477
carbonate sources, phosgene, alkyne carbonate and dialkyl carbonate are used in
many literatures. Though transcarbonation involving phosgene seems to be a simplistic way for the production of organic carbonate, the handling issues regarding
this toxic gas make its applications very limited. Alkyne carbonate systems like
propylene carbonate or ethylene carbonate can be employed to prepare glycerol
carbonate from transcarbonation of glycerol. Chemical equilibrium calculations
revealed that cyclic carbonate preparations by glycerol transcarbonation were thermodynamically favourable for the production of glycerol carbonate [105]. While
taking ethylene carbonate, it involves a two-step reaction: first ethylene carbonate is
synthesized from carbon dioxide and ethylene oxide and then glycerol carbonate
formation takes place via transcarbonation between glycerol and ethylene carbonate
[106]. Among the various catalytic systems reported, zeolites, basic oxides and
mixed oxides derived from hydrotalcites are worth mentioning. Reduced pressure is
usually applied to facilitate the chemical equilibrium for the glycerol carbonate formation. Increasing temperature has a negative effect on chemical equilibrium in this
reaction, so most of reported reaction temperatures are lower than previous synthetic routes. Similar to ethylene carbonate, propylene carbonate is also used to
prepare glycerol carbonate where abolishing the propylene glycol by- product under
reduced pressure is an important step [107]. Dimethyl carbonate is extensively used
as a carbonate source to synthesis of glycerol carbonate by the transcarbonation
glycerol as it is quite environment friendly and can be prepared from urea and methanol. A large number of catalysts have been reported for this reaction: uncalcined
Mg-Al HT, Mg/Al/Zr mixed oxide, NaOH/γ-Al 2 O 3 , Mg-Al mixed oxide, Mg-Al
LDO, Mg-La mixed oxide, CaO, hydrotalcite, KF-HAP, Mg/Zr/Sr mixed oxide,
N-heterocyclic carbenes, Ti-SBA-1 and K 2 CO 3 [108–121]. Performance of some
catalysts in glycerol carbonylation with dimethyl carbonate as reported in literature
is summarized in Table 2.
Apart from the basic catalysts, some enzymes like lipase (Novozym 435) exhibited promising results towards glycerol carbonate synthesis [122]. Glycerol transcarbonation using alkyl carbonate is reversible in nature, so high mole ratio of alkyl
carbonate to glycerol will promote the chemical equilibrium towards the formation
of glycerol carbonate. Chemical equilibrium calculations also showed that increase
in temperature should increase the chemical equilibrium for the formation of glycerol carbonate [105]. Diethyl carbonate can also be used similar to dimethyl carbonate as carbonate source. Nonetheless some of these methods involve the use of some
organic solvents like THF, DMSO, DMF, benzene, etc., and the not easily recoverable or homogeneous nature of the catalysts has unfavourable ecological impacts.
4.3 Glycerol Carbonate from Glycerol and Urea
One of the most promising ways for glycerol carbonate production is from glycerol
using urea as a carbonating agent. The main utility for this route of preparation
besides having biomass glycerol as raw material is ammonia which is produced as
Catalytic Conversion of Biomass-Derived Glycerol to Value-Added Chemicals
carbonate sources, phosgene, alkyne carbonate and dialkyl carbonate are used in
many literatures. Though transcarbonation involving phosgene seems to be a simplistic way for the production of organic carbonate, the handling issues regarding
this toxic gas make its applications very limited. Alkyne carbonate systems like
propylene carbonate or ethylene carbonate can be employed to prepare glycerol
carbonate from transcarbonation of glycerol. Chemical equilibrium calculations
revealed that cyclic carbonate preparations by glycerol transcarbonation were thermodynamically favourable for the production of glycerol carbonate [105]. While
taking ethylene carbonate, it involves a two-step reaction: first ethylene carbonate is
synthesized from carbon dioxide and ethylene oxide and then glycerol carbonate
formation takes place via transcarbonation between glycerol and ethylene carbonate
[106]. Among the various catalytic systems reported, zeolites, basic oxides and
mixed oxides derived from hydrotalcites are worth mentioning. Reduced pressure is
usually applied to facilitate the chemical equilibrium for the glycerol carbonate formation. Increasing temperature has a negative effect on chemical equilibrium in this
reaction, so most of reported reaction temperatures are lower than previous synthetic routes. Similar to ethylene carbonate, propylene carbonate is also used to
prepare glycerol carbonate where abolishing the propylene glycol by- product under
reduced pressure is an important step [107]. Dimethyl carbonate is extensively used
as a carbonate source to synthesis of glycerol carbonate by the transcarbonation
glycerol as it is quite environment friendly and can be prepared from urea and methanol. A large number of catalysts have been reported for this reaction: uncalcined
Mg-Al HT, Mg/Al/Zr mixed oxide, NaOH/γ-Al 2 O 3 , Mg-Al mixed oxide, Mg-Al
LDO, Mg-La mixed oxide, CaO, hydrotalcite, KF-HAP, Mg/Zr/Sr mixed oxide,
N-heterocyclic carbenes, Ti-SBA-1 and K 2 CO 3 [108–121]. Performance of some
catalysts in glycerol carbonylation with dimethyl carbonate as reported in literature
is summarized in Table 2.
Apart from the basic catalysts, some enzymes like lipase (Novozym 435) exhibited promising results towards glycerol carbonate synthesis [122]. Glycerol transcarbonation using alkyl carbonate is reversible in nature, so high mole ratio of alkyl
carbonate to glycerol will promote the chemical equilibrium towards the formation
of glycerol carbonate. Chemical equilibrium calculations also showed that increase
in temperature should increase the chemical equilibrium for the formation of glycerol carbonate [105]. Diethyl carbonate can also be used similar to dimethyl carbonate as carbonate source. Nonetheless some of these methods involve the use of some
organic solvents like THF, DMSO, DMF, benzene, etc., and the not easily recoverable or homogeneous nature of the catalysts has unfavourable ecological impacts.
4.3 Glycerol Carbonate from Glycerol and Urea
One of the most promising ways for glycerol carbonate production is from glycerol
using urea as a carbonating agent. The main utility for this route of preparation
besides having biomass glycerol as raw material is ammonia which is produced as
Catalytic Conversion of Biomass-Derived Glycerol to Value-Added Chemicals