Positive effects of a halloysite-supported Cu/Co catalyst fabricated by a urea-driven deposition precipitation method on the CO-SCR reaction and SO2 poisoning

Abstract

Cu/Co catalysts were prepared on halloysite nanotube supports by a urea-driven deposition–precipitation method for CO oxidation and the selective catalytic reduction of NO (CO-SCR). First, the Cu/NH₃ molar ratio was investigated to identify the copper species in the catalysts and evaluate the CO oxidation ability. According to the results, the relative amount of [Cu(NH₃)₄]²⁺ species increases with increasing urea concentration, and the Cu/halloysite-1/6 catalyst exhibits strong metal–support interactions and has well-dispersed CuO particles at a Cu/NH₃ molar ratio of 1/6. Moreover, the interaction between [Cu(NH₃)₄]²⁺ and halloysite is enhanced by electrostatic effects, which helps suppress particle migration and sintering. In addition, the promotion effects of cobalt on CuCo/HNT in the NO + CO and NO + CO + SO₂ reactions were also examined. The results suggest that a strong synergistic effect between Cu and Co in the catalyst can improve their reducibilities; thus, the CO and NO conversions are greatly increased by 50% at 400 °C. Moreover, CuCo/HNT exhibits higher SO₂ resistance than Cu/HNT-1/6, and it can maintain 30% CO and NO conversion after SO₂ poisoning.