Insight into role of Co species on NiCo/CeMgAl for ethanol steam reforming: Enhanced activity and resistance to coke

Abstract

Bimetallic catalysts with unique geometric and electronic structure exhibit high performance compared to that of monometallic counterparts in the ethanol steam reforming (ESR). Herein, NiCo bimetals supported on CeO2 doped MgAl2O4 (NiCo/CeMgAl) with different ratio of Ni/Co were prepared for ESR. The synergies between Ni and Co in catalytic activities and ability to anti-coking were focused. The results demonstrate Co atoms trend to segregate toward the surface and are oxidized synchronously, forming the Ni-CoO hybrid surface. The reduced Ni particles are beneficial to maintain a stable catalytic activity for the C-C bonds scission, and the CoO particles formed by segregation and irreversible oxidation of Co0 are more conducive to activation of H2O, the resulting OH promotes the transformation of CHx species, which significantly reduces the selectivity of CH4 and prevents the formation of filamentous carbon. Controlling Co content and maintaining a stable M/Mδ+ are critical to balance the C-C bond scission reaction and the CH3* conversion reaction on the NiCo bimetallic catalysts. The optimal catalyst 9Ni1Co/CeMgAl shows the ethanol conversion of 93.9 % at TOS of 100 h, and the average rate of coke formation is 0.50 mgc·gcat-1·h−1.