Physicochemical characteristics according to aging of Fe-zeolite and V2O5–WO3–TiO2 SCR for diesel engines

• Thermal durability of Fe-zeolite (2) was strong in terms of hydrothermal aging.
• Coking and sulfur poisoning of V2O5–WO3–TiO2 SCR were the least occurred.
• V2O5–WO3–TiO2 SCR is ideal for the reduction of exhaust gas from ship engines.

The purpose of this study is to investigate the physicochemical characteristics according to hydrothermal aging, sulfur poisoning and HCs co-existence of Fe-zeolite (1), (2) and V2O5–WO3–TiO2 SCR which are appropriate for diesel engines. Fe-zeolite (1) is a zeolite with low Fe content (∼1 wt.%) while Fe-zeolite (2) is a zeolite with a high Fe content (1.8 wt.%). The BET specific surface area of Fe-zeolite (2) was smaller than that of Fe-zeolite (1) but its NH3 storage capacity was larger than Fe-zeolite (1) because Fe-zeolite (2) has a large amount of Al content that can absorb NH3. In the case of Fe-zeolite (2), thermal durability was strong, When mildly set in hydrothermal aging for 12 and 24 h at 600 and 700 °C respectively, the NOx conversion rate was higher than the Fresh catalyst above 350 °C. The active site of the catalyst, which is an Fe site, was damaged during the hydrothermal aging process, resulting in a decline in low-temperature performance. However, at higher temperatures, the NH3 oxidation was largely hindered by the damage to the Fe site. The highest degree of coking arose for Fe-zeolite (1). On the other hand, V2O5–WO3–TiO2 SCR, exhibited high durability against HCs, and experienced less coke deposition. Of the three catalysts V2O3–WO3–TiO2 SCR suffered the least sulfur poisoning (0.007 g/L). Due to the effects of Brønsted acid site, its resistance to sulfur poisoning is sufficient for reduction catalysts for exhaust gases from ship engines.

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