(71r) High Throughput Discovery of Families of High Activity Water-Gas-Shift Catalysts

Current state-of-art water gas shift catalysts (FeCr for high temperature shift and CuZn for low temperature shift) are not active enough for use in fuel processors for the production of hydrogen from gasoline for fuel cells for power generators in vehicles or stationary applications. The need to drastically lower catalyst volumes has triggered a search for novel WGS catalysts that are an order of magnitude more active than current systems; and moreover, are resistant to air and moisture during shut down. High-throughput synthesis and screening methods have been developed for the discovery of families of high activity WGS catalysts. The discovery libraries, for primary screening, consisted of 16x16 arrays of 256 catalysts on 4? quartz wafers. Catalysts were prepared by robotic liquid dispensing techniques and screened for catalytic activity in Symyx' Scanning Mass Spectrometer in the temperature range of 200C to 450C. The ScanMS is a fast serial screening microreactor that uses flat wafer catalyst surfaces, local laser heating, a scanning/sniffing nozzle and a quadrupolar mass spectrometer to compare relative catalytic activities. The feed consisted of CO, CO2, H2, H2O with Kr as internal standard in Ar carrier gas. More than 250 wafers were screened and more than 250,000 experiments were conducted to comprehensively examine catalyst performance for various binary, ternary and higher-ordered compositions. The discovered lead compounds encompass supported noble metal systems as well as base metal compositions. Examples of discovered WGS catalysts that operate in the temperature regime of 200C-350C are the binaries Pt-Ce, Re, Co, V, Mo, Na, supported on zirconia, ceria and titania carriers. The ternary Pt-Fe-K is a decent LTS shifter whereas Fe alone is an inhibitor of Pt. Synergistic mixed oxide systems have been identified, for instance, Pt-Ru-Co-Fe/CeO2 and Pt-Fe-Ce/ZrO2 are active and selective MTS catalysts. Basic dopants (alkaline metals, Y, La) were found to suppress the methanation side reaction. Pt-Na/ZrO2 has been discovered as highly active LTS system. For HTS, Rh and Ru are efficient activators for Pt whereas Cu, Ag, Au are soft and selectivity-enhancing moderators. The combination of activator and moderator into Sinfelt-type Grp VIII ? Pt ? Grp IB ternary alloys allows an activity and selectivity fine-tuning for a given set of process conditions and broadens the temperature operation window.