(678e) Highly Active Atomically Dispersed Gold/Titania Methanol Steam Reforming Catalysts Stabilized By Sodium Ions
AIChE Annual Meeting
2015
2015 AIChE Annual Meeting Proceedings
Catalysis and Reaction Engineering Division
Atomically Dispersed Supported Metal Catalysts
Thursday, November 12, 2015 - 1:50pm to 2:10pm
The gold-catalyzed reaction of steam reforming of methanol (SRM) has been studied on various oxide supports (e.g. CeO2, ZnO, and ZrO2) and demonstrated to achieve a wide temperature window for CO-free hydrogen production[1-3]. The apparent activation energy of the SRM reaction rate is 110±8 kJ/mol for all supported gold catalysts regardless of the support oxide employed, indicating a similar reaction mechanism, with Au-Ox as the active site. However, the overall activity of the catalyst relies on the capacity of the support oxide to anchor gold active center through Au-Ox-support linkages[4]. In this work, Au/TiO2 was investigated for the first time as a low-temperature SRM catalyst. Applying gold by deposition-precipitation, the anatase TiO2 surface failed to preserve active gold species under the reaction conditions. Gold nanoparticles (~ 6.2 nm) were formed, resulting in poor SRM catalytic performance.
Inspired by the concept of the alkali stabilized Au-Ox- species for the WGS reaction on inert support oxides[5], we developed a one-step synthesis route to create exclusively single-gold-atom centric clusters stabilized by the –O-Na linkages in an alkaline solution, without the involvement of the TiO2 support. A simple incipient impregnation (IWI) of the new gold precursor on the TiO2 support achieved the atomic dispersion (100 %) of the cationic gold up to 1 wt.%. Without further treatment, the new Au-Na-TiO2 catalysts give high activity, H2-selectivity, and stability in the low-temperature SRM reaction (200-300˚C). The identified single-site Au(I)-O(OH)x- species serve as the catalytic centers for the reaction, showing similar intrinsic activity as other atomically dispersed gold anchored on CeO2[2] or composite oxides, such as Au-ZnZrOx[1]. The present work opens a new practical route to prepare a new group of heterogeneous gold catalysts that may be active for other low-temperature fuel-gas processing reactions.