Low temperature automotive exhaust abatement catalysts with high OSC and thermal stability

Devendra  Pakhare, Pyrochem Catalyst Company

In addition to CO2 and H2O, other by-products of IC engines are CO, NOx, and unconverted hydrocarbons (HCs), which need to be converted to less toxic CO2, H2O, and N2 in a catalytic converter. Environment protection agency (EPA) sets limits on the amount of CO, NOx, and HCs that can be emitted from a vehicle and these limitations are stricter than ever.  Thus, a catalytic converter is an integral part of the auto exhaust assembly and plays a pivotal role in helping automobiles meet US and EU emission standards. Pyrochem Catalyst Company’s (PCC) proprietary, novel PyroCat™ catalyst materials, based on its pyrochlore structure, exceed the current commercial catalytic converter technology.

PyroCat is a highly tailorable pyrochlore crystal structure which allows for isomorphic substitution of catalytically active metals and other promoters into the lattice. This substitution increases the metals dispersion compared to conventional supported catalysts and creates strong interactions between the active metal (Pt, Pd, Rh) and the pyrochlore crystal framework (La, Ce, Zr, Ca, Y, Ba) which results in significant resistance to sintering of metals post 1000C+ aging. In addition to enhancing low temperature conversions of CO, HCs and NOx, PyroCat’s structural ordering yields increased Ce utilization to maximize OSC. The inherent structural benefits of the pyrochlore structure and PCC’s proprietary manufacturing process improves the oxygen mobility within the Ce-Zr lattice which maximizes the dynamic and total OSC of the catalyst. The performance of PyroCat and OSC suffered minimal degradation even after lean/rich aging at 1100C compared to a conventional catalyst.

Unique fundamental attributes of PyroCat give it low temperature activity without compromising high temperature stability, which is crucial for the next generation TWCs in helping the auto industry to comply with the stringent EPA regulations.

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