The conversion of biomass into energy carriers in the condensed phase involves reactions in the presence of water mainly as a solvent. These chemical transformation of lignin-derived compounds to hydrocarbon fuels are performed at elevated temperature (473 K) and pressure (up to 50 bar H2) and therefore the state and stability of supported metal catalysts during reaction in the presence of water is not clear. Using in situ extended X-ray absorption fine structure spectroscopy, to better define the chemical state under dynamic variations of the environment, the noble metal Pd, the base metal Ni, and a bimetallic mixture of Ni and Fe were investigated under hydrothermal conditions. For Pd on various supports (C, Al2O 3, SiO2) water had no effect allowing its active phase (PdH x) to perform phenol hydrogenation. In the presence of water, Ni was found to be stable supported on HZSM-5 and sulfonated carbon while it transformed to Ni(II) phyllosilicate when supported on SiO2. This chemical state change lowers the hydrogenation activity of Ni on this support. Lastly, alloying Ni with Fe inhibits this undesired chemical state change for Ni(0) supported on SiO2 yet it also leads to a lowering of the hydrogenation activity that is speculated to be the result of a decreased amount of surface Ni available for reaction. Sum Frequency Generation was also used in a fundamental study to investigate diverse conformation of different interfaces to give a general understanding of surface interactions.
|Commitee:||Camaioni, Don, Ha, Su, Lin, Hingfei|
|School:||Washington State University|
|School Location:||United States -- Washington|
|Source:||DAI-B 80/03(E), Dissertation Abstracts International|
|Subjects:||Bioengineering, Chemical engineering|
|Keywords:||Bulk and surface interactions, Condensed phase, Spectroscopic|
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