(271b) Supported Nanocomposite Catalysts for High Temperature Reactions: Building a Catalyst from the Nanoparticle up

Nanomaterials have become the focus of intense catalysis research after first reports on nanosized gold particles indicated that nano-scaled materials can show fundamentally different properties from their bulk (macroscopic) equivalent. Furthermore, the extremely large surface-to-volume ratio of nanoparticles makes such materials highly interesting for catalytic applications. However, the thermal stability of particles decreases strongly with decreasing diameter, which currently restricts the application of metallic nanoparticles to low and moderate temperatures (T<500°C). Previously we have demonstrated the first successful approach to overcome this barrier by anchoring noble metal nanoparticles in a high-temperature stabilized alumina matrix. In this way, we were able to synthesize exceptionally active and sinter-resistant platinum-barium hexaaluminate (Pt-BHA) powders which combine the high reactivity of nanosized Pt metal particles with the excellent high-temperature stability of structured aluminas. This was the first step in ?building? our nanocomposite catalyst. However, concerns with handling of these nanoparticle powders, including health risks and problems with catalyst packing, require an anchoring of the nanocomposite catalyst in a uniform manner onto a support structure as a second ?building? step. We investigated several methods of coating catalyst supports (foams, monoliths, felts) with Pt-BHA gels. Reactive testing, carbon monoxide adsorption, and electron microscopy studies show that quartz glass fiber mats have the most promise as novel support materials to obtain well dispersed Pt-BHA and efficient and stable catalytic activity. Quartz glass mat-supported Pt-BHA catalysts showed strongly improved synthesis gas yields in partial oxidation of methane with orders of magnitude in reduction in the Pt content in comparison to traditional Pt/Al₂O₃ catalysts. At the same time, the novel catalysts showed excellent long-term stability even at the extreme conditions (T=800-1200°C) of high-temperature catalysis. Overall, we therefore see a great potential for these catalysts for energy applications, in particular the production of synthesis gas and/or hydrogen from methane via steam reforming, autothermal reforming or partial oxidation.