Production of Ammonium Sulfate

Of the total US ammonium sulfate capacity, 75% is a by-product of caprolactam production. The balance comes primarily from the sources shown in Table 12.3. Direct synthesis accounts for less than 15% of US capacity. AS demand will probably fluctuate in the range of 2.2 to 2.6 million tons per year for the foreseeable future. And it has been in this same range since 1970. Any real demand growth may be more a factor of increased supply as a by-product of the caprolactam marker243. 

AS prices vary by geographic region and depend on grade. The price is also affected by ammonia prices. In 2000 the list price was 105 per ton FOB, and between 1995 and 1998 the average price varied from US 63 to US 84 per 

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NH1CONH2 + H2O. The processing is complicated because of the severe corrosiveness of the reactants, usually requiring reaction vessels that are lined with lead, titanium, zirconium, silver, or stainless steel. The second step of the process requires a temperature of about 200 C to effect the dehydration of the ammonium carbamate. The processing pressure ranges from 160 to 250 atmospheres. Only about one-half of the ammonium carbamate is dehydrated in the first pass. Thus, the excess carbamate, after separation from the urea, must be recycled to the urea reactor or used for other products, such as the production of ammonium sulfate. 

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 ... 

By a basic quench the removal of catalyst fines and ammonia take place separately. Due to the neutral pH in the first stage the loss in acrylonitrile is higher than previously. On the contrary, the production of ammonium sulfate is increased. 

The worldwide production of ammonium sulfate in 1995 is given in Table 2.2-4. 

In the USA in 1993, 14% of the total production of ammonium sulfate was manufactured from ammonia and sulfuric acid. 

The Bureau of Mines is a source of many chemical statistics. The monthly Coke and Coal Chemicals report, part of the bureau s Mineral Industry Surveys, contains, in addition to data on oven and beehive coke production, figures on production of ammonium sulfate, ammonia liquor, naphthalene, benzene, toluene, xylene, solvent naphtha, pyridine, crude coal tar, and cresote oil. Sales and end-of-month stock figures are also shown in the report. A useful feature of the report is the year-end supplement which gives year s totals by months. 

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 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 ... 

The arrangement of the oxime to caprolactam is earned out by oleum, which is then neutralized by ammonia with the production of ammonium sulfate, by the following reaction ... 

In conventional processes, hvdroxylamine preparation, oximation and the Beckmann rearrangement produce a total of up to 4.41 of ammonium sulfate per ton of caprolactam. The molar yield of lactam is around 70 per cent of theory in relation to cyclohexane, and 91 per cent in relation to phenol. With the BASF technology, only 2.61 of ammonium sulfate is produced per ton of caprolactam, and the molar yield in relation to cyclohexane is 70 per cent of theory. The use of the HPO process reduces the production of ammonium sulfate to 1.8 t per ton of caprolactam, and the molar yield is 61 per cent in relation to cyclohexane, and 93 per cent in relation to phenoL... 

Stamicarbon attempted to eliminate the co-production of ammonium sulfate completely in a variant of the HPO process, in which, during the effluent neutralization and the Beckmann rearrangement, ammonium bisulfate is formed instead of the neutral sulfate (bisulfate process). The sulfate is then pyrolysed to yield S02, nitrogen and water. The... 

Allied Chemical recently proposed a simplified technique, producing caprolactam from cyclohexanone, ammonia and oxygen in a single step, in the vapor phase, on a sffica or alumina-based catalyst However, the drawback of this process resides in the fact that only half of the oxime is converted in situ to caprolactam. This makes it necessary to resort to the Beckmann rearrangement For a 50 per cent conversion of cyclohexanone, the molar selectivity of oxime and caprolactam is 68 per cent Although this method considerably reduces the production of ammonium sulfate, the yields are still too low for it to appear to be more economical than the foregoing routes. 

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... 

All processes proceeding via the oxime produce large amounts of ammonium sulfate during the Beckmann rearrangement. The ammonium sulfate is used as a fertilizer but is only profitable if the transport costs are low. Consequently, the size of caprolactam facilities in many cases is limited by the market potential of the ammonium sulfate. For this reason, ways of producing caprolactam without production of ammonium sulfate are being sought. 

On September 9,1913 the first ammonia synthesis plant was opened at Oppau, Germany, near Ludwigshafen, with a production of 10,000 kg of NH3 per day. The plant was designed for the production of ammonium sulfate, a fertilizer. 

Razon, L. F. Life cycle energy and greenhouse gas profile of a process for the production of ammonium sulfate from nitrogen-fixing photosynthetic cyanobacteria. Bioresour. Technol. 2012, 107, 339-346. 

At the beginning of the twentieth century the global output of nearly 500,000 t of ammonium sulfate contained about 120,000 t N, compared to about 200,000 t N in that year s export of Chilean nitrates. By 1910 German production of ammonium sulfate surpassed the British total, and in 1913 it accounted for nearly % of the global output, which was equivalent to about 270,000 t N. But the shipments of Chilean nitrates were still larger, providing almost 410,000 t of fixed N (appendix F). ... 

Work on the site proceeded without major problems, and the plant produced its first ammonia on September 9,1913, after less than fifteen months of construction/ By October 24 the plant was synthesizing more than 101 of NH3 a day. Fahrenhorst became Oppau s first director, Philipp Borchardt was responsible for Linde liquefaction of air producing nitrogen, Wilhelm Wild ran the purification of the feedstock gas, and Hans Keller supervised the coal gasification and production of ammonium sulfate. 

Extraction of Guano and Chilean Nitrate, and Production of Ammonium Sulfate, Cyana-mide, and Calcium Nitrate, 1850-2000 Exports of Chilean Nitrate, 1835-1932... 

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