Nitrosyl sulfuric add

Unconverted nitrosyl sulfuric add is recycled. The gaseous mixture of NOG and HD is introduced into liquid cydohexane. 

If the nitrosyl-sulfuric acid content is high (more than 1%) as determined by permanganate (see further) add another 1 ml of water and evaporate again... 

With the screw clamp open, the pyrites is gently heated with a wing burner in a slow stream of air drawn in by the aspirator. The clamp is then partially closed so that air also passes through the capillary into the nitric add. The pyrites may now be heated more strongly the current of air through the nitric add is adjusted by means of the clamp so that red fumes of nitrogen oxides are always present in the bottle or chamber, If not enough vapor of nitric acid is provided, colorless crystals of nitrosyl sulfuric acid ( chamber crystals ) will form on the walls of the bottle. 

The action of sulfuric add at atmospheric pressure yields a solution of nitrosyl sulfuric acid in sulfuric add. 

The hydrogen chloride gas evolved is absorbed in dilute hydrochloric add, and then sent to the production of nitrosyl chloride. The solution of lactam in sulfuric add is neutralized by ammonia. Two phases are formed the upper layer is the crude caprolactam which is purified1l5 and the bottom layer is an aqueous solution of ammonium sulfate. The molar yield of caprolactam is 81 per cent of theory in relation to cydohexane. Co-production of ammonium sulfate is 1.7 kg/kg of product... 

Caprolactam is obtained at atmospheric pressure, in the presence of a solvent (cyclohexane) in a multistage reactor. Hexahydrobenzoic add and oleum, previously mixed at 35 C, are introduced into the reactor. Nitrosyl sulfuric acid (prepared by the absorption of NO—NO in oleum) is injected at each stage in predetermined quantities. Once-through conversion of hexahydrobenzoic add is limited to 50 per cent The temperature is kept at 80 C by the evaporation of cyclohexane. The reactor effluent is then diluted with water at low temperature. The cyclohexane evaporated is recondensed and used to extract unconverted hexahydrobenzoic add and allow its recycle, while the caprolactam formed goes into the aqueous solution. This phase is neutralized by ammonia. Ammonium sulfate, formed at the rate of 4.2 t/t of product, is recovered by centrifuging. The lactam is extracted with the toluene, reextracted with water and dehydrated. The final yield of the operation is 72 per cent weight in relation to toluene. 

AMINO-2,4-DIMETHYLBENZENE (95-68-1) Combustible liquid (flash point 205°F/ 96°C). Violent reaction with strong oxidizers, strong acids, nitrosyl perchlorate. Mixtures with hypochlorites form sensitive explosive chloroamines. Incompatible with aldehydes, nonoxidizing mineral acids, cellulose nitrate (of high surface area), cresols, isocyanates, nitrates, nitric acid, organic anhydrides, phenols, sulfuric add. 

The main field of application for benzoic acid is the production of phenol however, the significance of this phenol route has declined in recent years. Additionally, benzoic acid is used in the production of benzoyl chloride and sodium benzoate. In Italy, benzoic acid is used as the raw material for the production of 8-caprolactam, in a process developed by Snia Viscosa, This involves hydrogenating benzoic add at 170 °C and 15 bar over a palladium catalyst, purifying the cyclohexane carboxylic acid by distillation followed by its reaction with nitrosyl-sulfuric acid to yield 8-caprolactam. 

The benzoic acid is now hydrogenated to cyclohexane eaiboxylie acid with a palladium/carbon catalyst at 170°C and 10-19 bar, whereas originally a nickel catalyst was used. Reaction with nitrosyl sulfuric acid in olenm solntion at 80°C then gives e-caprolactam. In the original Snia-Viscosa process, abont 25% more ammonium sulfate was formed than in the conventional proeess. However, solvent extraction of the eaprolactam from the add solntion nsing alkyl phenols does avoid the prodnetion of the ammonium salt. 

Hydrochloric add displaces sulfuric acid at 75°C to produce nitrosyl chloride HNOSO + HCI - NOD + H2SO ... 

---