The influence of low-temperature hydration methods on the stability of Cu-SAPO-34 SCR catalyst

Low-temperature hydration experiments are designed to explore the influence of hydration time and cycle hydration on the stability of Cu-SAPO-34 catalyst. All the hydration treatments are conducted at 80 degrees C. Experiments on the impact of hydration time reveal that a fast activity loss for Cu-SAPO-34 occurs at the initial hydration stage of 30 min, and further extending the time until 24 h only leads to a much slower drop rate. Conversely, cycle hydration, which is close to the working conditions of the SCR catalyst, causes a continuous activity drop as the increase of hydration cycles (steaming for 30 min/cycle). Multiple characterizations reveal that in comparison with hydration time method, cycle hydration induces a faster loss of acid sites and decrease of reducibility of isolated Cu2+ to Cu+, both of which cause the severer deactivation of the catalyst. This occurs due to the repeated high-temperature treatments involved in the cycle hydration treatment, which promote the migration of Cu ions among the CHA cages, cause a fast deterioration of Bronsted acid sites, and thus obviously alter the micro-environments of Cu ions and their reducibility.