Removal of elemental mercury in flue gas at lower temperatures over Mn-Ce based materials prepared by co-precipitation

- Mn0.1Ce0.2Al-400 was highly active for mercury removal at low temperature without HCl.
- Higher calcination temperature resulted in grain growth and decreased the activity.
- NO promoted mercury removal but SO2 suppressed it.
- High concentration of amorphous MnOX and nano-crystalline CeO2 was supported by Al2O3.
- Synergistic effect between MnOX and CeOX improved the activity further.

A series of Mn-Ce based materials were synthesized by co-precipitation method and were examined for mercury removal at lower temperatures (50-250 °C) in the absence of HCl. The effect of preparation conditions (metal oxides and calcination temperature) and reaction conditions (reaction temperature and gas constituents) was investigated. Results showed that Mn0.1Ce0.2Al-400 was found to be the most active catalyst for mercury removal, achieving around 96% Hg0 removal efficiency in the presence of 6% O2 at 150 °C. Higher calcination temperature could result in the grain growth and particle agglomeration, thus decreasing the activity. The optimum reaction temperature for mercury removal over Mn0.1Ce0.2Al-400 was about 150 °C. NO was observed to promote mercury removal over Mn0.1Ce0.2-400 catalyst but SO2 generally suppressed it. Various techniques (BET, XRD, TEM, H2-TPR and XPS) were used to characterize the samples. The results substantiated the formation of a composite material consisted of high concentration of amorphous MnOX and nano-crystalline CeO2 supported by Al2O3, which might lead to an enhanced interaction of Ce with Mn. Moreover, the adsorbed Hg0 mainly interacted with the lattice oxygen in MnO2 to form HgO which was replenished by gas-phase O2. CeOx could facilitate the activation and transfer of oxygen and consequently improve the activity for oxidation removal of Hg0 over manganese oxides further.