Novel SCR catalyst derived from Mn@Yeast materials: Insight to covalent Mn[sbnd]C[tbnd]N roles and NH3 activation on coordination sites.

The β-Mn-Y-1 (Mn@Yeast-1) catalyst is successfully synthesized by introducing yeast into Mn-ions solution using one-step method, which show good catalytic activity in NH 3 -SCR DeNO x process benefiting from the Mn-organic complexes in covalent Mn C N roles and NH 3 activation on coordination sites. [Display omitted] • Perfectly effective NH 3 -SCR activity is achieved on β-Mn-Y-1 prepared by one-step method. • Mn-organic complexes are derived from the coordination between amorphous Mn and yeast. • Covalent Mn3+ C N coordination sites can activate L-NH 3 adsorbed on Mn C O during NH 3 -SCR. • The σ-π bond of Mn3+ C N sites can weaken C N and generate N-N between C N and NH 3. • Gaseous NO react with Mn-CN-NH 2 intermediates rather than B-NH 4 + from Mn-COOH by E-R mechanism. The yeast was innovatively used to participate in the catalyst synthesis. Herein, the β-Mn-Y-1 (Mn@Yeast-1) catalyst for NH 3 -SCR DeNO x was produced by introducing yeast into the solution of Mn ions using one-step method during the process of synthesizing β-MnO 2. β-Mn-Y-1 catalyst achieved the NO x conversion more than 90 % at 175 ∼ 225 °C, and still kept at > 80 % at 250 °C, in contrast, β-Mn-Y-2 (Mn@Yeast-2 by two-step method) has no catalytic activity similar to β-MnO 2 that all the NO x conversion were below 10 % at 50 ∼ 250 °C. The abundant organic functional groups on yeast surface mostly were complexed with amorphous Mn ions to generate various Mn-organic groups (Mn3+ C N, Mn C O, Mn-COOH, etc) on β-Mn-Y-1 catalyst, and some could work as acid and coordination sites to adsorb and activate NH 3 to participate in low-temperature SCR process, but rather than the traditional Mnm+-O in β-MnO 2 crystal structure in both β-MnO 2 and β-Mn-Y-2, which indicated that the pre-obtained MnO 2 crystalline phase was difficult to cooperate with yeast. More importantly, the covalent Mn3+ C N due to the effect of σ-π bond can activate L-NH 3 adsorbed on Mn C O to react with NO (g) by Eley-Rideal mechanism belonging to the coordination catalysis, while B-NH 4 + species from Mn-COOH cannot react with NO at low temperatures. [ABSTRACT FROM AUTHOR]