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Journal of Catalysis 268 (2009) 106–114
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Journal of Catalysis
Valorization of bio-glycerol: New catalytic materials for the synthesis
of glycerol carbonate via glycerolysis of urea
a
a
b
Michele Aresta a, , Angela Dibenedetto , Francesco Nocito , Carla Ferragina
*
a Dipartimento di Chimica and CIRCC, University of Bari, Campus Universitario, 70126 Bari, Italy
b Istituto di Metodologie Inorganiche e dei Plasmi (IMIP)-CNR Roma 1, via Salaria km 29,300, 00016 Monterotondo (Roma), Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
The glycerolysis of urea plays an important role in the conversion of glycerol into glycerol carbonate
because it is a phosgene-free process that uses easily available and low-cost raw materials that have a
low toxicity. c-Zirconium phosphate shows a good activity as catalyst as it affords 80% of conversion
of glycerol under mild reaction conditions. The catalyst is easily recoverable and reusable in subsequent
cycles of reaction.
Received 29 May 2009
Revised 3 September 2009
Accepted 6 September 2009
Available online 9 October 2009
The kinetics of the reaction has been studied considering the full parameter space. The best tempera-
ture is 418 K, with 3 h of reaction using an equimolar amount of the two reagents (glycerol and urea) with
a catalyst load of 0.6–1.5% w/w with respect to glycerol. The behaviour of the catalyst has been investi-
gated by using the TPD technique. Multinuclear 1H and 13C NMR and FTIR have been used for the char-
acterization of intermediates and by-product. The reaction mechanism is fully elucidated.
Ó 2009 Elsevier Inc. All rights reserved.
Keywords:
Glycerolysis of urea
Reaction mechanism
Glycerol carbonate
Heterogeneous catalysis
1. Introduction
toxicity, good biodegradability and high boiling point. For its prop-
erties it finds several applications in different industrial sectors,
Glycerol (1, Scheme 1) is the by-product with the largest eco-
nomic impact in the modern oleochemical industry [1], being
formed in different processes such as glycerides transesterification,
alcoholysis, hydrolytic cleavage under pressure and saponification
with alkalies [2,3]. It is also produced by dedicated processes such
as the synthesis from propene [4] or the fermentation of simple
sugars [5]. The production of biofuels and biolubricants from bio-
mass is much expanding (and will continue to grow) so that the
production of bio-glycerol, in the past considered of great value
for a successful closing of the economic balance of the lipid-utiliza-
tion process, is now exceeding the request.
The risk that large amounts of glycerol are produced and will
accumulate as a waste has speed-up the industry and academia
research towards the identification of new opportunities for using
such by-product either directly (as fuel even in the same biodiesel
production plants [6]), or by converting it into useful derivatives.
The latter option finds several new applications for the production
of improvers of the cetane number (additives to diesel fuels: i.e.
tertbutyl ether of glycerol) [7] or intermediates in the production
of fine chemicals (e.g. dihydroxyacetone, glyceric acid, pyruvic acid
and 1,3-propanediol) either by fermentation [8–10] or using
chemical routes [11] (Scheme 1). Glycerol carbonate (3, Scheme
1) represents an important derivative of glycerol that shows low
especially as a polar high boiling solvent or intermediate in organic
syntheses (i.e. monomer in the synthesis of polycarbonates and
other polymeric materials in the plastic field [12]), as a precursor
in biomedical applications and as a protection group in the carbo-
hydrates chemistry. It is also used as a component in membranes
for gas separation, in the synthesis of polyurethanes [13] and in
the production of surfactants [14].
The commonly used routes to glycerol carbonate are the reac-
tion of glycerol with phosgene [15] and its transesterification with
other carbonates [16a,b] (Scheme 2).
More recently, the direct carboxylation of glycerol with carbon
dioxide (Scheme 2 middle part) has been discovered [17a–c], an
interesting reaction that converts two wastes into an added value
product. Such reaction requires an improvement of the catalyst in
order to find a practical application.
An alternative route is the glycerolysis of urea (Scheme 3), a
reaction that has been recently described in the scientific [18]
and patent literature [19–21].
Several catalysts have been used, mainly based on metal oxides
of variable basicity [18–21] which suffer the drawback of a difficult
separation from the reaction medium as they dissolve in it or are
converted into micro-powders. As matter of fact, the scientific
and patent reports often do not describe the recovery of the pure
carbonate from the reaction mixture.
We searched and tested several catalysts which do not dissolve
in the reaction mixture (glycerol–urea–glycerol carbonate) nor are
* Corresponding author. Fax: +39 080 544 36 06.
0021-9517/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved.
doi:10.1016/j.jcat.2009.09.008