Experimental study of mayenite-based catalysts effectiveness in reducing pollution from biomass gasification in fluidized bed reactors

Efficiency of catalyst materials used for tar reduction in biomass gasification plants is strongly affected by carbon deposition. For such reason, techniques for reducing catalyst poisoning are actively studied. Here the authors experimentally investigate the effectiveness of using a Mayenite support for Nickel catalyst. Mayenite was selected because it has a large number of free Oxygen anions that are able to combine with carbon producing COx and eventually prevent carbon deposition. Experiments are carried out with a bench scale gasifier coupled with a catalytic reactor in order to test the Nickel/Mayenite catalyst performance in the conversion of tar and methane. Ni/Mayenite catalyst is characterized by means of XRD, BET and SEM analyses before and after its use in the reactor, aiming to study carbon deposition and tar conversion efficiency. In the tests carried out the tars present in major quantities like benzene, toluene and naphthalene reached conversions close to 100% in the first hour of test, and then stabilized to values of respectively 30%, 85% and 93%. The catalyst was then subject to a regeneration procedure and then tested for some further hours, showing again very high conversion rates: benzene 92%, toluene 93% and naphthalene 96%. The residual tars measured in the syngas are found to be lower than the limits imposed by the Biomass Technology Group for feeding gas turbines; the syngas treated with the catalyst here developed can be thus considered suitable for the use in these energy production devices.