Mixed metal oxide preparation

For mixed metal oxides obtained from their hydroxide or carbonate precursors after calcination, it is generally difficult to determine whether the as-prepared precursor is a single-phase or multiphase solid solution [35]. Non-aqueous solvents appear superior for achieving two dissimilar metal oxides such as MM Oz or MM 04 precipitates such reactions cannot be carried out simultaneously in aqueous solution due to the large variations in pH necessary to induce precipitations [41,42]. Table 6.1 summarizes some of the nanoparticulate semiconducting metal oxides and mixed metal oxides prepared via co-precipitation techniques. The general procedure of achieving metal loaded nanoparticles on an oxide support is shown in Fig.6.5. 

Vitry, D., Moriwaka, Y., Dubois, J.L., and Ueda, W. Mo-V-Te-(Nb)-0 mixed metal oxides prepared by hydrothermal synthesis for catalytic selective oxidations ofpropane and propene to acrylic acid./Ipp/. Catal. A Gen. 2003, 251,411-424. 

Manganaies IV), manganites. Mixed-metal oxides containing Mn(IV). Prepared by solid state reactions. 

Today the most efficient catalysts are complex mixed metal oxides that consist of Bi, Mo, Fe, Ni, and/or Co, K, and either P, B, W, or Sb. Many additional combinations of metals have been patented, along with specific catalyst preparation methods. Most catalysts used commercially today are extmded neat metal oxides as opposed to supported impregnated metal oxides. Propylene conversions are generally better than 93%. Acrolein selectivities of 80 to 90% are typical. 

MAA and MMA may also be prepared via the ammoxidation of isobutylene to give meth acrylonitrile as the key intermediate. A mixture of isobutjiene, ammonia, and air are passed over a complex mixed metal oxide catalyst at elevated temperatures to give a 70—80% yield of methacrylonitrile. Suitable catalysts often include mixtures of molybdenum, bismuth, iron, and antimony, in addition to a noble metal (131—133). The meth acrylonitrile formed may then be hydrolyzed to methacrjiamide by treatment with one equivalent of sulfuric acid. The methacrjiamide can be esterified to MMA or hydrolyzed to MAA under conditions similar to those employed in the ACH process. The relatively modest yields obtainable in the ammoxidation reaction and the generation of a considerable acid waste stream combine to make this process economically less desirable than the ACH or C-4 oxidation to methacrolein processes. 

Cobalt provides only a few examples of this oxidation state, namely some fluoro compounds and mixed metal oxides, whose purity is questionable and, most notably, the thermally stable, brown, tetraalkyl, [Co(l-norbomyl)4]. Prepared by the reaction of C0CI2 and Li(l-norbomyl), it is the only one of a series of such compounds obtained for the first row transition... 

Nonstoichiometry is relatively common among mixed metal oxides, in which more than one metal is present. In 1986 it was discovered that certain compounds of this type showed the phenomenon of superconductivity on cooling to about 100 K, their electrical resistance drops to zero (Figure 20.9). A typical formula here is YBa2Cu30 where x varies from 6.5 to 7.2, depending on the method of preparation of the solid. 

Preparation of mixed metal oxides - The sulfated metal oxides (zircoiua, titaiua and tin oxide) were synthesized using a two-step method. The first step is the hydroxylation of metal complexes. The second step is the sulfonation with H2SO4 followed by calcination in air at various temperatures, for 4 h, in a West 2050 oven, at the temperature rate of 240°C hSulfated zirconia Zr0Cl2.8H20 (50 g) was... 

Sadakane, M., Asanuma, T., Kubo, J. et al. (2005) Facile procedure to prepare three-dimensionally ordered macroporous (3DOM) perovskite-type mixed metal oxides by colloidal crystal templating method, Chem. Mater. 17, 3546. 

In current research work, mixed metal oxide based heterogeneous catalysts were prepared and employed for the triglyceride transesteriftcation as well as glycerol esterification reaction to produce triacetin and glycerol carbonate. 

The W-Nb mixed metal oxide was prepared by sonicating the solution containing the precursors. Treatment of the mixed metal oxide precursors in H2S produced the Nb doped WS2 nanotubes (Fig. 14). The mechanism of formation of the com-... 

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