Metal oxide catalyst synthesis

The catalysts which have been tested for the direct epoxidation include (i) supported metal catalysts, (ii) supported metal oxide catalysts (iii) lithium nitrate salt, and (iv) metal complexes (1-5). Rh/Al203 has been identified to be one of the most active supported metal catalysts for epoxidation (2). Although epoxidation over supported metal catalysts provides a desirable and simple approach for PO synthesis, PO selectivity generally decreases with propylene conversion and yield is generally below 50%. Further improvement of supported metal catalysts for propylene epoxidation relies not only on catalyst screening but also fundamental understanding of the epoxidation mechanism. 

As catalysis proceeds at the surface, a catalyst should preferably consist of small particles with a high fraction of surface atoms. This is often achieved by dispersing particles on porous supports such as silica, alumina, titania or carbon (see Fig. 1.2). Unsupported catalysts are also in use. The iron catalysts for ammonia synthesis and CO hydrogenation (the Fischer-Tropsch synthesis) or the mixed metal oxide catalysts for production of acrylonitrile from propylene and ammonia form examples. 

The molecular design of supported metal oxide catalysts requires that we specify the synthesis method, oxide support, catalyst composition, calcination... 

Niobium Products Co., 50 m /g). Many different synthesis methods have been used to prepare supported metal oxide catalysts. In the case of supported vanadium oxide catalysts, the catalysts were prepared by vapor phase grafting with VOCI3, nonaqueous impregnation (vanadium alkoxides), aqueous impregnation (vanadium oxalate), as well as spontaneous dispersion with crystalline V2O5 [4]. No drastic reduction of surface area of the catalysts was observed. 

To investigate the effect of the synthesis method on the structure-reactivity relationship of the supported metal oxide catalysts, a series of V205/Ti02 catalysts were synthesized by equilibrium adsorption, vanadium oxalate, vanadium alkoxides and vanadium oxychloride grafting [14]. The dehydrated Raman spectra of all these catalysts exhibit a sharp band at 1030 cm characteristic of the isolated surface vanadium oxide species described previously. Reactivity studies with... 

In addition, ligands of type O and related species have been used for the stabilization of middle and late high oxidation state transition metal complexes and the synthesis of oxidation catalysts... 

Some other oxo complexes are shown in Fig. 1539. Although the oxide ligand is generally thought of as O2- rather than neutral O, its similarity to the carbene ligand. CR2 (which could also be viewed as CR> ), lends to be obscured as a result. Interest in oxo complexes is tied to their relationship to metal oxide catalysts which are widely used in organic synthesis. 

Lanthanide-containing porous materials have found many applications in various fields [20-22], They are known as active and selective catalysts for synthesis of higher hydrocarbons (mostly ethane and ethylene) from methane [23], which is of considerable importance for utilizing the reserves of natural gas around the World. Cerium oxide has been employed as a catalyst or as a structural promoter for supported metal oxide catalysts... 

In the second step, the synthesis gas and additional steam are passed over a metal oxide catalyst at about 400°C. Under these conditions, the carbon monoxide component of the synthesis gas and the steam are converted to carbon dioxide and more hydrogen. This reaction of CO with H20 is called the water-gas shift reaction because it shifts the composition of synthesis gas by removing the toxic carbon monoxide and producing more of the economically important hydrogen ... 

Each bead represents one catalyst as a member of a library of solid catalysts. It may consist of an unporous material like a-Al2C>3 or Steatit or of typical porous support materials - such as A1203, Si02, Ti02, or the like. These beads can be subjected to different synthesis procedures and sequences like impregnation, coating etc. In addition, full mixed metal oxide catalysts can also be formed as spherical particles. 

D. Synthesis of Metal Oxide Catalysts and Supported Metals... 

Analytical Chemistry of the Transition Elements Coordination Numbers Geometries Coordination Organometallic Chemistry Principles Hydride Complexes of the Transition Metals Oxide Catalysts in Sohd-state Chemistry Periodic Table Trends in the Properties of the Elements Sol Gel Synthesis of Solids Structure Property Maps for Inorganic Solids Titanium Inorganic Coordination Chemistry Zirconium Hafnium Organometallic Chemistry. 

Properties, Synthesis and Applications of Highly Dispersed Metal Oxide Catalysts... 

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