Ammonia reactions atmosphere

Uses Manufacture of ammonia, inert atmosphere for chemical reactions, metal treating, enhanced oil recovery, food processing (freezing), electronics. 

Tri-tert-butoxidesilanethiolate forms complexes with both Co11 and Co111. Reaction of the thiol with a Co11 ammine in water yields a dimer which undergoes oxidation in an ammonia-saturated atmosphere to form octahedral [Co(SSi(0-t-Bu)3)2(NH3)4]+, the first silanethiolate characterized structurally.1044... 

Hydrogen or ammonia in the reaction atmosphere increase the a content, the fineness of microstructure, and the strength, they reduce the dependence of the nitridation process on variations in green density and powder properties... 

Ostwald process. This, the most widely used method for the production of nitric acid, depends on the oxidation of ammonia by atmospheric oxygen in the presence of a catalyst consisting of gauze made of platinum or platinum and rhodium. The reaction... 

The rate o oxidation o ammonia at atmospheric pressure on single wires and ribbons has been determined as a function of a gas flow rate and catalyst size. In agreement with boundary layer diffusion theory the function rx, where r is the average rate of reaction/unit area, and x is the length of the surface measured in the direction of gas flow, is directly proportional to gas velocity. 

Atmospheric pressure CVD of NbCi-yN, using NbCl, NH3, and CH4 has been employed in three separate approaches toward the optimization of reaction characteristics [69]. These were (i) simultaneous deposition of niobium, carbon, and nitrogen by hydrogen reduction of NbCls with decomposition of methane and ammonia at a temperature of 900-1000°C (ii) deposition of a niobium amide complex derived from NbCl.s/NHi in nitrogen as a carrier gas at 250-350 °C, and subsequent conversion in ammonia/methane at 1 000-1 100 °C (iii) separate deposition of elemental niobium or NbCl.3 by hydrogen reduction at 500-1000°C and subsequent conversion to NbCi yNy in an ammonia/methane atmosphere at 1000-1 100°C. The results of these three approaches are given below. 

In order to verify this hypothesis and to verify the predicted influence of water on the equilibrium concentration of the imine and, therefore, on the rate of formation of oxime, a new set of catalytic experiments was carried out vaaring the concentration at low ammonia concentration and in the presence of water added to the reaction atmosphere. Figure 5 shows the influence of the concentration of molecular oxygen on the reaction rates at low ammonia content (2.5 mol%). In these conditions no dependence of the product formation rates on P02 is observed. On the other hand, some catalytic tests carried out adding different amounts of water to the reaction atmosphere showed a negative effect on the conversion and on the imine concentration in the outlet gas phase. 

Acids are converted to nitriles by reaction with ammonia at atmospheric pressure at 280-360 C in the presence of catalysts such as bauxite, zinc oxide, or manganese or cobalt salts. Hydrogenation of the nitrile proceeds via the aldimine (RCH=NH) at 120-180 °C and 20-100 bar in the presence of nickel or cobalt catalysts. 

One of the earliest studies about the smface compositions of ammonia sjmthesis catalysts is the classical works conducted by means of chemisorption method by Emmett et al. The results are as follows Under the reaction atmosphere, molecular state carbon dioxide is chemisorbed particularly on those potassimn atoms or ions on surfaces, while the atomic state hydrogen and nitrogen, molecular state CO and ionic state oxygen can be used to probe the iron atoms on sm-faces. According to the interactions between the chemisorption of CO and CO2, it can be inferred that the promoters emich on catalyst surfaces and disperse effectively, so as to make the most of iron atoms being closer to promoter atoms. It was found... 

Handling, Storage, and Precautions a light sensitive, hygroscopic solid. It should be stored in a dark container under an inert atmosphere. It is extremely destructive to tissues of the mucous membranes and upper respiratory tract, eyes, and skin. It emits toxic fumes under fire conditions. It also forms explosive adducts with ammonia reactions involving liquid or gaseous ammonia should be carried out with extreme caution. Use in a fume hood. 

The nitrogenase system reduces hundreds of millions of kilograms of nitrogen gas to ammonia each year, catalysing tire reaction at ambient temperatures and atmospheric pressure. Nitrogenase consists of two proteins tliat contain... 

The reaction of adipic acid with ammonia in either Hquid or vapor phase produces adipamide as an intermediate which is subsequentiy dehydrated to adiponitrile. The most widely used catalysts are based on phosphoms-containing compounds, but boron compounds and siHca gel also have been patented for this use (52—56). Vapor-phase processes involve the use of fixed catalyst beds whereas, in Hquid—gas processes, the catalyst is added to the feed. The reaction temperature of the Hquid-phase processes is ca 300°C and most vapor-phase processes mn at 350—400°C. Both operate at atmospheric pressure. Yields of adipic acid to adiponitrile are as high as 95% (57). 

Chemica.1 Properties. With few exceptions, SF is chemically inert at ambient temperature and atmospheric pressure. Thermodynamically SF is unstable and should react with many materials, including water, but these reactions are kineticaHy impeded by the fluorine shielding the sulfur. Sulfur hexafluoride does not react with alkah hydroxides, ammonia, or strong acids. 

Formamide decomposes thermally either to ammonia and carbon monoxide or to hydrocyanic acid and water. Temperatures around 100°C are critical for formamide, in order to maintain the quaUty requited. The lowest temperature range at which appreciable decomposition occurs is 180—190°C. Boiling formamide decomposes at atmospheric pressure at a rate of about 0.5%/min. In the absence of catalysts the reaction forming NH and CO predominates, whereas hydrocyanic acid formation is favored in the presence of suitable catalysts, eg, aluminum oxides, with yields in excess of 90% at temperatures between 400 and 600°C. 

Peroxide-Ketazine Process. Elf Atochem in France operates a process patented by Produits Chimiques Ugine Kuhhnaim (PCUK). Hydrogen peroxide (qv), rather than chlorine or hypochlorite, is used to oxidize ammonia. The reaction is carried out in the presence of methyl ethyl ketone (MEK) at atmospheric pressure and 50°C. The ratio of H202 MEK NH2 used is 1 2 4. Hydrogen peroxide is activated by acetamide and disodium hydrogen phosphate (117). Eigure 6 is a simplified flow sheet of this process. The overall reaction results in the formation of methyl ethyl ketazine [5921-54-0] (39) and water ... 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Iron(III) bromide [10031-26-2], FeBr, is obtained by reaction of iron or inon(II) bromide with bromine at 170—200°C. The material is purified by sublimation ia a bromine atmosphere. The stmcture of inoa(III) bromide is analogous to that of inon(III) chloride. FeBr is less stable thermally than FeCl, as would be expected from the observation that Br is a stronger reductant than CF. Dissociation to inon(II) bromide and bromine is complete at ca 200°C. The hygroscopic, dark red, rhombic crystals of inon(III) bromide are readily soluble ia water, alcohol, ether, and acetic acid and are slightly soluble ia Hquid ammonia. Several hydrated species and a large number of adducts are known. Solutions of inon(III) bromide decompose to inon(II) bromide and bromine on boiling. Iron(III) bromide is used as a catalyst for the bromination of aromatic compounds. 

Ma.nufa.cture. Nickel carbonyl can be prepared by the direct combination of carbon monoxide and metallic nickel (77). The presence of sulfur, the surface area, and the surface activity of the nickel affect the formation of nickel carbonyl (78). The thermodynamics of formation and reaction are documented (79). Two commercial processes are used for large-scale production (80). An atmospheric method, whereby carbon monoxide is passed over nickel sulfide and freshly reduced nickel metal, is used in the United Kingdom to produce pure nickel carbonyl (81). The second method, used in Canada, involves high pressure CO in the formation of iron and nickel carbonyls the two are separated by distillation (81). Very high pressure CO is required for the formation of cobalt carbonyl and a method has been described where the mixed carbonyls are scmbbed with ammonia or an amine and the cobalt is extracted as the ammine carbonyl (82). A discontinued commercial process in the United States involved the reaction of carbon monoxide with nickel sulfate solution. 

Ammonium Phosphates. In the manufacture of ammonium phosphates, an atmosphere of ammonia may need to be maintained because the partial pressure of ammonia rises rapidly as either the temperature or the NH2/P20 mole ratio of the reaction mass increases. Phosphoric acid reacts quickly with ammonia vapor and is used in multistage reactor systems as a scmbber fluid to prevent NH emissions and recover ammonia values. For example, H PO scmbbing of coke-oven off-gases produces ammonium phosphates of relatively good purity. 

Temperatures in excess of 140°C are required to complete the reaction and pressurized equipment is used for alcohols boiling below this temperature provision must be made for venting ammonia without loss of alcohol. The reaction is straightforward and, ia the case of the monomethyl ether of ethylene glycol [109-86-4] can be carried out at atmospheric pressure usiag stoichiometric quantities of urea and alcohol (45). Methylolation with aqueous formaldehyde is carried out at 70—90°C under alkaline conditions. The excess formaldehyde needed for complete dimethylolation remains ia the resia and prevents more extensive usage because of formaldehyde odor problems ia the mill. 

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