Fred R. Brown

Raman spectra of supported molybdena catalysts: II. Sulfided, used, and regenerated catalysts☆

Abstract Raman spectroscopy has been used to investigate the structural changes that two supported molybdenum oxide catalysts undergo upon specific chemical treatments. Molecular MoS2 structures are indicated after sulfidation by a mixture of H 2 H 2 S . Catalyst samples used in a coal hydrodesulfurization process yield spectra dominated by intense scattering from carbon deposited in the pores of the catalyst. Spectra of used catalyst samples, subjected to controlled air-firing to 600 °C, show that all of the spectral features of the unused catalyst are not recovered after this “regeneration” procedure.

A surface spectroscopic study of Coz.sbnd;MoAl2O3 catalysts using ESCA, ISS, XRD, and Raman spectroscopy, I

Abstract Laser Raman spectroscopy, X-ray photoelectron spectroscopy, low-energy ion-scattering spectroscopy, and X-ray diffraction have been used to characterize a series of Coz.sbnd;Mo Al 2 O 3 catalysts containing 15 wt% MoO 3 and 0 to 8 wt% CoO in their oxide, reduced, and sulfided forms. These data show that the catalyst surface contains CoMoO 4 and irreducible Co 2+ ions of tetrahedral symmetry when the CoO concentration is 0 to 6%. With 7 to 8% CoO, additional surface species includes Co 3 O 4 crystallites on the γ-Al 2 O 3 surface. Formation of Co 3 O 4 coincides with an increased Mo reducibility and a decreased BET surface area. These results are compared to previously published data on Coz.sbnd;Mo Al 2 O 3 and suggest that the state of dehydration-dehydroxylation of the Al 2 O 3 surface before impregnation of Co and Mo affects their subsequent speciation. Autoclave studies investigating the hydrodesulfurization (HDS) and hydroconversion of coal using these catalysts are also reported. Significance of the surface speciation with respect to these activity studies is discussed.

Stability studies of coal-derived liquids

Abstract The ageing characteristics of liquid products derived from the hydrogenation of coal have been studied. Viscometric, spectrometric, ultimate analysis, solvent separations and oxygen consumption measurements have been employed to monitor the storage properties of the coal-derived liquids under a variety of environmental conditions. These studies show that the coal-derived liquids are very susceptible to oxidative degradation. Rates of this degradation process, based on viscosity measurements, are related to the initial viscosity of the coal-derived liquid, storage temperature and concentration of oxygen in the gaseous environment over the liquids. Analysis of aged samples show the components of higher molecular weight with functional components are most susceptible to the oxidation process. Although the total coal-derived liquids are more susceptible to oxidative degradation than the petroleum-derived boiler feedstocks, removal of the most reactive components from the coal-derived liquids, by solvent separation, results in a fuel that has analogous stability characteristics as the petroleum products.

Supported transition metal compounds: I. A new method for the preparation of alumina-supported iridium and osmium carbonyls☆

An extraction technique for the preparation of alumina-supported iridium and osmium carbonyls from Ir4(CO)12 and Os3(CO)12 is reported. It is concluded that the metal carbonyl species produced are highly dispersed and of small particle size (less than 50 A diameter) in contrast to the large crystallites of iridium and osmium carbonyls obtained by either the dry grinding or wet impregnation techniques. Partial decarbonylation of the metal carbonyl species can be effected by varying the conditions of the preparation and by heating the samples in air, the species [Ir(CO)2]+ and [Os(CO)n]2+, n = 2,3, have been identified from their infrared spectra. Strong interactions between the metal carbonyl species and the alumina support are present.

Infrared and Raman Spectra of a Sulfur-Resistant Methanation Catalyst

The infrared and Raman spectra of a sulfur-resistant NiO/Cr2O3/MgSiO3 methanation catalyst are presented and compared to the spectra of the catalyst after being reduced, sulfided, and tested for methanation activity. The molecular structure of the catalyst is shown to be represented by NiO and MgO dispersed in a quasi-tridimensional Cr-O-Si network. Reduction and sulfiding reorders this network and alters the SiOn coordination while reducing Cr6+ to Cr3+ or Cr2+. The data indicate that the SO4−2 which is present after sulfiding and methanation testing may have been formed during the methanation reaction.