Reforming of tar contained in a raw fuel gas from biomass gasification using nickel-mayenite catalyst

Catalytic steam reforming of tar is a very efficient process to clean the gas produced by biomass gasification. Ni catalysts remain an affordable solution for this problem, even if this catalytic material suffers degradation due to carbon deposition and sulphur poisoning. In this study, the properties of a new catalyst Ni/Mayenite (Mayenite as binder), prepared by impregnation method and tested with a real gas obtained from a bench scale fluidized bed steam gasification of biomass, were investigated. Experiments were carried out in a microreactor fed by a slipstream coming from the bench scale gasifier to evaluate gas cleaning and upgrading options. Preliminary tests were carried out at three different temperatures, 700, 750 and 800 °C. In all the tests, the catalysts showed high activities reaching to a conversion rate of 90% in the case at highest temperature (800 °C). The conversion efficiency remained stable around this value during a 3 h test. A decrease in the performance was observed at 700 and 750 °C, even if the conversion remained stable around a lower value. An increase of H2 (>50%) and a decrease of CH4 were observed at all the temperatures, due to the occurrence of steam reforming reaction. A long duration test (12 h) was carried out at 800 °C and demonstrated that, at this temperature, the conversion was stable for a longer period.