Characterization and performance analysis of an innovative Ni/Mayenite catalyst for the steam reforming of raw syngas

摘要

Biomass gasification represents a very effective way to produce syngas, a gaseous fuel exploitable in different devices for energy production, such as ICE, micro-turbines, fuel cells or for the production of pure H_2. For these reasons the syngas must be cleaned and conditioned in order to remove the pollutants that will cause damage to the downstream systems; in particular tars concentration must be really low and the H_2 content in the syngas must be maximized. For these purposes catalytic steam reforming of tar and CH4 is necessary; Nickel catalysts at the moment are the preferable candidates for this purpose but still have some deactivation problems related to carbon deposition and sulphur poisoning. Various studies demonstrated that the use of Mayenite as binder for Nickel has various advantages such as the presence of free oxygen ions O_2 and O_2~(2-) in the Mayenite structure that can protect the catalyst from coke formation and H_2S poisoning [1]. Most of the studies on this catalyst are carried out with simulated gas using just few hydrocarbons as tar representative (for example toluene) [2]; in this study the new catalyst was instead tested with real raw syngas produced by biomass gasification in a bench scale gasifier, thus containing CH_4, benzene and different types of tars. Ni/Mayenite was prepared, characterized before its utilization, tested for several tens of hours in a catalytic reactor downstream the bench scale gasifier and finally again characterized in order to study its degradation in time.