Acid strength and bifunctional catalytic behavior of alloys comprised of noble metals and oxophilic metal promoters

作者：Hibbitts David; Tan Qiaohua; Neurock Matthew^*

来源：Journal of Catalysis, 2014, 315: 48-58.

DOI：10.1016/j.jcat.2014.03.016

• Hydrogenolysis
• Ring opening cyclic ethers
• DFT, bifunctional catalysis
• Hydrodeoxygenation
• Oxophilic metal promoters
• Deprotonation energies
• Hydroxymethyl tetrahydrofuran

The promotion of metal catalysts with partially oxidized oxophilic MOx species, such as ReOx-promoted Rh, has been demonstrated to produce Bronsted acid sites that can promote hydrogenolysis of oxygenate intermediates such as those found in biomass-derived species. A wide variety of alloy compositions and structures are examined in this work to investigate strongly acidic promoters by using DFT-calculated deprotonation energies (DPE) as a measure of acid strength. Sites with the highest acid strength had DPE less than 1100 kJ mol(-1), similar to DPE values of heteropolyacids or acid-containing zeolites, and were found on alloys composed of an oxophilic metal (such as Re or W) with a noble metal (such as Rh or Pt). NH3 adsorbs more strongly to sites with increasing acid strength and the activation barriers for acid-catalyzed ring opening of a furan ring decrease with increasing acid strength, which was also shown to be stronger for OH acid sites bound to multiple oxophilic metal atoms in a three-fold configuration rather than OH sites adsorbed in an atop configuration on one oxophilic metal, indicating that small MOx clusters may yield sites with the highest acid strength.

• 出版日期2014-6