Identifying the time-dependent predominance regimes of step and terrace sites for the Fischer–Tropsch synthesis on ruthenium based catalysts

Abstract

The Fischer–Tropsch synthesis (FTS) is an appealing process to generate liquid fuels from syngas. The elusive nature of FTS active sites is clarified here through a comprehensive theoretical-experimental study of CO dissociation on supported Ru catalysts. Our theoretical calculations show that boron (B) adsorption is stronger than that of CO on step-edge sites. In view of this, we deposited 2D-like Ru islands on the rutile phase of TiO₂, and blocked step-edge sites by addition of B. Our results show that the initial reaction rate for the FTS of boron-dosed Ru/TiO₂ is lower than that of clean Ru/TiO₂ but the steady-state rates are identical. This indicates that CO dissociation can take place on Ru catalysts on steps and on terraces, but the contribution of each type of site to the overall CO dissociation rate varies during the reaction course: both types of reaction sites are simultaneously active on fresh catalysts under realistic FTS conditions, while only terraces sites are active under steady-state operation conditions.