Effect of the preparation conditions on the catalytic activity of calcined Ca/Al-layered double hydroxides for the synthesis of glycerol carbonate

Identificador:  PC:3200

Handle: https://hdl.handle.net/20.500.11797/PC3200

Autors:  Salagre, P.; Granados-Reyes, J.; Cesteros, Y.

Resum:
The effect of the preparation conditions of several calcined Ca/Al layered double hydroxide compounds (CaAl-LDH) on the catalytic transesterification of glycerol with dimethyl carbonate to obtain glycerol carbonate has been studied. The CaAl-LDH precursors were prepared by aging under microwaves or conventional heating, and using chlorides or nitrates as interlayer anions. Calcination conditions, such as temperature, time and calcination system, were modified. After 3 h of reaction, the catalysts obtained by calcination at 450 ºC for 15 h in air exhibited moderate-high glycerol conversion (46-76%) and moderate selectivity to glycerol carbonate (41-65%). Calcination at 450 ºC at longer calcination time or the use of a dynamic inert-atmosphere system during calcination led to higher conversion (89-94%) and higher selectivity to glycerol carbonate (72-73%). This has been related to the higher basicity of these catalysts. Finally, calcination at 750 ºC resulted in high conversion (88-98%) and high selectivity to glycerol carbonate (60-85%) due to the presence in the catalysts of highly basic CaO. Several catalytic reuses favoured the decarboxylation of glycerol carbonate resulting in the formation of higher amounts of glycidol (42%). The progressive loss of conversion and selectivity to glycerol carbonate observed has been attributed to the loss of some CaO basic centres during reaction.