Nitration reactor conditions

The above observations allow the selective formation of RDX, HMX or the two linear nitramines (247) and (248) by choosing the right reaction conditions. For the synthesis of the linear nitramine (247), with its three amino nitrogens, we would need high reaction acidity, but in the absence of ammonium nitrate. These conditions are achieved by adding a solution of hexamine in acetic acid to a solution of nitric acid in acetic anhydride and this leads to the isolation of (247) in 51 % yield. Bachmann and co-workers also noted that (247) was formed if the hexamine nitrolysis reaction was conducted at 0 °C even in the presence of ammonium nitrate. This result is because ammonium nitrate is essentially insoluble in the nitrolysis mixture at this temperature and, hence, the reaction is essentially between the hexamine and nitric acid-acetic anhydride. If we desire to form linear nitramine (248) the absence of ammonium nitrate should be coupled with low acidity. These conditions are satisfied by the simultaneous addition of a solution of hexamine in acetic acid and a solution of nitric acid in acetic anhydride, into a reactor vessel containing acetic acid. 

However, it is possible to obtain a numerical solution corresponding to a specific set of reactor conditions. The model described here can be used to simulate any one stage of the nitration reactors. 

The cmde phthaUc anhydride is subjected to a thermal pretreatment or heat soak at atmospheric pressure to complete dehydration of traces of phthahc acid and to convert color bodies to higher boiling compounds that can be removed by distillation. The addition of chemicals during the heat soak promotes condensation reactions and shortens the time required for them. Use of potassium hydroxide and sodium nitrate, carbonate, bicarbonate, sulfate, or borate has been patented (30). Purification is by continuous vacuum distillation, as shown by two columns in Figure 1. The most troublesome impurity is phthahde (l(3)-isobenzofuranone), which is stmcturaHy similar to phthahc anhydride. Reactor and recovery conditions must be carefully chosen to minimize phthahde contamination (31). Phthahde [87-41-2] is also reduced by adding potassium hydroxide during the heat soak (30). 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

Nitric acid is one of the three major acids of the modem chemical industiy and has been known as a corrosive solvent for metals since alchemical times in the thirteenth centuiy. " " It is now invariably made by the catalytic oxidation of ammonia under conditions which promote the formation of NO rather than the thermodynamically more favoured products N2 or N2O (p. 423). The NO is then further oxidized to NO2 and the gases absorbed in water to yield a concentrated aqueous solution of the acid. The vast scale of production requires the optimization of all the reaction conditions and present-day operations are based on the intricate interaction of fundamental thermodynamics, modem catalyst technology, advanced reactor design, and chemical engineering aspects of process control (see Panel). Production in the USA alone now exceeds 7 million tonnes annually, of which the greater part is used to produce nitrates for fertilizers, explosives and other purposes (see Panel). 

OS 31] ]R 16a] ]P 23] For benzene nitration, the results achieved in the capillary-flow micro reactor were benchmarked against results claimed in the patent literature (see Table 4.2) [97]. An analysis of conversion, by-product level, reaction time and reaction rate showed that the results achieved in micro reactors and conventional equipment are competitive, i.e. were similar. As tendencies, it seemed that the micro reactor can lead to a lower by-product level owing to its better temperature guiding and that reaction times can be further shortened. However, the corresponding results are not absolutely comparable in terms of reaction conditions and hence further data are required here. 

OS 51] [R 17] [R 19] [R 26] [P 37] Methane and hexane nitration were successfully performed under safe conditions in micro reactors [37]. The very preliminary character of these experiments did not allow any detailed process information to be derived apart from demonstrating feasibility and the fact that selectivity was low in the first runs. No significant improvement over the batch processing was obtained here. The formation of many imdesired products was particularly high for nitration of hexane [37]. 

This latter point was stressed by some of us in a recent report studying NO storage and reduction on commercial LSR (lean storage-reduction) catalysts, in order to catch valuable information about the behaviour of typical NO storage materials in real application conditions. Nature, thermal stability and relative amounts of the surface species formed on a commercial catalyst upon NO and 02 adsorption in the presence and in the absence of water were analysed using a novel system consisting of a quartz infrared reactor. Operando IR plus MS measurements showed that carbonates present in the fresh catalyst are removed by replacement with barium nitrate species after the first nitration of the material. Nitrate species coordinated to different barium sites are the predominant surface species under dry and wet conditions. The difference in the species stabilities suggested that barium sites possess different basicity and, therefore, that they are able to stabilize nitrates at different temperatures. At temperatures below 523 K, nitrite species were observed. The presence of water at mild temperatures in the reactant flow makes unavailable for NO adsorption the alumina sites [181]. 

Use of a screw feeder to charge a reactor with the 2-anisidine salt led to ignition of the latter. It was known that the salt would decompose exothermically above 140°C, but later investigation showed that lower-quality material could develop an exotherm above 46°C under certain conditions [1]. Fast flame propagation occurs on moderately heating anisidine nitrate powder [2],... 

For the prepn of AEG with a N content of ca 20%, BRL treated a small amt of cellulose with a large excess of ethyleneimine in a bomb reactor at 160-200° for 6—20 hrs and recycled the product 2 or 3 times under the same conditions to get a higher N content (Refs 2 3) Later work(Ref 4) raised the N content to a max of 28.8%. This material was used for the prepn of fast burning salts, such as the perchlorates and nitrate. A detailed description of the prepn of high nitrogen AEC is given in Ref 4, Rept No l,p 6... 

When dealing with precipitated salts it is important to know the physical state in which the salt is present inside the reactor, either solid or liquid. For example, sodium nitrate has melting point 306.8 °C, lower than the operating temperature. Therefore, once saturating conditions are surpassed, sodium nitrate does not adhere to the reactor walls as a solid but drains itself downwards. Since it is denser than supercritical water [27], care should be taken to prevent its accumulation at the bottom of the reactor. 

An intermediate for a dyestuff is prepared by sulfonation and nitration of an aromatic compound at 40 °C. The intermediate product has to be precipitated by dilution of the sulfuric acid with water to a final concentration of 60%. This dilution is performed under adiabatic conditions (no cooling) and the final temperature is 80 °C. This temperature of 80 °C is important for the crystallization and for the following filtration. After the temperature has reached 80 °C, the mixture is immediately cooled down to 20 °C by applying the full cooling capacity of the reactor. 

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