Ammonia Converters

Step 4 Proton transfer from ammonia converts the alkenyl anion to an alkene ... 

We saw m Section 9 10 that the combination of a Group I metal and liquid ammonia is a powerful reducing system capable of reducing alkynes to trans alkenes In the pres ence of an alcohol this same combination reduces arenes to nonconjugated dienes Thus treatment of benzene with sodium and methanol or ethanol m liquid ammonia converts It to 1 4 cyclohexadiene... 

Manganese metal reacts with many compounds (21). Although Mn is fairly stable against water at room temperature, a slow reaction accompanied by the evolution of hydrogen takes place at 100°C. Most dilute acids dissolve manganese at a fast rate. At 350—875°C, anhydrous ammonia converts Mn... 

These gases are then fed to the water gas converter as in the steam-reforming process, after which they are compressed to ca 20.3 MPa (ca 200 atm) for processing in the catalytic ammonia converter. 

In both arrangements the synthesis gas deUvered to the ammonia converter is extremely pure because of the washing action the condensing ammonia has on the incoming make-up gas ridding it of impurities. The result is an extremely long catalyst life, even up to 20 years (54). 

Selection of the high pressure steam conditions is an economic optimisation based on energy savings and equipment costs. Heat recovery iato the high pressure system is usually available from the process ia the secondary reformer and ammonia converter effluents, and the flue gas ia the reformer convection section. Recovery is ia the form of latent, superheat, or high pressure boiler feedwater sensible heat. Low level heat recovery is limited by the operating conditions of the deaerator. 

Hydroisoquinolines. In addition to the ring-closure reactions previously cited, a variety of reduction methods are available for the synthesis of these important ring systems. Lithium aluminum hydride or sodium in Hquid ammonia convert isoquinoline to 1,2-dihydroisoquinoline (175). Further reduction of this intermediate or reduction of isoquinoline with tin and hydrochloric acid, sodium and alcohol, or catalyticaHy using platinum produces... 

Treatment of the oxazole (699) with ammonia converts it into 5-hydroxy-4,6-dimethyl-pyrimidine (700) and homologues may be made similarly 60CB1998). 

These reactors are of shell-and-tnbe configuration and mostly have the catalyst in the tubes, although some ammonia converters have the... 

The compressed synthesis gas is dried, mixed with a recycle stream, and introduced into the synthesis reactor after the recycle compressor. The gas mixture is chilled and liquid ammonia is removed from the secondary separator. The vapor is heated and passed into the ammonia converter. The feed is preheated inside the converter prior to entering the catalyst bed. The reaction occurs at 450-600°C over an iron oxide catalyst. The ammonia synthesis reaction between nitrogen, N2, and hydrogen, Hj, is... 

The most spectacular failure of this sort occurred when the exit pipe from a high-pressure ammonia converter was constructed from carbon steel instead of l A% Cr, 0.5% Mo. Hydrogen attack occurred, and a hole appeared at a bend. The hydrogen leaked out, and the reaction forces pushed the converter over. 

Cations of these metals invariably exist in aqueous solution as complex ions. Consider, for example, the zinc(II) cation. In a water solution ofZn(N03)2, the Zn(H20)42+ ion is present. Treatment with ammonia converts this to Zn(NH3)42+ addition of sodium hydroxide forms Zn(OH)42-. 

Figure 40.4. Selectivity to products in n-hexane ammoxidation as a function of the reaction temperature. Symbols selectivity to CO (X), CO2 ( ), iV-containing compounds ( , calculated with respect to n-hexane converted) and N2 (A, calculated with respect to ammonia converted). Carbon balance ( ). Catalyst Sn/V/Nb/Sb 1/0.2/1/3.

Using the parameters defined in Table II, the ODE system characterizing the ammonia converter can be reduced to dimensionless form with the following dimensionless groups ... 

Kjaer (K9) gives a very comprehensive study of concentration and temperature profiles in fixed-bed catalytic reactors. Both theoretical and experimental work is reported for a phthallic anhydride reactor and various types of ammonia converters. Fair agreement was obtained, but due to the lack of sufficiently accurate thermodynamic and kinetic data, definite conclusions as to the suitability of the dispersed plug flow model could not be reached. However, the results seemed to indicate that the... 

Reaction of the imidazole (7-4) with the benzofuran derivative (6-7) leads to the displacement of the benzylic halogen and the formation of the alkylation product (8-1). Treatment of that intermediate with trifluoroacetic acid breaks open the urethane to afford the corresponding free amine. This is allowed to react with ttiflic anhydride to afford the trifluoromethyl sulfonamide (8-2). The ester group on the imdidazole is then saponified, and the newly formed acid is reacted with carbonyl diimidazole. Reaction with ammonia converts the activated carboxyl group to the amide. There is thus obtained the angiotensin antagonist saprisartan (8-3) [6]. 

Figure 17.22. Representative ammonia converters operating at various pressures and effluent concentrations (Vancini, 1971). (a) Original Uhde design operating at 125 atm typical dimensions, 1.4 x 7 m. (b) Haber-Bosch-Mittasch converter operating at 300 atm typical dimensions, 1.1 x 12.8 m. (c) Claude converter operating at 1000 atm typical dimensions 1.2 x 7 m. (d) Fauser-Montecatini (old style) converter operating at 300 atm with external heat exchange, showing axial profiles of temperature and ammonia concentration.

In the case of a reactor cooled by incoming feed flowing countercurrent to the reaction mixture (Fig. 3.21 d), and typified by the ammonia converter sketched in... 

Methanators are usually used in the ammonia production line to guard the catalyst of the ammonia converters from the ill effect of carbon monoxide and carbon dioxide. This section includes precise models for different types of methanators using the dusty gas model with reliable kinetic expression and the results are compared with those of the simplified models (A) and (B). 

Industrial fixed-bed catalytic reactors have a wide range of different configurations. The configuration of the reactor itself may give rise to multiplicity of the steady states when other sources alone are not sufficient to produce the phenomenon. Most well known is the case of catalytic reactors where the gas phase is in plug flow and all diffusional resistances are negligible, while the reaction is exothermic and is countercurrently cooled. One typical example for this is the TVA type ammonia converter [38-40]. 

A sacrificial carrier polymer approach was reported by Sneddon in 1988.64 Here, an organic polymer with a pentaborane side group was prepared by addition polymerization as shown in reaction (18). Treatment of this polymer with ammonia converted the borane side group to a fused borazine (naphthalene-type) side unit. Subsequent pyrolysis in ammonia resulted in loss of the organic polymer and hydrogen and the formation of boron nitride. 

Aqueous ammonia converts a-halo acids to a-amino acids. 

Treatment of compound D with ammonia converts it to isoleucine by nucleophilic substitution. 

It is well known that colchicine exhibits U V maxima at 243 and 350 nm in CHC13 and ethanol. The latter is associated with the tropolonic moiety since it disappears on ring contraction to allocolchicine (12) which has a six-membered benzenoid ring C (25). TLC analysis of very small amounts of deacetylcolchicine and deacetylisocolchicine was made possible by making their DADF (dihydrofluorescein diacetate) derivatives (Fig. 7). Hydrolysis of the DADF derivatives with aqueous ammonia converted the... 

Just as acids may be used to lower the concentration of anions in solution, so complexing agents may be used in some cases to lower the concentration of cations. In this problem, the addition of ammonia converts most of the silver to the complex ion, [Ag(NH3 )2]+. The upper limit for uncomplexed [Ag+] without formation of a precipitate can be calculated from the solubility product. 

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