FeMo catalysts

AI2O3 and NiMo/Al203 catalysts with the corresponding AC-supported catalysts. The HDN activity of the latter catalysts was superior compared with that of the alumina-supported catalysts. Because of the diminished interaction of N-bases with AC support, the coke deposition and catalyst deactivation associated with it were much less evident on the carbon-supported catalysts. The HDS activity was similar for both AC-supported and alumina-supported catalysts. In a similar study, Hubaut et compared the FeMo catalyst supported on AC with that supported on 7-AI2O3. The experiments were conducted in a continuous system at 623 K and 7 MPa using a heavy VGO as the feed. Among several catalysts prepared by different methods, the... 

Bl-MoOg was prepared by the method of Vedrlne et al O). Bl CMoO ) and Bl-FeMo 0.- were prepared by copreclpltatlon of bismuth nitrate, ferrlc nltrate and ammonium molybdate. After drying, the catalysts... 

Sellmann, D., Utz, J., Blum, N., and Heinemann, F. W. (1999) On the function of nitrogenase FeMo cofactors and competitive catalysts chemical principles, structural blue-prints, and the relevance of iron sulfur complexes for N2 fixation, Coord. Chem. Rev. 190-192, 607-627. 

Introduction of a support (i.e. Ti02) to these systems can induce positive effects on the active phase (FeMo), as to avoid an excessive sintering of the particles during the thermal treatment and/or modification of the reduction capacity and the acid properties. The synergy of iron molybdate and the support is therefore another way for improving the catalytic performance of these solids. Such benefitial effects have been detected in bismuth-molybdenum-titania mixed oxides prepared via sol-gel, in addition these solids resulted to be amorphous materials with a unique morphology and extraordinary dispersion of the active phase [12]. These results encouraged us to extend this field to iron molybdenum oxide catalysts. 

A number of patents have been filed claiming the processing of waste rubber, either vulcanized or unvulcanized, by hydrocracking.10-13 The degradation usually proceeds in the presence of catalysts CoNi/Al203, FeMo/Cr203, Mo acetates, Cp2ZrCl2, etc. In some cases, a certain positive effect has been derived from the presence of sulfur compounds, which may either be the sulfur contained in the used tyre or H2S added to the reaction mixture. 

Rather different observations on the HDS of thiophene were made by Hubaut et who used a series of the FeMo/Al203 and FeMo/AC catalysts prepared by different methods. The FeMo/Al203 catalysts were consistently more active than the corresponding FeMo/AC catalysts for every pair of catalysts prepared by the same method. In this study, thiophene was introduced in the solution of heptane rather than in a vapor phase as it was the case of the Other studies. Moreover, in the former study, the experiments were conducted at much lower temperatures e.g., 553 K atmospheric pressure). 

The NiMo catalyst supported on the hollow spherical high surface area CB was compared with the commercial NiMo/Al203 catalyst during the HYD of methyl-naphthalene in an autoclave at 673 K and 9 MPa for 40 min.The CB support ensured very efficient dispersion of metals. The result of this was a markedly higher HYD activity than that of the commercial NiMo/Al203 catalyst. Furthermore, the HYD activity of this NiMo/CB catalyst was compared with Fe/CB, NiFe/CB and FeMo/CB under similar experimental conditions.After 60 min, the conversions were 50, 2, 4 and 7%, respectively. For these experiments, the solution of methyl-naphthalene in tetraline was used as the feed. 

Since the binding site for N2 in the enzyme seems to be a rectangular array of four Fe atoms in the waist region of FeMo-co, perhaps the most relevant model system is Holland s four-iron complex. On reduction with the powerful reductant, KCg, N2 can be split into two coordinated nitrides as shown in Eq. 16.20. In the Haber process, N2 is believed to be split into two coordinated nitrides bound to the surface of the Fe catalyst, so there may be a mechanistic similarity with N2ase. 

Liu, K., et al., 2010. An active Eischer—Tropsch synthesis FeMo/Si02 catalyst prepared by a modified sol—gel technique. Catalysis Communications 12 (2), 137—141. 

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