Ammonia synthesis with barium-promoted iron–cobalt alloys supported on carbon

Hagen, Stefan; Barfod, Rasmus; Fehrmann, Rasmus; Jacobsen, Claus J. H.; Teunissen, Herman T.; Chorkendorff, Ib

doi:10.1016/s0021-9517(02)00182-3

Cited by 155 publications

(118 citation statements)

References 25 publications

Supporting

Mentioning

107

Contrasting

Unclassified

Order By: Relevance

“…Consequently, researchers have been motivated to find replacements for supported copper catalysts, focusing on inexpensive and earth-abundant metals that work effectively, such as cobalt. Cobalt is widely used in industry as a catalyst for Fischer-Tropsch synthesis 31 , also drawing attention for CO oxidation 32 and ammonia synthesis 33 . But cobalt is regarded as inappropriate for the selective methanol formation, because of the its high activity for C-O dissociation 34 , and CO and hydrocarbons usually form rather than methanol 35 .…”

mentioning

confidence: 99%

Silica accelerates the selective hydrogenation of CO2 to methanol on cobalt catalysts

et al. 2020

View full text Add to dashboard Cite

The reaction pathways on supported catalysts can be tuned by optimizing the catalyst structures, which helps the development of efficient catalysts. Such design is particularly desired for CO 2 hydrogenation, which is characterized by complex pathways and multiple products. Here, we report an investigation of supported cobalt, which is known for its hydrocarbon production and ability to turn into a selective catalyst for methanol synthesis in CO 2 hydrogenation which exhibits good activity and stability. The crucial technique is to use the silica, acting as a support and ligand, to modify the cobalt species via CoO -SiO n linkages, which favor the reactivity of spectroscopically identified *CH 3 O intermediates, that more readily undergo hydrogenation to methanol than the CO dissociation associated with hydrocarbon formation. Cobalt catalysts in this class offer appealing opportunities for optimizing selectivity in CO 2 hydrogenation and producing high-grade methanol. By identifying this function of silica, we provide support for rationally controlling these reaction pathways.

show abstract

mentioning

confidence: 99%

Silica accelerates the selective hydrogenation of CO2 to methanol on cobalt catalysts

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Following high-temperature reduction, a significant amount of cobalt in the bimetallic preparation remained as a dispersed surface alloy as would be expected based on surface free energy [23]. Similar bimetallic preparations have demonstrated a high degree of alloying [24,25]. Figure S1 in the Supplementary Information shows the pre-and post-reaction XRD patters of Fe, CoFe and Co.…”

Section: Catalyst Structure and Chemical Compositionmentioning

confidence: 68%

Transient Kinetic Experiments within the High Conversion Domain: The Case of Ammonia Decomposition

et al. 2019

View full text Add to dashboard Cite

In the development of catalytic materials, a set of standard conditions is needed where the kinetic performance of many samples can be compared. This can be challenging when a sample set covers a broad range of activity. Precise kinetic characterization requires uniformity in the gas and catalyst bed composition. This limits the range of convecting devices to low conversion (generally <20%). While steady-state kinetics offer a snapshot of conversion, yield and apparent rates of the slow reaction steps, transient techniques offer much greater detail of rate processes and hence more information as to why certain catalyst compositions offer better performance. In this work, transient experiments in two transport regimes are compared: an advecting differential plug flow reactor (PFR) and a pure-diffusion temporal analysis of products (TAP) reactor. The decomposition of ammonia was used as a model reaction to test three simple materials: polycrystalline iron, cobalt and a bimetallic preparation of the two. These materials presented a wide range of activity and it was not possible to capture transient information in the advecting device for all samples at the same conditions while ensuring uniformity. We push the boundary for the theoretical estimates of uniformity in the TAP device and find reliable kinetic measurement up to 90% conversion. However, what is more advantageous from this technique is the ability to observe the time-dependence of the reaction rate rather than just singular points of conversion and yield. For example, on the iron sample we observed reversible adsorption of ammonia and on cobalt materials we identify two routes for hydrogen production. From the time-dependence of reactants and product, the dynamic accumulation was calculated. This was used to understand the atomic distribution of H and N species regulated by the surface of different materials. When ammonia was pulsed at 550 °C, the surface hydrogen/nitrogen, (H/N), ratios that evolved for Fe, CoFe and Co were 2.4, 0.25 and 0.3 respectively. This indicates that iron will store a mixture of hydrogenated species while materials with cobalt will predominantly store NH and N. While much is already known about iron, cobalt and ammonia decomposition, the goal of this work was to demonstrate new tools for comparing materials over a wider window of conversion and with much greater kinetic detail. As such, this provides an approach for detailed kinetic discrimination of more complex industrial samples beyond conversion and yield.

show abstract

“…7c). In turn, the interaction of La 2 O 3 with H 2 O leads to the formation of La(OH) 3 or LaO(OH) phases 16, 29 , which decompose to lanthanum oxide at approx. 330 o C, as indicated by the additional peak in the mass signal of water (Fig.…”

Section: Calcination Studiesmentioning

confidence: 99%

Cobalt-lanthanum catalyst precursors for ammonia synthesis: determination of calcination temperature and storage conditions

Zybert

Tarka

Mierzwa

et al. 2017

Polish Journal of Chemical Technology

View full text Add to dashboard Cite

A thermal decomposition of a cobalt-lanthanum catalyst precursor containing a mixture of cobalt and lanthanum compounds obtained by co-precipitation were studied using thermal analysis coupled with mass spectrometry (TG-MS). Studies revealed that the calcination in air at 500 o C is suffi cient to transform the obtained cobalt precipitate into Co 3 O 4 , but it leads to only partial decomposition of lanthanum precipitate. In order to obtain Co/La catalyst precursor containing La 2 O 3 the calcination in air at the temperature about 800 o C is required. However, it is unfavorable from the point of view of textural properties of the catalyst precursor. A strong effect of storage conditions on the phase composition of the studied cobalt-lanthanum catalyst precursor, caused by the formation of lanthanum hydroxide and lanthanum carbonates from La 2 O 3 when contacting with air, was observed.

show abstract

Ammonia synthesis with barium-promoted iron–cobalt alloys supported on carbon

Cited by 155 publications

References 25 publications

Silica accelerates the selective hydrogenation of CO2 to methanol on cobalt catalysts

Silica accelerates the selective hydrogenation of CO2 to methanol on cobalt catalysts

Transient Kinetic Experiments within the High Conversion Domain: The Case of Ammonia Decomposition

Cobalt-lanthanum catalyst precursors for ammonia synthesis: determination of calcination temperature and storage conditions

Contact Info

Product

Resources

About