471
synthesized different niobium-zirconium mixed oxide catalysts for this reaction.
They investigated the relation between acidity-basicity and the catalytic activity.
Niobium oxide supported on zirconia proved to be the best one with 98% conversion of glycerol and 72% selectivity for acrolein. Again in another research by
Lauriol-Garbey and their co-workers, studied the effect of SiO 2 doping on WO 3 /
ZrO 2 catalyst for glycerol dehydration at 573 K [44]. From different characterization techniques, it was revealed that modification with silica formed large mesopores limiting the production of undesirable coke. The catalyst exhibited 78%
acrolein selectivity at total conversion of glycerol, and also it showed stable catalytic activity even after 100 h time on stream. WO 3 /TiO 2 catalysts prepared by Ulgen
and Hoelderich [87] achieved around 85% selectivity towards acrolein at almost
total glycerol conversion. They observed that using oxygen could inhibit formation
of by-products. Due to gradual deactivation rate and being inexpensive, titaniasupported tungsten oxide is a good catalyst for glycerol dehydration. Cavani et al.
[88] synthesized sulphated zirconia catalyst for this reaction and also used cofeeding of oxygen. They could achieve 49% glycerol conversion with 42% selectivity towards acrolein. Liu et al. [89] prepared Cr-, Cu- and La-modified aluminium
phosphate (AlPO) catalysts for dehydration at 443 K in gas phase. The mesoLaCuCrAlPO catalyst showed very good catalytic activity results of 80% selectivity
towards acrolein with 99% glycerol conversion at 613 K. Massa et al. [40] synthesized monoclinic zirconia-supported niobium and tungsten oxide for this reaction.
The tungsten oxide supported zirconia showed 78% yield for acrolein at 100% conversion for glycerol. Though oxygen flow decreased the deactivation rate a little, it
had no serious effect on acrolein yield. Gu et al. [66] prepared different supported
nickel sulphate catalysts for gas phase glycerol dehydration where 17NiSO 4 –623
catalyst achieved up to 70 mol.% selectivity for acrolein with more than 90% conversion of glycerol during 10 h time on stream. Also in this case, oxygen co-feed did
not help to improve acrolein yield, but it could reduce the catalyst deactivation. Tao
et al. [41] scrutinized the activity of tantalum oxide (Ta 2 O 5 ) catalyst prepared in different calcination temperatures for glycerol dehydration. Acrolein selectivity of
75% was obtained at 40% glycerol conversion using Ta 2 O 5 –350 at 623 K temperature. The catalyst showed excellent long-life stability even after 100 h time on
stream. Apart from the above heteropolyacids, zeolites, metal oxides and phosphates, recently some interesting catalyst systems have been reported for glycerol
dehydration to acrolein. Huang et al. [67] synthesized a metal-organic frameworkmediated alumina catalyst and tested for glycerol dehydration reaction. The M-Al 2 O 3
catalyst achieved a conversion of about 80% with nearly 74% acrolein selectivity
for a long 200 h time on stream. Zhou et al. [68] synthesized acid-activated sepiolite
catalyst for glycerol dehydration reaction and achieved an acrolein yield of 52% at
320 °C. In a different and new investigation, Xie et al. prepared microwaveabsorbing catalyst WO 3 /ZrO 2 @SiC and performed microwave-assisted catalytic
dehydration of glycerol. The acrolein selectivity could reach over 70% with complete glycerol conversion at 250 °C with microwave heating [69].
Catalytic Conversion of Biomass-Derived Glycerol to Value-Added Chemicals
synthesized different niobium-zirconium mixed oxide catalysts for this reaction.
They investigated the relation between acidity-basicity and the catalytic activity.
Niobium oxide supported on zirconia proved to be the best one with 98% conversion of glycerol and 72% selectivity for acrolein. Again in another research by
Lauriol-Garbey and their co-workers, studied the effect of SiO 2 doping on WO 3 /
ZrO 2 catalyst for glycerol dehydration at 573 K [44]. From different characterization techniques, it was revealed that modification with silica formed large mesopores limiting the production of undesirable coke. The catalyst exhibited 78%
acrolein selectivity at total conversion of glycerol, and also it showed stable catalytic activity even after 100 h time on stream. WO 3 /TiO 2 catalysts prepared by Ulgen
and Hoelderich [87] achieved around 85% selectivity towards acrolein at almost
total glycerol conversion. They observed that using oxygen could inhibit formation
of by-products. Due to gradual deactivation rate and being inexpensive, titaniasupported tungsten oxide is a good catalyst for glycerol dehydration. Cavani et al.
[88] synthesized sulphated zirconia catalyst for this reaction and also used cofeeding of oxygen. They could achieve 49% glycerol conversion with 42% selectivity towards acrolein. Liu et al. [89] prepared Cr-, Cu- and La-modified aluminium
phosphate (AlPO) catalysts for dehydration at 443 K in gas phase. The mesoLaCuCrAlPO catalyst showed very good catalytic activity results of 80% selectivity
towards acrolein with 99% glycerol conversion at 613 K. Massa et al. [40] synthesized monoclinic zirconia-supported niobium and tungsten oxide for this reaction.
The tungsten oxide supported zirconia showed 78% yield for acrolein at 100% conversion for glycerol. Though oxygen flow decreased the deactivation rate a little, it
had no serious effect on acrolein yield. Gu et al. [66] prepared different supported
nickel sulphate catalysts for gas phase glycerol dehydration where 17NiSO 4 –623
catalyst achieved up to 70 mol.% selectivity for acrolein with more than 90% conversion of glycerol during 10 h time on stream. Also in this case, oxygen co-feed did
not help to improve acrolein yield, but it could reduce the catalyst deactivation. Tao
et al. [41] scrutinized the activity of tantalum oxide (Ta 2 O 5 ) catalyst prepared in different calcination temperatures for glycerol dehydration. Acrolein selectivity of
75% was obtained at 40% glycerol conversion using Ta 2 O 5 –350 at 623 K temperature. The catalyst showed excellent long-life stability even after 100 h time on
stream. Apart from the above heteropolyacids, zeolites, metal oxides and phosphates, recently some interesting catalyst systems have been reported for glycerol
dehydration to acrolein. Huang et al. [67] synthesized a metal-organic frameworkmediated alumina catalyst and tested for glycerol dehydration reaction. The M-Al 2 O 3
catalyst achieved a conversion of about 80% with nearly 74% acrolein selectivity
for a long 200 h time on stream. Zhou et al. [68] synthesized acid-activated sepiolite
catalyst for glycerol dehydration reaction and achieved an acrolein yield of 52% at
320 °C. In a different and new investigation, Xie et al. prepared microwaveabsorbing catalyst WO 3 /ZrO 2 @SiC and performed microwave-assisted catalytic
dehydration of glycerol. The acrolein selectivity could reach over 70% with complete glycerol conversion at 250 °C with microwave heating [69].
Catalytic Conversion of Biomass-Derived Glycerol to Value-Added Chemicals