(674e) Hydrothermal Stability and so2 Poisoning Resistance of High Silica Pd/SSZ-13 Minicores for CH4 Oxidation

Methane (CH₄) emissions from natural gas-powered automobiles have become an immediate environmental concern. CH₄ has a ⁓25-fold greater global warming potential than CO₂ and thus possesses a substantial environmental impact. Complete CH₄ oxidation can reduce emissions and Pd-based catalysts have a promising CH₄ oxidation activity [1]. Pd/zeolite catalysts with high Si/Al molar ratios are more hydrophobic, compared to lower Si/Al molar ratio zeolites, and have an improved CH₄ oxidation activity. Pd/SSZ-13 catalysts with low Si/Al molar ratios have shown a promising CH₄ oxidation activity, but Pd/SSZ-13 catalysts (Si/Al >100) are under investigated. Herein, 2 wt.% Pd/SSZ-13(156) was washcoated (1.1 g_washcoat/in³) on cordierite minicores and its CH₄ oxidation performance was evaluated under rich, moderate lean, and lean conditions under realistic conditions (Table 1). The Pd/SSZ-13(156) minicores were pretreated (20% O­₂/Ar at 500^oC/20 min) and evaluated under rich, moderate lean, and lean conditions as single successive CH₄ oxidation cycles (200-650^oC (5^oC/min)). The results showed that the temperature that 90% CH₄ conversion was achieved was the lowest (353^oC) under moderate lean conditions compared to rich (384^oC) and lean (357^oC) conditions over Pd/SSZ-13(156) minicores (Fig. 1). The effect of hydrothermal aging (HTA) and SO₂ poisoning on the CH₄ oxidation performance of Pd/SSZ-13(156) minicores is reported here for the first-time with T₉₀'s decreasing from lean (401^oC) to rich (396^oC) to moderate lean (376^oC). The majority of the deactivation was observed after HTA with a greater increase in the average T₉₀ of 26^oC compared to SO₂ poisoning (1^oC) over all conditions. The decrease in performance after HTA can be attributed to Pd sintering. Nevertheless, Pd/SSZ-13(156) exhibits excellent CH₄ oxidation performance with maximum T₉₀ observed under all studied conditions ≤401^oC after HTA and SO₂ poisoning, demonstrating hydrothermal stability and resistance to SO₂ poisoning for the abatement of CH₄.