Stabilizing cobalt catalysts for aqueous-phase reactions by strong metal-support interaction

High-temperature calcination and reduction treatments of cobalt particles (17-20 nm) supported on TiO2 create cobalt particles covered with a TiOy layer. The layer thickness ranges from 2.8 to 4.0 nm. These phenomena, commonly called strong metal-support interaction (SMSI), can be used to improve the catalyst stability and change the catalyst selectivity. For example, non-overcoated cobalt catalysts leached during aqueous-phase hydrogenation (APH) of furfuryl alcohol, losing 44.6% of the cobalt after 35 h time-on-stream. In contrast, TiOy-overcoated cobalt catalysts did not lose any measurable cobalt by leaching and the cobalt particle size remained constant after 105 h time-on-stream. The 1,5-pentanediol selectivity from furfuryl alcohol hydrogenolysis increased with increasing TiOy layer thickness. The stabilized cobalt catalyst also had high yields for APH of xylose to xylitol (99%) and APH of furfural to furfuryl alcohol (95%). These results show that the SMSI effect produces a catalyst with a similar structure as catalysts prepared by atomic layer deposition, thereby opening up a cheaper and more industrially relevant method of stabilizing base-metal catalysts for aqueous-phase biomass conversion reactions. In addition, the SMSI effect can be used to tune catalyst selectivity, thus allowing the more precise atomic scale design of supported metal catalysts. (C) 2015 Elsevier Inc. All rights reserved.