Promoting Effect of Ni Addition on Cu-SSZ-13 Zeolites for NH₃-SCR

Abstract

The nitrogen oxides (NO_x) in the exhaust gas of diesel vehicles cause a series of severe environmental problems. The development of highly active catalysts for ammonia selective catalytic reduction (NH₃-SCR) of NO in a wide temperature range and the exploration of efficient catalytic active sites is attractive, but there are great challenges. At present, Cu²⁺ exchanged SSZ-13 zeolite (Cu-SSZ-13) as the core of NH₃-SCR technology, although it has been commercialized in diesel vehicle exhaust treatment, it still faces the problems of poor high-temperature hydrothermal stability and poor sulfur resistance. In this work, a series of Cu-Ni-SSZ-13 zeolites were synthesized by aqueous ion exchange strategy. The result turned out that the NH₃-SCR activity and hydrothermal stability of Cu-SSZ-13 were effectively enhanced by introducing Ni²⁺ ions. After hydrothermal aging, the NO conversion rate of Cu-Ni-SSZ-13 achieved 10~30% higher than the original Cu-SSZ-13 in the temperature range of 460–550 ℃, and the sulfur resistance is significantly enhanced. Combined with the characterization analysis, the introduction of secondary Ni²⁺ promoted the dispersion of Cu²⁺, effectively inhibited the formation of CuO_x, and obtained more highly active Cu²⁺ species. Meanwhile, the increase of chemisorbed oxygen species improved the activation ability of NO. This work provides a new insight for constructing Cu-SSZ-13 zeolite by introducing secondary metal cation to improve the performance of NH₃-SCR.