Hydroxylamine ammonium sulfate

An additional mole of ammonium sulfate per mole of final lactam is generated duting the manufacture of hydroxylamine sulfate [10039-54-0] via the Raschig process, which converts ammonia, air, water, carbon dioxide, and sulfur dioxide to the hydroxylamine salt. Thus, a minimum of two moles of ammonium sulfate is produced per mole of lactam, but commercial processes can approach twice that amount. The DSM/Stamicarbon HPO process, which uses hydroxylamine phosphate [19098-16-9] ia a recycled phosphate buffer, can reduce the amount to less than two moles per mole of lactam. Ammonium sulfate is sold as a fertilizer. However, because H2SO4 is released and acidifies the soil as the salt decomposes, it is alow grade fertilizer, and contributes only marginally to the economics of the process (145,146) (see Caprolactam). 

Other Applications. Hydroxylamine-O-sulfonic acid [2950-43-8] h.2is many applications in the area of organic synthesis. The use of this material for organic transformations has been thoroughly reviewed (125,126). The preparation of the acid involves the reaction of hydroxjlamine [5470-11-1] with oleum in the presence of ammonium sulfate [7783-20-2] (127). The acid has found appHcation in the preparation of hydra2ines from amines, aUphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. It is also an important reagent in reductive deamination and specialty nitrile production. 

Concentrations are controlled to yield a molten oxime product layer and a saturated (ca 40 wt %) ammonium sulfate solution ca 125% (theoretical) ammonium sulfate or 2.9 kg/kg caprolactam is produced as a result of side reactions in the hydroxylamine synthesis. 

Hydroxylamine sulfate is produced by direct hydrogen reduction of nitric oxide over platinum catalyst in the presence of sulfuric acid. Only 0.9 kg ammonium sulfate is produced per kilogram of caprolactam, but at the expense of hydrogen consumption (11). A concentrated nitric oxide stream is obtained by catalytic oxidation of ammonia with oxygen. Steam is used as a diluent in order to avoid operating within the explosive limits for the system. The oxidation is followed by condensation of the steam. The net reaction is... 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

Besides Fe-, other reducing agents that may be used in conjunction with H2O2 are aliphatic amines, Na2S203 thiourea, ascorbic acid, glyoxal, sulfuric acid, NaHSOs, sodium nitrite, ferric nitrate, peroxidase, AgNOs, tartaric acid, hydroxylamine, ethylene sulfate, sodium phosphite, formic acid, ferrous ammonium sulphate, acetic acid, ferrous sulphate, and HNO2, etc,... 

Hydroxylamine (hyam) is used in the production of caprolactam, a key raw material for the manufacture of Nylon-6. Several technologies exist for the production of caprolactam with a key difference being the amount of byproduct ammonium sulfate, a low cost fertilizer, formed. The hyam used in the process is produced by... 

HPO [Hydroxylamine phosphate oxime] A process for making caprolactam, an intermediate in the manufacture of polyamides. It differs from related processes, such as HSO, in producing less of the ammonium sulfate by-product. Developed by DSM Research, The Netherlands, operated by DSM Polymers and Hydrocarbons, and offered for license by Stamicarbon. 

Hydroxylamine sulfate may be prepared by mixing stoichiometric amounts of hydroxylamine and sulfuric acid. It also may be prepared by electrolytical-ly reducing an aqueous solution of ammonium sulfate. 

The hydroxylamine hydrochloride used was the crude material prepared as described in Org. Syn. 3, 61. Preliminary experiments showed that this reagent must be present in considerable excess. Equally good results were obtained by using a solution of crude hydroxylamine sulfate which also contained sodium sulfate and ammonium sulfate with a little excess sulfuric acid. The hydroxylamine content was determined in this solution by titration with potassium permanganate solution. When this crude solution is used, the addition of sodium sulfate is not always necessary. 

Hydroxylamine sulfate is usually prepared in a modified Raschig method that starts with air oxidation of ammonia. The nitrogen oxides are reacted with ammonium carbonate to produce ammonium nitrite and carbon dioxide [see Eq. 21.3)]. The ammonium nitrite solution then reacts with sulfur dioxide to give hydroxylamine diammonium sulfate, which is hydrolyzed to hydroxylamine sulfate and by- product ammonium sulfate46,266. 

Of the processes based on modification of the conventional route, only Stamicarbon s hydroxylamine phosphate oxime (HPO) process completely avoid all production of ammonium sulfate before the Beckmann rearrangement. The steps in the HPO process are listed below and shown in Figure 21.146, 264 ... 

The Inventa-NO process is similar to the BASF process in that the first source of by-product ammonium sulfate is eliminated. Like the BASF process the Inventa process prepares hydroxylamine sulfate by the reduction of nitric oxide with hydrogen over a noble metal catalyst suspended in sulfuric acid. The differences between the BASF and Inventa processes are ... 

Current production of s-caprolactam is mainly based on the reaction of cyclohexanone with hydroxylamine and subsequent rearrangement of the intermediate oxime. Undesirable ammonium sulfate is co-produced well in excess of s-caprolactam, i.e., 0.9-2.9 kg in the oximation step and 1.5-1.8 kg in subsequent Beckmann rearrangement, for 1 kg of product. The salt, of little commercial value, is sold for use in fertilizers or can be incinerated for the recovery of sulfur (Figure 23). 

Alternatives to the use of hydroxylamine include the reaction of nit-rosylsulfuric acid with cyclohexanecarboxylic acid, obtained by the hydrogenation of benzoic acid, to produce s-caprolactam directly, and by the photochemical nitrosation of cyclohexane with NOCl, that yields cyclohexanone oxime hydrochloride. In both cases excess ammonium sulfate is also produced. 

The hydroxylamine content in this solution, which also contains ammonium sulfate, is ca. 70g/L. In an integrated caprolactam manufacturing plant using the Raschig process for hydroxylamine production, ca. 1.8 kg of ammonium sulfate is produced per kg of caprolactam. 

The quantity of ammonium sulfate byproduct is this process is ca. 0.8 kg per kg of caprolactam produced. The hydroxylamine content in the solution amounts to ca. 115 g/L. 

In the classical caprolactam process, in which hydroxylamine sulfate produced by the Raschig process and the oxime is rearranged in sulfuric acid, 4.4 t of ammonium sulfate are produced per t caprolactam. In recently developed processes the incidence of byproducts has been significantly reduced or even eliminated. 

The conventional process (Figure 2.32a) involves the reaction of cyclohexanone tvith hydroxylamine sulfate (or another salt), producing cyclohexanone oxime that is subjected to the Beckmann rearrangement in the presence of stoichiometric amounts of sulfuric acid or oleum. The overall process generates about 4.5 kg of ammonium sulfate per kg of caprolactam, divided roughly equally over the two steps. The Sumitomo process (Figure 2.32b) instead produces virtually no waste and allows caprolactam to be obtained in >98% yield (based on cyclohexanone 93% based on FI2O2). 

The three hydroxylamine preparation processes produce the following amount of ammonium sulfate ... 

Finally, hydrolysis of the hydroxylamine disuifonate at 9S°C yields hydroxylamane sulfate, with the co-production of ammonium sulfate at the rate of 805 kg/t of hydroxyl-amine sulfate ... 

The co-production of such a large amount of ammonium sulfate, which is often difficult to utilize economically, has led to research on new processes to synthesize hydroxylamine. 

The HPO (hydroxylamine phosphate oxime) process, developed byDSMand licensed by Siamicarbon, totally eliminates the production of ammonium sulfate, both in the production of hydroxylamine itself and in die oxime production stage. It consists of the catalytic hydrogenation of the nitrate ions resulting from the oxidation of ammonia to hydroxylamine ions in a solution buffered by phosphates. The nitrate reduction reaction is as follows ... 

This can be carried out in several (4) agitated reactors in series or in a column with several injection levels. In the former case, hydroxylamine sulfate reacts with an approximately equal-weight mixture of cyclohexanone and oxime in the primary reactor. The sulfuric acid is then neutralized by ammonia. The liquid oxime rises above the solution of ammonium sulfate and hydroxylamine sulfate. In the secondary reactor, this solution reacts with the fresh cyclohexanone feed. This is followed by a second neutralization by ammonia, in order to obtain the initial effluent (50 50) of cyclohexanone and oxime fed to the primary reactor. 

The oxime is obtained by the action of hydroxylamine hydrogen sulfate on cydododecanone. This operation takes place in a solvent that is immisdble with water or with concentrated sulfuric add, which are used in the next step. The most widely used solvent is isopropylcydohexane (or hydrocumene) which dissolves the oxime at the reaction temperature of 100 G Conversion is practically quantitative. It takes place in a series of reactors equipped with effective agitators, into which aqueous solutions of hydroxyl-amine sulfate are introduced, together with ammonia to keep the pH about 7. The effluent is cooled aad settled. The aqueous layer containing ammonium Sulfate is removed. The organic phase is washed with concentrated sulfuric add. The oxime sulfate solution... 

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