caa a22 4500 475844408 CHVBK 20180406123909.0 cr unu---uuuuu 170329e20000701xx s 000 0 eng 10.1023/A:1009028804712 doi (NATIONALLICENCE)springer-10.1023/A:1009028804712 Preparation and characterization of alumina‐supported metal‐carbonyl‐derived model catalytic systems in UHV conditions [Elektronische Daten] [M. Kaltchev, W.T. Tysoe] Active catalysts for metathesis of alkenes, hydrodesulfurization, and hydrogenation can be prepared by exposing a high‐surface‐area alumina support to molybdenum hexacarbonyl at room temperature. This strategy is mimicked in ultrahigh vacuum by adsorbing molybdenum hexacarbonyl onto an ultrathin hydroxylated alumina film grown onto a Mo(100) substrate. In contrast to results found on high surface area, no Mo(CO)6 is found to adsorb on alumina at 300 K, and significant molybdenum deposition is only found by heating the sample to above 670 K. Alternatively, molybdenum hexacarbonyl adsorbs on alumina when cooled to 80 K. In this case the majority of the carbonyl desorbs intact and temperature‐programmed desorption and X‐ray photoelectron spectroscopy indicate that ∼2% of a monolayer of the carbonyls undergoes decarbonylation. Auger and X‐ray photoelectron spectroscopy measurements reveal that molybdenum carbide (MoC) is deposited onto the alumina surface heated to 700 K forming a monolayer after an exposure of ∼50 L. This layer is reduced to the metal by heating to ∼1500 K by reaction with the alumina substrate to evolve CO and form metallic molybdenum. The carbide can be reformed by heating the metal‐covered alumina sample in ethylene at 900 K, and the carbide can once again be reduced to the metal by heating to 1500 K. This process can be repeated so that the carbide can be regrown by reaction with ethylene and reduced by annealing in vacuo to 1500 K. Subcarbonyl species are detected after adsorbing Mo(CO)6 on hydroxylated alumina at 80 K as the sample is heated to ∼200 K. At higher temperatures, the molybdenum is oxidized to an approximately 4+ oxidation state and deposits primarily oxalate species on the surface. The adsorbed oxalates thermally decompose at ∼300 K to evolve CO to form surface formates. These are stable to ∼560 K and react to evolve CO at this temperature. It is also found that the extent of decarbonylation depends on the degree of alumina hydroxylation so that heating hydroxylated alumina to 900 K, which removes ∼50% of the surface hydroxyls, decreases the both CO desorption yield and the oxalate coverage by 50%. Kluwer Academic Publishers, 2000 alumina nationallicence thin films nationallicence molybdenum hexacarbonyl nationallicence molybdenum carbides nationallicence reflection-absorption infrared spectroscopy (RAIRS) nationallicence X‐ray photoelectron spectroscopy nationallicence Auger spectroscopy nationallicence temperature‐programmed desorption nationallicence Kaltchev M. Department of Chemistry and Laboratory for Surface Studies, University of Wisconsin‐Milwaukee, 53211, Milwaukee, WI, USA aut Tysoe W.T. Department of Chemistry and Laboratory for Surface Studies, University of Wisconsin‐Milwaukee, 53211, Milwaukee, WI, USA aut Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 13/1-2(2000-07-01), 121-130 1022-5528 13:1-2<121 2000 13 11244 https://doi.org/10.1023/A:1009028804712 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1009028804712 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kaltchev M. Department of Chemistry and Laboratory for Surface Studies, University of Wisconsin‐Milwaukee, 53211, Milwaukee, WI, USA aut NATIONALLICENCE 700 1- Tysoe W.T. Department of Chemistry and Laboratory for Surface Studies, University of Wisconsin‐Milwaukee, 53211, Milwaukee, WI, USA aut NATIONALLICENCE 773 0- Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 13/1-2(2000-07-01), 121-130 1022-5528 13:1-2<121 2000 13 11244 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer