The Formation of Glycerol Oligomers with Two New Types of End Groups in the Presence of a Homogeneous Alkaline Catalyst

Abstract

The purpose of this work was to synthesize and characterize oligoglycerols with the chains of more than four repeating units. Those oligoglycerols may have some interesting applications, among others, as polyoxyalkylation starters. The glycerol oligomerization process was carried out during 12 h, at 230 °C, under the pressure of 0.4 bar, with the use of sodium carbonate as a homogeneous basic catalyst; various concentrations of the catalyst in the reaction medium were used. The reaction products were analyzed with the use of direct infusion electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (13C NMR) and Fourier transform infrared spectroscopy (FTIR) techniques. Based on the analytical findings, the compositions of the obtained product mixtures and the structures of oligoglycerols present in individual fractions were determined. The effect of catalyst concentration on the composition of the post-reaction mixture was observed. Moreover, in addition to the conventional linear oligomers (α,α-oligoglycerols), two new types of the oligomers were for the first time detected in the post-reaction mixture: one with two hydroxyl groups and the other with a carboxylate group at the α-carbon atom.

Ionic Liquids as Homogeneous Catalysts for Glycerol Oligomerization

“…In contrast, alkaline homogeneous catalysts, such as hydroxides, carbonates, or oxides of alkali metals, lead to products of various structures [ 5 ]. Our previous studies showed that, as a result of glycerin oligomerization carried out with the use of sodium carbonate as a basic homogeneous catalyst, it is possible to obtain a mixture of linear oligoglycerols with an average molecular weight exceeding even 400 g/mol containing an additional hydroxyl group at the α carbon atom [ 12 ]. The disadvantages of homogeneous catalysts, however, include their insufficient thermal stability and difficulties with their isolation from the post-reaction mixture, and at the same time they often cause corrosion of the equipment and generate the need to process a large amount of liquid waste.…”

Microwave-Assisted Continuous Flow for the Selective Oligomerization of Glycerol

“…Several chemical modifications obtained by oxidation, hydrogenolysis, etherification, esterification, dehydration and oligomerisation of glycerol have led to the production of various value-added chemicals. These glycerol derivatives have specific applications in the polymer, agrochemical and pharmaceutical industries [9][10][11][12][13].…”

Assessment on the Effect of Sulfuric Acid Concentration on Physicochemical Properties of Sulfated-Titania Catalyst and Glycerol Acetylation Performance

“…Several chemical transformation processes have been used for glycerol to improve its commercial availability and biodiesel economics. These processes are known as carboxylation [3], hydrogenolysis [4,5], selective oxidation [6], dehydration [7], oligomerization [8], etherification [9] and esterification or acetylation [10].…”