Ammonia as reactant

FIGURE 9.10 These graphs show the changes in composition that can be expected when additional hydrogen and then ammonia are added to an equilibrium mixture of nitrogen, hydrogen, and ammonia. Note that the addition of hydrogen results in the formation of ammonia, whereas the addition of ammonia results in the decomposition of some of the added ammonia as reactants are formed. In each case, the mixture settles into a composition in accord with the equilibrium constant of the reaction. 

The ahphatic alkyleneamines are strong bases exhibiting behavior typical of simple aUphatic amines. Additionally, dependent on the location of the primary or secondary amino groups iu the alkyleneamines, ring formation with various reactants can occur. This same feature allows for metal ion complexation or chelation (1). The alkyleneamines are somewhat weaker bases than ahphatic amines and much stronger bases than ammonia as the piC values iadicate (Table 2). 

Yourcompany. a nitric acid manufacturer, uses ammonia in a waste treatment system to neutralize an acidic wastewater stream containing nitric acid. The reaction of the ammonia and nitric acid produces an ammonium nitrate solution. Ammonium nitrate solution is a listed toxic substance, as are nitric acid and ammonia. Your facility otherwise uses ammonia as a reactant and manufactures ammonium nitrate solution as a byproduct. If the ammonium nitrate solution is produced in a quantity that exceeds the threshold (e.g., 25,000 pounds for 1989), the facility must report for ammonium nitrate solution. If more than 10,000 pounds of ammonia is added to the wastewater treatment system, then the facility must report (or ammonia. 

Co-adsorption experiments show a complex role of the nature and concentration of chemisorbed ammonia species. Ammonia is not only one of the reactants for the synthesis of acrylonitrile, but also reaction with Br()>nsted sites inhibits their reactivity. In particular, IR experiments show that two pathways of reaction are possible from chemisorbed propylene (i) to acetone via isopropoxylate intermediate or (ii) to acrolein via allyl alcoholate intermediate. The first reaction occurs preferentially at lower temperatures and in the presence of hydroxyl groups. When their reactivity is blocked by the faster reaction with ammonia, the second pathway of reaction becomes preferential. The first pathway of reaction is responsible for a degradative pathway, because acetone further transform to an acetate species with carbon chain breakage. Ammonia as NH4 reacts faster with acrylate species (formed by transformation of the acrolein intermediate) to give an acrylamide intermediate. At higher temperatures the amide may be transformed to acrylonitrile, but when Brreform ammonia and free, weakly bonded, acrylic acid. The latter easily decarboxylate forming carbon oxides. 

If it s assumed that there is no ammonia when the reaction starts, then the reactants initially combine according to the forward reaction to produce ammonia. As the ammonia is... 

In a number of petrochemical processes, a gas (hydrogen) is present as reactant. In hydrodesulfurization (HDS), hydrocracking (HC), and hydrodenitrogenation (HDN), the reaction products H2S and ammonia, respectively, are known to decrease the catalyst activity, but are partly transferred to the gas phase. Therefore, also these processes profit from reactive stripping. 

Choose a reaction sequence so that each of the Nc reactive sites adds a reactant B, possessing new Nb (Nb > 1) reactive sites (thereby introducing multiplicity) to obtain dendrimer D0 of generation 0. With ammonia as initiator core, a p-alanine derivative (Nb = 2) might be chosen as reactant. 

The selective hydrogenation of the nitrophenyl-nitroimidazole, 8, was accomplished in 85-90% yield by careful attention to reaction conditions.29 The maximum yield of 9 (Eqn. 19.13) was obtained using a Pd/C catalyst with concentrated aqueous ammonia as the solvent at 20-35°C and 2.7 atmospheres. Variation from these conditions resulted in a significant decrease in selectivity. The need for these exacting conditions arose because of two critical requirements (1) the imidazole ring should exist as its anion to inhibit the hydrogenation of the imidazole nitro group and (2) the concentration of reactant in solution should be... 

Telomerizations have been among the first reactions tested under biphasic conditions [45, 190], starting with butadiene and methanol on Pd/TPPMS catalysts and yielding l-methoxy-2,7-octadiene. The telomerization in the presence of water as reactant (hydrodimerization cf Scheme 1) has been commercialized [15, 31, 42-44]. These biphasic developments of the Kuraray Corporation yield 1-octanol or 1,9-nonanediol, respectively (cf [15, 31, 42 4, 86, 133, 137, 244 e] and Section 2.3.5). Similar developments (but without technical realization) have been described by BASF [134], Mitsubishi [135], and Shell [136], and others [215 d, 242, 268]. The telomerization of butadiene and ammonia may also be biphasic [243]. 

The initial alcohol/amine ratio can determine the product distribution. In the synthesis of primary amines a rather high ammonia/alcohol molar ratio (up to 10-25), and usually high pressure, are required to compensate for the low reactivity of ammonia and suppress the formation of secondary amines. Selectivity for primary diamines could be improved in the amination of 1,3-dihydroxy compounds when using supercritical ammonia as solvent and reactant in a continuous fixed-bed reactor [12]. The remarkable changes in selectivity in the near-critical region (100-110 bar) are attributed to the increased concentration of ammonia on the metal surface as a result of elimination of mass-transport limitations in the two-phase system, and to suppression of hydrogenolysis and water elimination reactions which lead to monofunctional by-products. An example is shown in Figure 1. 

There are few reports of successful one-step synthesis of primary diamines, and the examples are limited to amines with a special structure. Amination of 1,4-cy-clohexanediol in supercritical ammonia (135 bar) over a Co-Fe catalyst alforded 67 % 1,4-diaminocyclohexane [21]. Excess ammonia, as both supercritical solvent and reactant, and short contact time in the continuous fixed-bed reactor favored the desired reactions. In the best example the cumulative selectivity for the diamine and the intermediate amino alcohol was 97 % at 76 % conversion. Recycling of the unreacted diol and amino alcohol can provide an alternative to the eurrent process, the hydrogenation of pnra-phenylenediamine. The high seleetivity was because of the rigid structure and the relative positions of OH functionality in the substrate. For comparison, amination of 1,4-butanediol under similar conditions yielded pyiTolidine as the major product 1,4-diaminobutane was barely detectable. When 1,3-cyclohexanediol was aminated with the same catalyst in the continuous system, the yield of 1,3-diaminoeyclohexane dropped below 5%, mainly because elimination of water led to undesired monofunctional products via a,/9-unsaturated alcohol, ketone, and/or amine intermediates [22]. 

Toluene can be readily ammoxidized to benzonitrile, usually over supported vanadium oxide and vanadium phosphate catalysts [e. g. 9,57]. Besides catalyst choice, catalytic performance mainly depends on the reaction conditions. Excess ammonia, as mentioned above, significantly increases nitrile selectivity by blocking sites responsible for consecutive oxidation ammonia also frequently reduces catalyst activity [1]. Water vapor in the reactant stream can also improve selectivity by blocking sites for total oxidation [38] or providing Brdnsted sites for the activation of ammonia [51]. 

Leuckart-like reactions have been noted for the co-phosphinoylalkanals 304 and related compounds In these reactions, and also for those with analogous ketones the carbonyl reactant is subjected to reductive amination with ammonia (as ammonium acetate) or amines and NaBH3CN in MeOH at pH 7-7.5 the process is very sensitive to steric hindrance and probably proceeds via an enaminophonate intermediate. The sequence is illustrated (Scheme 38) by a direct synthesis of racemic phosphinothricin, but the involvement of the optically active 1,2-azaphospholidine 118 led to an optically active product ". ... 

Liquid ammonia may be introduced into reaction systems, and am-monolysis then carried out at temperatures higher then the critical temperature. These are really examples of the use of gaseous ammonia as the aminating agent or of ammonia dissolved in one of the reactants or in an inert organic solvent. 

Since the technical manufacture of many important amines employs ammonia as a reactant, a resume on its manufacture is presented. 

The Paal-Knorr Synthesis of Pyrroies. The Paal-Knorr method makes use of a 1,4-di-carbonyl compound (aldehyde or ketone) in reaction with primary amines or ammonia. Many pyrroles have been made by this general process. Alkyl and some other substituents are allowed on the dicarbonyl chain. Diketones, dialdehydes, and ketoalde-hydes all serve as reactants. Primary amines give rise to 1-alkylpyrroles. Examples of the overall process are shown in Scheme 4.2. 

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