Ammonia thermodynamic data

Ethyleneimine (El) and its two most important derivatives, 2-methyla2iridine [75-55-8] (propyleneimine) (PI) and l-(2-hydroxyethyl)a2iridine [1072-52-2] (HEA) are colodess Hquids. They are miscible ia all proportions with water and the majority of organic solvents. Ethyleneimine is not miscible with concentrated aqueous NaOH solutions (>17% by weight) (24). Ethyleneimine has an odor similar to ammonia and is detectable only at concentrations >2 ppm. The physical properties of ethyleneimine and the derivatives mentioned are given ia Table 1. Thermodynamic data can be found ia the Hterature (32). 

Table 6.4 Thermodynamic data for ammonia at various temperatures5.

From the thermodynamic data of Appendix C, show that the product of the reaction of ammonia gas with oxygen would be nitrogen, rather than nitric oxide, under standard conditions and in the absence of kinetic control by, for example, specific catalysis of NO formation by platinum. (Assume the other product to be water vapor.)... 

Although the entire discussion of electrochemistry thus far has been in terms of aqueous solutions, the same principles apply equaly well to nonaqueous solvents. As a result of differences in solvation energies, electrode potentials may vary considerably from those found in aqueous solution. In addition the oxidation and reduction potentials characteristic of the solvent vary with the chemical behavior of the solvent. as a result of these two effects, it is often possible to carry out reactions in a nonaqueous solvent that would be impossible in water. For example, both sodium and beryllium are too reactive to be electroplated from aqueous solution, but beryllium can be electroplated from liquid ammonia and sodium from solutions in pyridine. 0 Unfortunately, the thermodynamic data necessary to construct complete tables of standard potential values are lacking for most solvents other than water. Jolly 1 has compiled such a table for liquid ammonia. The hydrogen electrode is used as the reference point to establish the scale as in water ... 

Classical methods of group analysis and separation take advantage of the stability of the [Ag(NH3)2]+ ion to separate silver from mercury. Treatment of a precipitate containing AgCl with dilute ammonia leads to the reaction in equation (3) bringing the silver into solution. To confirm the presence of Ag+, nitric acid must then be added to cause reprecipitation of AgQ. In aqueous ammonia, the diammine was the highest species formed, and thermodynamic data for its formation are collected in Table 3.20-23... 

The kinetics of the acid cleavage of the trihydroxobridged complexes with the tridentate amines dien and tach have also been studied (186). These systems are very similar to the ammonia system, and the kinetic and thermodynamic data are therefore likely to be interpretable in the same way (Table XXXV). The cleavage of the NH3, dien, and tach complexes in chloride media has also been studied (186). These reactions were found to give dihydroxo-bridged species in two... 

Physical chemical studies of dilute alkali metal-ammonia solutions indicate the principal solution species as the ammoniated metal cation M+, the ammoniated electron e , the "monomer M, the "dimer" M2 and the "metal anion" M. Most data suggest that M, M2, and M are simple electrostatic assemblies of ammoniated cations and ammoniated electrons The reaction, e + NH3 - lf 2 H2 + NH2 is reversible, and the directly measured equilibrium constant agrees fairly well with that estimated from other thermodynamic data. Kinetic data for the reaction of ethanol with sodium and for various metal-ammonia-alcohol reductions of aromatic compounds suggest that steady-state concentrations of ammonium ion are established. Ethanol-sodium reaction data allow estimation of an upper limit for the rate constant of e + NH4+ 7, H2 + NH3. 

All thermodynamic data for air, the reaction gas mixture, and feed ammonia are taken from Ref.TDI (Section 3). Heat capacities for the various gas mixtures are calculated from the correlations in Ref.TD2. (Table E.1, p.538). Steam tables in Ref.TD3 are also used. Nitric acid properties are taken from Ref.TD4 (p.D-126 and D-77). Reaction equilibrium data are obtained from Refs. PT1 and PT2. 

In 2001 Hyprotech and Synetix announced an ammonia plant simulation that can be used for modeling, on-line monitoring and optimization of the plant. The simulation includes Synetix reactor models, customized thermodynamic data and information to simulate the performance of a range of catalysts. The reactor models in the simulation include Primary and Secondary Reformers, High Temperature Shift converter, Low Temperature Shift Converter, Methanator and Ammonia Synthesis Converter80. 

In 1905 Haber reported a successful experiment in which he succeeded in producing NH3 catalytically. However, under the conditions he used (1293 K) he only found minor amounts of NH3. He extrapolated his value to lower temperatures (at 1 bar) and concluded that a temperature of 520 K was the maximum temperature for a commercial process. This was the first application of chemical thermodynamics to catalysis, and precise thermodynamic data were not then known. At that time Haber regarded the development of a commercial process for ammonia synthesis as hopeless and he stopped his work. Meanwhile, Nernst had also investigated the ammonia synthesis reaction and concluded that the thermodynamic data Haber used were not correct. He arrived at different values and this led Haber to continue his work at higher pressures. Haber tried many catalysts and found that a particular sample of osmium was the most active one. This osmium was a very fine amorphous powder. He approached BASF and they decided to start a large program in which Bosch also became involved. 

Without referring to the tables of thermodynamic data, predict the signs of AH° and AS° for the reaction NH3(aq) -5= NH3(g). Explain why the odor of NH3(g) that collects above an aqueous solution of ammonia becomes more intense as the temperature is increased. ... 

In their discussion of ammonia metabolism, the authors have used other compilations of thermodynamic data to compute Gibbs energy changes for these processes. 

Kelley s collection of data on metal carbides and nitrides includes thermodynamic data for methane and ammonia because some of the... 

Din was the editor of a series of books designed to provide reliable thermodynamic data for industrially important gases. Temperature-entropy diagrams were chosen as the most generally useful graphical presentations and these are supplemented by tables of entropy, enthalpy, volume, heat capacity at constant pressure and at constant volume, and Joule-Thomson coefficients. Unfortunately, there is no consistency in the choice of units, although the thermochemical calorie is employed. The report on each substance (i.e. ammonia, carbon dioxide, carbon monoxide, air, argon, acetylene, ethylene, and propane) consists of a brief introduction, a survey of experimental data, a description of methods used for the thermodynamic calculations, and a set of tables. 

Table 4.9. Thermodynamic data for adsorption of ammonia by activated carbon. Domingo-Garcia et al. (2002).

The first industrial SCF applications utilised SCCO2 for the extraction of natural compounds (caffeine, hops) and were successfully established in the early 1970 s. In the following decades, research focus also shifted towards reactions in SCCO2 and SCH2O (however, it is noteworthy that ammonia and methanol syntheses were sometimes considered as supercritical processes). From all these processes, fundamental thermodynamic data and practical experience in high-pressure reaction engineering are available and promote the development of supercritical oxidation processes. 

As we did several times in our design of the ammonia process, we investigate the possibility of separating the n-heptane by phase differences. We begin with the most efficient separation, gas/liquid or gas/solid, for which we need to know boiling points. Again we make a table of the relevant thermodynamic data. 

Ammonia Solution. For the ammonolysis of gaseous NH2 at 240 K, a value of AS° = -239.6 J-K -mol was determined from experiments with NaNH2 and from estimated data [2]. A value of AH°= -289kJ/mol at 233 K for the solvolysis is given in [3]. Similar thermodynamic data for the amide formation in NH3 solution at 298 K were calculated from data measured on ions in aqueous solution [4]. 

From thermodynamical data it may be shown that, in ammonia synthesis gas, water is required in percent amounts in order to oxidize bulk metallic iron to the oxide (magnetite or wustite). On the other hand, it is very clear from the poisoning studies to be discussed later in this chapter that water in the low ppm range exerts a definite poisoning action. 

---