Fig. 1. XRD patterns of samples before and after SO₂ treatment at 673 K. Ba/Al₂O₃ (a) before and (b) after SO₂ treatment and Pt/Ba/Al₂O₃ (c) before, (d) after SO₂ treatment, and (e) after H₂ regeneration.

Fig. 2. TPRS of NO (dashed line) and NO₂ (solid line) released from Pt/Ba/Al₂O₃ on sample (a) without SO₂ treatment, (b) after SO₂ treatment in N₂, and (c) after SO₂ treatment in air and then exposure to 750 ppm NO₂ in N₂/air at 673 K and cooled to 298 K, and then heated to 873 K at 4 K min⁻¹ in a 7.98% air/balance N₂ gas mixture (50 cm³ min⁻¹).

Fig. 3. TPRS of NO (dashed line) and NO₂ (solid line) released from Pt/Ba/Al₂O₃ after exposure to 750 ppm NO₂ in N₂/air at 673 K and cooled to 298 K, and then heated to 873 K at 4 K min⁻¹ in a 7.98% air/balance N₂ gas mixture (50 cm³ min⁻¹) on samples which had been exposed to SO₂ in air at 673 K and then regenerated with (a) H₂, (b) CO, or (c) C₃H₆.

Fig. 4. Summary of the relative amounts of NO_x released from different pretreated Pt/Ba/Al₂O₃ samples as a percentage of total NO_x released from fresh sample. (1) Fresh sample, (2) exposed to SO₂/N₂, exposed to SO₂/air with (3) no regeneration, or (4) regenerated with H₂ or (5) regenerated with CO or (6) regenerated with C₃H₆.

Fig. 5. FTIR spectra of Pt/Ba/Al₂O₃ after NO₂ adsorption at 673 and cooling to 298 K with different pretreated samples. (a) Without SO₂ treatment, (b) after SO₂ treatment at 673 K in N₂, or exposed to SO₂ in air at 673 K with subsequently (c) no regeneration, (d) regeneration in H₂, (e) regeneration in CO, and (f) regenerated in C₃H₆.

Fig. 6. TPRS of NO (dashed line) and NO₂ (solid line) released from support Ba/Al₂O₃ on sample (a) without SO₂ treatment, (b) after SO₂ treatment in N₂ at 673 K, or (c) after SO₂ treatment in air and then exposure to 750 ppm NO₂ in N₂/air at 673 K and cooled to 298 K and then heated to 873 K at 4 K min⁻¹ in a 7.98% air/balance N₂ gas mixture (50 cm³ min⁻¹).

Fig. 7. TPRS of NO (dashed line) and NO₂ (solid line) released from support Ba/Al₂O₃ after exposure to 750 ppm NO₂ in N₂/air at 673 K and cooled to 298 K, and then heated to 873 K at 4 K min⁻¹ in a 7.98% air/balance N₂ gas mixture (50 cm³ min⁻¹) on samples which had been exposed to SO₂ in air at 673 K and then regenerated with (a) H₂, (b) CO, or (c) C₃H₆.

Fig. 8. Summary of the relative amounts of NO_x released from different pretreated supports as a percentage of total NO_x released from fresh sample. (1) Fresh sample, (2) exposed to SO₂/N₂ at 673 K or exposed to SO₂ in air at 673 K and either (3) no regeneration or (4) regenerated with H₂ or (5) regenerated with CO or (6) regenerated with C₃H₆.

Fig. 9. FTIR spectra of support Ba/Al₂O₃ (a) before NO₂ adsorption, then after exposure to NO₂ at 673 K and cooling to 298 K with different pretreated sample (b) without SO₂, (c) after SO₂ treatment in N₂, or after exposure to SO₂ in air and (d) no regeneration, (e) regeneration in H₂, (f) regeneration in CO, (g) regeneration in C₃H₆.

Fig. 10. Summary of the amounts of NO_x released from different pretreated supports as a percentage of total NO_x released from fresh treated support. (1) Fresh sample, (2) exposed to SO₂ in N₂ at 673 K or exposure to SO₂ in air with subsequently (3) no regeneration, or (4) regeneration with H₂ or (5) regeneration with CO.

Fig. 11. FTIR spectra of (a) HCl-treated Ba/Al₂O₃ support then after NO₂ exposure between 673 and 298 K for different pretreated samples, (b) without SO₂ treatment, (c) after SO₂ treatment in N₂ at 673 K, and (d)–(f) exposed to SO₂ in air at 673 K with (d) no regeneration or (e) regenerated with H₂ or (f) regenerated with CO.

Fig. 12. FTIR spectra of HCl-treated Ba/Al₂O₃ support after SO₂ treatment in air and exposure to 750 ppm NO₂ in N₂/air at 673 K and cooling to 298 K. Sample was heated in 7.98% air/N₂ mixture to 873 K with spectra recorded at (a) 298, (b) 373, (c) 473, (d) 573, (e) 673, (f) 773, and (g) 873 K.

Summary of NO_x released during TPRS experiments