Ultrafine Pt particles directed by polyvinylpyrrolidone on zeolite beta as an efficient low-temperature H2-SCR catalyst

A novel ultrafine Pt/Beta catalyst supported on carbon paper was prepared and applied to selective catalytic reduction of NOx by H-2 at a low temperature below 90 degrees C. Here, 0.8 wt.% Pt/Beta reached approximately 100 % NO conversion at 90 degrees C under oxygen-rich conditions (1000 ppm NO, 1 % H-2, and 4 % O-2). The influence of the dispersion and particle size of Pt on the catalytic performance was investigated using Polyvinylpyrrolidone (PVP) as a structure directing agent to regulate the Pt particles. The feeding amount of PVP significantly influenced the catalytic activity of the catalysts. When the feeding amount was less than 50 mg, the Pt particle size was smaller, and the dispersion was higher, providing a higher NO conversion. However, when the feeding amount exceeded 50 mg, the dispersion no longer increased, and the activity slightly decreased. N-2 physisorption (BET) confirmed that excessive PVP decreased the specific surface area, which suppressed the catalytic activity of Pt/Beta. Moreover, the NO conversion efficiency was dependent on the dispersion and particle size of Pt and was minimally affected by the surface area of the catalysts. The Pt/Beta catalyst system was deactivated, and an irreversible poisoning phenomenon for SO2 was observed. Zr, Ce, and V were introduced into the catalyst system as metal auxiliaries. The Ce-modified Pt-Ce/Beta catalyst prepared in this study showed resistance to SO2.