Water-Gas-Shift Catalyst Development and Optimization for a D-EGR
Dedicated Exhaust Gas Recirculation (D-EGR®) technology provides a novel means for fuel efficiency improvement through efficient, on-board generation of H2 and CO reformate [1, 2]. In the simplest form of the D-EGR configuration, reformate is produced in-cylinder through rich combustion of the gasoline-air charge mixture. It is also possible to produce more H2 by means of a Water Gas Shift (WGS) catalyst, thereby resulting in further combustion improvements and overall fuel consumption reduction. In industrial applications, the WGS reaction has been used successfully for many years. Previous engine applications of this technology, however, have only proven successful to a limited degree. The motivation for this work was to develop and optimize a WGS catalyst which can be employed to a D-EGR configuration of an internal combustion engine.
This study consists of two parts. For the first part, a statistical matrix of 45 catalyst formulations was designed utilizing a previously tested prototype WGS catalyst as the basis. The catalysts were prepared as core samples and evaluated in a Universal Synthetic Gas Reactor® (USGR®). The results indicated that Rhodium and Barium have beneficial effects on performance, whereas Palladium has no effect or even a slightly detrimental effect. The most promising four formulations were further tested to directly quantify H2 production. Finally, the formulation with the greatest potential was selected and full size catalysts were prepared for on-engine evaluation. In the second part of this study, the optimized catalyst was installed in the exhaust stream of a modern gasoline engine to quantify performance under real exhaust conditions. The on-engine tests demonstrated the catalyst's capability of producing significant quantities of H2. However, the formulation was not stable in the exhaust operating environment, leading to an activity loss over a period of approximately 12 hours.