Enhanced sulfur tolerance on binary Rh-Ni metals is examined for the propane steam reforming process on close packed metal surfaces of Rh, Ni, Rh1Ni2, and Rh2Ni1 with and without co-adsorbed S atoms. Scaling and Brønsted-Evans-Polanyi (BEP) correlations are constructed from density functional theory (DFT) methods. The combined use of these methods produces significant errors among these similar metal surfaces; however, BEP relations applied within reaction types are reliable across Rh, Ni, and binary Rh-Ni surfaces with and without co-adsorbed S atoms. The potential energy surface of propane steam reforming, estimated using the BEP correlations, shows that the C-C cleavages of CHC*, CH3CC* and CH2C* along with the O addition to CH* are kinetically significant elementary steps. Three of these steps show only slight barrier increases with co-adsorbed S on the Rh2Ni1 surface, suggesting an energetic explanation for enhanced S tolerance. The average poisoning effect by the presence of co-adsorbed sulfur for bond breaking is minimized on binary Rh-Ni metals, suggesting a high sulfur resistance can be induced using a bimetallic formulation of Rh and Ni.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry