(641b) In Situ FTIR Identification of the Reactive Sites of a Ni/TiO2 Steam Reforming Catalyst

CO₂ accumulation in the atmosphere, which is a major concern in global warming, has caught more and more attention all over the world. Tri-reforming is one of the potential processes for CO₂ mitigation, which reacts steam methane reforming (SMR) effluents with natural gas and O₂ to produce syngas (CO and H₂).  Industrial SMR catalysts contain nickel supported on metal oxide, such as TiO₂, MgO, CeO₂, ZrO₂, or a combination of them.  It is generally thought that Ni is responsible for the dissociation of H atoms while CO₂ is activated on the oxygen vacancy support to form CO and O atom. However, little is known about the different surface species within the support for oxygen dissociation from CO₂ at reaction conditions.

The synergistic interaction between the support and metallic sites responsible for the adsorption of CO and CO₂ has been investigated in our work.  Ni/TiO₂, which was synthesized by incipient wetness, was the selected catalyst, since TiO₂ has an abundance of oxygen vacancies within its lattice structure.  These oxygen vacancies lend themselves to accept donor oxygen atoms from CO₂, H₂O, or O₂.  In situ FTIR was used to investigate surfacing reacting species while using CO and CO₂ as probe molecules.  The in situ reactor was temperature programmed (25 - 350°C) at 3°C/min while taking IR spectra throughout the temperature range.  The results indicate a multiplicative of reacting surface species (including lattice TiO₂ lattice vibrations, Ti³⁺ and Ti⁴⁺) that can form at elevated reaction temperature conditions. This dynamic behavior explains the oxygen transport reaction mechanism necessary for tri-reforming reactions. In addition, a surface site mechanism has been proposed and is supported by reaction coordinate calculations.