D-EGR™ WGS Catalyst Development and Optimization, 03-R8326
Principal Investigators
Gordon J. Bartley
Terrence Alger
Jess Gingrich
Raphael Gukelberger
Inclusive Dates: 07/01/12 – 07/01/13
Background — SwRI has been actively developing its Dedicated Exhaust Gas Recirculation™ (D-EGR™) concept and system within the HEDGE II Consortium. A key to successful application is the amount of hydrogen (H2) that can be efficiently produced and fed
back into the intake mixture. Rich operation of the D-EGR cylinder produces a significant amount of H2, but more would be beneficial. The D-EGR cylinder exhaust also contains substantial amounts of carbon monoxide (CO) and water (H2O). A water gas shift (WGS) catalyst can react CO with H2O to form H2 and carbon dioxide (CO2), but no WGS catalyst has ever been developed for this application or environment. Catalysts that SwRI has used to evaluate the concept have been traditional three-way (TWC) exhaust formulations that have achieved about 45 percent H2 production efficiency with minimal durability. If this efficiency can be increased to 70 percent and durability improved, an additional 2 to 3 percent brake thermal efficiency (BTE) is possible, a very significant technological advance.
Approach — Three different catalysts received from catalyst companies were evaluated on the D-EGR engine. The one that provided the best performance became the reference formulation for this work. The catalyst was analyzed to obtain the overall elemental composition of the catalyst washcoat. Starting with this reference formulation, a matrix of 45 varying formulations was prepared on core samples for testing. SwRI's Universal Synthetic Gas Reactor® (USGR®) is being used to perform the testing. Each catalyst's WGS activity is being evaluated over a fixed set of test conditions. Sensitivities to individual independent and dependent variables are being used in a statistical approach to identify the direction of optimum formulation for WGS reactivity in the anticipated temperature regions. The optimum operating conditions for that formulation will also be extracted from the data.
Accomplishments — All of the matrix catalyst samples were prepared and received for testing. The initial performance testing is under way and partially complete. Already it is clear that rhodium is an important component for both activity and durability. On the other hand, palladium does not appear to benefit the WGS reaction, and actually caused coking, which fouls the catalyst and reduces the activity. The rhodium seems to reduce coking. Increased high surface area alumina appears to increase activity, and the other components appear to have minimal benefits or no effects on overall performance. It appears probable that an improved formulation will be determined that has both higher intrinsic activity and significantly improved durability.
