The catalytic oxidation removal of low-concentration HCHO at high space velocity by partially crystallized mesoporous MnOx

- A simple redox precipitation combined with NaBH4 post-treatment approach has been developed to prepare partially crystallized mesoporous MnOx.
- The synthesized MnOx features large amount of surface adsorbed oxygen species and multiple valence states of Mn.
- Oxidative decomposition of low concentration formaldehyde on PC-MnOx occurs at room temperature.
- The accumulation of intermediate on the catalyst surface at prolonged reaction leads to the catalyst deactivation and it can be removed by heating the catalyst at mild temperature.

Efficient removal of low-concentration HCHO at room temperature and high space velocity without using noble metals is still a great challenge to date. In this work, we have fabricated partially crystallized mesoporous MnOx by redox precipitation reaction between potassium permanganate and oxalic acid, followed by NaBH4 post-treatment at room temperature. The as-synthesized MnOx was coated on honeycomb ceramics and the obtained monolithic catalyst exhibited high efficiency in removing low-concentration HCHO (1 ppm and 0.2 ppm) at a space velocity of ∼48,000 h−1. When operated at 85 °C, the monolithic catalyst showed further improved HCHO removal efficiency and durable performance. And with humidity, the catalyst also showed enhanced catalytic activity and prolonged life. The multiple valence states of Mn, high surface area together with the high content of surface-adsorbed oxygen species have been identified and proposed to be responsible for its high catalytic activity in HCHO oxidation removal.

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