• absorption;
  • calcium;
  • carbon dioxide capture;
  • copper;
  • sol–gel processes


Using a sol–gel technique, new copper-functionalised, calcium-based CO2 sorbents were developed to integrate chemical looping combustion into the calcium looping scheme. In this process, the exothermic reduction of copper oxide with methane, carbon monoxide or hydrogen is used to provide the heat required to calcine (regenerate) calcium carbonate. The materials contained CuO and CaO in a molar ratio of either 1.3:1 or 3.3:1, were supported on Al2O3, MgO or MgAl2O4 and were characterised by means of X-ray diffraction, N2 physisorption, scanning electron microscopy and temperature-programmed reduction. All materials, independent of the precursors and support material used, possessed excellent cyclic oxygen-carrying capacities. However, it was found that the presence of magnesium in the support stabilised the CO2 uptake and minimised carbon deposition. CuCa-MgAl-1.3:1 was the material that possessed the highest CO2 uptake of 0.13 gmath image gmaterial−1 after 15 cycles of repeated carbonation/calcination–redox reactions.