Synthesis of hydrotalcite-type mixed oxide catalysts from waste steel slag for transesterification of glycerol and dimethyl carbonate

The mixed metal oxides S-CaMgAl MO prepared by acidolysis, coprecipitation and calcination under different temperatures from S95 steel slag of Shanghai Baosteel Co., Ltd. were used to catalyze the transesterification of dimethyl carbonate (DMC) and glycerol for synthesizing glycerol carbonate (GC). The catalysts were characterized by EDS, XRD, FT-IR, SEM, CO2-TPD and nitrogen adsorption-desorption isotherms. S-CaMgAl MO calcined at 600 degrees C had excellent catalytic performance due to the large pore size and proper alkalinity. The effects of reaction temperature, reaction time and the amount of catalyst on transesterification were investigated to obtain the optimal reaction conditions. The glycerol carbonate yield reached 96.2% and the glycerol conversion was 98.3% under the condition of 3 wt% catalyst, 1:3 molar ratio of glycerol and DMC, 75 degrees C reaction temperature and 90 min reaction time. In addition, the GC yield and glycerol conversion still achieved above 90% after five cycles of S-CaMgAl MO.