Abstract
The chemical equilibrium for the preparation of glycerol monostearate (GMS) from glycerol carbonate (GC) and stearic acid (SA) was investigated. The chemical equilibrium constant K of the base-catalyzed synthesis of GMS from GC and SA was much smaller than that of the acid-catalyzed synthesis of (2-oxo-1,3-dioxolan-4-yl) methyl stearate (ODOMS) from GC and SA. In other words, it was thermodynamically difficult to obtain GMS with a high yield from GC and SA catalysed by basic catalysts. To prove this argument, we used magnesium oxide (MgO) as a catalyst to synthesize GMS from GC and SA. As expected, the yield of GMS was quite low. To increase the yield of GMS, a two-step procedure was proposed. First, pure ODOMS was synthesized by the esterification of GC with SA using copper p-toluenesulfonate (CPTS) as the catalyst. The conversion of SA reached 96.14% under the following conditions: reaction temperature, 140 °C; catalyst amount, 3% CPTS (based on the SA weight); reaction time, 3 h; GC-to-SA molar ratio, 1.5:1. Second, GMS was produced at a yield of 64.4% by the hydrolysis of ODOMS in the presence of triethylamine. The syntheses of ODOMS and GMS were confirmed by 1H- and 13C-NMR, FTIR and LC-MS analysis.
Original language | English |
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Pages (from-to) | 34137-34145 |
Number of pages | 9 |
Journal | RSC Advances |
Volume | 6 |
Issue number | 41 |
DOIs | |
Publication status | Published - 2016 |
Externally published | Yes |