Bi-functional two-dimensional cobalt silicate catalyst for selective catalytic oxidation of ammonia

We have newly synthesized the zeolitic cobalt silicate catalysts via a simple hydrothermal treatment of borosilicate MWW precursor with Co precursor solution. As the hydrothermal temperature increased, a structural transformation occurred, shifting from three-dimensional (3D) to two-dimensional (2D) delaminated MWW layers (DML), and further to 2D amorphous phyllosilicate, accompanied by a continuous increase in Co content. The synthesized bi-functional 2D cobalt silicate facilitates the selective catalytic oxidation of NH3 (NH3-SCO), a process that requires both surface acidity and redox characteristics. In particular, Co-DML-160 prepared by hydrothermal treatment at 160 °C exhibited the coexistence of Co3O4 and framework Co species resulting in a strong redox ability and high Lewis acidity, respectively, due to their synergetic effect. [Display omitted] •Hydrothermal transformation of 3D to 2D cobalt silicates (Co-DMLs) by raising temp.•Changes of chemical compositions and states of Co in Co-DMLs depending on temp.•Framework Co and Co3O4 as Lewis acid and redox active sites in bi-functional Co-DML.•Co-DML as an efficient NH3-SCO catalyst with high NH3 conversion and N2 selectivity.•Suggestion of i-SCR reaction mechanism in NH3-SCO over bi-functional Co-DMLs.