Three-Dimensional Spherical CuCoAlO_<i>x</i> Catalyst with a Micro-/Nanoporous Structure for Low-Temperature CO-SCR Denitration

Abstract

Selective catalytic reduction (SCR) is the most effective method to remove NOx from flue gas. Since the flue gas contains CO gas, using CO as a reducing agent to selectively remove NO (CO-SCR) is greatly convenient. In this paper, we developed an improved coprecipitation method combined with spray drying technology to design and synthesize a CuCoAlOx CO-SCR denitration catalyst having a three-dimensional micro/nanoporous spherical morphology. The structural features of the catalyst offer the following advantages: (1) the micron size of metal oxide materials provides sufficient mechanical strength to avoid material wear and consumption; (2) the porous structure increases the specific surface area, exposes more active sites, and facilitates the contact of CO and NO with active substances, thereby improving the reactivity; (3) the spherical morphology provides the catalyst with excellent fluidity, dispersion, uniformity, and compactness, which are beneficial characteristics for coating formation and to achieve satisfactory process operation performance. The surface reaction mechanism of the CuCoAlOx catalyst was elucidated on the basis of in situ Fourier-transform infrared spectroscopy and density functional theory calculation results, which revealed that the preferential adsorption of NO in the presence of a CO + NO mixture enhances the subsequent adsorption of CO, with the adsorption energy decreasing from −0.47 for single CO adsorption to −1.51 eV, thus improving the CO-SCR denitration performance. The as-prepared CuCoAlOx catalyst reached an NO conversion of 46.1% at 50 °C and 90.1% at 200 °C.