Enhanced hydrothermal stability of Cu-SAPO-34 with an ultrathin TiO 2 coated by atomic layer deposition for NH 3 -SCR

Reducing pollution and carbon emissions is an important step toward peaking CO 2 emissions before 2030 and reaching carbon neutrality before 2060, and heavy diesel vehicle pollution, particularly nitrogen oxides (NO x ) emissions, is an essential part. Cu-SAPO-34 is a CHA-type small pore molecular sieve with excellent ammonia (NH 3 ) selective catalytic reduction (NH 3 -SCR) catalytic activity, but it cannot be stored or applied because of severe degradation caused by low-temperature hydrothermal aging. To improve the hydrothermal stability, TiO 2 was coated on the surface of Cu-SAPO-34 by the ALD method to form a uniform nanolayer. Though this ultrathin TiO 2 nanolayer has little effect on NH 3 -SCR catalytic activity of Cu-SAPO-34, the resistance to low-temperature hydrothermal aging in liquid water at 80°C for 24 h has greatly been improved. A study carried out by SEM, XRD, NH 3 -TPD, and EPR, showed that the ultra-thin TiO 2 nanolayers were covered uniformly and hydrolysis of frameworks silicon and the migration of Cu 2+ was retarded. This method has some implications for the future preparation of highly robust Cu-SAPO-34 catalysts for industrial applications. This research could inspire the development of highly robust Cu-SAPO-34 catalysts to control the NO x emissions from diesel engines.