Search

Abstract: The transesterification of dimethyl carbonate (DMC) with glycerol to produce glycerol carbonate was investigated in the presence of CaO under various reaction conditions. CaO was completely dissolved in the reaction mixture of glycerol and DMC in 5min at 75°C and at the molar ratio of glycerol/DMC/CaO of 1/2/0.01. The isolation and the characterization of the dissolved Ca species by means of TOF-SIMS, elemental analysis, and FT-IR revealed that an active species, Ca(C3H7O3)(OCO2CH3) is generated from the interaction of CaO with glycerol and DMC. The mechanistic pathways to the formations of Ca(C3H7O3)(OCO2CH3) and glycerol carbonate are discussed on the basis of experimental and spectroscopic results. [Copyright &y& Elsevier]

Zn(OAc) 2 -catalyzed carbonylation and decarboxylation of glycerol and urea for the synthesis of glycidol were conducted at 150 °C, 2.7 kPa for 2 h and 170 °C, 2.0 kPa for 1.5 h, respectively. When the reaction conducted in a one-pot consecutive way, the yield of glycidol was 20%. However, when the formed zinc glycerolate (Zn(C 3 H 6 O 3 )) was filtered out after the carbonylation, the yield increased to 50% with respect to the amount of glycerol, whereas the yields of glycidol were very low when other zinc salts such as ZnCl 2 , ZnSO 4 and Zn(NO 3 ) 2 , were used as catalysts. The high catalytic activity of Zn(OAc) 2 for this carbonylation and decarboxylation of glycerol and urea could be ascribed to the formation of Zn(NH 3 ) x (OAc) 2 , which was determined from IR and TOF-SIMS studies. [ABSTRACT FROM AUTHOR]

Abstract: Decarboxylation of glycerol carbonate (GLC) to produce 2,3-epoxy-1-propanol (glycidol) was conducted using various kinds of ionic liquids (ILs) as catalysts. ILs bearing an anion with medium hydrogen-bond basicity such as and I− exhibited the higher glycidol yields than those having an anion with low or strong hydrogen-bond. FT-IR spectroscopic analysis shows that both GLC and glycidol interact with anions of ILs through their hydroxyl groups. It was possible to improve the yield of glycidol when a zinc salt with a medium Lewis acidity was co-present along with an IL. The yield of glycidol was greatly increased up to 98% when the decarboxylation was conducted in the presence of a high-boiling aprotic solvent. Computational calculations on the mechanism using 1-butyl-3-methylimidazolium nitrate as a catalyst revealed that the first step is the -assisted ring-opening of GLC followed by the ring closure, resulting in the formation of a 3-membered ring intermediate species. [Copyright &y& Elsevier]

Abstract: Homogeneous zinc-catalyzed synthesis of glycerol carbonate from the reaction of glycerol with urea was investigated. Among the zinc-based catalysts tested, ZnCl2 showed the highest catalytic activity. Spectroscopic and elemental analyses of the zinc species, isolated from the reaction conducted in the presence of ZnCl2, revealed that Zn(NH3)Cl2 was generated first as an intermediate species, which in turn reacted with glycerol to produce zinc glycerolate, Zn(C3H6O3) and NH4Cl. The activity of Zn(C3H6O3) was considerably lower than that of ZnCl2, but the activity was greatly enhanced by the combined use of NH4Cl, implying that both Zn(C3H6O3) and NH4Cl were functioning as essential ingredients for the carbonylation of glycerol by urea. The formation of Zn(C3H6O3) was also observed when ZnBr2, ZnI2, ZnF2, Zn(NO3)2, Zn(CH3CO2)2, or ZnO was used as the catalyst. [Copyright &y& Elsevier]