One-pot synthesis of rare earth modified Cu/SAPO-34 for enhanced selective catalytic reduction denitration performance

Four rare earth elements (gadolinium (Gd), dysprosium (Dy), neodymium (Nd), cerium (Ce)) modified Cu/SAPO-34 are synthesized by one-step hydrothermal method, and the effects of rare earth on the selectivity catalytic reduction (SCR) denitration (de-NO_x) performance of Cu/SAPO-34 are systematically studied. Among them, Dy-modified Cu/SAPO-34 (Dy-Cu) exhibits the best de-NO_x efficiency (100% NO conversion between 210–500 °C, and 100 % N₂ selectivity between 210–390 °C) under a gas hourly space velocity (GHSV) of 36,000 h⁻¹. It is revealed that rare earth modification effectively reduces the formation of CuO, enhances the Cu²⁺ content, increases the number of acid sites, and improves the NO oxidation performance, which are beneficial to improve the de-NO_x performance of Cu/SAPO-34. Compared with Gd, Nd and Ce, Dy is more favorable for Cu²⁺ to move toward the eight-membered ring of Cu/SAPO-34, and Cu²⁺ in the eight-membered ring is more beneficial to improve the NH₃-SCR activity. The in-situ diffuse reflectance infrared Fourier-transform spectra show that the NH₃-SCR reaction on Dy-Cu and Cu/SAPO-34 follows the Langmuir-Hinshelwood mechanism.