R&D on Hydrogen Production by Autothermal Reforming

The gas obtained was analyzed using TCD or FID gas chromatogram; an oxygen combustion
type carbon analyzer was used to analyze the volume of carbon accumulated on catalyst after
the reaction.
3.3.2 Autothermal Reforming Reaction with Each Type of Catalyst
Figure 3.3.1 presents the results of a comparison of the dependency on reaction temperature of
autothermal reforming reaction activity with each type of catalyst. The catalysts can be arranged
in sequence as follows.
Catalyst B > Catalyst C > Catalyst A (standard) > Catalyst D > Catalyst E
At 750°C or above, a CO + CO2 selection rate of virtually 100% was exhibited with all the
catalysts.
The temperature distribution of each catalytic layer at this time is shown in Figure 3.3.2, with
600°C taken as sample reaction temperature. With all the catalysts, it was confirmed that the
temperature rises sharply near the inlet and declines as you go to the lower layers. Dissanayake
et al. 1) and Groote et al. 2) report that in autothermal reforming reaction with methane, a complete
oxidation reaction of methane takes place first, followed by water vapor reforming, CO2
reforming, and aqueous gas shift reaction. It is believed that in the latest results as well,
oxidation reaction advanced over the upper catalyst layer. When the catalysts are arranged in
order of highest temperature at the catalyst layer inlet, the following sequence obtains.
Catalyst E > Catalyst D > Catalyst C > Catalyst A (standard) > Catalyst B
This sequence manifests a trend virtually opposite that of the activity sequence. It shows that
when the catalyst inlet temperature is high (that is when the heat given off is great), the
complete oxidation reaction takes precedence over the reforming reaction (steam reforming
reaction or CO2 reforming reaction). In catalyst with low autothermal reforming activity, the
reforming reaction tends to advance less easily than the complete oxidation reaction.
Conversely, in catalyst with high autothermal reforming activity, the complete oxidation reaction
and reforming reaction both advance easily. The fact that the complete oxidation reaction and
reforming reaction take place at nearby locations on the catalyst suggests that the temperature
at catalyst inlet is kept relatively low. With catalyst A (standard) and catalyst C, however, this
trend is reversed, and the factors determining catalyst layer temperature distribution are not just
the catalyst’s complete oxidation activity or reforming activity. Such things as thermal
conductivity and filling density are also contributing factors.
In the development of autothermal reforming catalyst, it is not only high activity that is important
but also curtailment of carbon precipitation. Of the catalysts considered in Figure 3.3.1, ATR
catalyst A and ATR catalysts B and C, which manifest higher activity than ATR catalyst A, were
used in reactions that took place for 16 hrs at 600°C and the volumes of precipitated carbon
thereafter were compared as shown in
8