<span style="font-size:11.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:JA;mso-bidi-language:HI" lang="EN-GB">Synthesis of 1,2-glycerol carbonate from carbon dioxide: The role of methanol in fluid phase equilibrium</span>

Abstract

The effect of methanol on the synthesis of 1,2-glycerol carbonate from CO₂ and glycerol is studied in the presence of Bu₂Sn(OCH₃)₂, <i style="mso-bidi-font-style: normal">n</i>-Bu₂SnO, and <i style="mso-bidi-font-style:normal">tert</i>-Bu₂SnO. At 423 K, up to 2.7 mol% yield in glycerol carbonate, based on glycerol, could be obtained in the pressure range 14-20 MPa. Addition of acetonitrile promotes notably the yield to 7 mol%. Fluid phase equilibrium experiments with the ternary mixture CO₂/glycerol/methanol show that the reaction takes place in a liquid phase where methanol dissolves glycerol, CO₂, and the tin complexes. Above ~0.6 mole fraction, CO₂ behaves as an anti-solvent, separating methanol from glycerol, thus inhibiting the formation of 1,2-glycerol carbonate. Dimethyl carbonate is a side-product of glycerol carbonation resulting mainly from transesterification between glycerol carbonate and methanol. Glycerol coordination to tin center is evidenced by the isolation of di-<i style="mso-bidi-font-style:normal">tert</i>-Bu₂Sn(1,2-glycerolate) complex. Its structure determination by single-crystal X-ray diffraction shows that the remaining OH group of glycerol promotes the formation of one-dimensional polymeric chain.