The surface properties of iron catalyst for ammonia synthesis

Arabczyk, W.; Jasińska, Izabella; Lubkowski, Krzysztof

doi:10.1023/b:reac.0000046101.89184.b8

Cited by 29 publications

(19 citation statements)

References 13 publications

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“…All the calculations were carried out on the basis of (7a), (7b), and (9), and the results obtained are shown in Figure 2. Modeling shown in the present paper is based on the laboratory experience concerning iron ammonia synthesis catalyst [12][13][14][15][16]. For various concentrations of B,bulk , the equilibrium values of the surface coverage degree and gas pressure were determined.…”

Section: Resultsmentioning

confidence: 99%

Extended Surface of Materials as a Result of Chemical Equilibrium

Arabczyk

Pelka

Jasińska

2014

Journal of Nanomaterials

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A system consisting of at least two components was considered. In this system, nanocrystalline material is formed at high temperature, at which diffusion does not limit the mass transport. The structure results from establishing an equilibrium between surface and volume of the crystallites and their surroundings in isothermal-adiabatic conditions. The surface of each crystallite is covered with another substance. On the basis of the performed energy-balance calculations it was concluded that the reduction in the surface area is associated with a decrease in the surface coverage degree and thus with the necessity to provide energy to the system in order to remove chemisorbed atoms. An increase in the temperature of a nanocrystalline substance to a temperature higher than the preparation temperature results in the formation of a new state of equilibrium. At temperatures below the maximum temperature only the equilibrium between the gas phase and the surface exists.

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Section: Resultsmentioning

confidence: 99%

Extended Surface of Materials as a Result of Chemical Equilibrium

Arabczyk

Pelka

Jasińska

2014

Journal of Nanomaterials

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“…Fityk software as well as an online calculator by Pielaszek were used to analyze the diffraction patterns. The surface area of the catalyst determined by the BET method using a Quadrasorb SI apparatus (Quantachrome Instruments, Automated Surface Area & Pore Size Analyzer) was 12 m 2 /g …”

Section: Methodsmentioning

confidence: 99%

Study of the Iron Catalyst for Ammonia Synthesis by Chemical Potential Programmed Reaction Method

2017

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A new method, entitled chemical potential programmed reaction, for determining the physicochemical properties of iron ammonia synthesis catalyst has been proposed. Two model reactions were applied: nitriding of the iron catalyst and reduction of the obtained nitrides. Measurements of the rates of those reactions were carried out at 350 °C in a differential tubular reactor. The reactor is equipped with a system that allows us to perform simultaneous thermogravimetric measurements and a catharometric system to determine hydrogen concentration in the gas phase. The reactor was fed with a mixture of ammonia and hydrogen of varying composition, which was changing in a controlled way. Different accelerations of the nitriding potential change were applied. During the processes of nitriding of nanocrystalline iron and reduction of the obtained nanocrystalline iron nitrides rates of these processes were measured. The minimum nitriding potential, at which the phase transformation of nanocrystallites of a certain size took place, was determined. As a result, the relative nanocrystallite size distribution related to the active surface of nanocrystallites was calculated. Then, making use of the mean size of nanocrystallites the absolute size distribution was obtained. Bimodal size distribution of nanocrystallites in test samples was observed. The dependence of the minimum nitriding potential on the mass of crystallites was determined. During the reduction of iron nitrides, similarly as in the iron nitriding process, nanocrystallites underwent a phase transition in their entire volume in the order of the largest to the smallest in size.

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“…Previous theoretical research utilizing QM methods for the Fe(211) surface has focused on the non-reconstructed surface. 24 However, other studies have indicated Fe surfaces with exposed deep-layer sites sustain the greatest reaction efficiency 6,28,29 under industrial conditions, such as the relatively well-examined Fe(111) surface which contains exposed adsorption sites on the second and third Fe layers. Following this concept, this research seeks to explore the reaction mechanism and rates of reaction on the Fe(211) surface which has undergone missing row-type reconstruction due to the presence of hydrogen and nitrogen on the surface at industry standard temperatures and pressures, the presence and mechanism of which has been explored in previous experimental and theoretical research.…”

Section: Comparison With Previous Studiesmentioning

confidence: 99%