Three-way catalysts (TWCs), which can simultaneously oxidize carbon monoxide (CO), total hydrocarbons (THCs), and reduce nitrogen oxides (NOx) at temperatures &gt; 350 oC, have been successful for gasoline vehicle emission control in the past decades. However, with the development of highly efficient engines (lower emission temperatures) and increasing cost of Rh, developing new Rh-free TWCs with enhanced low temperature activity and lean/rich hydrothermal stability is highly desirable. Herein, a series of Rh-free TWCs containing 1 wt.% Pt supported on CeO2 nanocrystals anchored by penta-site rich γ-Al2O3 nanosheets (AlNS) were synthesized and evaluated under a simulated gasoline vehicle exhaust stream (U.S. DRIVE).1 The catalytic performance of Pt-Ce-AlNS (CeO2: 10-80wt.%) after a harsh lean/rich hydrothermal aging (800 oC/10h) is shown in Fig. 1. State-of-the-art Rh-based catalyst (0.5wt.% Rh-12wt.% TiO2-Al2O3 (Rh-Ti-Al)) was also tested for comparison.2 Increasing the CeO2 loading from 0 to 60wt.% led to a decrease in the T90 for NOx, CO and THC from 446 (NOx), 439 (CO), 439 oC (THC) to 241 (NOx), 192 (CO), 236 oC (THC) (Fig.1 (a-c)). Pt-Ce-AlNS catalysts showed comparable performance to the Rh-based catalyst that has T90’s equal to 264 (NOx), 184 (CO), 265 oC (THC). Further increase in the CeO2 loading to 80 wt.% led to a slight decrease in performance. The Pt-Ce-AlNS catalysts showed a significantly enhanced lean/rich hydrothermal aging stability compared to Pt-CeO2 and Pt-Al2O3. H2-TPR results indicated that there is a strong interaction between CeO2 and AlNS that is maximized at CeO2 loading of 60 wt.%. BET and XRD results showed that the CeO2 nanocrystal grain growth slows down by AlNS incorporation. This work illustrates that CeO2 deposition on the surface of penta-site rich AlNS can remarkably enhance the catalyst stability upon lean/rich hydrothermal aging.

Pt-CeO2-Al2O3 nanosheet catalysts with enhanced lean/rich hydrothermal aging stability for TWC applications

ACS Fall 2021

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