Multiple isotope tracing of methanation over nickel catalyst II. Deuteromethanes tracing

Happel, John; Cheh, H. Y.; Otarod, Masood; Ozawa, Sentaro; Severdia, A.J.; Yoshida, Takashi; FTHENAKIS, V.

doi:10.1016/0021-9517(82)90214-7

Cited by 73 publications

(8 citation statements)

References 8 publications

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“…35 Winslow and Bell showed the existence of two different carbon species, one being a reactive surface intermediate and the other one involved in deactivation. These two pools of carbidic carbon have also been observed by others such as Happel et al for nickel 15 and van Dijk et al for cobalt 36 albeit that, different from the work of Winslow and Bell, all of the species could be hydrogenated to methane. Van Dijk et al reported that C hydrogenation is the slow step in the mechanism of CO hydrogenation to methane by supported cobalt.…”

Section: Introductionsupporting

confidence: 68%

“…Transient techniques involving isotopes were developed by Happel, 13−15 Bennett 16,17 and Biloen. 18−20 Steady-state isotopic transient kinetic analysis (SSITKA) allows extracting kinetic information under steady-state conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Detailed insight into reaction mechanism, specifically into the way particular elementary reaction steps control reaction rate and selectivity, can be obtained by transient experiments. Transient techniques involving isotopes were developed by Happel, − Bennett , and Biloen. − Steady-state isotopic transient kinetic analysis (SSITKA) allows extracting kinetic information under steady-state conditions. The unique feature of SSITKA is that the chemical composition of the surface is not changed by the abrupt replacement of one reactant by its isotope .…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of Cobalt-Catalyzed CO Hydrogenation: 1. Methanation

et al. 2017

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The mechanism of CO hydrogenation to CH4 at 260 °C on a cobalt catalyst is investigated using steady-state isotopic transient kinetic analysis (SSITKA) and backward and forward chemical transient kinetic analysis (CTKA). The dependence of CHx residence time is determined by 12CO/H2 → 13CO/H2 SSITKA as a function of the CO and H2 partial pressure and shows that the CH4 formation rate is mainly controlled by CHx hydrogenation rather than CO dissociation. Backward CO/H2 → H2 CTKA emphasizes the importance of H coverage on the slow CHx hydrogenation step. The H coverage strongly depends on the CO coverage, which is directly related to CO partial pressure. Combining SSITKA and backward CTKA allows determining that the amount of additional CH4 obtained during CTKA is nearly equal to the amount of CO adsorbed to the cobalt surface. Thus, under the given conditions overall barrier for CO hydrogenation to CH4 under methanation condition is lower than the CO adsorption energy. Forward CTKA measurements reveal that O hydrogenation to H2O is also a relatively slow step compared to CO dissociation. The combined transient kinetic data are used to fit an explicit microkinetic model for the methanation reaction. The mechanism involving direct CO dissociation represents the data better than a mechanism in which H-assisted CO dissociation is assumed. Microkinetics simulations based on the fitted parameters confirms that under methanation conditions the overall CO consumption rate is mainly controlled by C hydrogenation and to a smaller degree by O hydrogenation and CO dissociation. These simulations are also used to explore the influence of CO and H2 partial pressure on possible rate-controlling steps.

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Section: Introductionsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanism of Cobalt-Catalyzed CO Hydrogenation: 1. Methanation

et al. 2017

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“…Tables 1 and 2 From these two tables, we are left with four parameter sets for further consideration. In an earlier work with deuterium tracing (Happel et al, 1982), it was shown that the combined CH, species were present at a higher concentration than that of the active carbon. On these grounds, it seems reasonable to rule out parameter set 1 in both Tables 1 and 2.…”

Section: Examplementioning

confidence: 95%

Identifiability and distinguishability of fundamental parameters in catalytic methanation

et al. 1986

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Methods are presented to determine structural identifiability and distinguishability of parametric models. Results are applied to transient isotope tracing of methanation over a nickel catalyst. More meaningful information is obtained in this way about fundamental parameters than is possible by empirical curve-fitting. SCOPEA large proportion of industrial reactions involves heterogeneous catalysis systems. In the study of such systems kinetic equations are often developed by means of the so-called Langmuir-Hinshelwood-HougenWatson (LHHW) method. This method assumes that the Langmuir theory of adsorption and the law of mass action apply to the individual steps of a reaction mechanism, that a single rate-controlling step exists with the other steps at equilibrium. Such assumptions have led to reservations in acceptance of the intrinsic significance of the parameters obtained and in the applicability of the equations developed to a wider range of process conditions.With transient isotope tracing, the parameters to be directly estimated are the concentrations of intermediates and the rates of elementary steps. These parameters may be functions of the temperature and gas phase composition. However, the exact functional relationships required to estimate them from overall kinetic data are generally not well established. Since these concentrations and rates are estimated in the present treatment without relying on the above mentioned assumptions (needed by the LHHW method), we propose to call them fundamental parameters.The technique employed is similar to compartmental modeling, which has often been employed in the biosciences. Each of the terminal species and chemisorbed intermediates is assumed to occupy a wellmixed compartment and the transfer of isotope is described by material balances on each compartment. The parameters to be obtained appear as constants in a set of first-order differential equations and can be estimated using readily available computer routines.In order to establish the extent to which parameters obtained are unique, it is necessary to consider problems of identifiability and distinguishability. This paper discusses how this can be accomplished with special reference to experimental studies in which transfer of 13C was used to study the kinetics of catalytic methanation of mixtures of carbon monoxide and hydrogen (synthesis gas). CONCLUSIONS AND SIGN IF I CANCE AIChE Journalequally well correlate given experimental data. For a suitable model we show how such a set can be used to generate all other possible sets consistent with the given model structure. These parameters can then be examined from the . standpoint of other information available on the basis of physical or theoretical knowledge of the system. If ambiguity still exists, it may be possible to alter the nature of tracer input or the tracer species employed to eliminate it.In practical systems there may exist more than a single plausible model. It is shown how such additional models can be studied structurally to determine whether th...

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“…Isotope tracer technique has been used to determine the mass transport in bioreactors 13 – 15 . This approach can also investigate cell metabolism by analyzing isotopomer of both proteinogenic amino acids and fast turnover free metabolites 16 .…”

Section: Introductionmentioning

confidence: 99%

Deciphering Clostridium metabolism and its responses to bioreactor mass transfer during syngas fermentation

Wan

Sathish

You

et al. 2017

Sci Rep

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This study used 13C tracers and dynamic labeling to reveal metabolic features (nutrients requirements, pathway delineation and metabolite turnover rates) of Clostridium carboxidivorans P7, a model strain for industrial syngas fermentation, and its implication with bioreactor mass transfer. P7 shows poor activity for synthesizing amino acids (e.g., phenylalanine) and thus, needs rich medium for cell growth. The strain has multiple carbon fixation routes (Wood-Ljungdahl pathway, pyruvate:ferredoxin oxidoreductase reaction and anaplerotic pathways) and Re-citrate synthase (Ccar_06155) was a key enzyme in its tricarboxylic acid cycle (TCA) pathway. High fluxes were observed in P7’s Wood-Ljungdahl pathway, right branch of TCA cycle, pyruvate synthesis, and sugar phosphate pathways, but the cells anabolic pathways were strikingly slow. In bioreactor culture, when syngas flowrate increased from 1 to 10 mL/min, P7 strain produced same amount of total extracellular products (acids and alcohols) but high flowrate favored alcohol accumulation. This observation was due to the mass transfer limitation influencing energy metabolism (CO/H2 oxidation for cofactor generations) more prominently than carbon fixation. When syngas flowrate increased from 10 of 20 mL/min, the alcohol productivity was not improved and the labeling rate (~0.03 h−1) of key metabolite acetyl-CoA reached to P7 strain’s metabolism limitation regime.

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Multiple isotope tracing of methanation over nickel catalyst II. Deuteromethanes tracing

Cited by 73 publications

References 8 publications

Mechanism of Cobalt-Catalyzed CO Hydrogenation: 1. Methanation

Mechanism of Cobalt-Catalyzed CO Hydrogenation: 1. Methanation

Identifiability and distinguishability of fundamental parameters in catalytic methanation

Deciphering Clostridium metabolism and its responses to bioreactor mass transfer during syngas fermentation

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