Water glasses with different modulus (mole ratio of SiO2 to Na2O) were applied as a raw material to prepare five solid base catalysts for the synthesis of glycerol carbonate (GC) by the transesterification reaction between glycerol and dimethyl carbonate (DMC). The structure and properties of the five water glass-derived catalysts were investigated by XRD, FT-IR, FESEM, BET and acid?base titration methods. The catalysts with relatively low modulus, including 1.0, 1.5 and 2.0, presented good catalytic abilities, among which the catalyst derived from water glass with 2.0 modulus (WG-2.0) was chosen as the optimal catalyst in the synthesis of GC. This was because WG- -2.0 showed the highest BET surface area, relatively high total basicity, and needed a less amount of NaOH during the preparation process. In the optimization experiments, this catalyst exhibited good catalytic ability with the glycerol conversion of 96.3 % and GC yield of 94.1 % under the condition of glycerol to DMC mole ratio of 1:4, WG-2.0 amount of 4 wt. %, reaction temperature of 348 K and reaction time of 90 min. Furthermore, the reusability experiment of WG-2.0 was also conducted and the results indicated that WG- -2.0 could be reused five times without significant reduction in its catalytic ability.
Solid base catalysts derived from Ca-M-Al (M = Mg, La, Ce, Y) layered double hydroxides for dimethyl carbonate synthesis by transesterification of methanol with propylene carbonate
