Hydrodesulfurization catalyst, preparation

Bimetallic Co-Mo-complexes with optimal localization on the support surface A way for highly active hydrodesulfurization catalysts preparation for different petroleum distillates... 

A cationic molybdenum sulfide cluster [Mo3S4(H20)9] " with incomplete cubane-type structure and a cationic nickel-molybdenum mixed sulfide cluster [Mo3NiS4Cl(H20)9p " with complete cubane-type structure were introduced into zeolites NaY, HUSY and KL by ion exchange. Stoichiometry of the ion exchange was well established by elemental analyses. The UV-visible spectra and EXAFS analysis data exhibited that the structure of the molybdenum cluster remained virtually intact after ion exchange. MoNi/NaY catalyst prepared using the molybdenum-nickel sulfide cluster was found to be active and selective for benzothiophene hydrodesulfurization. 

What is the structure of this Co-Mo-S phase A model system, prepared by impregnating a MoS2 crystal with a dilute solution of cobalt ions, such that the model contains ppms of cobalt only, appears to have the same Mossbauer spectrum as the Co-Mo-S phase. It has the same isomer shift (characteristic of the oxidation state), recoilfree fraction (characteristic of lattice vibrations) and almost the same quadrupole splitting (characteristic of symmetry) at all temperatures between 4 and 600 K [71]. Thus, the cobalt species in the ppm Co/MoS2 system provides a convenient model for the active site in a Co-Mo hydrodesulfurization catalyst. 

Data from tests at 250,275,300, and 325 C were used to calculate pseudo-first order rate constants for the formation of H2S. These data are expressed on a standard Arriienius plot (Fig. 2) for which the linear least squares coefficient of determination, r, is 0.98. The apparent activation energy calculated from the slope is 28.5 kcal/mol. This result is in excellent agreement with the recent work of Abotsi, who studied the performance of carbon-supported hydrodesulfurization catalysts (10). Using Ambersorb XE-348 carbon lo ed with sulfided ammonium molybdate (3% Mo loading) prepared by the same procedure reported here, Abotsi hydrotreated a coal-derived recycle solvent The apparent activation energy for... 

Hariita et al. (14) prepared spherical particles of molybdenum sulfide and cobalt sulfide with a narrow size distribution by reaction of dilute ammonium orthomolybdate or cobalt(II) acetate with sulfide ions liberated from thioacetamide as a reservoir of S2- ions in weakly acidic media. The compositions of these metal sulfides were estimated to be Mo S 0 = 1.0 1.7 3.0 and Co S 0 = 1,0 4.5 6.4 by chemical analysis. Figure 3.1.4 shows an SEM of a thus prepared uniform molybdenum sulfide particles sample. These sulfide particles were of no distinct crystal structure as shown by x-ray diffractometry. The isoelectric points of the Mo sulfide and Co sulfide particles in terms of pH were 1.9 and 3.1, respectively. Both of them are useful as hydrodesulfurization catalysts. 

Hydrodesulfurization catalysts are usually more active in the sulfide form with the external sulfur being applied either during the preparation from a sulfur-... 

In this study, a novel Monolith alumina structure was of interest as a base (or a carrier) material for Co-Mo-Alumina catalysts. The specific interest centered around assessing the suitability of the catalyst prepared by impregnating the novel alumina support with Co and Mo for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of a relatively high boiling stock. The Monolith catalyst was also tested on a low boiling coal-derived liquid. 

Kaluza, L. and Zdrazil, M. Carbon-supported Mo catalysts prepared by a new impregnation method using a Mo03/water slurry Saturated loading, hydrodesulfurization activity and promotion by Co. Carbon, 2001, 39, 2023. 

PREPARATION OF HIGHLY ACTIVE ZEOLITE-BASED HYDRODESULFURIZATION CATALYSTS ZEOLITE-SUPPORTED Rh CATALYSTS... 

The application of non-hydrothermally prepared stevensites as support for hydrodesulfurization catalysts... 

Three NiMo-HNaY-alumina catalysts with similar composition were prepared by different methods and tested in the hydrodesulfurization of dibenzothiophene (DBT) and 4,6-dimethyl-DBT. It was found that the catalyst preparation method induces some changes of the characteristics of the deposited metallic species as well as of the acidic properties of the zeolite component. These changes affect the catalytic behavior in the hydrodesulfurization of DBT and 4,6-DMDBT. Acidic properties of the catalyst seem to be more important for the conversion of alkyl-substituted DBT. 

A detailed description of a chromia-on-alumina catalyst prepared by impregnation has been given elsewhere . Another supported nonmetallic catalyst widely used commercially is cobalt molybdate-on-alumina. The preparation of this catalyst using an alumina support with controlled pore-size distribution is as follows. Silica-stabilized alumina, with greater than 50% of its surface area in 3-8 nm pores and at least 3% of the total pore volume in pores greater than 200 nm in diameter, is impregnated with an aqueous solution of cobalt and molybdenum. The finished oxysulfide catalyst was tested for hydrodesulfurization of petroleum residuum at 370°C and 100 atm for 28 days and compared with a convential cobalt-molybdate catalyst having a major portion of the surface area in 3-7 nm pores. The latter catalyst and controlled pore catalyst maintained 57 and 80% activity, respectively. 

Fig. 8. Fourier transforms (FTs) of MofC edge EXAFS data of hydrodesulfurization catalysts and of a model compound, a Mo/S-zeolite Y prepared by impregnation b Mo/S-zeolite Y prepared by loading with MofCOlg c Fe/Mo/S-zeolite Y prepared by loading with Mo(CO)g and FefCO) d Co/Mo/S-zeolite Y prepared by loading with Mo(CO)s and Co(NO)(CO)3 and e polycrystalline M0S2. After [64-66]...

Dhas NA, Ekhtiarzadeh A, Suslick KS. Sonochemical preparation of supported hydrodesulfurization catalysts. J Amer Chem Soc. 2001 123 8310-6. 

Addition of citric acid in the impregnation solutions during preparation of NrMo catalysts supported on SBA-15 resulted in an increase in both catalyst activity in hydrodesulfurization of DBT and selectivity towards the direct desulfurization route. Coimpregnation of Ni and Mo species in presence of citric acid seems to be a better way for catalyst preparation than their successive impregnation. Addition of citric add resulted in an increase in the M0S2 dispersion and formation of a larger amoimt of Ni-Mo-S species. 

A. Sampieri, Hydrodesulfurization of dibenzothiophene on M0S2/MCM4I and M0S2/SBA-15 catalysts prepared by thermal spreading of M0O3,2005, Catal. Today, 108-108,537-544. 

Rana, M.S., Capitaine, E.M.R., Leyva, C., Ancheyta, J. 2007. Effect of catalyst preparation and support composition on hydrodesulfurization of dibenzothiophene and maya crude oil Fuel 86 1254-1262. 

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