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Methane rates

This approach was applied to data obtained by Hausberger, Atwood, and Knight (17). Figure 9 shows the basic temperature profile and feed gas data and the derived composition profiles. Application of the Hougen and Watson approach (16) and the method of least squares to the calculated profiles in Figure 9 gave the following methane rate equation ... [Pg.23]

It is concluded that a fully satisfactory system for calculating simultaneous reactions of CO and COo with H2 and H20 will require a schedule of the effect of CO on C02 methanation as a function of temperature. This effect will probably be different with different particle sizes. From a commercial standpoint, the particle size range may be too small to require much difference in the treatment of the data, but in the laboratory very small particle size may lower the CO methanation rate. A simple kinetics system such as that derived from Equation 3 may be satisfactory for all the reactions. It is unlikely that reliable data will be collected soon for the shift reaction (since it is of a somewhat secondary nature and difficult to study by itself), and therefore a more complicated treatment is not justified. [Pg.78]

It is expected that the actual rate of CO methanation will always be high, at least under industrial conditions, whereas the C02 methanation rate will vary from about the same as that for CO down to zero, depending on operating pressure, temperature, CO content of the gas, and catalyst particle size. Meanwhile a water-gas shift (or reverse shift) reaction will be occurring at all times at a fairly high rate. [Pg.78]

Figure 2.43. Methanation rate, rCH4 as a function of S or P coverage on a Ni(100) catalyst at 120 Torr. pH2 /pco=4 and reaction temperature 600 K.132,136 Reprinted with permission from Elsevier Science. Figure 2.43. Methanation rate, rCH4 as a function of S or P coverage on a Ni(100) catalyst at 120 Torr. pH2 /pco=4 and reaction temperature 600 K.132,136 Reprinted with permission from Elsevier Science.
Figure 10.2 Methanation rate as a function of phosphorus and sulfur coverage on a Ni(100) catalyst. Pressure = 120 torr, H2/CO = 4. Reaction temperature = 600 K. (From Goodman, D.W., Appl. Surf. Sci. 19, 1-13, 1984. Used with permission from Elsevier Scientific Publishers.)... Figure 10.2 Methanation rate as a function of phosphorus and sulfur coverage on a Ni(100) catalyst. Pressure = 120 torr, H2/CO = 4. Reaction temperature = 600 K. (From Goodman, D.W., Appl. Surf. Sci. 19, 1-13, 1984. Used with permission from Elsevier Scientific Publishers.)...
A second set of experiments further supported the surface carbon route to methane. In these experiments a Ni(lOO) surface was precarbided by exposure to CO and then treated with hydrogen in the reaction chamber for various times. Steps (3) and (4) above were then followed to measure the carbide level This study showed that the rate of carbon removal in hydrogen compared favorably to the carbide formation rate in CO and to the overall methanation rate in H2/CO mixtures. Thus in a H2-CO atmosphere the reaction rate is determined by a delicate balance of the carbon formation and removal steps and neither of these is rate determining in the usual sense. [Pg.160]

Kinetic measurements over a Ni(lOO) catalyst containing well-controlled submonolayer quantities of potassium show a general decrease in the steady-state methanation rate with little apparent change in the activation energy associated with the kinetics (Fig. 22). However, the potassium did change the steady-state coverage of active carbon on the catalyst. This carbon level changed from 10% of a monolayer on the clean catalyst to 30% on the potassium covered catalyst. [Pg.190]

Bogner, J. E., and K. A. Spokas, Landfill Methane Rates, Fates, and Role in Global Carbon Cycle, Chemosphere, 26, 1-4 (1993). [Pg.830]

The Rh(lll) surface was covered with carbon by decomposing 5 x 10 7 torr of either acetylene or ethylene at 1100 K for 10 minutes and subsequent flashing to 1200 K (230. Pre-adsorbed carbon had a very strong inhibiting effect on carbon monoxide chemisorption. This is the same effect it had on the methanation rate (36). The low inelastic scattering intensity indicated relatively small CO coverages while the broad elastic peak and... [Pg.173]

An energy balance around the fumace/boiler unit, where heat is transferred from the combustion gases to the steam, allows calculation of the entering methane rate lien, ... [Pg.524]

Fig. 5.2. Methanation rate as a function of the In pea Left 519 K, three H2 pressures, as indicated. Fig. 5.2. Methanation rate as a function of the In pea Left 519 K, three H2 pressures, as indicated.
Lanthanides as modifiers to other oxides in aluminas In zirconias In iron oxide Lanthanide oxides in mixed oxides With aluminas With iron oxides With other transition metal oxides To maintain surface area To increase oxidation rates To increase methanation rates For conduction in electrocatalysis For ammonia synthesis promotion To provide sulfur oxides (SO.,) control For dehydrogenation in carbon monoxide reactions For oxidation... [Pg.904]

Fig. 5 Methanation rate on TiOx/Rh foil as a function of TiOx coverage. Reaction conditions were 553 K, 1 atm total pressure, and a H2 CO ratio of 2 1 (12). The indicated TiOx coverages should be multiplied by a factor of 3.3 to account for the corrections recently reported by Williams et al. (9). Fig. 5 Methanation rate on TiOx/Rh foil as a function of TiOx coverage. Reaction conditions were 553 K, 1 atm total pressure, and a H2 CO ratio of 2 1 (12). The indicated TiOx coverages should be multiplied by a factor of 3.3 to account for the corrections recently reported by Williams et al. (9).
The enhancement in CO hydrogenation activity of Rh is ascribed to the presence of Ti + sites at the perimeter of TiOx islands. It is proposed that these sites interact with the oxygen in CO chemisorbed on nearby Rh atoms and assist in the disociation of CO. Since the disociation of CO is believed to be the rate-limiting step in this reaction, the participation of Ti + in this step leads to a higher activity. The dependence of the methanation rate on TiOx coverage, seen in Fig. 5, is attributable to the variation in the concentration of Ti + centers with TiOx coverage. [Pg.193]

The first two conversions are limited by reducing the CO2 content in the synthesis gas employed, and also, and above ail, by limiting the reaction temperature to 400 C. Below this temperature, the methanation rate remains low, or even negligible, on the catalysts employed. [Pg.88]

We now investigate the dependence of the methanation rate rcn defined in Equation (1), on AEg. In Figure 2, the dependence of rcn on X is illusfrafed schematically. A volcano-t)q)e dependence on X is found. The maximum of the Sabatier volcano curve is located at... [Pg.140]

FIGURE 2 Schematic representation of normalized methanation rate rcH, as a function of X. The Sabatier maximum in the volcano curve results from the competition between the increase in rate of Cf hydrogenation and the decrease of 6 when X increases. Adapted from Ref (53). [Pg.140]

Fig. 5.2. Methanation rate as a function of the In pco- 519 K, three H2 pressures, as indicated. Right T, as indicated, PH2 =100 Torr. (From van Meerten et al. [21]). Fig. 5.2. Methanation rate as a function of the In pco- 519 K, three H2 pressures, as indicated. Right T, as indicated, PH2 =100 Torr. (From van Meerten et al. [21]).
The power of AES to identify the true nature of the surface of a working catalyst has been demonstrated by Dwyer and Somorjai." They used an apparatus in which the polycrystalline foil could be used as a catalyst for CO/H2 and CO2/H2 reactions at 6 atmospheres pressure. Clean iron at 300 °C gave CH4, 85%, and other C2 to C5 hydrocarbons in small amounts. It rapidly became covered with 1 monolayer of C with a reduction in rate. When multilayers of C had formed, methane alone was produced by H2/CO, but at a further-diminished rate. The H2/CO2 reaction on initially clean Fe produced 97% methane and a marked increase in methanation rate. Both C and O accumulated on the surface during this reaction. The authors point out that in the case of the H2/CO reaction the monolayer carbon may not be the active catalyst. There is one piece of evidence in their work which points to Fe, perhaps in clusters, being the active site. They studied the CO/H2 reaction on pre-oxidized Fe and... [Pg.29]

The importance of oxygen is also seen in the next paper on methanation over Co and Ni foils. Palmer and Vroom" used AES to monitor surface cleanliness and a line-of-sight mass spectrometer to study products. Pre-treatment with O2 followed by H2 reduction produced a very active Ni or Co surface believed to result from subsurface O. These authors also invoke the breakdown of CO via the Boudouard reaction, 2CO(g)->C(s) + CO 2(g), to explain their results in that the methanation rate in the presence of H2 matches the rate of disproportionation of CO. [Pg.30]

Chemisorption suppression via a simple site blocking mechanism is not consistent with enhanced methanation rates observed for Pt/Ti02 catalysts in the SMSI state.(2-5) A simple loss of CO adsorption sites without a substantial change in the adsorption energy should result in a decrease in catalytic activity. It is likely then that... [Pg.26]

The fact that E-states are not observed on the titania-containing surface does not necessarily suggest a weaker interaction between H-adatoms and adsorbed CO at reaction conditions. Indeed, the catalytic importance of the low-temperature E-states has not been demonstrated, since there is no detectable difference in the methanation rate for Ni(lll), Ni(100), and polycrystalline Ni (1 6, 1 7), surfaces which exhibit markedly different coadsorption behavior with respect to the E-states. [Pg.42]


See other pages where Methane rates is mentioned: [Pg.21]    [Pg.82]    [Pg.129]    [Pg.131]    [Pg.157]    [Pg.160]    [Pg.160]    [Pg.161]    [Pg.185]    [Pg.187]    [Pg.93]    [Pg.173]    [Pg.209]    [Pg.318]    [Pg.194]    [Pg.621]    [Pg.21]    [Pg.22]    [Pg.28]    [Pg.30]    [Pg.44]    [Pg.45]    [Pg.48]   
See also in sourсe #XX -- [ Pg.13 , Pg.21 ]




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