Nitrate ammonium

Ammonium nitrate is manufactured by the neutralization of nitric acid with gaseous ammonia in a strongly exothermic reaction  

The thermal instability of ammonium nitrate means that the volume of the reactors must be kept as small as possible, the acid used must be as free from impurities as possible and the reaction must be controlled so as to avoid the presence of excess acid. 

If nitric acid concentrations above 50% are used, it is possible, with appropriate process design, to evaporate all the water introduced without supplying additional energy. 

Posttreatment is necessary, because ammonium nitrate is highly hygroscopic. In view of its strong oxidizing power, only inorganic substances such as attapulgite, kieselguhr or clay can be used. 

In the Federal Republic of Germany, the use of pure ammonium nitrate as a fertilizer is forbidden on safety grounds. Mixtures, particularly with calcium carbonate, are used instead. Currently mixtures with N-contents of up to 28% are allowed. 

Ammonium nitrate (NH4N03), a colorless crystalline solid, occurs in two forms (1) a-ammonium nitrate (tetragonal crystals, stable between -16°C and 32°C melting point 169.9°C density 1.66) and (2) (3-ammonium nitrate (rhombic or monoclinic crystals, stable between 32°C and 84°C with decomposition occurring above 210°C density 1.725). 

When heated, ammonium nitrate yields nitrous oxide (N20) gas and can be used as an industrial source of that gas. Ammonium nitrate is soluble in water, slightly soluble in ethyl alcohol, moderately soluble in methyl alcohol, and soluble in acetic acid solutions containing ammonia. 

Ammonium nitrate is manufactured from ammonia and nitric acid. 

If properly proportioned and preheated, the reaction can be run continuously to produce molten ammonium nitrate containing very little water (1 to 5%), which can be formed into small spheres (prills) by dropping the reaction product through a shot tower or into flakes by cooling it on belts or drums. By fluidized bed treatment, it is possible to obtain a dry granular material as product batch processes have also been used. 

Ammonium nitrate finds major applications in explosives and fertilizers, and additional uses in pyrotechnics, freezing mixtures (for obtaining low temperatures), as a slow-burning propellant for missiles (when formulated with other materials, including burning-rate catalysts), as an ingredient in rust inhibitors (especially for vapor-phase corrosion), and as a component of insecticides. 

Ammonium nitrate (uh-MOH-ni-um NYE-trate) is a white crystalline substance first made artificially in 1659 by the German chemist Johann Rudolf Glauber (1604-1670). The compound does not occur in nature because it is so soluble that it is washed out of the soil by rain and surface water. Ammonium nitrate is stable at lower temperatures, but tends to decompose explosively when heated to temperatures above 2oo°C (390°F). Its two most important uses today are in fertilizers and explosives. In 2004, it ranked fourteenth among all chemicals manufactured in the United States. Just over six million metric tons (6.6 million short tons) of the compound were produced in 2004. 

Ammonium nitrate is made commercially by passing ammonia gas (NH3) and a water solution of nitric acid (HN03) through a pipe. The ammonia combines with the 

Ammonium nitrate. Red atoms are oxygen white atoms are hydrogen and blue atoms are nitrogen, publishers 

Large amounts of heat are released during the reaction, so the pipe and supporting equipment must be very strong. The solution of ammonium nitrate in water is allowed to evaporate, leaving behind pure white crystals of the compound. 

The primary use of ammonium nitrate is the manufacture of fertilizers. In 2005, about 2 million metric tons (2.2 million short tons) of ammonium nitrate fertilizer was used in the United States. The compound is added to soil to provide the nitrogen that plants need to grow. It may he used by itself or in combination with another nitrogen-rich compound, urea, in a mixture known as UAN. 

It contains 35% nitrogen, much of it as nitrate, so it is readily taken up by plants. 

Ammonium nitrate is a bit of a contradiction. It is made up of two ions, tetrahedral ammonium ions and flat, triangular, nitrate ions. 

On fairly gentle heating, to around 200°C, ammonium nitrate decomposes, forming nitrous oxide (laughing gas, see p371). 

Above around 240°C, it can explode, especially when molten and under pressure. The presence of impurities, such as organic molecules, makes this happen more readily, as in mixtures of 

Ammonium nitrate can also release oxygen on heating to higher temperatures  

Nitric acid has a 65 25 fertilizer explosive end use ratio. The production of ammonium nitrate makes up nearly all of these two uses. The other 10% is made into miscellaneous compounds adipic acid, nitroglycerin, nitrocellulose, ammonium picrate, trinitrotoluene, nitrobenzene, silver nitrate, and various isocyanates. 

Ammonium nitrate is a white hygroscopic solid, mp 169.6°C, is relatively unstable, and forms explosive mixtures with combustible materials or when contaminated with certain organic compounds. It is very soluble in water, 55% at 0°C. 

Ammonium nitrate has an 82 18 fertilizer explosive end use ratio. The chief use of ammonium nitrate until after World War II was as an explosive. Although it still accounts for more than 75% of all explosives, its major use is now as a fertilizer because of its high nitrogen content, 33.5% N. 

In 1867, the Swedish chemists Ohlsson and Norrbin found that the explosive properties of dynamites were enhanced by the addition of ammonium nitrate (NH4N03). Alfred Nobel subsequently acquired the patent of Ohlsson and Norrbin for ammonium nitrate and used this in his explosive compositions. 

Ammonium nitrate was first prepared in 1654 by Glauber but it was not until the beginning of the 19th century when it was considered for use in explosives by Grindel and Robin as a replacement for potassium nitrate in blackpowder. Its explosive properties were also reported in 1849 by 

Reise and Millon when a mixture of powdered ammonium nitrate and charcoal exploded on heating. 

Ammonium nitrate was not considered to be an explosive although small fires and explosions involving ammonium nitrate occurred throughout the world. 

Numerous shipments were made without trouble prior to 16 and 17 April 1947, when a terrible explosion occurred. The SS Grandchamp and the SS Highflyer, both moored in the harbour of Texas City and loaded with FGAN, blew up. As a consequence of these disasters, a series of investigations was started in the USA in an attempt to determine the possible causes of the explosions. At the same time a more thorough study of the explosive properties of ammonium nitrate and its mixtures with organic and inorganic materials was also conducted. The explosion at Texas City had barely taken place when a similar one aboard the SS Ocean Liberty shook the harbour of Brest in France on 28 July 1947. 

Following three phase transformations [951] ( 298 K), NH C decomposition begins [915] in the solid phase at 423 K but only becomes extensive well above the melting point ( 440 K). Decomposition with the evolution of N20 and H20 from the melt is first order [952,953] (E = 153—163 kJ mole-1), the mechanism suggested involving intermediate nitramide formation. Other proposed schemes have identified NOj [954] or the radical NH2NO [955] ( 473 K) as possible participants. Studies [956,957] have been made of the influence of additives on NH C decomposition. 

UV photolysis [958] of NH Os yields N20, H20, N2, 02, and traces of NO, while the same products, with the exception of 02 were detected in gases evolved during 7-radiolysis [959]. No N02 was detected in the irradiated salt. 

In general, ammonia is evolved before anion breakdown in the decompositions of ammonium metal nitrates [960,961], Decomposition of hydrazonium nitrate [962] obeys second-order kinetics and presumably occurs in a melt. 

EXPLOSIVE WHEN MIXED WITH COMBUSTIBLE MATERIALS 

Colorless crystals mp, 169°C bp decomposes at above 210°C, mostly into H20 and NA1 2 

Mixtures of ammonium nitrate and combustible material are readily ignited mixtures with finely divided combustible materials can react explosively. Extinguish fire with water spray.2 

Soluble in water.2 One gram dissolves in 0.5 mL of water, 0.1 mL of boiling water, about 20 mL of ethanol, and about 8 mL of methanol.1 

In the absence of impurities it is difficult, but not impossible, to cause ammonium nitrate 

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NH3) are of great commercial importance practically all modem explosives contain high proportions of ammonium nitrate or organic nitro-compounds. Nitrates are also employed as fertilizers. 

It is prepared by the direct nitration of toluene with a mixture of nitric and sulphuric acids. TNT is a very stable, violent and powerful high explosive, but less sensitive to shock and friction than picric acid. It is widely used as a filling for shells, bombs, etc. often mixed with ammonium nitrate and other high explosives. The lower grades of TNT may contain isomers which under hot storage conditions may give rise to exudation. 

The mixture of ammonium nitrate and powdered aluminium is an explosive known as ammonal. 

This can be prepared by the controlled reduction of a nitrite (nitrate(lll)) or nitrate. Cautious heating of ammonium nitrate gives dinitrogen oxide by an internal oxidation-reduction process ... 

Ammonium nitrate gives dinitrogen oxide and steam ... 

The impurities in ordinary iron assist dissolution in acid, and are responsible for the characteristic smell of the hydrogen from this source.) In dilute nitric acid, ammonium nitrate is formed ... 

Note, (i) Care should be taken to distinguish between a residue of carbon which may be very difficult to bum off completely, and a really non-volatile residue due to the presence of a metallic derivative. Thus for instance starch leaves a hard black residue of carbon which can best be burned away by moistening with a saturated solution of ammonium nitrate and then reheating. 

Oxidation of benzoin with concentrated nitric acid or by catalytic amounts of cupric salts in acetic acid solution, which are regenerated continuously by ammonium nitrate, yields the diketone benzil ... 

Method 2. Place 0-2 g. of cupric acetate, 10 g. of ammonium nitrate, 21 2 g. of benzoin and 70 ml. of an 80 per cent, by volume acetic acid -water solution in a 250 ml. flask fitted with a reflux condenser. Heat the mixture with occasional shaking (1). When solution occurs, a vigorous evolution of nitrogen is observed. Reflux for 90 minutes, cool the solution, seed the solution with a crystal of benzil (2), and allow to stand for 1 hour. Filter at the pump and keep the mother liquor (3) wash well with water and dry (preferably in an oven at 60°). The resulting benzil has m.p. 94-95° and the m.p. is unaffected by recrystallisation from alcohol or from carbon tetrachloride (2 ml. per gram). Dilution of the mother liquor with the aqueous washings gives a further 1 Og. of benzil (4). 

Ammonium nitrate Acids, metal powders, flammable liquids, chlorates, nitrites, sulfur, flnely divided organic or combustible materials, perchlorates, urea... 

Copper Acetylene and alkynes, ammonium nitrate, azides, bromates, chlorates, iodates, chlorine, ethylene oxide, fluorine, peroxides, hydrogen sulflde, hydrazinium nitrate... 

Elammable liquids Ammonium nitrate, chromic acid, the halogens, hydrogen peroxide, nitric acid... 

Lead Ammonium nitrate, chlorine trifluoride, hydrogen peroxide, sodium azide and carbide, zirconium, oxidants... 

The urea produced is normally either prilled or granulated. In some countries there is a market for Hquid urea—ammonium nitrate solutions (32% N). In this case, a partial-recycle stripping process is the best and cheapest system. The unconverted NH coming from the stripped urea solution and the reactor off-gas is neutralized with nitric acid. The ammonium nitrate solution formed and the urea solution from the stripper bottom are mixed, resulting in a 32—35 wt % solution. This system drastically reduces investment costs as evaporation, finishing (priQ or granulation), and wastewater treatment are not required. 

Urea processes provide an aqueous solution containing 70—87% urea. This solution can be used directiy for nitrogen-fertilizer suspensions or solutions such as urea—ammonium nitrate solution, which has grown ia popularity recentiy (18). Urea solution can be concentrated by evaporation or crystallization for the preparation of granular compound fertilizers and other products. Concentrated urea is sohdified ia essentially pure form as prills, granules, flakes, or crystals. SoHd urea can be shipped, stored, distributed, and used mote economically than ia solution. Furthermore, ia the soHd form, urea is more stable and biuret formation less likely. 

Mixed with additives, urea is used in soHd fertilizers of various formulations, eg, urea—ammonium phosphate (UAP), urea—ammonium sulfate (UAS), and urea—phosphate (urea + phosphoric acid). Concentrated solutions of urea and ammonium nitrate (UAN) solutions (80—85 wt%) have a high nitrogen content but low crystallization point, suitable for easy transportation, pipeline distribution, and direct spray appHcation. 

The Bachmann process, used in the United States and in some European countries, is a simplification of a series of complex reactions. In this process, a solution of one part hexamine in 1.65 parts acetic acid, and a solution of 1.50 parts ammonium nitrate dissolved in 2.0 parts nitric acid and 5.20 parts acetic anhydride are used. The reaction may be summarized as ... 

In the commonly used Welland process, calcium cyanamide, made from calcium carbonate, is converted to cyanamide by reaction with carbon dioxide and water. Dicyandiamide is fused with ammonium nitrate to form guanidine nitrate. Dehydration with 96% sulfuric acid gives nitroguanidine which is precipitated by dilution. In the aqueous fusion process, calcium cyanamide is fused with ammonium nitrate ia the presence of some water. The calcium nitrate produced is removed by precipitation with ammonium carbonate or carbon dioxide. The filtrate contains the guanidine nitrate that is recovered by vacuum evaporation and converted to nitroguanidine. Both operations can be mn on a continuous basis (see Cyanamides). In the Marquerol and Loriette process, nitroguanidine is obtained directly ia about 90% yield from dicyandiamide by reaction with sulfuric acid to form guanidine sulfate followed by direct nitration with nitric acid (169—172). 

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