Ammonium heptamolybdate

A NaY zeolite (Al/Si atomic ratio 0.41) was supplied by Shokubai Kasei Kogyo Ltd. After an evacuation at 673 K for 1 h (lx 10 Pa), the zeolite powder was exposed to a vapor of Mo(CO)5 or Co(CO)jNO at room temperature, followed by an evacuation at room temperature for 10 min to remove physisorbed metal carlxrnyl molecules on the external surface of the zeolite. Mo(CO)yNaY or Co(CO)3NO/NaY was sulfided in a stream of an atmospheric pressure of 10% HjS/Hj (0.2 dm min ). The sulfidation temperature was increased from room temperature to 373 K at a rate of 2 K min and kept at the tempeiatiue for 1 h. Subsequently, the temperature was increased up to 673 K at a rate of 5 K min and kept at 673 K for 1.5 h. After the sulfidation, the sample was cooled in the HjS/Hj stream to room temperature. The Mo and Co sulfide catalysts thus prepared are denoted MoSx/NaY and CoSx/NaY, respectively. Mo sulfide catalysts, MoSj/NaY, were also prepared by a conventional impregnation method by using ammonium heptamolybdate, for companson. 

Mo/HZSM-5 catalysts (3 wt% Mo nominal loading) were prepared by incipient wetness impregnation with an aqueous solution of ammonium heptamolybdate (Merck), drying at 100°C, and calcination at 500°C for 6 h. 

Figure 8.12 Raman spectra of alumina- and silica-supported molybdena catalysts after impregnation of the supports with solutions of ammonium heptamolybdate, (NH4)6Mo7024 4 H20 of different pH values, and after calcination in air at 775 K. See Table 8.3 for a list of characteristic Raman frequencies of molybdate species. The sharp peaks in the spectra of the calcined MoOySiOj catalyst are those of crystalline Mo03 (from Kim el at. [43J).

Sample Preparation. The preparation of the unsupported Co-Mo catalysts has been carried out using the homogeneous sulfide precipitation (HSP) method as described earlier (l8) and only few details will be given here. A hot (335 3 5 K) solution of a mixture of cobalt nitrate and ammonium heptamolybdate with a predetermined Co/Mo ratio is poured into a hot (335 3it5 K) solution of 20 ammonium sulfide under vigorous stirring. The hot slurry formed is continuously stirred until all the water has evaporated and a dry product remains. This product is finally heated in a flow of 2% H2S in H2 at 675 K and kept at this temperature for at least b hr. Catalysts with the following Co/Mo atomic ratios were prepared 0.0, 0.0625, 0.125, 0.25, 0.50, 0.75, and 1.0. 

Ammonium ion forms isopolymolybdates, such as di-, tri-, or heptamolyb-dates with the molybdate anion. Only the dimolybdate, (NH4)2Mo20 , and ammonium heptamolybdate (NH4)6Mo7024 4H2O [12027—67—7], have commercial apphcations. 

Catalyst. A pure precipitated Si02 sample (grade Si 4-5P, AKZO product BET S.A., 395 m g" Pore Volume, 1.14 cm -g" ) has been used "as received", while 4% MoOj/SiOj (BET S.A., 187 m g-l) and 5% V205/Si02 (BET S.A., 231 m2.g-i) catalysts have been prepared by incipient wetness impregnation of the "Si4-5P" Si02 with a basic solution (pH=11) of ammonium heptamolybdate and ammonium metavanadate respectively (23). The impregnated samples were dried at 90°C for 24h and then calcined at 6C)0°C for 16h. 

The intensities of signals at —14, 0, and 30 ppm increased with increasing molybdenum loading (152). A series of Al MAS NMR spectra indicated that, with increasing amounts of ammonium heptamolybdate, a dealumination occurred as a... 

Aqueous ammonium heptamolybdate (Alfa, (NH4)6Mo70244H20, 99.999%) solutions were prepared so that a metal loading of 6 wt % Mo would fill 80% of the available pore volume of the mesoporous synthetic clays. Following Mo impregnation and recalcination at 400°C for 5 hr, the pore volumes were measured again using an established LN2 physisorption... 

Carbon-supported Co-Mo catalysts used in terpene hydrodesulfurization (SM = sodium molybdate, AHM = ammonium heptamolybdate, CN = cobalt nitrate). All the catalysts contain 7 wt.-% CoO and 4.4 wt.-% M0O1 corresponding to a Co-to-Co+Mo atomic ratio of 0.75. J... 

Figure 9.24 Mo 3d and Co 2p XPS spectra of a calcined CoMo/AljCtySiClOO) catalyst during sulfidation, in which Co and Mo have been impregnated from cobalt nitrate and ammonium heptamolybdate. The spectra indicate that calcination establishes firm bonding between the support and cobalt and molybdenum. As a result, the sulfidation of both is retarded to roughly the same temperature range (from Sanders et al. [80J).

The successful application of sulfanyl amines in the diastereoselective and enantioselective synthesis of as-3,4-disubstituted /3-sultams has been reported (Scheme 56). The protocol is based on the oxidation of the 1,2-aminothiols 178 with hydrogen peroxide and ammonium heptamolybdate. Chlorination of the resulting /3-aminosulfonic acids was achieved using phosgene. The /3-aminosulfonyl chlorides 179 obtained were cyclized under basic conditions and without epimerization to yield the t -3,4-disubstituted /3-sultams 180 (>96% de, ee) (Table 13) <2005S1807>. 

MoOa/SiOa was prepared by impregnation with solution of ammonium heptamolybdate at pH=ll and calcined at 500°C for 2 hr. The samples contained about 17 wt.% Mo. 

Figure 27. Distribution of cobalt among the various species of an activated HDS catalyst, as determined by emission Mossbauer spectroscopy. The catalyst, prepared by impregnation of ammonium heptamolybdate and 57Co nitrate, was as similar as possible to the commercial one used for obtaining the results presented in the previous figures (3wt% as CoO, 13 wt% as M0O3 on -/-alumina). All precautions were taken to avoid possible errors due to noninstantaneous charge compensation in the sequence of nuclear events in 57Co decay (this has to be taken into account in the nonconducting M0S2 matrix) [155, 156].

Wienold et al. (2003) XAS, TGA Ammonium heptamolybdate Phase formation ligand removal, sub-oxides + + + Propene oxidation, oxidation and reduction of oxide... 

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