Promoted Iron Catalyst Research Articles

Isotopic Mixing in Nitrogen over Fe-Al203(Singly Promoted Iron) and Fe-K20 Catalysts

The isotopic mixing in nitrogen molecules over singly promoted iron catalyst (Fe-Al203) was carried out at 280-330°. The rate of displacement of adsorbed nitrogen was in agree- ment with the rate of isotopic mixing, suggesting that the adsorbed nitrogen is mostly dis- sociated.The isotopic mixing over Fe-Al203 was much faster than over Fe and Fe-Al203-K20. But the isotopic mixing was retarded by the presence of hydrogen contrary to the result on FeAl208--K20 where hydrogen markedly accelerated the isotopic mixing. The hydrogen effect on the isotopic mixing over Fe-K20 was investigated at 400°C, and the accelerating effect of hydrogen was clearly observed.From these facts, it is concluded that Al203 promotes the dissociative adsorption of nitrogen on iron but the rate is retarded in the presence of hydrogen, and K20 markedly promotes the dissociative adsorption on iron in the presence of hydrogen by the mechanism of N2 2NH

The inhibition by nitrogen of the chemisorption of carbon monoxide on an unpromoted iron catalyst

The effect of chemisorbed nitrogen on the adsorption of carbon monoxide at −195 °C was studied on an unpromoted iron catalyst. The results indicate that the adsorption of 1 cm 3 of nitrogen at 300 °C causes a decrease of 0.5 cm 3 in the amount of carbon monoxide adsorbed at −195 °C. The inhibition appears to be greater the lower the temperature at which the nitrogen is chemisorbed, being as high as 0.75 cm 3 when the nitrogen is adsorbed at 200 ° and as low as 0.25 cm 3 when it is adsorbed at 400 °C. The inhibitive effect of chemisorbed nitrogen is greater on the pure iron sample than previously noted for a promoted iron catalyst, though for both promoted and unpromoted iron the chemisorbed nitrogen at a synthesis temperature of 450 °C appears to be primarily in an atomic rather than molecular form on the surface.

Isotopic mixing in nitrogen over a doubly promoted iron

The rate of displacement of adsorbed nitrogen under the adsorption equilibrium over a doubly promoted iron catalyst was determined at 250 and 350 ° C by means of isotopic nitrogen, and compared with the rate of isotopic exchange of nitrogen molecule. Although the rate of displacement is not uniform with respect to the adsorbed nitrogen, the highest rate of displacement is in agreement with the rate of isotopic mixing. It is accordingly concluded that the adsorbed nitrogen is mostly dissociated. A remarkable acceleration of the isotopic exchange is observed in the presence of hydrogen, and a normal isotope effect of 1.07 is determined for the acceleration by hydrogen. It is accordingly concluded that the acceleration effect is chemical in nature and that the promoter K 2O is responsible for the acceleration by hydrogen as well as for the increase in the rate of isotopic exchange in the absence of hydrogen.

REVIEW OF AMMONIA CATALYSIS

Abstract A review of the chemical and physical processes involved in the synthesis of ammonia in a reactor charged with a promoted iron catalyst is given. In order to discuss the chemistry of the reaction the structure of the surface in which the chemical reaction takes place will be discussed and in order to discuss the diffusion in the catalyst pore system, the pore structure will be treated.

An investigation on promoted iron catalysts for the synthesis of ammonia, third edition, Anders Nielsen, Jul. Gjellerups Forlag (1968). 264 pages

An investigation on promoted iron catalysts for the synthesis of ammonia, third edition, Anders Nielsen, Jul. Gjellerups Forlag (1968). 264 pages

Kinetics of benzene hydrogenation over a nickel catalyst: Reactions in the kinetic region

The hydrogenation of benzene over a singly promoted iron catalyst was studied at temperatures from 130 to 190 °C, benzene partial pressures from 6.67 × 10−3 to 0.48 kPa and hydrogen partial pressures from 26.7 to 105.3 kPa, in a differential plug-flow microreactor at a total pressure just above atmospheric. Cyclohexane could be considered as the only product of the reaction, although cracking products were also found in very low concentrations at temperatures above 170 °C. No cyclohexene or cyclohexadiene was detected.The data from 130 to 180 °C were correlated with an equation of the form: r0 = kKBKH3PBPH23(1.0 + KBPB + (KHPH2)12)7, suggesting that one molecule of adsorbed benzene simultaneously reacts with three molecules of dissociatively chemisorbed hydrogen as the rate-controlling step. Above 180 °C, a change in the mechanism occurs.

The effect of alkaline promoter on decomposition of ammonia over the doubly promoted iron catalyst

The effect of alkaline promoter on decomposition of ammonia over the doubly promoted iron catalyst

Kinetics and mechanism of the ammonia synthesis

The reaction rate in stoichiometric mixtures of nitrogen and hydrogen or deuterium has been measured on two different doubly promoted iron catalysts, between 218 and 302 °C, ⅓ and 1 atm and over a 300-fold range of efficiencies. The kinetic data as well as the isotope effect indicate that the rate-determining step is the chemisorption of nitrogen on a surface mainly covered with NH radicals. The presence on the surface of NH radicals instead of nitrogen atoms opens new perspectives on the kinetics and mechanism of ammonia synthesis.

Reaction rates in the synthesis of ammonia

AbstractA study has been made of the reaction rates of mixtures of hydrogen and nitrogen to form ammonia over a doubly promoted iron catalyst at 400° and 450°C. and at pressures up to 1,000 atm. In this work particular care has been taken to obtain data representing the true kinetics of the reaction. The reactor used was essentially isothermal, and the effects of diffusion have been reduced to a minimum. The results have been correlated by the use of the mechanism proposed by Temkin and Pyschev (19) with moderate success.

An Investigation on Promoted Iron Catalysts for the Synthesis of Ammonia.

An Investigation on Promoted Iron Catalysts for the Synthesis of Ammonia.

(161)鉄触媒によるアンモニア分解反応機構

(161)鉄触媒によるアンモニア分解反応機構

(237)Al<SUB>2</SUB>O<SUB>3</SUB> ならびに Al<SUB>2</SUB>O<SUB>3</SUB>, K<SUB>2</SUB>O 添加鉄触媒による窒素, 水素, 一酸化炭素の活性化吸着

(237)Al<SUB>2</SUB>O<SUB>3</SUB> ならびに Al<SUB>2</SUB>O<SUB>3</SUB>, K<SUB>2</SUB>O 添加鉄触媒による窒素, 水素, 一酸化炭素の活性化吸着

(272)鉄触媒によるアンモニア分解反応に関する研究(第1報)分解反応に於ける履歴現象と窒化鉄の形態

(272)鉄触媒によるアンモニア分解反応に関する研究(第1報)分解反応に於ける履歴現象と窒化鉄の形態

Adsorption and Reaction of Carbon Monoxide on Promoted Iron Catalysts

Adsorption and Reaction of Carbon Monoxide on Promoted Iron Catalysts

An Investigation of Promoted Iron Catalysts for the Ammonia Synthesis, vonAnders Nielsen. Jul. Gjellerups Forlag, Kopenhagen 1950. 123 S., 36 Abb., 11.00 dän. Kronen

Angewandte ChemieVolume 64, Issue 4 p. 119-119 Literatur An Investigation of Promoted Iron Catalysts for the Ammonia Synthesis, von Anders Nielsen. Jul. Gjellerups Forlag, Kopenhagen 1950. 123 S., 36 Abb., 11.00 dän. Kronen Hummel, HummelSearch for more papers by this author Hummel, HummelSearch for more papers by this author First published: 21. Februar 1952 https://doi.org/10.1002/ange.19520640419AboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume64, Issue421. Februar 1952Pages 119-119 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

Microwave Spectroscopic Investigation of the Kinetics of the Heterogeneous Ammonia-Deuterium Exchange

A method is described for analyzing a mixture of gases using microwave spectroscopy. Relatively simple microwave measurements are employed on single resolved collision broadened spectral lines. For binary mixtures, only the peak absorption coefficients need to be measured if the microwave collision diameters are known. Mixtures of isotopically substituted molecules can also be analyzed because the microwave absorption lines of the isotopic species are easily resolved. The technique is applied to determining the mole fraction of NH3 in mixtures of deuterated ammonias, and to a study of the kinetics of the NH3—D2 isotopic exchange reaction on a singly promoted iron catalyst. It is found that rates of desorption of molecules from surfaces are markedly increased on adsorption of other molecules, a fact that can be explained only in terms of strong interactions between adsorbed molecules. The rate of the exchange reaction is proportional to the square root of the deuterium pressure. With increasing ammonia pressure the rate passes through a maximum, showing that the mechanism involves reaction between adsorbed ammonia and adsorbed deuterium atoms. The activation energy diminishes significantly with increasing ammonia pressure, providing additional evidence for the existence of strong interactions between adsorbed molecules.

The Rate Equation of Ammonia-Synthesis on Iron-Type Catalysts of Different Composition

Investigations on the rate equation of ammonia synthesis on iron catalysts have been carried out. The results agree in a general way with the rate equation of Temkin and Pyzhev. An improvement of this equation is given, which leads to a better agreement between observed and calculated synthesis rates. Experiments carried out at low temperatures show that the rate equation is the same for the three catalysts which have been investigated: (1) pure iron, (2) iron containing 3 percent alumina, and (3) iron containing 3 percent alumina and 2 percent potassium oxide. By means of the improved Temkin and Pyzhev equation a formal explanation can be given for the results obtained by Love and Emmett on ammonia decomposition on a singly promoted iron catalyst between 400 and 450C.

The Effect of Alkali Promoter Concentration on the Decomposition of Ammonia Over Doubly Promoted Iron Catalysts*

The Effect of Alkali Promoter Concentration on the Decomposition of Ammonia Over Doubly Promoted Iron Catalysts^*