Regeneration and sulfur poisoning behavior of In/H-BEA catalyst for NO _x reduction by CH ₄

Sulfur poisoning and regeneration behavior of In/H-BEA catalyst were carried out in NO _x reduction by CH ₄ . In/H-BEA catalyst exhibited a poor resistance to sulfur dioxide after addition of 200 ppm SO ₂ and 10 vol.% H ₂ O into NO reduction with CH ₄ at 450 °C for 45 h. Sulfur poisoning of In/H-BEA was attributed to the inhibition of NO _x adsorption on Brønsted acid sites, suppression of reaction intermediates generation on the active sites, and the formation of surface sulfate species. The formation of surface sulfate reduced the availability of surface active sites, blocked the pore structure and decreased the surface area of catalyst. These changes in chemical and textural properties resulted in a severe loss in the activity of sulfated In/H-BEA catalyst for NO reduction with CH ₄ . H ₂ reduction is a promising technology for regeneration of In/H-BEA deactivated by SO ₂ for removing NO _x from lean-burn and diesel exhausts. Indium sulfate could be reduced by H ₂ to InO ⁺ with In ₂ O ₃ and In(OH) ₂ ⁺ as the intermediates. The optimal parameters of H ₂ reduction was regeneration temperature of 400 °C and regeneration time of 60 min which completely recovered the catalytic activity of In/H-BEA.