Platinum molybdates

Platinum Molybdates.—Simple molybdates of platinum have not been obtained. A number of complex platinomolybdates of the alkali metals, containing tetravalent Jlatinum, have been described, but their existence as compounds has not been confirmed. 

Platinum phthalocyanine (PcPt) is prepared by the reaction of phthalonitrile286,288 or isoindolinediimine114,117,288 with platinum(ll) chloride in a solvent such as 2-(dimethyl-amino)ethanol under the catalytic influence of l,8-diazabicyclo[5.4.0Jundec-7-ene. Another possibility is the fusion of phthalonitrile and pialinum(II) chloride58,156,157 or dipotassium tet-rachloroplatinate(II) (K2PtCl4) in the presence of urea, ammonium molybdate(Vl) and sodium sulfate.289... 

The first example of a heterogeneously catalyzed hydroamination of an alkene appeared in a 1929 patent in which it is claimed that NHj reacts with ethylene (450°C, 20 bar) over a reduced ammonium molybdate to give EtNH2 [24]. An intriguing reaction was also reported by Bersworth, who reacted oleic acid with NH3 in the presence of catalysts like palladium or platinum black or copper chromite to give the hydroamination product in quantitative yields [25]. However, this result could not be reproduced [26]. 

Espig A process for making synthetic emeralds by the flux reaction technique. Beryllia and alumina are dissolved in molten lithium molybdate, and silica is floated on the melt. The emerald crystals form at the base of the melt, but because they tend to float and mix with the silica, a platinum screen is suspended in the middle of the melt. Invented by H. Espig. 

Ruthenium on platinum was found to promote the oxidation of AoCOad while tin on platinum was found effective for eoCOad. Enhancement of the methanol oxidation to CO2 was confirmed on platiniua with either rutheniiim or tin. Molybdates on platinum was also found to promote the oxidation of botheoCOad ai d methanol. 

In this chapter, the effects and roles of secondary materials on platinum were investigated using electrochemically modified electrodes with ruthenimn, tin and molybdates. 

Then, the potential was cycled up to 1.0 V to desorb molybdates in oreder to expose the platinum surface as shown in the previous figure (Fig. 4—20) and held at 50 mV again while CO was introduced. In Fig. 4-21, the voltammogram of the COad oxidation is shown with the voltammograms for pure Ft with COad and Pt-Mo without COad (second cycle). The peak position for the oxidation of AoCOad is unaffected. Beside this peak, there are two peaks at 280 mV and 420 mV. It is hardly possible to judge whether these peaks are the results of the COad oxidation or the oxidation of molybdates because the oxidation peaks of eoCOad and adsorbed molybdates are in the same potential region. 

Ruthenium on platinum was found to facilitate the oxidation of oCOad but noteoCOad interacting water, appeared to play a role of the oxygen source, replacing Pt-OH. Contrarily, tin and molybdates on platinum showed promoting effects for the oxidation of eoCOad but not AoCOad Redox couples of tin or molybdenum oxides appeared to play a role of a mediator as well as the ox en source. The active potentials were the bwest for molybdates and the second for tin. 

A continuous process based on hydrodynamic cavitation can be employed to prepare a wide variety of metal oxides in grain sizes of 1 -10 nm, such as iron oxide, bismuth molybdate, perovskites, platinum-loaded zeolite, and other ceramics and superconductors [170]. The method uses a microfluidiser for mechanically generating hydrodynamic cavitation and the internal pressure of the liquid media is elevated from ambient pressure to between 1000 to 25 000 psi. 

The dissociation also is rapid helow this temperature (between 450°C to 850°C), however, only in the presence of a catalyst, such as sdica, platinum sulfide or cohalt molybdate. Other sulfur species are also produced in the reaction. 

F,SCH, Methanesulfonic acid, trifluoro-iridium, manganese and rhenium complexes, 26 114, 115, 120 platinum complex, 26 126 OiFeCgH, Iron, acetyl dicarbonyl (if -cyclopentadienyl)-, 26 239 0,FeN2C2 Hll(, Iron, tricarbonylbis(2-isocy-ano-l,3-dimethylbenzene)-, 26 54 0.iMoNaCHH5-2 C4H ,02, Molybdate 1 -), tricarbonyl(T) -cyclopentadienyl)-sodium, compd. with 1,2-dimethoxy-ethane-(l 2), 26 343 0,NaWC H5-2 C4H ,02, Tungstate(l -), tricarbonyl(ris-cyclopentadienyl)-... 

Preparation of Materials and Samples. The source of the molybdenum oxide vapor was M0O3 containing "Mo tracer. The "Mo was supplied as ammonium molybdate in NH4OH solution (Nuclear Science and Engineering Co.). The solution was evaporated to dryness in a platinum crucible, and the ammonium molybdate was heated in air at about 500°C. for several hours to decom ose it to M0O3. 

A range of metal oxides have been compared as methane combustion catalysts. The effect of modification to generate superacidic behaviour on Zr02 and Fe203 systems has been studied. It has been shown that whilst sulfation lowers the activity of Fe203, sulfation and, particularly, molybdation enhance the performance of Zr02. Despite enhancing the activity of the unmodified base oxides, the addition of low levels of platinum has been demonstrated to poison the activity of superacidic zirconias. Potential reasons for these observations are discussed. 

A. Place about 5 mg of sample into a platinum cmcible, mix with 200 mg of anhydrous potassium carbonate, and ignite over a burner at a red heat for about 10 min. Cool, dissolve the melt in 2 mL of freshly distilled water, warming if necessary, and slowly add 2 mL of ammonium molybdate TS. A deep yellow color appears. 

Place a little of the solid silicate in a small lead or platinum crucible, add a little sodium fluoride and a few drops of concentrated sulphuric acid. Cover the crucible with a small sheet of cellophane from which is suspended a drop of 2m sodium hydroxide solution (freshly prepared from the A.R. solid). Warm gently for 3-5 minutes over a micro burner with the crucible about 8 cm from the flame. Transfer the drop of sodium hydroxide solution to a porcelain micro crucible, add 2 drops ammonium molybdate reagent and then 2m acetic acid until feebly acidic. Then add a few drops 0-25m tin(II) chloride followed by sufficient sodium hydroxide solution to dissolve the tin(II) hydroxide. A blue colouration is obtained. 

---