Glass-melting furnaces emit more than 25 tons of nitrogen oxides (NOx) per year, which are well known as extremely harmful pollutants. In this respect, the development of in-situ, cheap and robust techniques, like electrochemical gas sensors, becomes urgent to on-board control NOx emissions. One of the main issues is the presence of sulfur oxides (SOx) in the stream, which can significantly poison the NOx sensor. This study aims to develop a "trap" to sulfur oxides, located up-stream, to protect NOx sensors from sulfur poisoning. Such materials must exhibit a good catalytic activity for the oxidation of SO₂ to SO₃ with a high SOx storage capacity (SSC) into sulfates. Furthermore, the overall NOx concentration in the stream must be unchanged, excluding the NOx storage on the trap material.

Different traps have been evaluated at 500°C.The organized mesoporous silica SBA-15 with high specific surface area (406 m²/g) and pore volume (0.95 cm³/g), was selected to support CuO and BaO active phases. Two traps with the same CuO loading (6.5 wt.%) and different BaO loading (5 and 24.5 wt.%) were tested during 3 successive SO₂ storage/regeneration cycles. The exhaust stream was composed of 75 ppm of SO₂, 0.9 vol.% O₂ and 2 vol.% H₂O and the regeneration was carried out under helium up to 700°C. The 6.5%CuO/5%BaO/SBA-15 trap shows better efficiency/stability compromise after the third cycle, with higher storage capacity (SSC = 395 µmol_SO2/g) than the 6.5%CuO/24.5%BaO/SBA-15 trap (SSC = 121 µmol_SO2/g).

To study the capacity of these traps to protect our NOx sensor, the response of this sensor to NO and SO₂ was studied in the absence and in the presence of traps heated at 500°C (base gas: 5 mol.% O₂, 1.5 vol.% H₂O in N₂). Without trap, the sensor is significantly poisoned by SO₂, becoming almost unable to respond to NO (T_sensor= 510°C). However, in the presence of the 6.5%CuO/5%BaO/SBA-15 trap, a total SO₂ storage was observed with a very low NO adsorption. Consequently, the NOx sensor was completely protected from SO₂ poisoning showing a stable response to NO. The same protection was obtained with the 6.5%CuO/24.5%BaO/SBA-15 trap. The total SSC of each trap will be explored during multiple NO-SO₂ exposures and the influence of sulfation on the textural properties and the active phase dispersion will be discussed.