Ammonium perchlorate, decomposition

R. H. Waesche, "Workshop in the Relationship of Ammonium Perchlorate Decomposition to Dedagration," Proceedings of the 7th JMNNMF Combustion Meeting, Vol. 1, CPIA Pubhcation 204, CPIA, Johns Hopkins University, Laurel, Md., 1971, p. 15. 

Heath and Majer (H3) have recently used a mass spectrometer to study the decomposition of ammonium perchlorate. Decomposition was detected in the range from 110° to 120°C. At this temperature, there were ions in the mass spectrum caused by NH3, HC104, Cl2, HC1, nitrogen oxides, and 02. The appearance of the species NO, N02,02, and Cl2 in the decomposition products under very low pressure (i.e., in the absence of gas-phase molecular collisions) indicates that the principal decomposition reactions take place in the crystal and not in the gas phase. 

Varying the semiconducting properties of the catalyst crystal affects the rate of ammonium perchlorate decomposition. 

Akerman, L. A. et al., Combustion, Explos., Shockwaves, 1987, 23, 178 Calcium chloride and oxide catalyse the second, violent, stage of ammonium perchlorate decomposition and increase the shock sensitivity of mixtures with sugar. 

J.R. Ward J J. Rocchio, Effect of Neutron Radiation on the Rate of Ammonium Perchlorate Decomposition Reactions Involved in Combustion , Ibid, paper 6.4, pp 271—80 (1975) 246) Ibid, Effect of Neutron Radia-... 

Calcium chloride and oxide catalyse the second, violent, stage of ammonium perchlorate decomposition and increase the shock sensitivity of mixtures with sugar. 

Ammonium perchlorate decomposition Cn/MWCNT Catalytic performances of a snpported catalyst are fonnd to be better than those of an nnsnpported catalyst. 357... 

Fig. 1. The postulated flame stmcture for an AP composite propellant, showing A, the primary flame, where gases are from AP decomposition and fuel pyrolysis, the temperature is presumably the propellant flame temperature, and heat transfer is three-dimensional followed by B, the final diffusion flame, where gases are O2 from the AP flame reacting with products from fuel pyrolysis, the temperature is the propellant flame temperature, and heat transfer is three-dimensional and C, the AP monopropellant flame where gases are products from the AP surface decomposition, the temperature is the adiabatic flame temperature for pure AP, and heat transfer is approximately one-dimensional. AP = ammonium perchlorate.

Because of the use of ammonium perchlorate as a soHd oxidizer for rocket propeUants, the thermal decomposition has been much studied (29—32). Three separate activation energies have been observed for AP decompositions an activation energy of 123.8 kJ/mol (29.6 kcal/mol) is found below 240°C of 79.1 kj/mol (18.9 kcal/mol) above 240°C and finally, of 307.1 kj/mol (73.4 kcal/mol) between 400—440°C (33,34). Below 300°C, the equation... 

The U.S. domestic capacity of ammonium perchlorate is roughly estimated at 31,250 t/yr. The actual production varies, based on the requirements for soHd propellants. The 1994 production ran at about 11,200 t/yr, 36% of name plate capacity. Environmental effects of the decomposition products, which result from using soHd rocket motors based on ammonium perchlorate-containing propellants, are expected to keep increasing pubHc pressure until consumption is reduced and alternatives are developed. The 1995 price of ammonium perchlorate is in the range of 1.05/kg. Approximately 450 t/yr of NH ClO -equivalent cell Hquor is sold to produce magnesium and lithium perchlorate for use in the production of batteries (113). Total U.S. domestic sales and exports for sodium perchlorate are about 900 t/yr. In 1995, a solution containing 64% NaClO was priced at ca 1.00/kg dry product was also available at 1.21/kg. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Ammonium perchlorate [7790-98-9] M 117.5, d 1.95, pK -2.4 to -3.1 (for HCIO4). Crystd twice from distilled water (2.5mL/g) between 80° and 0°, and dried in a vacuum desiccator over P2O5. Drying at 110° might lead to slow decomposition to chloride. POTENTIALLY EXPLOSIVE. 

Factors which Catalyze the Decomposition of Ammonium Perchlorate. Irradiation of AP with X-rays or gamma radiation causes it to decomp at a lower temp, presumably by the formn of holes or active sites in the cryst (Ref 36). Metal salts have been found to lower the decompn point of AP by as much as 80° (Ref 39), and to lower the induction period for its expln at 233° by 21 minutes (Ref 41). Inorg salts which have been found to catalyze the decompn of AP are listed below ... 

Adiabatic Decomposition of Ammonium Perchlorate , SRI Report PU-3573 (1965), AD 640084 33) M.L. Essick, Literature Search. ... 

F. Solymosi K. Fonagy, Effect of Cadmium Oxide and Cadmium Perchlorate on the Decomposition and Ignition of Ammonium Perchlorate , in 11th Symposium (International) on Combustion, 14 Aug 1966, The Combustion Inst (1967), 429 40) L. LoFiego, Practical... 

The Thermal Decomposition of Ammonium Perchlorate — A Literature Review , U of Miami. Dept of Chem Special Report 6 (1968), AD 673542 43) O, Svejka, CzechP 129074... 

A considerable amount of research has been conducted on the decomposition and deflagration of ammonium perchlorate with and without additives. The normal thermal decomposition of pure ammonium perchlorate involves, simultaneously, an endothermic dissociative sublimation of the mosaic crystals to gaseous perchloric acid and ammonia and an exothermic solid-phase decomposition of the intermosaic material. Although not much is presently known about the nature of the solid-phase reactions, investigations at subatmospheric and atmospheric pressures have provided some information on possible mechanisms. When ammonium perchlorate is heated, there are three competing reactions which can be defined (1) the low-temperature reaction, (2) the high-temperature reaction, and (3) sublimation (B9). 

Catalysts which enhance the burning rate of composite propellants are generally believed to accelerate the decomposition of ammonium perchlorate, but the catalytic mechanism is still not very clear. The important observed aspects of this catalysis can be summarized as follows ... 

Horton (H9, H10) has obtained additional acoustic-admittance data for a series of composite propellants. At a given frequency, decreasing the mean oxidizer particle size increases the acoustic admittance and thereby the tendency for instability. Horton also investigated the effects on the acoustic admittance of the incorporation of traces of copper chromite, a known catalyst, for the decomposition of ammonium perchlorate, lithium fluoride (a burning-rate depressant), and changes in binder these data are difficult to analyze because of experimental errors. 

Accumulatory pressure measurements have been used to study the kinetics of more complicated reactions. In the low temperature decomposition of ammonium perchlorate, the rate measurements depend on the constancy of composition of the non-condensable components of the product mixture [120], The kinetics of the high temperature decomposition [ 59] of this compound have been studied by accumulatory pressure measurements in the presence of an inert gas to suppress sublimation of the solid reactant. Reversible dissociations are not, however, appropriately studied in a closed system, where product readsorption and diffusion effects within the product layer may control, or exert perceptible influence on, the rate of gas release [121]. 

Some limitations of optical microscopy were apparent in applying [247—249] the technique to supplement kinetic investigations of the low temperature decomposition of ammonium perchlorate (AP), a particularly extensively studied solid phase rate process [59]. The porous residue is opaque. Scanning electron microscopy showed that decomposition was initiated at active sites scattered across surfaces and reaction resulted in the formation of square holes on m-faces and rhombic holes on c-faces. These sites of nucleation were identified [211] as points of intersection of line dislocations with an external boundary face and the kinetic implications of the observed mode of nucleation and growth have been discussed [211]. 

Although it would appear that plots of ln[—ln(l — a)] against ln(f — t0) provide the most direct method for the determination of n from experimental a—time data, in practice this approach is notoriously insensitive and errors in t0 exert an important control over the apparent magnitude of n. An alternative possibility is to compare linearity of plots of [—ln(l — a)]1/n against t this has been successful in the kinetic analysis of the decomposition of ammonium perchlorate [268]. Another possibility is through the use of the differential form of eqn. (6)... 

The Avrami—Erofe ev equation, eqn. (6), has been successfully used in kinetic analyses of many solid phase decomposition reactions examples are given in Chaps. 4 and 5. For no substance, however, has this expression been more comprehensively applied than in the decomposition of ammonium perchlorate. The value of n for the low temperature reaction of large crystals [268] is reduced at a 0.2 from 4 to 3, corresponding to the completion of nucleation. More recently, the same rate process has been the subject of a particularly detailed and rigorous re-analysis by Jacobs and Ng [452] who used a computer to optimize curve fitting. The main reaction (0.01 < a < 1.0) was well described by the exact Avrami equation, eqn. (4), and kinetic interpretation also included an examination of the rates of development and of multiplication of nuclei during the induction period (a < 0.01). The complete kinetic expressions required to describe quantitatively the overall reaction required a total of ten parameters. 

Fig. 16. Graphical representation of Arrhenius parameters for the low temperature decomposition of ammonium perchlorate (pelleted, orthorhombic, o, and cubic, , forms). Compensation behaviour is observed. Data from Jacobs and Ng [452]. N = nucleation, B = branching, G = growth processes.

Fig. 17. Unified reaction scheme for the thermal decomposition of ammonium perchlorate, proposed by Jacobs et al. [59,925,926], In the low temperature reaction, the interaction occurs between adsorbed species (a) whereas the high temperature reaction and sublimation process involved volatilization intermediates (g). X] and X2 represent mixtures of intermediates.

Materials for a batch of ammonium perchlorate castable propellant were charged into a mechanical mixer. A metal spatula was left in accidentally, and the contents ignited when the mixer was started, owing to local friction caused by the spatula. A tool-listing safety procedure was instituted [1]. The literature on the kinetics of thermal decomposition has been reviewed critically [2],... 

In a review of the course and mechanism of the catalytic decomposition of ammonium perchlorate, the considerable effects of metal oxides in reducing the explosion temperature of the salt are described [1], Solymosi s previous work had shown reductions from 440° to about 270° by dichromium trioxide, to 260° by 10 mol% of cadmium oxide and to 200°C by 0.2% of zinc oxide. The effect of various concentrations of copper chromite , copper oxide, iron oxide and potassium permanganate on the catalysed combustion of the propellant salt was studied [2], Similar studies on the effects of compounds of 11 metals and potassium dichromate in particular, have been reported [3], Presence of calcium carbonate or calcium oxide has a stabilising effect on the salt, either alone or in admixture with polystyrene [4],... 

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