Mixed metal oxide

Poly (vinyl chloride). PVC is a hard, brittle polymer that is self-extinguishing. In order to make PVC useful and more pliable, plaslict/ers I qv) are added. More often than not the plasticizers are flammable and make Ihe formulation less flame-resistant. The Maine resistance of the polyf vinyl chloride) can he increased by ihe addition of an inorganic llamc-rctardunl synergist, e.g., antimony oxide, mixed metal antimony synergists, zinc borate, molybdenum oxide, zinc stannates. and alumina trihydrale. 

Bismuth oxide forms a number of complex mixed-metal phases with the divalent metal oxides of calcium, strontium, barium, lead, and cadmium, and these show a wide variety in composition. With transition metal oxides, mixed-metal oxide phases have been observed which are based upon a Perovskite-type lattice (10) containing layers of Bi202. It is notable that the high Tc superconducting materials which include bismuth also have this Perovskite-type of lattice with layers of copper oxide interleaved with bismuth oxide layers. 

Keywords Hydrogen Iron oxide Mixed metal oxides Titanium dioxide Visible-light activation... 

The epoxide-initiated approach has been used to prepare a wide variety of metal oxide, mixed metal oxide, and composite aerogel materials, as illustrated in Figure 8.7. This section is intended to provide a general overview of the different aerogel materials prepared using... 

As for the four-electron oxygen reduction catalysts, (i) metal-based catalysts noble-metals (Pt, Ag, Au), noble-metal alloys, (ii) ceramic-based catalysts mono-metal oxides, mixed-metal oxides (spinel type, pyrochlore type, perovskite type), metal-sulfides, metal-carbides, metal-nitrides, (iii) organometallic catalysts metal-porphyrin, metal-phthalocyanine, have been reported. 

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

Manganates III), again mixed-metal oxides present in the spinel Mn304, Mn Mn 204. 

Titanium IV) oxide, T1O2. See titanium dioxide. Dissolves in concentrated alkali hydroxides to give titanates. Mixed metal oxides, many of commercial importance, are formed by TiOj. CaTiOj is perovskite. BaTiOa, per-ovskite related structure, is piezoelectric and is used in transducers in ultrasonic apparatus and gramophone pickups and also as a polishing compound. Other mixed oxides have the il-menite structure (e.g. FeTiOj) and the spinel structure (e.g. MgjTiO ). 

Vanadium dioxide, VO2 is dark blue (V2O5 plus SO2) but is readily reduced further to Vo.i86-V,.6a. VO2 gives the (VO) ion with acids and vanadates(IV) with alkalis and as mixed metal oxides. 

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. 

The vapor-phase reduction of acrolein with isopropyl alcohol in the presence of a mixed metal oxide catalyst yields aHyl alcohol in a one-pass yield of 90.4%, with a selectivity (60) to the alcohol of 96.4%. Acrolein may also be selectively reduced to yield propionaldehyde by treatment with a variety of reducing reagents. 

Although acrylonitrile manufacture from propylene and ammonia was first patented in 1949 (30), it was not until 1959, when Sohio developed a catalyst capable of producing acrylonitrile with high selectivity, that commercial manufacture from propylene became economically viable (1). Production improvements over the past 30 years have stemmed largely from development of several generations of increasingly more efficient catalysts. These catalysts are multicomponent mixed metal oxides mostly based on bismuth—molybdenum oxide. Other types of catalysts that have been used commercially are based on iron—antimony oxide, uranium—antimony oxide, and tellurium-molybdenum oxide. 

Numerous patents have been issued disclosing catalysts and process schemes for manufacture of acrylonitrile from propane. These include the direct heterogeneously cataly2ed ammoxidation of propane to acrylonitrile using mixed metal oxide catalysts (61—64). 

Mixed Metal Antimony Synergists Worldwide scarcities of antimony have prompted manufacturers to develop synergists that contain less antimony. Other metals have been found to work in concert with antimony to form a synergist that is as effective as antimony alone. Thermoguard CPA from Elf Atochem NA, which contains zinc in addition to antimony, can be used instead of antimony oxide in flexible poly(vinyl chloride) (PVC) as well as some polyolefin appHcations. The Oncor and AZ products which contain siUcon, zinc, and phosphoms from Anzon Inc. can be used in a similar manner. The mixed metal synergists are 10 to 20% less expensive than antimony trioxide. 

Also present are 0.3 wt % mixed metal oxides (R2O2) and 5 ppm of arsenic. Impurities in fluorspar may affect yield, plant operabiUty, or product quaUty. 

Mixed-Meta.1 Oxides. Generally, iron oxide is the principal component of mixed-metal oxides. These affect the sulfuric and oleum consumption in HF production. 

In the vapor phase, acetone vapor is passed over a catalyst bed of magnesium aluminate (206), 2iac oxide—bismuth oxide (207), calcium oxide (208), lithium or 2iac-doped mixed magnesia—alumina (209), calcium on alumina (210), or basic mixed-metal oxide catalysts (211—214). Temperatures ranging... 

The first-stage catalysts for the oxidation to methacrolein are based on complex mixed metal oxides of molybdenum, bismuth, and iron, often with the addition of cobalt, nickel, antimony, tungsten, and an alkaU metal. Process optimization continues to be in the form of incremental improvements in catalyst yield and lifetime. Typically, a dilute stream, 5—10% of isobutylene tert-huty alcohol) in steam (10%) and air, is passed over the catalyst at 300—420°C. Conversion is often nearly quantitative, with selectivities to methacrolein ranging from 85% to better than 95% (114—118). Often there is accompanying selectivity to methacrylic acid of an additional 2—5%. A patent by Mitsui Toatsu Chemicals reports selectivity to methacrolein of better than 97% at conversions of 98.7% for a yield of methacrolein of nearly 96% (119). 

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