A Brief History of the Southwest Catalysis Society

Water Gas Shift Reaction: The turn-over-rate (TOR) for the water gas shift (WGS) reaction of 1.4 nm Au/Al2O3 is approximately 20 times higher than that of 1.6 nm Pt/Al2O3. In addition, Au has high activity at lower reaction temperature than Pt. Operando XAFS experiments at both the Au and Pt L3 edges reveal that under reaction conditions, the catalysts are fully metallic. Adsorption of CO, H2 and H2O leads to changes in the XANES spectra that can be used to determine the surface coverage of each adsorbate under reaction conditions. During WGS, the coverage of CO, H2O, and H2 are obtained by the linear combination fitting of the difference XANES, or ∆XANES, spectra. Pt catalysts adsorb CO, H2, and H2O more strongly than the Au, in agreement with the lower CO reaction order. At low reaction temperature, the low rate of Pt is due to saturation of the metallic surface by adsorbed CO, while on Au there is little CO coverage and higher rates. Density Functional Theory of XANES Spectra: In order to better understand these changes in XANES spectra with adsorbates and particle size, Pt nano-particles from about 1 to 10 nm have been prepared on different supports. The EXAFS spectra of the reduced catalysts in He show a contraction of the Pt-Pt bond distance as particle size is decreased below 3 nm. The bond length decreased as much as 0.13 Å for 1 nm Pt particles. Adsorption of CO and H2 lead to a increase in Pt-Pt bond distance to that near Pt foil, e.g., 2.77 Å. In addition to changes in the Pt bond distance with size, as the particle size decreases below about 5 nm there is a shift in the XANES to higher energy at the L3 edge, a decrease in intensity near the edge and an increase in intensity beyond the edge. At the L2 edge, there are only small shifts to higher energy at the edge. However, beyond the edge, there are large increases in intensity with decreasing particle size. At the L1 edge there are no changes in position or shape of the XANES spectra. Adsorption of CO and H2 also lead to changes in the L3 and L2 edges, however, no changes are observed at the L1 edge. Density Functional Theory and XANES calculations show that the trends in the experimental XANES can be explained in terms of the d electron density of states available near the Fermi level. A Peek into a Black Box: A Brief Review of Research in the Lunsford Group Jack Lunsford Texas A&M University Over the past four decades several types of spectroscopy have been effectively used to elucidate active sites and intermediates in catalytic reactions. Among these are electron spin resonance, laser induced fluorescence, and laser Raman spectroscopies. Each type of spectroscopy is limited in scope and unique in the information that can be revealed; yet, when appropriately applied the secrets of catalysis can be probed at a very elementary level. Study of Renewable Diesel Production via Hydroprocessing Vegetable Oils Steve Xie Chevron Corporation Diesel of -15°C cloud point meeting ASTM D 975 ULSD specifications can be produced by hydrotreating canola oil and palm oil followed by a dewaxing step, with ~87 vol% yield of 350-650°F+ cut at 1,000 psig and 1 hr-1 LHSV. While hydrodeoxygenation is the predominant reaction pathway of hydrocarbons formation from the dissociation of triglycerides, the relative contribution of decarboxylation pathway to the overall reaction scheme increases with decreasing pressure and increasing temperature. The catalyst lost at least 20°F activity after 2,000 hours on stream, and rejuvenation by injecting DMDS into feed stream to re-sulfide the catalyst can recover some but not all lost activity. In-situ Characterization of Fe-based Fischer-Tropsch Catalysts Bert Weckhuysen University of Utrecht An increasing demand for clean fuels and chemicals are expected to lead to an important shift from crude oil to natural gas as well as bio-feed as feedstock for chemical industries. This will certainly involve the use of Fischer-Tropsch (FT) technology, in which high molecular weight hydrocarbons are synthesized by catalytic hydrogenation of CO using cobaltor iron-based Fischer-Tropsch catalysts. These GTL and BTL (Gas-to-liquid and Biofeed-to-liquid) processes currently deserve a lot of attention both in academia and chemical industries and as a consequence a lot of research is focusing on the development of improved catalyst compositions and understanding their behavior. In this lecture, two novel characterization approaches will be discussed to elucidate in more detail the catalyst phase changes occurring during FT catalysis. These methods involve in-situ Scanning Transmission X-ray Microscopy (STXM) and combined in-situ XAFS/XRD/Raman spectroscopy. The iron oxide-iron carbide phase transformations will be explained in terms of the chemical potential of carbon as a function of reaction temperature, pressure and gas feed composition.