Vidareutveckling av katalysatorer för pre-reforming i bränslecellssystem

Sammanfattning: Heterogeneous catalysts to be used in a pre-reformer for fuel cell systems have been investigated based on active phase composition and catalyst preparation methods for granulate and monolithic catalysts. The catalysts were manufactured using θ – aluminum oxide as carrier, promoted with lanthanum and cerium, with active phases consisting of noble metal X and nickel in various concentrations. Analysis was performed by letting a mixture of propane and water vapor, with a steam to carbon ratio of 2:1, pass through the catalyst sample at 500 °C at different space velocities determining the propane conversion and product selectivity using a GC/MS. At a space velocity of 15 000 /h the propane conversion is high (99%) when the active phase of the catalyst consists of solely noble metal X with a concentration of 0,5 wt. %. It seems to be possible to reduce the noble metal content from 0,5 to 0,25 % by weight without affecting the propane conversion. Doing so reduces the raw material cost. However, when catalysts are subjected to a higher space velocity, 30 000/h, catalyst with 0,5 wt. % noble metal X seem to withhold a high propane conversion (97%) while for the catalyst with 0,25 wt. % noble metal X the propane conversion drops significantly (66%). To obtain granulate catalysts with high propane conversion they should be produced by first impregnating the powdery carrier with active phase and in the following step add a binder to generate larger catalyst particles. In order to get granulate catalysts with a small as possible quality variation the catalyst should be manufactured by mixing the powdery carrier and binder and sequentially impregnating it with active phase. The one manufacturing procedure for monolithic catalysts that gives the highest propane conversion could not be determined. Analysis showed no significant difference in propane conversion between monolith catalysts produced in different ways. However, by mixing carrier, binder and active phase all at once and then covering the monolith in this solution the production time can be reduced without affecting propane conversion. Further work is needed to give more clarity to what effect the preparation method has on monolithic catalyst performance.