Oxides and oxide-supported catalysts

INS spectroscopy has been applied to characterising hydroxo and aquo components of oxide catalysts and adsorbed hydrogenous reactant molecules and intermediates. The INS spectra are complementary to infrared and Raman spectra, which have been used widely in the study of oxide catalysts. In an INS spectrum background scattering from an oxide is weak and can be subtracted from the spectrum the lower energy region (below 600 cm ) is readily accessible. For an introduction to industrial applications of oxide catalysts see [91]. 

In this section we describe INS studies of molybdenum trioxide, a precmsor of molybdenum disulfide catalysts ( 7.5), and transition metal oxides which catalyse complete or partial oxidation of hydrocarbons, and copper zinc oxide catalysts, which catalyse methanol synthesis from carbon monoxide and dihydrogen ( 7.3.3). 

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The catalytic activities of oxides and oxide-supported catalysts are affected by their electrical properties (21,181). When these properties are measured on powder samples, the experimentally determined values are strongly dependent upon interparticle spacing, particle size, etc., and so numerical results of different observers are not directly comparable. However, each individual group of investigators has followed its own uniform procedure, and the over-all results of various studies are comparable. 

Thermal decomposition of layered double hydroxides typically involves endothermic processes of dehydration, dehydroxylation, and the removal of anions. These treatment processes are of great importance in the production of oxide and oxide-supported catalysts (see Sec. VI.C). For this reason, because of the wide range of metal and anion combinations of interest in this context and because of various preparative methods available, this remains an active area of research. It is, however, a difficult area because of the problems of observing metastable intermediate phases and the poor crystallinity of the thermolyzed material for this reason it employs a range of old and new techniques (1,4,13). 

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