Kinetic explosion

GP 11] [R 19] Based on an analysis of the thermal and kinetic explosion limits, inherent safety is ascribed to hydrogen/oxygen mixtures in the explosive regime when guided through channels of sub-millimeter dimensions under ambient-pressure conditions [9], This was confirmed by experiments in a quartz micro reactor [9],... 

Figure 3.50 Extending kinetic explosion (squares) and thermal explosion limits by using a micro reactor with 300 pm channel diameter (filled symbols). Calculated values for (circles) and 7 3 = (triangles). Comparison with 1 m...

The kinetics of reactions on metal surfaces is strongly affected by the structures of reaction intermediates, especially by the incorporated metal adatoms in their structures (Sect 11.5). hi the mid 1970s, Falconer and Madix observed a surface- kinetic explosion for the decomposition of formate and acetate adsorbed on the Ni (110) surface [23, 24], Recently, with the help of STM, TPRS, and XPS, we were able to determine that Ni atoms are incorporated into the structures of the carboxylate intermediates. Remarkably, the incorporation of metal atoms into the carboxylate structure is an important aspect of the origin of the kinetic explosion. 

In the mid 1970s, Falconer and Madix observed a surface- kinetic explosion for the decomposition of formic acid (HCOOH) [23] and acetic acid (CH COOH) [24] on the Ni(llO) surface, characterized by very narrow product desorption peaks in TPRS. Such autocatalytic reactions have also been observed in the decomposition of acetic acid on Pd(llO), Rh(llO), Rh(lll), and even supported Rh catalyst by Bowker et al. [70-75]. In general, these reactions exhibit accelerations in rate as the reaction proceeds to completion. Earlier work hypothesized that decomposition of the carboxylate species formed following adsorption of the acids on the surface was initiated at vacancies (i.e. bare metal sites) and propagated by the further creation of vacancies as the products desorbed from the surface [23, 24]. The rate of decomposition was well described by the rate equation r = -k(C / Cj )(Cj - c+/Cj), in which C is the instantaneous surface concentration of carboxylate, C, is the initial surface concentration, and/is the density of initiation sites. Since the decomposition produced an ever-increasing concentration of vacant sites, a kinetic explosion occurred. 

Annealing the formate-covered Ni(llO) surface to 340 K, the leading edge of formate decomposition produces scattered Ni islands of monatomic step height amidst the c(2 x 2)-formate domains and the small number of pits of monatomic step depth (Fig. 11.15) [21]. The Ni islands are apparently formed by Ni adatoms released during the decomposition of a small fraction of formate. The Ni islands were also observed when annealing the acetate-covered Ni(llO) surface to 360 K [21]. These observations provide a more detailed explanation for the kinetic explosion in the decomposition of formate and acetate. It appears that the released Ni atoms catalyzed the further decomposition of the carboxylates. The released Ni atoms can either catalyze the reaction before they nucleate into islands or provide unoccupied metal sites, which are produced exponentially due to desorption of the carboxylates with the exponential rate, for decomposition. This ultimately leads to a kinetic explosion in the decomposition of the carboxylates on Ni(llO). 

Reaction (5) proceeds mostly heterogeneously, reaction (6) mostly homogeneously. This mechanism can be integrated with simplifying assumptions to demonstrate the main features of gas-phase explosion kinetics [8]... 

Diperoxyketals, and many other organic peroxides, are acid-sensitive, therefore removal of all traces of the acid catalysts must be accompHshed before attempting distillations or kinetic decomposition studies. The low molecular weight diperoxyketals can decompose with explosive force and commercial formulations are available only as mineral spirits or phthalate ester solutions. 

Impacts and Explosives. The coUision of high velocity bullets or other projectiles with soHds causes rapid conversion of kinetic to thermal energy. Plasmas result iacidentaHy, whereas the primary effects of impact are shock and mechanical effects in the target. Impact-produced plasmas are hot enough to cause thermonuclear bum (180). 

Exothermic Decompositions These decompositions are nearly always irreversible. Sohds with such behavior include oxygen-containing salts and such nitrogen compounds as azides and metal styphnates. When several gaseous products are formed, reversal would require an unlikely complex of reactions. Commercial interest in such materials is more in their storage properties than as a source of desirable products, although ammonium nitrate is an important explosive. A few typical exampes will be cited to indicate the ranges of reaction conditions. They are taken from the review by Brown et al. ( Reactions in the Solid State, in Bamford and Tipper, Comprehensive Chemical Kinetics, vol. 22, Elsevier, 1980). 

E Explosion energy available to generate blast and fragment kinetic... 

In classical examples of kinetics, such as the hydrolysis of cane sugar by acids in water solution, the reaction takes hours to approach completion. Therefore Whilhelmy (1850) could study it successfially one and a half centuries ago. Gone are those days. What is left to study now are the fast and strongly exothermic or endothermic reactions. These frequently require pressure equipment, some products are toxic, and some conditions are explosive, so the problems to be solved will be more difficult. All of them require better experimental equipment and techniques. 

The kinetics and thermodynamics of the reaction, and of possible side reactions, need to be understood. The explosive potential of chemicals liable to exothermic reaction should be carefully appraised. 

Unfortunately, there is no consensus on the measure for defining the energy of an explosion of a pressure vessel. Erode (1959) proposed to define the explosion energy simply as the energy, ex,Br> must be employed to pressurize the initial volume from ambient pressure to the initial pressure, that is, the increase in internal energy between the two states. The internal energy 1/ of a system is the sum of the kinetic, potential, and intramolecular energies of all the molecules in the system. For an ideal gas it is... 

Fragments. As will be explained in Section 6.4, between 20% and 50% of available explosion energy may be transformed into kinetic energy of fragments and liquid or solid contents. 

The main sources of deviation lie in estimates of energy and in release-process details. It is unclear whether the energy equations given in preceding sections are good estimates of explosion energy. In addition, energy translated into kinetic... 

The most prominent chemical property of HOF is its instability. It decomposes spontaneously (sometimes explosively) to HF and O2 with a half-life of ca. 30 min in a Teflon apparatus at room temperature and lOOmmHg. It reacts rapidly with water to produce HF, H2O2 and O2 in dilute aqueous acid H2O2 is the predominant product whereas in alkaline solution O2 is the principal O-containing product. The kinetics of these processes have been studied and, by use of 0-enriched H2O2, it has... 

Viewed in conjunction with the solid-like, nonvolatile nature of ionic liquids, it is apparent that TSILs can be thought of as liquid versions of solid-supported reagents. Unlike solid-supported reagents, however, TSILs possess the added advantages of kinetic mobility of the grafted functionality and an enormous operational surface area (Figure 2.3-1). It is this combination of features that makes TSILs an aspect of ionic liquids chemistry that is poised for explosive growth. 

Large-scale crude oil exploitation began in the late nineteenth century. Internal combustion engines, which make use of the heat and kinetic energy of controlled explosions in a combustion chamber, were developed at approximately the same time. The pioneers in this field were Nikolaus Otto and Gottleib Daimler. These devices were rapidly adapted to military purposes. Small internal-combustion motors were used to drive dynamos to provide electric power to fortifications in Europe and the United States before the outbreak of World War I. Several armies experimented vith automobile transportation before 1914. The growing demand for fossil fuels in the early decades of the twentieth centuiy was exacerbated by the modernizing armies that slowly introduced mechanization into their orders of battle. The traditional companions of the soldier, the horse and mule, were slowly replaced by the armored car and the truck in the early twentieth century. 

The writer (Ref 8a) detd explosion times of Petrin rapidly heated in small stainless steel tubes (Wenograd test). The measurement scatter was too large to obtain reliable kinetic data. 

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