Improvement of low-temperature properties of hydrocarbon selective catalytic reduction activity by developing copper-based zeolite catalyst

Selective catalytic reduction (SCR) is the most effective exhaust after-treatment technology used to reduce NOx (nitrogen oxides) emissions from diesel engines. This system converts NOx into harmless nitrogen (N2) and water (H2O) with the help of a specified catalyst and a reductant. In this work, samarium (Sm) doped two distinct copper-based zeolite (Y and Beta) catalysts produced with the ion exchange method. Scanning Electron Microscopy (SEM), Energy Dispersive X-rat Spectroscopy (EDS), X-ray diffraction (XRD), Fourier-Transform infrared (FTIR), and Brunauer-Emmet-Teller (BET) analyses were conducted to determine the chemical characterization of the produced catalysts. Additionally, the catalysts were tested in a real exhaust flow under temperatures ranging from 150 °C to 240°C, with loads of 0, 2, and 4 kW at two different space velocities. The predominance of Si, O, and Al was observed in all catalysts, while the presence of other utilized chemicals was also confirmed through analyses. For all catalysts, conversion rates increased with higher temperatures. While an increase in engine load positively affected the conversion rates, a higher space velocity (SV) had a negative impact. Under a load of 4 kW, the highest NOx conversion rates were observed at a temperature of 240°C. For the Y zeolite set, the Sm1-Y catalyst achieved the highest conversion rate of 95.7481% at an SV of 30000 h-1, while the Sm2-Y catalyst demonstrated a conversion rate of 94.6600% at an SV of 40000 h-1. Similarly, in the BEA zeolite set, the Sm4-BEA catalyst achieved the highest conversion rate of 95.7754% at an SV of 30000 h-1, whereas the Sm1-BEA catalyst exhibited a conversion rate of 94.4719% at an SV of 40000 h-1. The incorporation of Sm showed beneficial effects across both catalyst sets. The results indicated that the optimal Sm loading levels were 1% and 2%. Keywords: Selective Catalytic Reduction, Nitrogen Oxides, Low Temperature, Real Exhaust Flow, Zeolite