Research on the Optimization of One-step Hydrothermal Synthesis Process to Synchronously Enhance the Low-temperature Activity and N2 Selectivity of the Aging-resistant Cu-SAPO-34 Catalyst

The NH₃-SCR technology using ammonia as a reducing agent is an important technology for controlling the NOₓ emissions of diesel engines at present. Considering the actual operating conditions of the engine and the regeneration of the DPF upstream of the SCR system, the NH₃-SCR catalyst should have a wide active temperature window, high nitrogen selectivity, and good hydrothermal aging stability. The small-pore molecular sieve catalyst Cu-SAPO-34 has attracted widespread attention due to its good low-temperature activity and high-temperature hydrothermal aging stability. However, the low-temperature hydrothermal aging stability of Cu-SAPO-34 is a key issue that needs to be addressed. Aiming to find a catalyst with excellent NH₃-SCR performance and low-temperature hydrothermal aging stability, this paper prepared the Cu-SAPO-34 molecular sieve catalyst by the one-step hydrothermal synthesis method, and tested its SCR performance and characterized its physical and chemical properties. In this work, the conditions of the one-step synthesis method were optimized. By setting different calcination temperatures and calcination heating rates, Cu-SAPO-34 catalysts with different calcination temperatures and heating rates were prepared. Then, SCR performance tests and characterizations including BET and XRD were carried out. The results show that the calcination temperature and heating rate have a significant impact on the SCR performance of the catalyst. When the calcination temperature is 700 °C and the heating rate is 5 °C/min, the catalyst has a large specific surface area and pore volume, and a relatively high CHA crystallinity, which endows the catalyst with excellent NH₃-SCR performance.