Direct carbonylation of glycerol with CO2 to glycerol carbonate over Zn/Al/La/X (X=F, Cl, Br) catalysts: The influence of the interlayer anion

Halogen anions (F-, Cl- and Br-) modified Zn-Al-La (Zn/Al/La = 4:1:1) mixed oxides derived from calcination of re-constructed hydrocalcites were prepared and their catalytic activities for the synthesis of glycerol carbonate (GC) form glycerol and CO2 were investigated. The re-formed hydrotalcites with the introduction of halogen anions formed more thin plates which improved the specific surface area that lead to more exposured active sites. The binding energies of Zn 2p(3/2) increased with the introduction of halogen anions while the basicity decreased with the change of the catalysts' composition. The halogen anions entered hydrotalcites followed the sequence of: F- > Cl- >Br-. The halogen anions modified catalysts showed high catalytic activities toward the reaction. The improved catalytic activities were suggested to be closely associated with the structure properties, such as large specific surface area, high surface content of Zn atoms, higher binding energy of Zn 2p(3/2) and high dispersion of metal oxides, which could provide more "accessible" active sites for the reaction. In addition, the changing of halogen anions may also had some influence on the catalytic activity; the introduction of Cl-had more advantageous for the reaction. (C) 2015 Elsevier B.V. All rights reserved.