Ammonia direct synthesis

Haber process The process for the direct synthesis of ammonia from and Hj over a catalyst. 

Even though form amide was synthesized as early as 1863 by W. A. Hoffmann from ethyl formate [109-94-4] and ammonia, it only became accessible on a large scale, and thus iadustrially important, after development of high pressure production technology. In the 1990s, form amide is mainly manufactured either by direct synthesis from carbon monoxide and ammonia, or more importandy ia a two-stage process by reaction of methyl formate (from carbon monoxide and methanol) with ammonia. 

However, BASF developed a two-step process (25). After methyl formate [107-31-3] became available in satisfactory yields at high pressure and low temperatures, its conversion to formamide by reaction with ammonia gave a product of improved quaUty and yield in comparison with the earlier direct synthesis. 

The estimated capacity of formamide was approximately 100,000 t/yr worldwide in 1990. In 1993, there are only three significant producers BASE in Germany is the leading manufacturer. Smaller quantities of formamide are produced in the former Czechoslovakia (Sokolov) and Japan (Nitto) by direct synthesis from carbon monoxide and ammonia. Most of the formamide produced is utilized direcdy by the manufacturers. The market price for formamide (ca 1993) is about 2.00/kg. 

Direct synthesis from nitrogen and finely divided titanium metal can be achieved at temperatures of >ca 1200° C (4). Typically, titanium sponge or powder is heated in an ammonia- or nitrogen-filled furnace and the product is subsequently milled and classified. 

An even more effective homogeneous hydrogenation catalyst is the complex [RhClfPPhsfs] which permits rapid reduction of alkenes, alkynes and other unsaturated compounds in benzene solution at 25°C and 1 atm pressure (p. 1134). The Haber process, which uses iron metal catalysts for the direct synthesis of ammonia from nitrogen and hydrogen at high temperatures and pressures, is a further example (p. 421). 

Figure 4. shows the route from the high boiling residue of the direct synthesis to silicon carbo-nitride fibers. Methylchlorodisilanes and trichlorosilanes as additives are mixed in a specific ratio and react with methylamine and a small amount of ammonia to form an aminodisilane/oligosilazane. The subsequent polycondensation reaction of this mixture by heating to 250 °C yields a soluble and melt spinnable polysilazane. In comparision with the polysilane the properties of the polysilazane depend on the ratios of the disilanes/silanes and methylamine/ammonia and also on the reaction conditions. 

Haher experimented with the direct synthesis of ammonia. 

A diverse group of secondary and tertiary amines are readily synthesized from the reaction of primary and secondary amines with allylic carbonates in the presence of preformed iridium metalacycles, but the direct synthesis of primary amines via iridium-catalyzed allylic amination requires the use of ammonia as a nucleophile. The asymmetric allylation of ammonia had not been reported until very recently, and it is not a common reagent in other metal-catalyzed reactions. Nonetheless, Hartwig and coworkers developed the reactions of ammonia with allylic carbonates in the presence of la generated in situ [89]. Reactions conducted in the initial work led exclusively to the products from diallylation (Scheme 16). Further advances in... 

A flow diagram of (he direct synthesis of ammonia as practiced at the TVA(Tennessee Valley Authority), is given on pp A298-9 Following is the list of "direct synthesis" processes practiced currently in various countries a)Haber-Bosch(Refs 19,32,38,39, 42,48 80) b)Casale(Refs 19,38,39 80)... 

This route gives a much better yield and a purer compound than when K2[PtCl4] is treated with ammonia directly. A disadvantage, however, is the necessity to use silver salts (usually nitrate) with overnight stirring, resulting in the possibility of side products formed by hydrolysis of the intermediate aqua species cis-[Pt(NH3)2(H20)2]2+.12 We here present a rapid and facile one-step synthesis of cisplatin. The experimental conditions are based on Lebedinsky s method,8 slightly modified as specified. 

In Ihe 1990s. formamide is mainly manufactured cither by direct synthesis from carbon monoxide and ammonia, or more importantly in a two-stage process by reaction of methyl formate (front carbon monoxide and methanol) with ammonia. 

The direct synthesis of ethyleneurea from ethylene glycol, ammonia, and carbon dioxide under pressure was investigated until it became evident that rather high pressures probably would be required. Best results (58% yield) were obtained from a charge consisting of 1 mole of glycol, 8 moles of... 

Ammonium sulfate (AS) is produced from many sources. The first commercial synthesis started around the time of World War I. Since then direct synthesis from ammonia and sulfuric acid has become a major production route. Ammonium sulfate is generated from several chemical processes. The nitrogen or sulfur values are recovered either to avoid pollution problems or to obtain a commercial return for these elements241. The basic chemical reaction is ... 

The second reaction used to illustrate various features of adsorptive reactors is the direct synthesis of hydrogen cyanide from ammonia and carbon monoxide ... 

Isothiazolo[5,4-6]pyridine-l, 1-dioxides (513) have been prepared by a direct synthesis (Equation 46) (90M281). 3-Carboethoxy-4,6-diphenylpyridine-2-sulfonamide (512) cyclizes in butanol at reflux temperature to give 3-oxo-2,3-dihydro-4,6-diphenylisothiazolo[5,4-6]pyridine-l,1-dioxide (513) (50%). Similarly, the reaction of 3-cyano- and 3-acetyl-4,6-diphenyl-2-pyridinesulfonyl chlorides (514) with ammonia afforded the corresponding 3-amino- and 3-methylisothiazolo[5,4-6]pyridine-1,1-dioxides (515) (Equation 47). 

Pure tin was also used for the direct synthesis of organotin compounds. In 1948, unlike previous investigations, Harada obtained sodium stannite Na2Sn not by the metal fusion, but by the reaction of tin with sodium in liquid ammonia . The reaction of Na2Sn with EtBr led to (Et2Sn) . 

The low solubility of the salts and the by-products helps to gain product of sufficient purity (>95%) after evaporation of the solvent. The procedure generates stoicho-metric amounts of by-product which prohibits the scale-up of the procedure. Given the cost of boranes according to [58], the development and use of an optimized direct synthesis from ammonia and diborane seems to be mandatory. 

---