Chemical interference effects with copper-doped mordenite for dilute methane emissions mitigation

Methane, a short-lived climate pollutant, has gained increasing attention as a key target for reducing the rate of global climate change in the next decades. Catalytic approaches have shown promise for low-level methane conversion, but tolerance to poisoning by anticipated interferents in target applications must be demonstrated. Here, we investigated the impact of known atmospheric components, such as water vapor, nC₁-nC₅ alkanes, hydrogen sulfide, ammonia, and nitric oxide, on the efficacy of copper-doped mordenite catalysts for methane conversion. The results indicated that water vapor, nitric oxide, and hydrogen sulfide can reduce methane conversion efficiency (up to 20%, 9%, and 30% over the 0-28,000 ppm H₂O, 0-30 ppm NO, and 0-10 ppm H₂S ranges, respectively), but this effect was mitigated by higher temperatures. In contrast, adding up to 20 ppm alkanes (100 ppm total alkanes) and up to 20 ppm ammonia exposure did not hinder methane conversion (i.e., anticipated levels that might be expected in coal and dairy applications). Additionally, copper zeolites converted all light alkanes from effluent streams, dominantly to CO₂, illustrating a promising avenue for emission control from a low-cost, Earth abundant material. This study provides insights into the feasibility of copper-doped mordenite as a catalyst for reducing methane emissions in regimes with humidity, sulfur co-production (e.g., lacustrine or coal enrichments), and a variety of nitrogen-containing substances (e.g., dairy or combustion sources).