistic KDIE correlation of the thermal decomposition process with explosive sensitivity was accomplished with the thermally initiated nonsteady—state thermal explosion event. The HMX thermal explosion event has been discussed and represents an intermediate temperature/pressure regime between the less drastic combustion event and the high order steady—state detonation event. Mechanistic KDIE detonation investigations recently have been conducted and provide the first correlation between the thermochemical decomposition process and shock—induced detonation using an exploding foil driven flyer plate test. i ... 

High temperature (often exceeding 1000 K) drives the endothermic chemical reactions. Multistep cycles for water splitting are used because very high temperatures are required before an appreciable amount of water decomposes in single-step cycles. Thus, in one or more subsequent chemical reactions, the intermediary compounds can be recovered to the original substance, which is used repeatedly. The thermochemical water decomposition steps involve the following five principal reactions ... 

Flame temperatures can be measured directly, using special high-temperature optical methods. They can also be calculated (estimated) using heat of reaction data and thermochemical values for heat of fusion and vaporization, heat capacity, and transition temperatures. Calculated values tend to be higher than the actual experimental results, due to heat loss to the surroundings as well as the endothermic decomposition of some of the reaction products. Details regarding these calculations, with several examples, have been published [5]. 

The thermochemical properties of tetraperchloratoborates have been studied in detail.136 The estimated heats of dissociation for BX (g) BX3(g) + X ) decrease in the order F>H> Cl > C104. The sulfatoborates are probably ionic compounds with highly polymeric anions and are sensitive to hydrolysis. The chlorosulfatoborates are stable up to 80-150 °C their decomposition seems to give, as a first step, M[BCU] and SO3. 

No such substance as CaCl has been isolated however, the CaCl molecule has been observed spectroscopically in gaseous mixtures at high temperatures, and a number of its molecular constants have been measured. Before asking whether CaCl exists or not, it is necessary to specify whether you are talking about the molecule or the substance. We may presume that the substance calcium(I) chloride would, if isolated, take the form of an ionic solid at room temperature. Thermochemical calculations of the kind described in Chapter 5 show that this substance should be stable with respect to decomposition to the elemental substances. It is definitely unstable, however, towards the disproportionation reaction ... 

The weakness of F-O bonds compared with the bond in the 02 molecule is clearly important, as for F03(0H). But an additional factor is likely to be the high lattice energy of NaF compared with NaF04 the thermochemical radius of F04 is expected to be larger than the crystal radius of F. Note, however, that NaC104 - a well-known substance - is likewise thermodynamically unstable. For the decomposition ... 

Both X-ray crystallography and electronic structure calculations using the cc-pVDZ basis set at the DFT B3LYP level have been employed to study the explosive properties of triacetone triperoxide (TATP) and diacetone diperoxide (DADP).32 The thermal decomposition pathway of TATP has been investigated by a series of calculations that identified transition states, intermediates, and the final products. Calculations predict that the explosion of TATP is not a thermochemically highly favoured event. It rather involves entropy burst, which is the result of formation of one ozone and three acetone molecules from every molecule of TATP in the solid state. 

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