Methane, exchange with deuterium

Figure 6.2. Compensation plots of Arrhenius parameters for methane exchange with deuterium O stepwise exchange multiple exchange A total exchange based on reactant removal (see Table 6.1). (A) Ru-Pd powders(B)Rh-Pd powders(C) Pd-Au powders (D) films (open, ref. 2 shaded, ref. 7) and blacks (half-filled) of single metals. Identical lines are used in each part 7 = 461K points for palladium are filled.

A. Frennet, Chemisorption and exchange with deuterium of methane on metals, Catal. Rev.- Sci. Eng., 10 ... 

Utiyama, M. Hattori, H. Tanabe, K. Exchange reaction of methane with deuterium over solid base catalysts. J. Catal. 1978, 53, 237-242. 

Fio. 20. Geometrical relationships for the simple exchange of methane with deuterium involving adjacent surface atoms each of which has available two octahedral bonding directions suitable for the reaction. 

The exchange of methane with deuterium has been followed on nickel films 12), on a cobalt-thoria Fischer-Tropsch catalyst 13) and on films of rhodium, platinum, palladium, and tungsten 30). The important features of the exchange over the metal films may be summarized as follows ... 

In most cases the slow step of the reaction is not simply the activation or chemisorption of hydrogen, but involves other chemisorbed species. Thus, the exchange of deuterium with methane and with other saturated hydrocarbons is much slower than with hydrogen and probably proceeds through dissociative adsorption of the hydrocarbon. 

The exchange reaction of methane with deuterium has been found to show a decrease in specific activity upon alloying of palladium with gold (82), reflecting the decrease in number of reactive surface metal atoms upon alloying. 

The exchange reactions of methane with deuterium over several metals (21, 39,146,147,195, 215, 216, 229) exhibited compensation behavior (Table III, G), as has been pointed out previously (3). No such relationship was found in the data available for exchange reactions of C2-C6 hydrocarbons. This is consistent with discussion given above (see Section III, B, 4) in which it was concluded that the differences in the kinetic behavior of the exchange reactions between methane and the other hydrocarbons varied with the individual metals concerned. 

Fig. 68. The dependence of the catalytic activity of metals on the heat of their sublimation, Ak, for isotopic exchange of deuterium (a) with hydrogen (b) with acetone (c) with methylamine (d) with methane (curve 1) and cyclohe.xane (curv-e 2) 477).

When D2O was substituted for H2O no deuterium was found in the unreacted methane analysed mass spectrometrically at 10% conversion of methane to carbon monoxide. No H-D exchange with hydrogens of methane has been observed in the CH4 -h H2O -h D2 system. In the case of nickel catalyst supported on y-alumina F containing 7.0% Ni) the kinetic dependences (log rate versus log Pch4 nd log Ph2o) e different. Some incorporation of deuterium into methane was found when the CH4 -h D2O reaction was carried out at 10 torr of CH4. The rate of the reaction Wfor low methane pressures (at constant hydrogen pressure) has been found to be... 

Activation studies for methane carried out by isotopic experiments may be considered the first indicator of catalytic activation for the exchange reaction. The reaction investigated was the exchange of methane with deuterium. 

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