Sulfuric acid nitrous process

A key feature of the chamber process is that nitrous acid in the vapor state is the oxidant used to convert sulfurous acid to sulfuric acid (Eq. 9.32). Unlike platinum, or V2O5 catalysts of the... 

The oxidation of ammonia to nitrous gases is a fast high-temperature reaction for the production of nitric acid (Ostwald process). The Claus process is an important petrochemical process for obtaining sulfur from H2S, which results from the desulfurization of petroleum and natural gas (hydrodesulfurization). One-third of the H2S is combusted to SO2, which reacts with the remaining H2S (see Table 8-1). 

Nitrogen compounds must be absorbed in several chemical and related processes, the most important of which is the absorption of nitrogen peroxide in water for the manufacture of nitric acid. Absorption of nitrous gases also takes place in the lead-chamber process used for the production of sulfuric acid, in the metallurgical industries where metals are treated with nitric acid, and in the purification of several tail gases. 

It is especially important to control the acidity when aromatic diamines are treated with nitrous acid to form either the mono- or bis-diazonium salts, a process of some importance in the synthesis of disazo dyes and pigments (see later). jj-Phenylenediamine is an example of a diamine in which either one or both of the amino groups may be diazotised by careful selection of reaction conditions. The use of dilute hydrochloric acid can result in smooth formation of the monodiazonium salt. The use of nitrosyl sulfuric acid is required to diazotise the second amino group, since the strong electron-withdrawing effect of the diazo group in the monodiazonium salt reduces the basicity of the amino group which remains. 

Mist formation may also occur in gas/liquid reactions reactants may evaporate, react in the gas phase and form a liquid mist that will not coalesce with the other liquid phase. The temperature of the mist may rise, and uncontrolled reactions may take place in the mist particles. Examples of these are found in the processes for the manufacture of nitric and sulfuric acids, and in the preparation of ammonium nitrite from ammonium carbonate solution and nitrous oxides. In the nitric acid production, the product in the mist may be recovered by an effective separation of the mist particles (with demisters, wet scrubbers or electrostatic filters). But in the ammonium nitrite process, the product formed in the mist phase may subsequently decompose into nitrogen and water, thus reducing the process yield. 

Usually, the cyclohexanone intermediate is made from the oxidation of cyclohexane. However, cyclohexanone is also made from phenol (Honeywell) or toluene (BASF, DSM). With the new processes, ammonia is oxidized to nitrous oxide (NjO), which is hydrogenated in the presence of sulfuric acid into hydroxylamine sulfate, which in turn is reacted with cyclohexanone to form cyclohexanone oxime. This chemical product is subjected to a Beckmann rearrangement with oleum to produce caprolactam. 

In the SCR process, NOX impurities are reduced with added ammonia in the presence of some residual oxygen from the furnace. The main NOX reduction reactions are shown in Table 11.5 together with some of the undesirable oxidation reactions, which can both produce sulfur trioxide and waste some of the added ammonia. Between 0.6-0.9 moles of ammonia per mole of NOX are added to limit the aimnonia shp to downstream equipment where it would deposit as sulfates. NOX conversion is therefore hmited to between 60-90%. At low NOX levels, there is little conversion to itrous oxide. Nitrous oxide formation is also inhibited by water. Gas leaving the boiler is usually at a temperature in the range 300-430°C and contains dust Dust is removed in an elee-trostatic precipitator with little heat loss before sulfur dioxide is removed as gypsum by reaction with lime. Alternatively, sulfur dioxide can also be eonvert-ed to sulfuric acid. The effluent is then vented to atmosphere. In the first power plants to be retrofitted with SCR units there were three possible loeations for the catalyst bed ... 

This question is discussed in detail in the book by Skarchenko [52], It is noted that dehydrogenation of paraffin hydrocarbons dominates by selectivity over thermal cracking in the presence of iodine or other halogens, sulfur-containing compounds, oxygen and nitrous oxide. For example, in the presence of iodine dehydration dominates in the system, whereas in the case of other additives, independently of their amounts—oxygen, ethylene oxide and nitric acid—the main shift of the process toward cracking is preserved. 

The first 1,2,3-thiadiazole synthesized, 1,2,3-benzothiadiazole, was prepared by diazotiz-ation of o-aminothiophenol with nitrous acid (equation 31) (B-61MI42400), and recently sodium nitrite-acetic acid has been substituted for nitrous acid (B-79MI42400),. Another modification, thermal decomposition of diazonium acetate (34), affords benzothiadiazole in good yield in contrast to the variable yields usually experienced in the diazotization of o-aminothiophenols (equation 32) (78SST(5)43l). Benzothiadiazoles are also available directly from aromatic amines (equation 33) (70JCS(C)2250). Sulfur monochloride reacts with the amine to form a benzothiazothiolium salt which reacts with nitrous acid to yield a chlorinated 1,2,3-benzothiadiazole (35). This process, depending on the aromatic ring substitution, may afford a number of products, and yields are variable. 

The nitrous oxides (NOx) and sulfurous oxides (SOx) result from the combustion of any petroleum, coal, and natural gas fuels. Various industrial processes and almost a majority of the households employ natural gas for energy and heating purposes. Natural gas-fueled vehicles also are NOx and SOx producers. These compounds are the main contributors to the greenhouse effect and acid rain. Hence, it is imperative that methods have to be developed to save the environment and future generations from this problem. There are... 

Hofmann s classical synthesis of 3,5-disubstituted 1,2,4-thiadiazoles by the oxidation of thioamides (1869)3 continues to be further exemplified. The oxidants employed include iodine,9-11 bromine,12 chlorine,13 and nitrous acid,14 as well as /V-chlorobenzamidine (which is recovered as benzamidine)15 and IV-sulfinyl-p-toluenesulfonamide (which evolves sulfur dioxide in the process).16 Irradiation with UV light in the presence of oxygen effects the same reaction, but has not been used on a preparative scale.17... 

A number of methods are available for the synthesis of saccharin. For many years, the most popular process was one developed by the Maumee Chemical Company of Toledo, Ohio, in 1950. This method begins with anthranilic acid (oaminobenzoic acid C6H4(NH2)C00H), which is treated successively with nitrous acid (HN02), sulfur dioxide (S02), chlorine (Cl2), and ammonia (NH3) to obtain saccharin. Another process discovered in 1968 starts with o-toluene, which is then treated with sulfur dioxide and ammonia to obtain saccharin. 

---