Nitroglycerin from glycerin

Experiments on the use of mixtures of nitric add with phosphoric anhydride showed this to be impracticable, since separate layers were formed with the phosphoric acid at the bottom and nitroglycerine remaining dissolved in the nitric add layer from which it had to be separated by adding water. Nor was replacement of sulphuric acid by anhydrous calcium nitrate of any practical value, as predpitation of nitroglycerine by the addition of water was necessary. The yield attained by application of both these methods does not exceed 2 parts of nitroglycerine from 1 part of glycerol. At the time when concentrated nitric add was very expensive, attempts were made to nitrate glycerine with a mixture of sulphuric acid and sodium nitrate (Huntley and Kessel [1]). However, this method found no practical use. 

The limit for the heat test of nim>glycerine extracted from dynamite. etc. is hf een minutes at 160 F. The nitroglycerine must be dry, as moisture pro taking care that it does not >vet the sides of the tube. 

Nitroglycerin (NG) production provides a good example of the reductions in inventory that can be achieved by redesign. It is made from glycerin and a mixture of concentrated nitric and sulfuric acids. The reaction is very exothermic if the heat is not removed by cooling and stirring, an uncontrollable reaction is followed by explosive decomposition of the NG. 

Originally, nitroglycerine was manufactured by batch process. This represented a significant hazard because literally tons of product and spent acid were maintained for several hours at elevated temperatures. In an attempt to reduce the hazard, the operation was changed from batch to continuous, a process in which the glycerine and nitrating mixture were separately fed into a reaction chamber. In this way, the residence time was reduced to several seconds, which obviously resulted in a safer operation. 

The late 19th century saw the development of a new family of "smokeless" powders, as modern organic chemistry blossomed and the nitration reaction became commercially feasible. Two "esters" - nitrocellulose and nitroglycerine - became the major components of these new propellants. An ester is a compound formed from the reaction between an acid and an alcohol. Figure 6.1 illustrates the formation of NC and NG from nitric acid and the precursor alcohols cellulose and glycerine. 

Heat of nitration of glycerin. Suppose we wish to estimate the heat evolved in nitrating 1 mole of glycerin with mixed acid. To simplify this illustrative example we will assume initial mixture — 1 mole glycerin/3 moles 100% nitric acid/6 moles 100% sulfuric acid final mixture -1 mole nitroglycerin completely separated from the spent acid which is now diluted by 3 moles of water the entire heat of dilution is due to 3 moles water dissolving in 6 moles of 100% sulfuric acid. Thus... 

According to information from different sources the heat of nitration of glycerol to nitroglycerine varies from 120 to 170 kcal per 1 kg of glycerine. 

This equation does not comprise the whole complex of simultaneous chemical reactions, which have already been discussed (p. 7). Later investigators (Vignon and Bay [53] Silberrad and Fanner [54], Berl and Delpy [55]) also found such products as aldehyde resins, oxalic add and ammonia. It is characteristic that from nitroglycerine hydrolysed in an alkaline medium no glycerine is recovered. Glycerine can however be obtained again when the hydrolysis is carried out in the presence... 

In the recently introduced continuous methods of nitroglycerine manufacture nitrators made from acid resistant steel are used since the art of welding stainless steel had progressed remarkably by the 1930 s. The design and construction of nitrators for nitrating glycerine are included in the descriptions of individual methods of nitration. 

Temperatures below 12°C are not usually used, since crystallization of nitroglycerine could take place. Lower temperatures (e.g. 5-7°C) can be applied only when a mixture of glycerine with glycol or diglycerol is nitrated and if there exists no fear that the mixture of esters resulting from the reaction can freeze. In factory practice, nitration is performed mainly at temperatures of about 20-25°C or at 25-30°C. The temperature is measured by means of at least two thermometers, immersed in the vessel at different depths. 

From 100 parts by weight of glycerine, 228.7 parts by weight of nitroglycerine were obtained. 

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