MgFeAl layered double hydroxide prepared from recycled industrial solid wastes for CO2 fixation by cycloaddition to epoxides

Abstract

MgFeAl trimetallic layered double hydroxide (LDH) was prepared using industrial solid wastes of red mud and ferronickel slag, and exfoliation of the LDH by acetone washing resulted in a final product with high surface area (319 m2/g). It showed a CO2 adsorption capacity of 70.2 mg/g at 298 K and 1 bar, which was somewhat higher than that of a similar LDH synthesized using pure chemicals (63.8 mg/g). The LDH was tested as a catalyst for solvent-free CO2 cycloaddition to various epoxides. Significant conversion of epoxides and high selectivity to the corresponding cyclic carbonates were obtained under mild reaction conditions. The LDH achieved an excellent result of 98.0% conversion of epichlorohydrin and 98.2% selectivity to the cyclic carbonate in the presence of tetrabutylammonium bromide as co-catalyst at 50 °C and 5 bar after 7 h, catalyzed by the combination of Lewis acidic metal sites and bromide ions. The LDH was recovered after the reaction and maintained good catalytic performances after five repeated runs without any significant loss in catalytic activity. This work demonstrated that effective CO2 capture/utilization could be achieved simultaneously using a porous material easily prepared from industrial wastes.