474
3.5 Methods for Inhibiting Catalyst Deactivation
Although high yield of acrolein has been achieved over a large number of catalyst
systems, deactivation remains a serious problem for this reaction. The prime reason
for deactivation mainly applies to the coke formation which is caused by glycerol/
acrolein polycondensation. According to the investigation led by Chai et al. [98], the
co-feed of O 2 with a molar ratio of N 2 /O 2 = 9/1 effectively maintains the catalytic
activity up to 10 h. On the other side, high concentration of O 2 feed results in formation of acetaldehyde, thus decreasing the acrolein yield. From various studies it can
be found that the oxygen feed decreases the carbon species which are adsorbed and
can be transformed to coke. On the other hand, high O 2 concentration escalates the
selectivity towards oxidative decomposition products like acetic acid and acetaldehyde, so the true concentration of the O 2 feed is very decisive. The alteration of solid
acid catalysts with the doping of precious metals can result in higher catalytic activity than unmodified catalysts. According to Ma et al. [99], Pd-doped H 3 PW 12 O 40 /
Zr-MCM-41 is more effective than doping with Pt. It is studied that doping with Pd
escalates the Brønsted acidic sites and reduces the amount of Lewis acid sites which
eventually contributes to the stable and selective production of acrolein from the
dehydration of glycerol.
4 Catalytic Carbonylation of Glycerol
Glycerol carbonate (glycerine carbonate or 4-hydroxymethyl 2-oxo-1,3-dioxolane)
has gained great interest over the last two decades owing to its versatile reactivity
and as a way for waste glycerol valorization. The main uses of glycerol are as solvents, carrier in pharmaceutical preparations, carrier in lithium and lithium-ion batteries, solid laundry detergent compositions, building ecocomposites, polymers
(hyperbranched polyethers, polycarbonates, polyurethanes, non-isocyanate polyurethanes), chemical intermediates and beauty and personal care. Glycerol carbonate is acknowledged as a green substitute for crucial petroderivative compounds like
ethylene carbonate or propylene carbonate. Glycerol carbonate is synthesized by
the reaction of glycerol using urea or dimethyl carbonate or by direct reaction with
carbon dioxide which ultimately results in the chemical fixation of CO 2 in glycerol
(Schemes 8, 9, 10, 11, and 12).
4.1 Glycerol Carbonate from Direct Carboxylation of Glycerol
with CO 2
Direct carboxylation of glycerol with CO 2 seems the most superior process as this
has the potential to transform two waste products into value-added chemical. Among
the first catalysts to be reported for the direct carboxylation of glycerol with CO 2 are
K. Bhaduri et al.
3.5 Methods for Inhibiting Catalyst Deactivation
Although high yield of acrolein has been achieved over a large number of catalyst
systems, deactivation remains a serious problem for this reaction. The prime reason
for deactivation mainly applies to the coke formation which is caused by glycerol/
acrolein polycondensation. According to the investigation led by Chai et al. [98], the
co-feed of O 2 with a molar ratio of N 2 /O 2 = 9/1 effectively maintains the catalytic
activity up to 10 h. On the other side, high concentration of O 2 feed results in formation of acetaldehyde, thus decreasing the acrolein yield. From various studies it can
be found that the oxygen feed decreases the carbon species which are adsorbed and
can be transformed to coke. On the other hand, high O 2 concentration escalates the
selectivity towards oxidative decomposition products like acetic acid and acetaldehyde, so the true concentration of the O 2 feed is very decisive. The alteration of solid
acid catalysts with the doping of precious metals can result in higher catalytic activity than unmodified catalysts. According to Ma et al. [99], Pd-doped H 3 PW 12 O 40 /
Zr-MCM-41 is more effective than doping with Pt. It is studied that doping with Pd
escalates the Brønsted acidic sites and reduces the amount of Lewis acid sites which
eventually contributes to the stable and selective production of acrolein from the
dehydration of glycerol.
4 Catalytic Carbonylation of Glycerol
Glycerol carbonate (glycerine carbonate or 4-hydroxymethyl 2-oxo-1,3-dioxolane)
has gained great interest over the last two decades owing to its versatile reactivity
and as a way for waste glycerol valorization. The main uses of glycerol are as solvents, carrier in pharmaceutical preparations, carrier in lithium and lithium-ion batteries, solid laundry detergent compositions, building ecocomposites, polymers
(hyperbranched polyethers, polycarbonates, polyurethanes, non-isocyanate polyurethanes), chemical intermediates and beauty and personal care. Glycerol carbonate is acknowledged as a green substitute for crucial petroderivative compounds like
ethylene carbonate or propylene carbonate. Glycerol carbonate is synthesized by
the reaction of glycerol using urea or dimethyl carbonate or by direct reaction with
carbon dioxide which ultimately results in the chemical fixation of CO 2 in glycerol
(Schemes 8, 9, 10, 11, and 12).
4.1 Glycerol Carbonate from Direct Carboxylation of Glycerol
with CO 2
Direct carboxylation of glycerol with CO 2 seems the most superior process as this
has the potential to transform two waste products into value-added chemical. Among
the first catalysts to be reported for the direct carboxylation of glycerol with CO 2 are
K. Bhaduri et al.