603
4.1 Reaction Mechanism for Steam Reforming
of Glycerol (SRG)
The overall glycerol steam reforming process is endothermic in nature. The process
is mainly a combination of glycerol decomposition and water-gas shift reaction [94]:
C 3 H 8 O 3 + 3H 2 O ↔ 3CO 2 + 7H 2 (ΔH = +123 kJ/mol).
C 3 H 8 O 3 ↔ 3CO + 4H 2 (ΔH = +245 kJ/mol).
CO + H 2 O ↔ CO 2 + H 2 (ΔH = −41 kJ/mol).
Additionally, other side reactions also occur based on catalyst activity and reaction operating conditions. Methane is formed from CO, CO 2 and H 2 by two exothermic reactions:
CO + 3H 2 ↔ CH 4 + H 2 O (ΔH = −206 kJ/mol).
CO 2 + 4H 2 ↔ CH 4 + 2H 2 O (ΔH = −165 kJ/mol).
A key function of steam reforming catalysts is the cleavage of C–C and O–H
bonds in the oxygenated hydrocarbon reactant leading to H 2 and CO and facilitate
the water-gas shift reaction to convert CO to CO 2 , as opposed to cleavage of C–O
bonds leading to alkanes [96].
4.2 SRG with Different Mesoporous Supported Catalysts
4.2.1 Comparison of Different Mesoporous Supported Catalysts Based
on Catalyst Characterization
Table 5 shows the N 2 adsorption-desorption analysis results of different mesoporous
supported catalysts.
4.2.2 Comparison of Different Mesoporous Supported Catalysts Activity
Glycerol, the by-product of the biodiesel industry, has received wide attention
because it contains high H 2 compared to methanol and ethanol [101]. Theoretically,
seven moles of H 2 can be produced from glycerol steam reforming reaction [99].
Table 6 shows the different mesoporous supported catalysts activity for glycerol
steam reforming reaction.
SRG reaction was carried out with two directly synthesized catalysts
(1Ni-2Al 2 O 3 -2ZrO 2 and 1Ni-2SiO 2 -2ZrO 2 ) and one impregnated catalyst (Ni/
SBA-16) at 600 °C by Lee and Lee [102]. They mainly found H 2 , CO and CO 2 and
very less amount of CH 4 as products in the SRG reaction. All the catalysts showed
good catalytic activity at that temperature. However, in comparison to catalyst activity, directly synthesized catalyst was superior to the impregnated catalyst. They
reported that enhanced Ni dispersion was the key factor to give better activity of
1Ni-2Al 2 O 3 -2ZrO 2 and 1Ni-2SiO 2 -2ZrO 2 catalysts. Calles et al. [97] investigated a
Steam Reforming of Methanol, Ethanol and Glycerol over Catalysts with Mesoporous…
4.1 Reaction Mechanism for Steam Reforming
of Glycerol (SRG)
The overall glycerol steam reforming process is endothermic in nature. The process
is mainly a combination of glycerol decomposition and water-gas shift reaction [94]:
C 3 H 8 O 3 + 3H 2 O ↔ 3CO 2 + 7H 2 (ΔH = +123 kJ/mol).
C 3 H 8 O 3 ↔ 3CO + 4H 2 (ΔH = +245 kJ/mol).
CO + H 2 O ↔ CO 2 + H 2 (ΔH = −41 kJ/mol).
Additionally, other side reactions also occur based on catalyst activity and reaction operating conditions. Methane is formed from CO, CO 2 and H 2 by two exothermic reactions:
CO + 3H 2 ↔ CH 4 + H 2 O (ΔH = −206 kJ/mol).
CO 2 + 4H 2 ↔ CH 4 + 2H 2 O (ΔH = −165 kJ/mol).
A key function of steam reforming catalysts is the cleavage of C–C and O–H
bonds in the oxygenated hydrocarbon reactant leading to H 2 and CO and facilitate
the water-gas shift reaction to convert CO to CO 2 , as opposed to cleavage of C–O
bonds leading to alkanes [96].
4.2 SRG with Different Mesoporous Supported Catalysts
4.2.1 Comparison of Different Mesoporous Supported Catalysts Based
on Catalyst Characterization
Table 5 shows the N 2 adsorption-desorption analysis results of different mesoporous
supported catalysts.
4.2.2 Comparison of Different Mesoporous Supported Catalysts Activity
Glycerol, the by-product of the biodiesel industry, has received wide attention
because it contains high H 2 compared to methanol and ethanol [101]. Theoretically,
seven moles of H 2 can be produced from glycerol steam reforming reaction [99].
Table 6 shows the different mesoporous supported catalysts activity for glycerol
steam reforming reaction.
SRG reaction was carried out with two directly synthesized catalysts
(1Ni-2Al 2 O 3 -2ZrO 2 and 1Ni-2SiO 2 -2ZrO 2 ) and one impregnated catalyst (Ni/
SBA-16) at 600 °C by Lee and Lee [102]. They mainly found H 2 , CO and CO 2 and
very less amount of CH 4 as products in the SRG reaction. All the catalysts showed
good catalytic activity at that temperature. However, in comparison to catalyst activity, directly synthesized catalyst was superior to the impregnated catalyst. They
reported that enhanced Ni dispersion was the key factor to give better activity of
1Ni-2Al 2 O 3 -2ZrO 2 and 1Ni-2SiO 2 -2ZrO 2 catalysts. Calles et al. [97] investigated a
Steam Reforming of Methanol, Ethanol and Glycerol over Catalysts with Mesoporous…