Ni-based catalytic fibrous ceramics for hydrogen production from methane in porous burners
Hydrogen is a clean alternative energy when used either directly or as a fuel in solid oxide fuel cells (SOFC’s). Systems for partial oxidation of light hydrocarbons have been developed for producing hydrogen in inert media or in presence of catalysts. The autothermal reform of light hydrocarbons in porous burners is a combination of two methods (catalytic partial oxidation and steam reforming) in the same reactor. This work describes a method for a one-step production of porous catalytic fibrous ceramics obtained from ceramic fibers with different size distributions: homogeneous (ASSF-amorphous silica short fibers) and heterogeneous (MF-mullite fibers), coated with Ni (catalyst) for hydrogen production from decomposition of methane. The ceramic fibers, bentonite (as binder) and Ni2O3 (5 and 10 wt%) were dry mixed and humidified. The obtained mixture was uniaxially pressed at 3.5 MPa so that green porous samples with porosities in the range of 15-45% were obtained. The green samples were then heated under a reducing atmosphere (5%H2/95%N2) at 500°C for 1h for reduction of the Ni2O3, with subsequent sintering in inert atmosphere at 1000°C for 1h, which resulted in fibrous structures with porosities in the range of 40-60%, respectively. Microstructural analysis revealed that the fibrous catalysts exhibited a homogeneous Ni distribution over the fibers. Fluidodynamic properties and CH4 to H2 conversion efficiency were evaluated and correlated with morphological features (porosity and fiber size distribution). The high permeability combined with the relatively high conversion efficiency makes the catalytic fibrous ceramics suitable for H2 production in methane based porous burners.