Kazuhiro Inamura

X-ray photoelectron spectroscopic study for the adsorption and the decomposition of alkylamines on nickel

Abstract The adsorption state of various alkylamines on evaporated nickel film has been investigated by XPS. All amines adsorb molecularly on the surface through nitrogen lone-pair electrons at the temperature below 200 K, like ammonia and other nitrogen bases. With the rise in temperature of the surface, various kinds of dissociative adsorption proceed depending on whether the adsorbates contain the amino hydrogens, α-hydrogens, or both. These surface complexes of amines can be characterized mainly by the N 1s core electron binding energies, in comparison with those for the intermediates from ammonia: R 3 N(a), R 2 N(a) and RN(a) (R = H, alkyl) give N 1s peaks at 400.0−399.7, 398.5−398.3 and 397.7−397.5 eV, respectively in the temperature range between 230 and 330 K. It is found that the surface complexes of primary amines are similar to those of nitriles.

Adsorption of benzonitrile and alkyl cyanides on evaporated nickel and palladium films studied by XPS

Abstract The adsorption states of benzonitrile and alkyl cyanides on evaporated nickel and palladium films have been studied by X-ray photoelectron spectroscopy. Two N 1s peaks are observed for adsorbed benzonitrile on nickel; one is located at the same binding energy as that of condensed benzonitrile (399.8 eV) and the other is located at much lower binding energy (397.9–397.6 eV). The former species is seen only at low temperature (170 K) and adsorbs weakly through nitrogen lone pair electrons. The latter species exists even at temperatures as low as ∼ 170 K but predominantly at room temperature. This species seems to adsorb with rehybridization of the CN triple bond, not to be bound through π electrons of the aromatic ring. On palladium, however, there are three kinds of adsorbed states for benzonitrile, giving three N 1s peaks (399.5, 398.0 and 397.4 eV). Two of them are similar to those on nickel and the other is assigned to the species rehybridized to less extent (nearly to sp 2 hybridization) giving the N1s peak at 398.0 eV. The other nitriles studied in this work show adsorption behavior similar to benzonitrile on nickel and palladium.

Preparation of active HDS catalysts by controlling the dispersion of active species

Abstract It is demonstrated that the structural control of the metal ion precursors in the impregnating solution by adding the chelating agents is effective to prepare the higher active CoMo supported on alumina catalysts ( Co-Mo Al 2 O 3 ) for hydrodesulfurization (HDS). Coordination structures of the Co and Mo complexes in the CoMo impregnating solution and distributions of the Co and Mo complexes were evaluated by spectroscopic characterization techniques and by using a computational calculation, respectively. An addition of a chelating agent, such as NTA (nitrilotriacetic acid) and Glu (L-glutamic acid), in the CoMo solution results in the selective formation of the Co complexes, while the amount of the Mo complex is negligibly small at the practical pH of 9.2. The addition of the chelating agent increases the thiophene HDS activity of the sulfided catalysts typically by 50%, compared with that prepared without the chelating agent. Dispersion results of Co and Mo species on both oxidic and sulfided catalysts indicate that the higher HDS activity is explained by the higher degree of surface exposure of Co sites (namely the dispersion of Co) rather than that of Mo sites. The selective formation of the Co-chelate complexes keeps Co ions stable in solution up to high concentration. Furthermore, the Co complexes are estimated to be stable on the support even in the initial step of calcination, which would depress the formation of crystalline Co compounds, such as CoAl2O4 and CoMoO4. These effects result in the higher dispersion of the active Co surface species.

Effect of cobalt on the sulfiding temperature of CoOMoO3/Al2O3 studied by temperature programmed sulfiding

Abstract The effect of cobalt on the sulfiding temperature of CoO MoO 3 /Al 2 O 3 was investigated by means of temperature programmed sulfiding (TPS). MoO 3 supported on alumina transforms into MoS 2− x by sulfidation via formation and subsequent hydrogenation of Mo oxi-sulfide or MoS 3 . The temperature of which the Mo oxi-sulfide or MoS 3 phase are hydrogenated (Ps temperature) decreased with increasing amount of cobalt in the CoO MoO 3 /Al 2 O 3 catalysts. A decrease in the Ps temperature was also observed in the case of ‘ Co/Al+ Mo/Al catalysts’ which were prepared by mechanical mixing of CoO/Al 2 O 3 and MoO 3 /Al 2 O 3 . On the other hand, the Ps temperature did not change by mechanical mixing of bulk CoO and the MoO 3 /Al 2 O 3 catalyst. The cobalt adsorption test suggested that the cobalt species preferably interact with the molybdenum species during impregnation. It was concluded that the well dispersed cobalt species have a capability to provide spillover hydrogen to accelerate the hydrogenation of the Mo oxi-sulfide. Furthermore, a correlation between the Ps temperature and HDS activity for light gas oil was obtained. This result suggests that the cobalt species facilitate the hydrogenation of sulfur atoms adsorbed on the HDS active sites (coordinatively unsaturated Mo sites) by supplying spillover hydrogen and consequently accelerate the HDS reaction.

Temperature-programmed sulfiding of precursor cobalt oxide genesis of highly active sites on sulfided cobalt catalyst for hydrogenation and isomerization

Abstract It was found that the method of sulfidation of cobalt oxide strongly affects the catalytic activities and selectivities of the resultant cobalt sulfide catalyst, as well as the calcination temperature of the cobalt oxide. When cobalt oxide was sulfided at 673 K by a temperature-programmed sulfiding method (a heating rate of 6 K min −1 ), catalytic activities for the hydrogenation of butadiene and the isomerization of 1-butene were considerably enhanced compared with those for cobalt sulfide prepared by isothermal sulfidation at 673 K. Results of temperature-programmed sulfiding (TPS), temperature-programmed reduction (TPR), and X-ray diffraction (XRD) suggest that the catalysts showing high catalytic activities after sulfidation are partially sulfided at 673 K and consist of the unsulfided cobalt core phases (COO or metallic Co). The sulfidation property of precursor cobalt oxides has been studied using TPS, simulating the sulfidation process of the cobalt sulfide catalysts. Two distinctly different kinds of sulfidation process are estimated by TPS measurements of the cobalt oxides. The calcination temperature of the precursor cobalt oxides strongly affects the sulfidation paths. They are differentiated in terms of the presence of a metallic Co intermediate. The relationship of the mechanism of sulfidation of the cobalt oxides to the generation of highly active sites is discussed.

Reduction and sulfidation properties of iron species in Fe-treated Y-zeolites for hydrocracking catalysts

Abstract Temperature programmed reduction (TPR) and temperature programmed sulfiding (TPS) were used to characterize reduction and sulfiding properties of Fe-treated Y-zeolites, which were prepared by treating NH4Y-zeolite with an aqueous ferric nitrate solution (Fe-treatment). It was demonstrated that three types of the Fe-species are present in the Fe-treated Y-zeolites: ion-exchanged type species, small Fe-oxide clusters, and Fe oxides without interaction with the zeolite framework (including aggregated ferric oxide), the proportion of which is dependent on the extent of the Fe-treatment. The small Fe-oxide clusters, which are probably situated inside the supercages through a coordination with the framework oxygen atoms, are responsible for high activity for toluene disproportionation. A realistic production control for the active Fe-treated Y-zeolite catalyst has been achieved for the first time by using the TPR and TPS techniques.