Fe-Mo Catalyst Research Articles

Promotion effects in bulk metal sulfide catalysts

As shown previously, an unsupported Fe-Mo sulfide catalyst is quite selective toward hydrodenitrogenation (HDN) relative to hydrodesulfurization (HDS). This paper is primarily concerned with the activity enhancement of that catalyst. It is shown that the HDN and HDS volumetric activities of the Fe-Mo catalyst can be significantly increased by promotion with nickel or cobalt. The increased activities are much higher than those observed with existing commercial catalysts. This was observed in tests with a petroleum distillate feed. The overall HDS kinetics are catalyst dependent; theoretical explanations for such a dependence are given.

FT‐IR studies on the evolution of different phases and their interaction in ferric molybdate—molybdenum trioxide catalysts

AbstractTwo samples of Fe–Mo catalysts have been prepared from ferric nitrate and ammonium paramolybdate, one following a conventional procedure and the other by a new precipitation procedure in a buffer medium. The evolution of different Fe–Mo phases, from the fresh precipitate to the aged and then to the calcined state, has been followed by FT‐IR spectroscopy. All the spectral vibrations have been related to different coordination spheres of Mo and Fe ions in the samples and a comparison with a commercial catalyst of similar composition has been made. The new preparation procedure leads to small, uniform (0·3 μm size) particles and a homogeneous morphology of phases as seen by scanning electron microscopy. Additionally, a higher surface area (10·3 m2 g−1), lower bulk density (0·66 g cm−3), a methanol conversion efficiency of > 90% and an HCHO selectivity of 95% distinguish this sample from the conventionally prepared one. Better thermal stability of this sample is inferred from the IR spectral and XRD analyses of the heat‐treated (up to 800°C) samples and is related to the interaction between Fe2(MoO4)3 and MoO3 phases.

Influence of temperature, catalysts and partial pressure of hydrogen on the co-processing of spanish lignites

Studies on coal-oil co-processing are one aspect of the research carried out in the field of coal liquefaction. The oil used in the process is likely to be a heavy petroleum residue due, in part, to the economic constraints of the process and, moreover, to the expected chemical compatibility. This project studies the influence of the kind of coal, vacuum residue, catalyst and temperature on the co-processing conversion and the quality of liquid products. The influence of partial pressure of hydrogen is studied. Two different Spanish lignites were co-processed with a typical commercial vacuum residue and in the presence or absence of solid catalysts. Two supported catalysts, one with 25% Fe, as oxide, and a second with 25% Fe plus 10% Mo, as oxides, were prepared. Prior to their utilization, the catalysts were sulphided. The range of temperatures studied was 350–470°C. Experimental results show that the temperature and the partial pressure of hydrogen are the most important variables. A maximum conversion and proportion of valuable liquid oil fraction was obtained between 375 and 425°C. Temperatures exceeding this range produce a negative value of conversion because of the retrograde recombination reactions of radicals and, consequently, a great increment in the gases formed. The comparison of the two lignites used, Berguedà and Utrillas, confirms the relation between the structural composition and the level of maximum conversion attained. The results obtained with catalysts suggest that their effect overlaps or competes with the compounds present in the ashes when the level of ashes is high. The only general conclusion about the use of Fe and Fe-Mo catalysts is that the amount of sulphur present in the oil fraction is lower than that obtained without catalyst. With respect to the effects of hydrogen partial pressure, the main conclusion refers to the comparison between the normal loading of solid reagents and 3/4 of this loading. A wide screening of temperatures was carried out with normal and with 3/4 loadings, and with the other loading only one temperature was checked. The lowest loading (highest H2 content) produced an increment in the conversions attained and a displacement of the region of maximum conversion toward lower temperatures.

Influence of Fe and FeMo high loading supported catalysts on the coprocessing of two Spanish lignites with a vacuum residue

The catalytic coprocessing of two Spanish lignites with a vacuum residue of petroleum has been studied. Two catalysts supported on γ-Al 2O 3, with loadings of 25% Fe 2O 3 and 25% Fe 2O 3/10% MoO 3, have been tested at temperatures from 400 to 425°C with an initial hydrogen pressure of 8 MPa. Results show that both catalysts improve the conversion of coal and upgrade the liquid product distribution. When a high ash lignite is used the catalytic effect of the own mineral matter overcomes the effect of added catalysts. The FeMo catalyst yields the highest coal conversion, oil production and desulphuration within the range of temperatures studied.

Hydrogenation of aromatics over hydrodenitrogenation-selective and hydrodesulfurization-selective catalysts

A denitrogenation-selective FeMo sulfide is evaluated against a commercial desulfurization-selective CoMo catalyst to understand better the effects of catalyst selectivity for heteroatom removal on aromatics hydrogenation. The experiments were done in an upflow fixed-bed reactor with an uncracked gas oil. Combined clay-gel separation and mass spectrometry were used to follow the saturate make and the distributions of aromatic compound classes as functions of the extent of heteroatom removal. The FeMo catalyst, despite its low desulfurization activity, shows a higher volumetric activity for total aromatics reduction than the conventional CoMo catalyst of much higher surface area. The behavioral differences between the two catalysts in aromatics hydrogenation are discussed.

Hydrodenitrogenation-selective catalysts I. Fe promoted Mo/W sulfides

This paper describes the development of a new catalyst system which gives an unusual combination of high hydrodenitrogenation and low hydrodesulfurization. This has been observed in tests with a highly aromatic distillate feed. The catalyst is an unsupported iron-promoted molybdenum or tungsten sulfide formed from thermal decomposition of bis(diethylenetriamine) iron thiomolybdate or thiotungstate. The results from a brief accelerated aging experiment have shown that this bulk sulfide system is thermally stable. Characterization of the Fe-Mo catalyst has indicated that it consists of a single sulfide phase which during activity testing partially transforms into an iron sulfide mixed with an MoS 2-like phase.

A multitubular reactor for obtention of acetaldehyde by oxidation of ethyl alcohol

In this work an alternative process for the obtention of acetaldehyde is presented. It is based on the oxidation of ethyl alcohol over commercial Fe-Mo catalyst. Experimental kinetic data, obtained in an integral reactor, were interpreted by a Temkin's type mechanism, although it is possible to treat the data by a known mechanism similar to the oxidation of methanol to formaldehyde. A new multitubular reactor is then proposed with the obtained rate equation. It is baffled but windowless, so that better temperature control is achieved when compared with conventional reactors. The process considered here exhibits better performance than the best known processes in terms of higher conversions, stability and yield in acetaldehyde.

A stable catalyst for heavy oil processing: III. Activity and selectivity

The catalytic activity and selectivity of two series of FeMo/Al 2O 3 catalysts for the simultaneous hydroconversion (HDC) and hydrodemetallization (HDM) of heavy crudes and residues have been studied. Two series of catalysts were prepared by successive impregnation: in series 1, the catalyst substrate was impregnated firstly with iron, whereas in series 2, it was first impregnated with molybdenum. A comparison was made between one of our FeMo catalysts and a CoMo commercial catalyst in terms of activity and stability. The CoMo catalyst showed an initial activity greater than that of the FeMo catalyst. However, the FeMo catalyst was deactivated more slowly. The catalysts to which molybdenum was added before iron (series 2) exhibited greater initial activity than those of series 1, although they were found to be less stable. It was also found that a pyrrhotite phase seemed to be needed in order to prevent catalyst poisoning and to control the selectivity. These catalysts were found to possess remarkable properties suitable for the hydroprocessing of heavy oils and particularly for HDM reactions.

The influence of phosphorus on the structure and hydrodesulfurization activity of sulfided Fe and Fe-Mo catalysts supported on carbon and alumina

Phosphorus-containing Fe and Fe−Mo sulfide catalysts supported on γ-Al2O3 and activated carbon were evaluated for their thiophene HDS activities at atmospheric pressure. The thiophene HDS activity of the carbon-supported catalysts decreased considerably in the presence of phosphorus, while the activity of the alumina-supported catalysts was not affected. It was shown by Mossbauer spectroscopy that in both the oxidic carbon- and alumina-supported catalyst precursors the presence of phosphorus resulted in an improved dispersion of the Fe phase. In the sulfided carbon-supported Fe and Fe−Mo catalysts, the presence of phosphorus resulted in the formation of an “Fe(II)-phosphate” phase, which was held responsible for the decrease in HDS activity. With regard to the sulfided alumina-supported catalysts, it was found that phosphorus did not influence the structure of the metal sulfide species.

The reactivity and stability of mixed-sulfide structures in unsupported MoS 2-based hydrodesulfurization catalysts promoted by group VIII metals

Unsupported CoMo, NiMo and FeMo catalysts have been prepared by the homogeneous sulfide precipitation method and the coprecipitation method. The presence of a group VIII metal (Me) causes a decrease in the reactivity with O 2 and an increase in the reducibility in H 2. These effects are correlated with the increase in the catalytic activity. The stability of cobalt and iron sulfide species in CoMo and FeMo catalysts was studied by Mössbauer spectroscopy. A significant amount of MeMoS structure remains stable after strong reducing treatment. Catalysts contain also sulfur-rich group VIII metal sulfide species which appear stabilized by MoS 2. The role of these species in promoting HDS activity is evaluated.