Thesis - Oztek_Muzaffer_T_200508_MA

Table 6. Percent hydrogen values for pure H 2 in the Parr reactor.
Mole % Al P H2 , atm. Weight % H
0.74 7.65 0.89
1.35 7.70 0.72
3.38 7.34 0.72
The pressure profiles for the samples that were pressurized with 50% (v/v) H 2 :He
(Figure 34) indicated that the reactions were complete also in 10 minutes. The percent
hydrogen values are presented in Table 7. In the batch reactor, the rate of reaction was
not affected from the presence of He. This observation suggests that, at high enough H 2
pressures (7 atm in 50:50 H 2 :He mixture), the surface occupation of LaNi 5 Al x by He was
not significant, compared to low H 2 pressures (5 atm). It could also be possible that the
interaction of the LaNi 5 Al x with hydrogen in the presence of helium was dependent on
the scale of the system. The volume of the Parr reactor was 2000 mL, as opposed to the
15.37 mL of volume of the DSC cell. Also, in the Parr reactor, the sample amount was
higher. Only the top layer was exposed to the He; therefore, the surface interaction of He
was limited, and a reduction in reaction rate was not observed.
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