Pt-Re Interactions under Hydrothermal Conditions for Aqueous Phase Reforming of Bio-derived Liquids

Wednesday, October 6, 2010 11:00 am – 12:00 pm
Room 610, M&M Building

David L. King
Pacific Northwest National Laboratory

Abstract

Hydrogen production from the aqueous phase reforming of glycerol over 3%Pt-Re/C  has beenstudied,  and the results compared with a Re-free 3%Pt/C catalyst. Although the Pt/C catalyst isvery selective toward the production of hydrogen, catalytic activity is low. Addition of Resignificantly increases the conversion of glycerol, at some loss of hydrogen selectivity to lighthydrocarbons and water-soluble oxygenates. This loss of H2 selectivity can be traced to anincrease in acid-catalyzed dehydration pathways.  The highest hydrogen productivity among thecatalysts tested is achieved with a 3%Pt-3%Re/C catalyst with added KOH base, whichmediates the acidity. The observed product distributions can be understood in terms of thedifferent reaction pathways that become emphasized depending on catalyst composition andpH.

The structure of Pt-Re nanoparticles supported on carbon following exposure to a hydrogenreducing environment and subsequent hydrothermal conditions has been studied using in-situ xray photoelectron spectroscopy (XPS) and aberration-corrected scanning transmission electronmicroscopy (STEM) with associated energy-dispersive spectroscopy (EDS). Thephysicochemical and electronic structure of PtRe nanoparticles under hydrothermal conditionshave been correlated to the catalyst selectivity in the aqueous phase reforming of glycerol. Weshow that Re addition to Pt results in charge transfer from Pt to Re-Ox under hydrothermalreaction conditions. The catalyst acidity increases with increasing Re:Pt ratio, and the higheracidity is shown to favor C-O over C-C cleavage. This results in higher selectivity to liquidproducts and alkanes at the expense of hydrogen production. We discuss the possible origins ofacidity enhanced by the addition of Re.

Biography

Dr. David L. King is a Laboratory Fellow (the highest rank that PNNL science and engineering staff canattain) and Team Lead of the Catalysis Science and Application Group at Pacific Northwest National Laboratory(PNNL) in Richland, Washington.  He is currently Associate Lead for the Energy Conversion Initiative, a laboratorylevel initiative which has as its goal to develop PNNL as a Center of Excellence for Air- and Water-NeutralHydrocarbon Conversions, with a major focus on clean coal. He has had a long-standing interest in production ofhydrocarbon liquids from coal and biomass. Dr. King holds fifteen patents, with several pending, and over forty peerreviewed publications. Dr. King has a Ph. D. from Harvard University in physical chemistry.


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