Sulfur nitric acid activation

Catalytic gas-phase reactions play an important role in many bulk chemical processes, such as in the production of methanol, ammonia, sulfuric acid, and nitric acid. In most processes, the effective area of the catalyst is critically important. Since these reactions take place at surfaces through processes of adsorption and desorption, any alteration of surface area naturally causes a change in the rate of reaction. Industrial catalysts are usually supported on porous materials, since this results in a much larger active area per unit of reactor volume. 

Acetylene can be deterrnined volumetricaHy by absorption in Aiming sulfuric acid (or more conveniently in sulfuric acid activated with silver sulfate) or by reaction with silver nitrate in solution and titration of the nitric acid formed ... 

Qualitative Analysis. Nitric acid may be detected by the classical brown-ring test, the copper-turnings test, the reduction of nitrate to ammonia by active metal or alloy, or the nitrogen precipitation test. Nitrous acid or nitrites interfere with most of these tests, but such interference may be eliminated by acidifying with sulfuric acid, adding ammonium sulfate crystals, and evaporating to alow volume. 

Nitric acid in any concentration attacks lead steadily, but mixtures of nitric and sulfuric—nitration acids—are not as active and can be handled in lead. 

Trinitro-N-methylaniline (N-methyl picra-mide), yellow needles from EtOH contg acid, mp /l4.8° (Refs 4 7) the UV spectrum has a peak at 340 and a shoulder at 410—20m (Ref 19) CA Registry No 1022-07-7. It is prepd by the hydrolysis of the N nitroso compd (see below) at 70—80° (Ref 5) by the action of coned sulfuric acid (Ref 8) or UV light (Ref 12) on Tetryl by the action of methyl amine on Ethyl Picrate (Ref 18) or Tetryl (Ref 7) or by the action of nitric acid (d 1.42g/cc) at 0° on N,N-dimethylaniline (Ref 10). It is present in crude Tetryl and is the active der-matitic agent in the latter (Ref 12). It can be isolated from crude Tetryl and identified by thin layer chromatography (Ref 21)... 

The production of nitrogen fertilizers is a major activity of the chemical industry. Every year, the top 15 chemicals in industrial production in the United States include several nitrogen-containing compounds whose major use is in fertilizers. Molecular nitrogen serves as the primary source of nitrogen for chemical production. Gaseous ammonia (NH3), which is synthesized from N2 and H2, can be injected directly into the ground, where it dissolves in moisture in the soil and serves as a fertilizer. Ammonia is more widely used in reactions with acids to produce other fertilizers Ammonia and nitric acid produce ammonium nitrate (NIL) NO3), while ammonia and sulfuric acid produce ammonium sulfate. These chemicals and urea,... 

Concentrated nitric acid can effect nitration but it is not as reactive as a mixture of nitric acid with sulfuric acid. The active nitrating species in both media is the nitronium ion, NOz+, which is formed by protonation and dissociation of nitric acid. The concentration of NOz+ is higher in the more strongly acidic sulfuric acid than in nitric acid. 

These compounds contain the fragment R as an alkyl or aryl moiety. In other words, they result from the esterification of an alcohol or a phenol with nitrous acid, nitric acid, phosphoric acid, sulfuric acid, or sulfamic acid, respectively. Many of the esters to be examined in this chapter must be activated prior to eliciting their effects, e.g., the organic nitrites and nitrates, which act as donors of nitric oxide or an analogous molecule, and phosphates, which are activated by hydrolysis or even by phosphorylation (antiviral agents). Sulfates are very seldom active or used as prodrugs, but they have significance as metabolites and as industrial xenobiotics. 

Nitric acid is used for nitration of many organic compounds. Many nitro derivatives are made by such reactions. Pure nitric acid or often its combination with concentrated sulfuric acid is employed in these syntheses. When pure nitric acid is dissolved in concentrated sulfuric acid, it forms nitronium ion, N02, the active species in nitration reactions ... 

Rhenium can be analyzed by various instrumental techniques that include flame-AA, ICP-AES, ICP-MS, as well as x-ray and neutron activation methods. For flame-AA analysis the metal, its oxide, or other insoluble salts are dissolved in nitric acid or nitric-sulfuric acids, diluted, and aspirated directly into nitrous oxide-acetylene flame. Alternatively, rhenium is chelated with 8-hydroxy quinoline, extracted with methylisobutyl ketone and measured by flame-AA using nitrous oxide-acetylene flame. 

The positively charged nitronium ion is isoelectronic with carbon dioxide and is a linear molecule. It is a strong oxidant with a reduction potential of + 1.6 V at pH 7.0, favoring electrophilic attack. Nitronium ion is the active agent in fuming nitric acid (a caustic mixture of sulfuric and nitric acids), where the nitric acid is effectively dehydrated to give nitronium ion. 

In the original German process acetylene is injected into an aqueous solution of mercuric sulfate acidified with sulfuric acid at 90-95°C and about 1-2 atm. As a result of side reactions, the catalytically active mercury(II) ions are reduced to mercury. To prevent this process ferric sulfate is continuously added to the reactor. Since ferric ions are reduced to ferrous ions, the catalyst solution requires reactivation, which is accomplished by hot nitric acid and air. Excess acetylene and acetaldehyde formed are removed, cooled, absorbed in water, and then separated by distillation. Excess acetylene is recycled. Conversion per pass is bout 55%. The Montecatini process89 operates at 85°C and provides 95% overall yield. A modification developed by Chisso90 allows lower operating temperature (70°C) without excess acetylene. Since side reactions are less important under these conditions, higher yields may be achieved. 

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