593
deactivation due to thermal sintering [35] and have triggered the search for other
catalysts. Group 8–10 catalysts have been reported by different groups to be promising with similar activity and high selectivity as observed with copper catalysts [36–
38]. In the case of ethanol steam reforming (SRE) and glycerol steam reforming
(SRG), many noble metals (e.g. Pd, Ru, Rh and Pt) and non-noble metals (e.g. Ni
and Co) have been investigated [39–49]. In order to minimize catalyst deactivation
rates via sintering, catalyst supports like SiO 2 , γ-Al 2 O 3 , ZrO 2 , CeO 2 , TiO 2 , MgO and
La 2 O 3 have been used to immobilize the metal active sites in the steam reforming
reactions [50–54].
Mesostructured supports with pore sizes of 2–50 nm have been extensively studied and employed for drug delivery, sensors, adsorbents, molecular sieves and heterogeneous catalysis. Generally, silica-based mesoporous frameworks (e.g.
MCM-41, MCM-48, SBA-15, KIT-6, FSM-16, zeolites) are more thermally stable
than the nonsiliceous metal oxides (e.g. TiO 2 , Al 2 O 3 , CeO 2 ) and mesoporous carbon.
Mesostructures are synthesized via either exotemplating in which the mesoporous
material is prepared within the channels of a porous supramolecular template or
endotemplating where by inorganic compounds are tethered on a template already
coated on a well-ordered porous material [55]. Compared to homogeneous catalysts, supported heterogeneous catalysts are usually less reactive, are more expensive to synthesize, requires large amounts to be used and have regeneration cost due
to occasional blocking of catalyst active sites. However, supported heterogeneous
catalysts are more widely preferred within the green energy research community
and green energy production industry because:
1. They are environmentally friendly and safe to handle as the active sites (e.g.
acids and bases) are anchored to the supports unlike aqueous phase homogeneous acids/bases that could be very corrosive and hazardous.
2. They can be easily separated from reaction medium, can be reactivated and are
reusable.
3. They have high selectivity for desired products due to the ability of tailored pore
structure and shapes to control the chemistry and molecular diffusion of reactants and products.
4. Their large surface areas provide strong adsorption sites for the metal catalysts,
thereby retarding or inhibiting sintering during reactions [56, 57].
This chapter provides an in-depth outlook of different mesoporous supported
catalysts and their activities for methanol, ethanol and glycerol steam reforming
reactions.
2 Steam Reforming of Methanol (SRM)
Methanol has the highest carbon-to-hydrogen ratio compared to all hydrocarbons
[25]. It is easy to perform methanol steam reforming studies compared to methane
due to the presence of –OH group. It can be used for on-board fuel cell applications
Steam Reforming of Methanol, Ethanol and Glycerol over Catalysts with Mesoporous…
deactivation due to thermal sintering [35] and have triggered the search for other
catalysts. Group 8–10 catalysts have been reported by different groups to be promising with similar activity and high selectivity as observed with copper catalysts [36–
38]. In the case of ethanol steam reforming (SRE) and glycerol steam reforming
(SRG), many noble metals (e.g. Pd, Ru, Rh and Pt) and non-noble metals (e.g. Ni
and Co) have been investigated [39–49]. In order to minimize catalyst deactivation
rates via sintering, catalyst supports like SiO 2 , γ-Al 2 O 3 , ZrO 2 , CeO 2 , TiO 2 , MgO and
La 2 O 3 have been used to immobilize the metal active sites in the steam reforming
reactions [50–54].
Mesostructured supports with pore sizes of 2–50 nm have been extensively studied and employed for drug delivery, sensors, adsorbents, molecular sieves and heterogeneous catalysis. Generally, silica-based mesoporous frameworks (e.g.
MCM-41, MCM-48, SBA-15, KIT-6, FSM-16, zeolites) are more thermally stable
than the nonsiliceous metal oxides (e.g. TiO 2 , Al 2 O 3 , CeO 2 ) and mesoporous carbon.
Mesostructures are synthesized via either exotemplating in which the mesoporous
material is prepared within the channels of a porous supramolecular template or
endotemplating where by inorganic compounds are tethered on a template already
coated on a well-ordered porous material [55]. Compared to homogeneous catalysts, supported heterogeneous catalysts are usually less reactive, are more expensive to synthesize, requires large amounts to be used and have regeneration cost due
to occasional blocking of catalyst active sites. However, supported heterogeneous
catalysts are more widely preferred within the green energy research community
and green energy production industry because:
1. They are environmentally friendly and safe to handle as the active sites (e.g.
acids and bases) are anchored to the supports unlike aqueous phase homogeneous acids/bases that could be very corrosive and hazardous.
2. They can be easily separated from reaction medium, can be reactivated and are
reusable.
3. They have high selectivity for desired products due to the ability of tailored pore
structure and shapes to control the chemistry and molecular diffusion of reactants and products.
4. Their large surface areas provide strong adsorption sites for the metal catalysts,
thereby retarding or inhibiting sintering during reactions [56, 57].
This chapter provides an in-depth outlook of different mesoporous supported
catalysts and their activities for methanol, ethanol and glycerol steam reforming
reactions.
2 Steam Reforming of Methanol (SRM)
Methanol has the highest carbon-to-hydrogen ratio compared to all hydrocarbons
[25]. It is easy to perform methanol steam reforming studies compared to methane
due to the presence of –OH group. It can be used for on-board fuel cell applications
Steam Reforming of Methanol, Ethanol and Glycerol over Catalysts with Mesoporous…