423
Zn, Fe) and oxide support (Al 2 O 3 , 12% CeO 2 -Al 2 O 3 , CeO 2 , CeO 2 -ZrO 2 , ZrO 2 ) combinations and found Rh, Ni giving the best performance with CeO 2 -ZrO 2 support for
ethanol steam reforming. They also reported that the degree of mobility of surface
OH-groups with ceria-based supports directly affects the steam reforming activity.
Noble metal–based catalysts are believed to be stable catalysts as they are recognized for breaking the C–C bond which results in less carbonaceous deposits. The
activity of noble metal catalysts to get a reduction in the C–C bond is of the following order Rh > Co > Ni > Pd [33]. In various oxides supported metal catalysts studied in the literature, Breen et al. [36] proposed that Al 2 O 3 -supported catalysts
promote dehydration of ethanol to ethylene while for CeO 2 /ZrO 2 -supported catalysts no formation of ethylene was observed. Also the combination of CeO 2 /ZrO 2 -
supported catalysts with alumina will inhibit ethylene, thereby coking in high
temperatures. Ru-catalyzed ethanol steam reforming studied in the range of
600–850 °C and found that 5% Ru was comparable to the performance of rhodium
with a marked increase in conversion and selectivity to H 2 . For low-temperature
steam reforming (300–450 °C) Panagiotopoulou et al. [37] found that catalytic performance for better selectivity to H 2 is varied in the order of Pt > Pd > Rh > Ru. The
effect of CeO 2 , ZrO 2 , and Al 2 O 3 support conducted on Pt catalyst in the range of
350–450 °C showed the highest performance of Pt/ZrO 2 followed by Pt/Al 2 O 3 and
lastly Pt/CeO 2 for better selectivity to H 2 . Compared with other literature it was also
reported that WGS reaction for Pt-supported catalysts occurs with high rates at temperatures above 350 °C. Apart from this, the selectivity of acetaldehyde at 320 °C
was reported to decrease in the order ZrO 2 > CeO 2 > Al 2 O 3 , while the selectivity of
CO was affected in the manner CeO 2 > Al 2 O 3 > ZrO 2 . This unexpected behavior
compared to alumina was attributed by low specific surface area which thereby
affects reducibility and hence WGS activity [37]. Most of these catalysts tested for
ethanol steam reforming are high-temperature catalysts. These catalysts reported
low hydrogen yield at a temperature of less than 350 °C. This makes the integration
of these catalysts with membrane followed by PEMFC (which operates at around
60–100 °C) very challenging. Further, the CO selectivity is also high at the higher
temperature. Hence, a low-temperature catalyst is needed.
The transition metal (member of the group 8–10) is used as a catalyst for methanol steam reforming. These metals have multiple oxidation states and can provide a
lower activation energy path which makes them attractive and enhances their catalytic active. Similar to ethanol reforming, noble metal catalysts show adequate
reforming activity for methanol too for a wide temperature range. However, their
high cost limits their use particularly for large-scale implementation. Pd and Ru are
considered as active catalysts amongst the noble metal for the methanol steam
reforming. However, both show high CO selectivity [38, 39] due to the increased
methanol decomposition which is not suitable for membrane reformer application
[39]. Cu, Ni, Au, Fe are also used as a non-precious metal catalyst for methanol
steam reforming. Among them, copper is a highly abundant low-cost metal which is
used for both methanol synthesis and methanol steam reforming. It is mainly preferred because of its high activity at a lower temperature. Further, it can catalyze
both oxidation-reduction reactions and shows high hydrogen selectivity. The
Steam Reforming Catalysts for Membrane Reformer
Zn, Fe) and oxide support (Al 2 O 3 , 12% CeO 2 -Al 2 O 3 , CeO 2 , CeO 2 -ZrO 2 , ZrO 2 ) combinations and found Rh, Ni giving the best performance with CeO 2 -ZrO 2 support for
ethanol steam reforming. They also reported that the degree of mobility of surface
OH-groups with ceria-based supports directly affects the steam reforming activity.
Noble metal–based catalysts are believed to be stable catalysts as they are recognized for breaking the C–C bond which results in less carbonaceous deposits. The
activity of noble metal catalysts to get a reduction in the C–C bond is of the following order Rh > Co > Ni > Pd [33]. In various oxides supported metal catalysts studied in the literature, Breen et al. [36] proposed that Al 2 O 3 -supported catalysts
promote dehydration of ethanol to ethylene while for CeO 2 /ZrO 2 -supported catalysts no formation of ethylene was observed. Also the combination of CeO 2 /ZrO 2 -
supported catalysts with alumina will inhibit ethylene, thereby coking in high
temperatures. Ru-catalyzed ethanol steam reforming studied in the range of
600–850 °C and found that 5% Ru was comparable to the performance of rhodium
with a marked increase in conversion and selectivity to H 2 . For low-temperature
steam reforming (300–450 °C) Panagiotopoulou et al. [37] found that catalytic performance for better selectivity to H 2 is varied in the order of Pt > Pd > Rh > Ru. The
effect of CeO 2 , ZrO 2 , and Al 2 O 3 support conducted on Pt catalyst in the range of
350–450 °C showed the highest performance of Pt/ZrO 2 followed by Pt/Al 2 O 3 and
lastly Pt/CeO 2 for better selectivity to H 2 . Compared with other literature it was also
reported that WGS reaction for Pt-supported catalysts occurs with high rates at temperatures above 350 °C. Apart from this, the selectivity of acetaldehyde at 320 °C
was reported to decrease in the order ZrO 2 > CeO 2 > Al 2 O 3 , while the selectivity of
CO was affected in the manner CeO 2 > Al 2 O 3 > ZrO 2 . This unexpected behavior
compared to alumina was attributed by low specific surface area which thereby
affects reducibility and hence WGS activity [37]. Most of these catalysts tested for
ethanol steam reforming are high-temperature catalysts. These catalysts reported
low hydrogen yield at a temperature of less than 350 °C. This makes the integration
of these catalysts with membrane followed by PEMFC (which operates at around
60–100 °C) very challenging. Further, the CO selectivity is also high at the higher
temperature. Hence, a low-temperature catalyst is needed.
The transition metal (member of the group 8–10) is used as a catalyst for methanol steam reforming. These metals have multiple oxidation states and can provide a
lower activation energy path which makes them attractive and enhances their catalytic active. Similar to ethanol reforming, noble metal catalysts show adequate
reforming activity for methanol too for a wide temperature range. However, their
high cost limits their use particularly for large-scale implementation. Pd and Ru are
considered as active catalysts amongst the noble metal for the methanol steam
reforming. However, both show high CO selectivity [38, 39] due to the increased
methanol decomposition which is not suitable for membrane reformer application
[39]. Cu, Ni, Au, Fe are also used as a non-precious metal catalyst for methanol
steam reforming. Among them, copper is a highly abundant low-cost metal which is
used for both methanol synthesis and methanol steam reforming. It is mainly preferred because of its high activity at a lower temperature. Further, it can catalyze
both oxidation-reduction reactions and shows high hydrogen selectivity. The
Steam Reforming Catalysts for Membrane Reformer