Graphical Differentiation in Ammonia Synthesis Kinetics

Anderson, R. B.

doi:10.1021/ie50601a053

Cited by 6 publications

(5 citation statements)

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“…where r = reaction rate, kmol NHs/h/m3 of catalyst, K2 = velocity constant of the reverse reaction, /n2, /h2> /nh:! = fugacities of nitrogen, hydrogen, and ammonia, K& = equilibrium constant of the reaction: I.5H2 + O.5N2 = NH:¡, and a = constant (according to Temkin a = 0.5 for all the iron catalysts (Morozov et al, 1965;Temkin et al, 1963;Temkin and Pyzhev, 1940); other authors have obtained experimental values ranging between 0.4 and 0.8 (Anderson, 1960;Bokhoven et al, 1955;Brill, 1951;Buzzi Ferraris and Donati, 1970; Cappelli and Collina, 1972; Dyson and Simon, 1968 Sholten, 1959).…”

Section: Resultsmentioning

confidence: 99%

On the Application of the Temkin Equation in the Evaluation of Catalysts for the Ammonia Synthesis

Guacci¹,

Traina²,

Ferraris³

et al. 1977

Ind. Eng. Chem. Proc. Des. Dev.

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Section: Resultsmentioning

confidence: 99%

On the Application of the Temkin Equation in the Evaluation of Catalysts for the Ammonia Synthesis

Guacci¹,

Traina²,

Ferraris³

et al. 1977

Ind. Eng. Chem. Proc. Des. Dev.

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“…The existence of dissolved nitrogen as N atoms is well established (Darken and Gurry, 1953). The presence of surface iron nitride has been confirmed by a number of other workers (Amenomiya and Pleizier, 1973;Anderson, 1960;Anderson, 1963;Annable, 1952). Evidently, hydrogen adsorbs dissociatively and reacts with either surface nitride or the dissolved nitrogen coming to the surface to form ammonia precursors which are further hydrogenated.…”

Section: Discussionmentioning

confidence: 95%

Influence of forced feed composition cycling on the rate of ammonia synthesis over an industrial iron catalyst part I — Effect of cycling parameters and mean composition

1983

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Studies have been carried out at 2.38 MPa total pressure and at 360 and 400°C of the synthesis of ammonia over a triply‐promoted iron catalyst (United Catalysts Inc.). Runs were carried out using a gradientless reactor in steady‐state and periodic modes, the latter employing forced composition cycling. The catalyst had a particle diameter of 0.30 mm; the resulting reaction rates were free from transport intrusions. The range of mean compositions for steady‐state measurements was from 0.1 to 0.9 mole fraction of hydrogen and for periodic operation from 0.5 to 0.9. The cycle‐split ratio (used to describe non‐uniform cycling) varied from 0.2 to 0.85. Effects of cycle period, mean composition, cycle‐split, and temperature were investigated. Instantaneous rate variations within the cycle are reported. Results showed that the cycling mode of operation results in an improvement in the time‐average rate of ammonia formation of up to 30%, depending upon the choice of operating parameters. Some implications for the mechanism of ammonia synthesis under periodic operation are presented.

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“…where rNH3 = reaction rate, kg-mol of NH3/(h m3 of catalyst), K2 = velocity constant of the reverse reaction, kg-mol/(h m3), /N¡¡, /Ha, /nh3 = fugacities of nitrogen, hydrogen, and ammonia, respectively, ka = equilibrium constant of the reaction: 1.5H2 + 0.5N2 -NH3, and a = constant. According to some workers a = 0.5 for all iron catalysts (Morozov et al, 1965;Temkin and Pyzhev, 1940;Temkin et al, 1963) whereas others obtained values ranging from 0.4 to 0.8 (Anderson, 1960; Bokhoven et Ferraris and Donati, 1970;Cappelli and Collina, 1972;Dyson and Simon, 1968;Emmett and Hummer, 1943;Guacci et al, 1977;Huber, 1962;Livshits and Sidorov, 1952;Love and Emmett, 1941;Mills and Bennett, 1959;Nielson, 1968;Ozaki et al, 1960;Sidorov and Livshits, 1947;Sholten, 1959).…”

Section: Rate Expressionsmentioning

confidence: 95%