Synergistic effect of Ce-Mn on cyclic redox reactivity of pyrite cinder for chemical looping process

Abstract

Pyrite cinder (Pc) is a solid waste from sulfuric acid production. The cleaner and efficient utilization of pyrite cinder is of great significance to achieve the recycling of industrial solid waste. In this study, we prepared different doped pyrite cinder-based oxygen carriers (Ce-Pc, Ce-Mn-Pc, Mn-Pc), and investigated the synergistic effect of Ce-Mn on cyclic redox reactivity of pyrite cinder in chemical looping process. The synergy between Ce and Mn in the modified pyrite cinder for fuel combustion reactivity was discussed in detail. The addition of Mn enhanced the cyclic stability of CeO2-doped pyrite cinder during sequential chemical looping cycles. The synergistic effect of Ce-Mn facilitated the generation of oxygen vacancies, which improved the mobility of lattice oxygen and enhanced the reducibility. The results indicated that the effect of CeO2 and MnOx on the cyclic redox reactivity of pyrite cinder was relatively weak compared with the synergistic effect of CeO2-MnOx. In addition, Ce-Mn could prevent grain growth and agglomeration of pyrite cinder. After the 20th cycle, the oxygen carrying capacity (OCC) of raw pyrite cinder decreased significantly from 3.63% in the 1st cycle to 2.45%. During the multiple redox cycles, the Ce-Mn-Pc presented the highest OCC (about 3.6%). The Ce-Mn co-doped pyrite cinder presented excellent cyclic durability with CH4 conversion more than 85% during successive cycles. This study provides an approach for the rational design of pyrite cinder-based oxygen carriers with high cyclic redox reactivity and durability.