Nitric acid catalyst used

Organic Reactions. Nitric acid is used extensively ia iadustry to nitrate aHphatic and aromatic compounds (21). In many iastances nitration requires the use of sulfuric acid as a dehydrating agent or catalyst the extent of nitration achieved depends on the concentration of nitric and sulfuric acids used. This is of iadustrial importance ia the manufacture of nitrobenzene and dinitrotoluene, which are iatermediates ia the manufacture of polyurethanes. Trinitrotoluene (TNT) is an explosive. Various isomers of mononitrotoluene are used to make optical brighteners, herbicides (qv), and iasecticides. Such nitrations are generally attributed to the presence of the nitronium ion, NO2, the concentration of which iacreases with acid strength (see Nitration). 

Aqueous solution nitric acid. Condensations using catalysts ... 

Additional uses of nitric acid are for oxidation, nitration, and as a catalyst in numerous reactions. Salts of nitric acid are collectively called nitrates, which are soluble in water. Nitric acid is used in the production of many items such as dyes, pharmaceuticals, and synthetic fabrics. It is also used in a variety of processes including print making. 

Stable nitronium salts, which are readily prepared from nitric acid (or nitrates) with HF and BF3 (and other Lewis acids such as PF5, SbF5, etc.) [Eqs. (5.171) and (5.172)], will nitrate aromatics in organic solvents generally with close to quantitative yield. Because HF and PF5 (or BF3) can be easily recovered and recycled, the method can be considered as a nitric acid nitration using a superacid catalyst [Eq. (5.173)]. 

Oxidation of methylated sugars with nitric acid was used extensively by early workers for locating the position of unsubstituted hydroxyl groups.116 Cleavage of carbon-carbon bonds appears to be facilitated by the presence of such catalysts as vanadium salts. As hot nitric acid acts as a hydrolyzing agent as well as an oxidant, oligo- and poly-saccharides may be used directly. 

Regioselective vapour phase nitration of o-xylene to 4-o-NX with dilute nitric acid (30%) using HBeta catalyst at 150 °C has been reported.[80,81] Under these... 

Normally, nitration of deactivated compounds (and therefore polynitration of toluene) is carried out using aggressive nitric acid - oleum mixtures. Dinitration of toluene with mixed acids produces a 4 1 ratio of 2,4- and 2,6-dinitrotoluenes, from which the former is isolated for manufacture of toluenediisocyanate (TDI) and toluenediamine, both of which are used in the manufacture of polyurethanes. Zirconium and hafnium derivatives catalyse nitration of o-nitrotoluene, but ratios of 2,4- 2,6-dinitrotoluene are modest (66 34).12 Dinitration of toluene using Claycop (copper nitrate on K10 clay), acetic anhydride and nitric acid in the presence of carbon tetrachloride produced dinitrotoluenes in a yield of 85% with a ratio of 2,4- 2,6-dinitrotoluene of 9 1.13 This method, however, requires a large excess of nitric acid, the use of an unacceptable solvent and long reaction times. The direct nitration of toluene to 2,4-dinitrotoluene using nitric acid over a zeolite P catalyst, with azeotropic removal of water, is reported to give a 2,4 2,6 ratio of 14, but full results are yet to be published.14... 

Platinum catalysts are also used to make compounds that end up as fertilizers, plastics, synthetic fibers, drugs and pharmaceuticals, and dozens of other everyday products. For example, platinum is used in the manufacture of nitric acid (HNO3). Nitric acid is used to produce ammonia, which, in turn, is used to make fertilizers. 

Oxidation of cyclohexanol alone by means of 67 per cent nitric acid at 55-60 C results in 90 per cent yields of adipic acid when vanadium is used as a catalyst. Ratios of 1-3 moles cyclohexanol per mole nitric acid were used. Without a catalyst, 82 per cent yields are obtained. ... 

A typical chromium-based catalyst is prepared similarly. It is usually supported by a 9 1 of Si02 Al203 carrier. Either Cr(N03)3 9H20 or C1O3 solutions in nitric acid are used to impregnate the support. The nitrates are decomposed in air at 400 to 1000 An optimum chromium content... 

Nitric acid is used to make nitrate salts for fertilizer application. Ammonium nitrate and potassium nitrate are common. Ammonium nitrate is also used for explosives. Nitric acid is used in the production of adipic acid which in turn is used to make nylon 6,6 and also some polyesters. In the synthesis of adipic acid, cyclohexane is oxidized by a radical process to a mixture of cyclohexanol and cyclohexanone. This mixture is then oxidized further with nitric acid and a catalyst to adipic acid. 

Thermal stability of raw TATP (but well washed to neutral pH) depends markedly on the type (Fig. 10.12) and amount (Fig. 10.13) of acid used as the catalyst used in its preparation. The decomposition of TATP begins around 145 °C when hydrochloric or nitric acid is used. The amount of catalyst in this case does not have a measurable influence on the thermal stability of prepared T ATP (acid to acetone molar ratio c/ a from 2.5 X 10 " to 5 X 10 ). A significant influence was however found when using sulfuric or perchloric acid. A low concentration of these two acids ( c/ a < 1 X 10 ) yields product that decomposes above 145 °C just as in the case of pure TATP. Higher concentrations however yield TATP that decomposes during melting, or even before that, in the solid phase (Fig. 10.13, Table 10.3). It is presumed that the lower thermal stability is a result of a combination of two factors—overall residual acidity within the TATP crystals and acid strength [57]. 

In 1839 Kuhlmann described ammonia oxidation to produce nitrogen oxides for nitric acid production using a platinum sponge catalyst at 300 C. At the same time he was also granted a patent for the oxidation of sulfur dioxide and used the process in his factoiy at Loos. He was apparently unaware of the Phillips patent granted in the United Kingdom, but he attempted to make sulfuric acid with a platinum catalyst. 

The most widely used reactions are those of electrophilic substitution, and under controlled conditions a maximum of three substituting groups, e.g. -NO2 (in the 1,3,5 positions) can be introduced by a nitric acid/sul-phuric acid mixture. Hot cone, sulphuric acid gives sulphonalion whilst halogens and a Lewis acid catalyst allow, e.g., chlorination or brom-ination. Other methods are required for introducing fluorine and iodine atoms. Benzene undergoes the Friedel-Crafts reaction. ... 

In the presence of catalyst, usually platinum, ammonia is oxidised by oxygen (and air) to nitrogen oxide. NO. This reaction, used to obtain nitric acid from ammonia (p. 238), can be demonstrated in the laboratory using the apparatus shown in Figure 9.4 the oxygen rate should be slow. 

To solve some of the environmental problems of mixed-acid nitration, we were able to replaee sulfuric acid with solid superacid catalysts. This allowed us to develop a novel, clean, azeotropic nitration of aromatics with nitric acid over solid perfluorinated sulfonic acid catalysts (Nafion-H). The water formed is continuously azeotroped off by an excess of aromatics, thus preventing dilution of acid. Because the disposal of spent acids of nitration represents a serious environmental problem, the use of solid aeid eatalysts is a significant improvement. 

Another possible route to 2-unsubstituted thiazoles is replacement of a mercapto group by a hydrogen. Various methods have been used hydrogen peroxide in acid medium (17-19) dilute nitric acid (17), and metallic catalysts (20-22). 

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

Acid—Base Chemistry. Acetic acid dissociates in water, pK = 4.76 at 25°C. It is a mild acid which can be used for analysis of bases too weak to detect in water (26). It readily neutralizes the ordinary hydroxides of the alkaU metals and the alkaline earths to form the corresponding acetates. When the cmde material pyroligneous acid is neutralized with limestone or magnesia the commercial acetate of lime or acetate of magnesia is obtained (7). Acetic acid accepts protons only from the strongest acids such as nitric acid and sulfuric acid. Other acids exhibit very powerful, superacid properties in acetic acid solutions and are thus useful catalysts for esterifications of olefins and alcohols (27). Nitrations conducted in acetic acid solvent are effected because of the formation of the nitronium ion, NO Hexamethylenetetramine [100-97-0] may be nitrated in acetic acid solvent to yield the explosive cycl o trim ethyl en etrin itram in e [121 -82-4] also known as cyclonit or RDX. 

Cyclohexane. The LPO of cyclohexane [110-82-7] suppUes much of the raw materials needed for nylon-6 and nylon-6,6 production. Cyclohexanol (A) and cyclohexanone (K) maybe produced selectively by using alow conversion process with multiple stages (228—232). The reasons for low conversion and multiple stages (an approach to plug-flow operation) are apparent from Eigure 2. Several catalysts have been reported. The selectivity to A as well as the overall process efficiency can be improved by using boric acid (2,232,233). K/A mixtures are usually oxidized by nitric acid in a second step to adipic acid (233) (see Cyclohexanol and cyclohexanone). 

Nitrates. Iron(II) nitrate hexahydrate [14013-86-6], Fe(N03)2 6H20, is a green crystalline material prepared by dissolving iron in cold nitric acid that has a specific gravity of less than 1.034 g/cm. Use of denser, more concentrated acid leads to oxidation to iron(III). An alternative method of preparation is the reaction of iron(II) sulfate and barium or lead nitrate. The compound is very soluble in water. Crystallisation at temperatures below — 12°C affords an nonahydrate. Iron(II) nitrate is a useful reagent for the synthesis of other iron-containing compounds and is used as a catalyst for reduction reactions. 

---