Abstract
Polyglycerols (PGs) are biocompatible and highly functional polyols with a wide range of applications, such as emulsifiers, stabilizers and antimicrobial agents, in many industries including cosmetics, food, plastic and biomedical. The demand increase for biobased PGs encourages researchers to develop new catalytic systems for glycerol polymerization. This review focuses on alkaline homogeneous and heterogeneous catalysts. The performances of the alkaline catalysts are compared in terms of conversion and selectivity, and their respective advantages and disadvantages are commented. While homogeneous catalysts exhibit a high catalytic activity, they cannot be recycled and reused, whereas solid catalysts can be partially recycled. The key issue for heterogenous catalytic systems, which is unsolved thus far, is linked to their instability due to partial dissolution in the reaction medium. Further, this paper also reviews the proposed mechanisms of glycerol polymerization over alkaline-based catalysts and discusses the various operating conditions with an impact on performance. More particularly, temperature and amount of catalyst are proven to have a significant influence on glycerol conversion and on its polymerization extent.
Highlights
In the last few years, in view of the environmental issues faced by humanity, the use of biofuels has been favored to try to limit the emissions of greenhouse gases and the global warning effect
This paper provides a view on polyglycerols applications, reaction mechanism involved alkaline-catalyzed
Under basic homogenous catalytic reactions, the reaction rate is high, the lack of control of the glycerol polymerization degree leading to low selectivity and the impossibility to separate the catalyst from the reaction medium are still issues to be solved [12]
Summary
In the last few years, in view of the environmental issues faced by humanity, the use of biofuels has been favored to try to limit the emissions of greenhouse gases and the global warning effect. While polyglycerols are currently produced from biosourced epichlorohydrin (Epicerol® ), the change in the customers’ demand, more in the cosmetic and food sectors, require products derived from nontoxic and preferably natural ingredients. This strongly encourages the manufacturers to produce PGs directly from glycerol. We use the general etherification [3,4,5], oligomerization [6,7] and polymerization [8]. PGs reaction, with a focus on the issue of leaching and on the stability of these in alkaline-catalyzed PGs reaction, with a focus on the issue of leaching and on the stability of these heterogeneous catalysts, addressed byby thethe previous reviews. The influence of the reaction parameters on catalytic performances is addressed
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