Oxygen carrier particles of CuO/ZrO2 were reacted with petroleum coke using chemical-looping with oxygen uncoupling (CLOU). The fuel was burnt in gas-phase oxygen released from the oxygen carrier particles during the fuel oxidation. The particles were then regenerated in 5-21% oxygen. In this process, the carbon dioxide from the combustion is inherently separated from the rest of the flue gases without the need for an energy intensive air separation unit. Copper oxide has thermodynamic characteristics that make it suitable as an oxygen carrier in CLOU. Particles were prepared by freeze granulation and were exposed cyclically with petroleum coke and oxygen in a laboratory fluidized bed reactor of quartz. The reaction temperature and oxygen concentration during the oxidation were varied. The average conversion rate of petroleum coke was a function of temperature and varied between 0.5%/s and 5%/s in the set-point temperature interval 885-985 degrees C. The conversion rate is considerably higher than rates obtained with the same fuel using iron-based oxygen-carrier in chemical-looping combustion. As for the regeneration with oxygen, the reduced particles reacted at low oxygen concentrations, with a considerable part of the reaction occurring near the thermodynamic equilibrium. (C) 2008 Elsevier Ltd. All rights reserved.