Natural gas engine and catalyst deactivation: accelerated ageing tests

Natural gas, utilised in dedicated engines, is a powerful ecological fuel, for its chemical and physical characteristics (1). On the other hand, as well known, the loss of conversion efficiency of dedicated catalysts, mainly due to the thermal and sulphur ageing, is an important matter to solve, in order to prevent decay in the pollutants abatement and therefore enhance the environmental benefits, especially, in urban areas (2). For this reason, many efforts are carrying out, in the development of appropriate catalyst formulation and in the comprehension of the ageing mechanisms (3). In the present paper, a methodology for accelerated thermal ageing of natural gas full-scale catalytic systems, at test bed, is proposed and analysed. This kind of methodology is already used for gasoline engines by some car manufacturers, but never applied to natural gas engines. Temperatures higher than 1000°C have been reached with the aim to simulate, with an ageing cycle of 40 hours, an on-road mileage of 80000 km. The results showed a fast degradation of the conversion efficiency of THC (mainly constituted by methane) during the first hours of engine operation, followed by a certain stabilisation of the catalyst performance.