| Abstrakt: |
In this study, we explore a novel approach to nitrogen oxide (NOx) purification based on the principles of the chemical looping (CL) platform. This technique harnesses the reducing power of natural gas (CH4), instead of ammonia, to eliminate NOxin the flue gas, addressing environmental concerns such as ammonia slip in the state-of-the-art selective catalytic reduction process. The CL scheme involves utilizing nickel oxide (NiO) as the solid oxygen carrier to facilitate oxygen transfer from NOxto CH4in two steps. In the first step (carrier oxidation), NOxin the flue gas reacts with reduced nickel (Ni), transferring its [O] to the carrier, thereby forming NiO. In the subsequent step (carrier reduction), CH4reacts with the lattice oxygen of the oxidized carrier, generating a pure stream of CO2and reducing NiO to Ni. We designed a high-performance carrier by dispersing NiO on an inert support to enhance the carrier’s kinetics and thermal stability. We evaluated various support materials, and among them, alumina (Al2O3) and zirconia (ZrO2) demonstrated significantly superior reactivity. Notably, the Al2O3-supported carrier outperformed the ZrO2-supported carrier in NO purification and CH4reduction and demonstrated stable performance over 10 redox cycles. Furthermore, fixed-bed experiments revealed 100% NO conversion during carrier oxidation, with optimal reaction kinetics achieved at lower space velocities, resulting in an overall high carrier utilization. Importantly, CO2showcased no adverse effects during the NOxpurification step. During the carrier reduction, complete combustion was favored, leading to CH4conversion exceeding 95% and a CO2selectivity of 90% at 400 °C. The CL NOxpurification approach represents a promising strategy for mitigating NOxemissions. |
