The effects of adding particles of CaO to a hot bed of quartz sand, fluidised by N-2, often containing small amounts of NO and CO, were investigated, especially to study the reduction of NO to N-2. These observations indicate that surfaces of CaO are efficient catalysts in the presence of NO of the Boudouard reaction: 2 CO -> C-s + CO2. In addition, CaO catalyses the reaction: NO + CO -> 1/2 N-2 + CO2. The kinetic parameters describing the nett rate constant for the overall conversion of NO to N-2 were measured for the first time with CaO as catalyst; the activation energy is 27 +/- 8 kJ/mol. This reaction was found to be more important for removing NO than: NO + C-s -> CO + 1/2 N-2 with graphite as the carbon, C-s. It also appears that CaO in a fuel-rich, fluidised bed containing graphite and NO at similar to 1000 K produces CaC2, which is demonstrated here to react readily and very exothermally with NO in: CaC2 + 5 NO -> 5/2 N-2 + CaO + 2 CO2, thereby quickly removing NO and producing CO2. The production of CaC2 from CaO and carbon continues for a long time; the mechanism is discussed and probably involves catalysis by NO. In a bed with excess air, NO can be produced by CaC2 fixing atmospheric N-2 to give CaCN2, which is oxidised later, i.e.: CaC2 + N-2 -> CaCN2 + C; CaCN2 + 5/2 O-2 -> CaO + 2 NO + CO2: Thus the conspicuous interaction between CaO and NO in a fluidised bed is complicated by the continued formation of CaC2, whose subsequent reaction depends on whether conditions are fuel-lean (oxidising) or rich (reducing). (C) 2015 Elsevier Ltd. All rights reserved.