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The thermal surface chemistry of 2(5H)-furanone (25HF) on Pd(111) and Pt(111) was studied using high-resolution electron energy loss spectroscopy (HREELS) and temperature-programmed desorption (TPD). After adsorbing 25HF on each surface at <140 K, increasing the temperature above 300 K resulted in opening and decomposition of the furanone ring. On both surfaces, 25HF undergoes decarbonylation and dehydrogenation to form CO and H2 as the principal desorption products. A key difference between Pd(111) and Pt(111) reactivity is the relatively high amount of CO2 produced from Pt(111), suggesting that 25HF decomposition proceeds in part through an additional surface intermediate on Pt(111). HREELS provides further indications that the reactions proceed through distinct pathways. On Pd(111), direct decarbonylation to surface CO and ethylidyne is observed. On Pt(111), two reaction pathways are proposed. One pathway is similar to the reaction pathway for Pd(111) and produces CO during TPD, and the other proceeds through an intermediate that retains the OCO functional group and results in CO2 as a desorption product.

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A combination of experimental surface science techniques and density functional theory calculations has been employed to understand the adsorption and surface chemistry of a variety of C 4 cyclic oxygenates on the (111) surface of Pd. These C 4 cyclic oxygenates represent important probe molecules for production of chemicals from biomass-derived carbohydrates. The surface level studies of these intermediates reveal that adsorption and reactivity trends are determined by ring size/strain, degree of unsaturation, nature of the oxygenate function, and composition of the metal surface.

Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al 2 O 3 -supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H 2 S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C 2 H 4 on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C 2 H 4 adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C 2 H 4 adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison.