NiMo sulfides

It is also of interest to compare the number of carbon atoms deposited per M0S2 stab. Table 2 shows large numbers of carbon atoms deposited per M0S2 slab for a 10 wt % C loading. Thus the mode of deactivation of both components is notably different. While it can be suggested that metal deposits deactivate the catalyst by contamination or promoter substitution of the NiMo sulfide active... 

Coronene adsorbs on catalyst sites present on both the alumina support and on the active NiMo sulfide phase 3). It has been found that adsorption decreases with coke content to a very Jow value at high coke levels (4), Therefore, it appears that coronene adsorption on the coke is nil. On this basis, it is assiimmed that the loss in adsorption with increasing coke is proportional to the loss in pore surface area due to coverage by coke. The results of coronene adsorption measurements on the VGO-coked catalysts show an initial drop for the 2% C sample, but little change thereafter for higher coked catalysts (Fig. lA) This implies that the coke Is concentrated near the mouth of the pores, On the other hand, catalyst dlffusivity measurements show a continual and sig-... 

P-15 - Model hydrocracking catalysts combining NiMo sulfide and large-pore zeolite effect of the zeolite nature on the location of NiMo sulfide in relation with catalytic properties... 

NiMo sulfide/large pore zeolites NiMo/Zr-HMS hydrotreatment catalyst Ni-MOR, deNOx catalyst... 

A. A. Andreev, A. J. Kafedjiysky, R. M. Edreva-Kardjiev, Active forms for water-gas shift reaction on NiMo-sulfide catalysts, Appl. Catal. A Gen. 179 (1999) 223-228. 

TMS catalyst, used in refineries, are mixed sulfides of cobalt-molybdenum (CoMo) or nickel-molybdenum (NiMo) with a promoter atomic ratio Co(Ni)/[Co(Ni) -I- Mo(W)] between 0.2 and 0.4 (2), supported on high surface area materials such as alumina to increase dispersion of the active component of the catalyst. Although CoMo sulfide is the favorite catalyst for HDS reactions, the use of NiMo sulfide is preferred in HDN reactions and hydrogenation processes, to treat feedstock with a high concentration of unsaturated compounds. 

Such a selective hydrodesulfurization must clarify the active sites of CoMo and NiMo sulfides supported on alumina for hydrodesulfurization and hydrogenation. CoMo is certainly more selective for hydrodesulfurization with limited hydrogenation activity than NiMo. Hence, cobalt is applied for the present purpose. Coordinatively unsaturated Co sulfide on M0S2 is often postulated as the active site for both reactions (see Fig.7). The metal with unsaturated valence is proposed as the hydrogenative site in cooperation with a Mo-S-H group while the metal with the unsaturated valences must be the hydrodesulfiiiization site. H2S concentration in HDS can be reduced to enhance the hydrodesulfiiiization selectivity. 

Zhao, Y. Czyzniewska, J., and Prins, R., Mechanism of the direct hydrodenitrogenation of naphtylamine on sulfided NiMo/A1203. Catal. Lett, 2003. 88 p. 155. 

Olive, J.-L. Biyoko, S. Moulinas, C., and Geneste, P., Hydroprocessing of Indole and o-Ethylaniline over Sulfided CoMo, NiMo, and NiW Catalysts. Appl. Catal, 1985. 19 pp. 165-174. 

Figure 9.17 Quick EXAFS measurements show the effect of temperature-programmed sulfidation on the Mo K edge in NiMo/SiOj catalysts (adapted from Cattaneo et al. [60]).

The coals used were PSOC 1098 Illinois 6 and Beulah-Zap North Dakota lignite from the Argonne coal bank. The analytical data of these coals are shown in Table I. The ratio of catalyst to coal was approximately 0.6 mmoles of metal per gram of coal. The organometallic catalysts were molybdenum(II) acetate dimer, Mo2(OAc)4, obtained from Strem, molybdenum(II) allyl dimer Mo2(OAc)4, was prepared by die method of Cotton and Pipal (25). The NiMo supported catalyst was prepared by addition of bis(l,5-cyclooctadiene) Ni(0) (Strem) to sulfided Mo on alumina (. Cp2Mo2( l-SH)2(p.-S)2, referred to as MoS2(OM), was prepared by modification of method of Dubois et al. (26), and Cp2Mo2Co2( i3-S)2(li4-S)(CO)4, CoMo(OM) was prepared by the method of Curtis et al. (27). Pentacarbonyl iron was obtained from Aldrich,... 

Rate constants (x 10 min. g.cat ) for hydrogenation of 4-chloronitrobenzene (k. ) and hydrogenolysi s of 4-chloroaniline (kg) over sulfided CoMo HR 306 and NiMo HR 348 catalysts at temperatures ranging from 50°C to 250°C and 20 bar of hydrogen pressure... 

Sulfiding enhances the HDM activity of CoMo and NiMo/Al203 catalysts relative to the performance of the oxide forms (Gajardo et al., 1982). Similar results were reported in model compound studies (Ware and Wei, 1985b). 

Deactivation of a Sulfided NiMo/y-AJ203 during the Hydrodeoxygenation of Bio-Oils Influence of a High Water Pressure... 

NiMo/y-Al203 catalyst Actually, the general consensus in the literature is that water may be detrimental to the activity and to the chemical stability of the active sulfided phases, but strong evidences are still lacking. 

---