468
3.1 Efficient Catalyst Systems for Gas Phase Glycerol
Dehydration to Acrolein
Various types of catalyst systems have been widely reported for the glycerol dehydration reaction like heteropolyacids, zeolites, metal oxides and phosphate catalysts. The catalytic performance of some reported catalysts for the dehydration
reaction of glycerol to acrolein is summarized in Table 1. To catalyse dehydration of
glycerol to form acrolein, the use of heteropolyacids is a very good option. Among
widely used common HPA catalysts is the tungstophosphoric acid. Chai et al. used
zirconia-supported HPA catalysts for glycerol dehydration to acrolein [57, 59]. The
results obtained by them showed zirconia-supported HPA is more effective than
silica-supported HPA.
Katryniok et al. explored glycerol dehydration to acrolein over silicotungstic
acid supported on zirconia-grafted SBA-15 [74]. The interaction between the support and HPA was modified by the grafting. The synergy between the zirconia and
HPA eventually reduced the strength of Brønsted acidic site and thus increased catalyst stability. An acrolein yield of 69% could be seen after 24 h time on stream
study. Dubois et al. scrutinized metal-substituted silicotungstic (SiW) and phosphotungstic (PW) acid salts [75]. Among the various metals used for substitution are
calcium (Ca), rubidium (Rb), caesium (Cs), bismuth (Bi), zirconium (Zr), iron (Fe)
and lanthanum (La). The caesium-substituted Cs 2.5 H 1.5 SiW 12 O 40 catalyst exhibited
the highest acrolein yield of 93%. Another important aspect demonstrated by the
authors was the oxygen co-feed in the reaction which helped to increase the acrolein
yield. The study performed by Alhanash et al. which also included caesium salts of
PW acids achieved an acrolein yield of around 98%, but its longevity was small
[76]. Atia et al. [62] prepared an array of supported silicotungstic acid from selected
silica and aluminosilicate supports. Alkaline metals were used to adjust the Brønsted
acidic sites. It was found that the unmodified supported HSiW catalysts displayed
the highest activity which was the indication about the strong connection of activity
with acidity (Brønsted). Kim et al. [77] explored dehydration of glycerol to acrolein
with silicotungstic acid (HSiW) using various different metal oxides (SiO 2 , TiO 2 ,
ZrO 2 , γ-Al 2 O 3 , CeO 2 , MgO, etc.) as supports. The use of zirconia-supported HSiW
resulted in highest selectivity of 58.1% for acrolein. All the studies on heteropolyacids proved them as potential candidates for glycerol dehydration reactions. Fast
deactivation was one drawback of this catalyst.
Zeolites are also largely reported for glycerol dehydration reaction. Two wellacknowledged zeolite segment catalysts (β-zeolite and ZSM-5) were patented by
Dubois et al. for glycerol dehydration [78]. β-Zeolite and HZSM-5 exhibited 57%
and 39% acrolein yield, respectively. Zuang et al. used MCM-based and ZSM-based
catalysts for glycerol dehydration and obtained 70–85% acrolein yield [79]. In
another patent by Okuno and co-workers [80], various metallo-silicate catalysts
with MFI structure were used for this reaction which actually reached up to 63%
acrolein yield. Zhou et al. [81] synthesized micro- and mesoporous ZSM-5 catalyst
in a dual template method which gave highest acrolein yield of 73.6%. In another
K. Bhaduri et al.
3.1 Efficient Catalyst Systems for Gas Phase Glycerol
Dehydration to Acrolein
Various types of catalyst systems have been widely reported for the glycerol dehydration reaction like heteropolyacids, zeolites, metal oxides and phosphate catalysts. The catalytic performance of some reported catalysts for the dehydration
reaction of glycerol to acrolein is summarized in Table 1. To catalyse dehydration of
glycerol to form acrolein, the use of heteropolyacids is a very good option. Among
widely used common HPA catalysts is the tungstophosphoric acid. Chai et al. used
zirconia-supported HPA catalysts for glycerol dehydration to acrolein [57, 59]. The
results obtained by them showed zirconia-supported HPA is more effective than
silica-supported HPA.
Katryniok et al. explored glycerol dehydration to acrolein over silicotungstic
acid supported on zirconia-grafted SBA-15 [74]. The interaction between the support and HPA was modified by the grafting. The synergy between the zirconia and
HPA eventually reduced the strength of Brønsted acidic site and thus increased catalyst stability. An acrolein yield of 69% could be seen after 24 h time on stream
study. Dubois et al. scrutinized metal-substituted silicotungstic (SiW) and phosphotungstic (PW) acid salts [75]. Among the various metals used for substitution are
calcium (Ca), rubidium (Rb), caesium (Cs), bismuth (Bi), zirconium (Zr), iron (Fe)
and lanthanum (La). The caesium-substituted Cs 2.5 H 1.5 SiW 12 O 40 catalyst exhibited
the highest acrolein yield of 93%. Another important aspect demonstrated by the
authors was the oxygen co-feed in the reaction which helped to increase the acrolein
yield. The study performed by Alhanash et al. which also included caesium salts of
PW acids achieved an acrolein yield of around 98%, but its longevity was small
[76]. Atia et al. [62] prepared an array of supported silicotungstic acid from selected
silica and aluminosilicate supports. Alkaline metals were used to adjust the Brønsted
acidic sites. It was found that the unmodified supported HSiW catalysts displayed
the highest activity which was the indication about the strong connection of activity
with acidity (Brønsted). Kim et al. [77] explored dehydration of glycerol to acrolein
with silicotungstic acid (HSiW) using various different metal oxides (SiO 2 , TiO 2 ,
ZrO 2 , γ-Al 2 O 3 , CeO 2 , MgO, etc.) as supports. The use of zirconia-supported HSiW
resulted in highest selectivity of 58.1% for acrolein. All the studies on heteropolyacids proved them as potential candidates for glycerol dehydration reactions. Fast
deactivation was one drawback of this catalyst.
Zeolites are also largely reported for glycerol dehydration reaction. Two wellacknowledged zeolite segment catalysts (β-zeolite and ZSM-5) were patented by
Dubois et al. for glycerol dehydration [78]. β-Zeolite and HZSM-5 exhibited 57%
and 39% acrolein yield, respectively. Zuang et al. used MCM-based and ZSM-based
catalysts for glycerol dehydration and obtained 70–85% acrolein yield [79]. In
another patent by Okuno and co-workers [80], various metallo-silicate catalysts
with MFI structure were used for this reaction which actually reached up to 63%
acrolein yield. Zhou et al. [81] synthesized micro- and mesoporous ZSM-5 catalyst
in a dual template method which gave highest acrolein yield of 73.6%. In another
K. Bhaduri et al.