Metal oxides summarized

Figure 17 summarizes the avadable sol—gel processes (56). The process on the right of the figure involves the hydrolysis of metal alkoxides in a water—alcohol solution. The hydrolyzed alkoxides are polymerized to form a chemical gel, which is dried and heat treated to form a rigid oxide network held together by chemical bonds. This process is difficult to carry out, because the hydrolysis and polymerization must be carefully controlled. If the hydrolysis reaction proceeds too far, precipitation of hydrous metal oxides from the solution starts to occur, causing agglomerations of particulates in the sol. 

The chemical composition from ICP analyses and nitrogen porosimetry data obtained by Quantachrome AUTOSORB-6 are summarized in Table 1 for all the five samples. Note that the catalytic metal oxide loadings in Samples B-E were adjusted so that the efficiency of each catalyst for step 3 can be directly compared on the same basis, per gram atom of metal. The... 

Since no information has been reported on the reaction, it seems necessary to make a character sketch of the catalytic function. Therefore, various kinds of metal oxides were tested as the catalysts. The results are summarized in Table 1. 

We have summarized below recent results concerning spectroscopic / flow reactor investigations of hydrocarbons partial and total oxidation on different transition metal oxide catalysts. The aim of this study is to have more information on the mechanisms of the catalytic activity of transition metal oxides, to better establish selective and total oxidation ways at the catalyst surface, and to search for partial oxidation products from light alkane conversion. 

Among the above four hypotheses, the first one, gold NPs supported on base metal oxides lead to the highest catalytic activity and stability. Their characteristic features can be summarized in the following points [11,12]. 

The last-mentioned line intersects the metal oxide line at a lower temperature than the line corresponding to the formation of carbon monoxide at 1 atm. It is, therefore, clear that the minimum temperature required for the carbothermic reduction of the metal oxide under vacuum is less than the minimum temperature for the same reaction at atmospheric pressure. Thus, by increasing the temperature and decreasing the pressure of carbon monoxide, it may be possible to reduce carbothermically virtually all the oxides. This possibility has been summarized by Kruger in the statement that at about 1750 °C and at a carbon monoxide pressure below 1CT3 atm, carbon is the most efficient reducing agent for oxides. 

On the basis of obtained data of cyclic voltammograms for 3d metals oxides electrodeposition the optimal conditions (current density, potential, process time, electrolyte composition, temperature) for dense oxide films (Ni, Cr and Co) deposition on steel foil have been elaborated. Data relating to several best films are summarized in Table 1. 

In this paper the extraction of gold chlorocomplexes on alternative metal oxide (FeOOH, Fe304 and AI2O3) sorbents was investigated. The investigations reported in this paper can be summarized as follows ... 

These studies have allowed the spectroscopic identification of a number of electronically excited states of the metal oxides, but there appear to have been no analytical applications of the reactions to date. The emitting states, as summarized by Toby [14], are CaO(A n), SrO(ATl), PbO(a32+, b32+), ScO(C2II), YO(C2n), FcO(C ), A10(A2ni B2X+), and BaO(A i)1, D 2+). Nickel carbonyl reacts with ozone to produce chemiluminescence from an excited electronic state of NiO, which is probably produced in the Ni + 03 reaction [42, 43],... 

This work summarizes some applications of in situ Mossbauer spectroscopy to the study of certain aspects of the electrochemistry of iron and iron containing transition metal oxides. A number of illustrations of the use of this technique to the investigation of a wide variety of interfacial phenomena may be found in two recent monographs. (2 ... 

Table 3 summarizes the results for the effect of pH of the feeds on uptake of arsenate. Uptake or removal of arsenate until 140 BV of the feed shows that the uptake slightly decreases with an increase of the pH of feeds as widely observed in ligand exchange uptake of arsenate by metal and/or metal oxide loaded ligand exchangers.3-15... 

Elsewhere (26) I have shown that the oxidation of Mn(II) in the presence of four metal oxides (a-Fe00H, y-FeOOH, amorphous silica, and 6-Al203) can be understood in terms of the coupling of surface coordination processes and redox reactions on the metal oxide surface. These results are not discussed here, but the conclusions with regard to y-FeOOH are summarized. 

In addition to silica and clay minerals, the subsurface contains a variety of minerals (e.g., oxides, carbonates), which may react with organic and inorganic contaminants. GiUces (1990), summarizing the properties of the metal oxides in earth... 

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. 

In the development of effective catalytic oxidation systems, there is a qualitative correlation between the desirability of the net or terminal oxidant, (OX in equation 1 and DO in equation 2) and the complexity of its chemistry and the difficulty of its use. The desirability of an oxidant is inversely proportional to its cost and directly proportional to the selectivity, rate, and stability of the associated oxidation reaction. The weight % of active oxygen, ease of deployment, and environmental friendliness of the oxidant are also key issues. Pertinent data for representative oxidants are summarized in Table I (4). The most desirable oxidant, in principle, but the one with the most complex chemistry, is O2. The radical chain or autoxidation chemistry inherent in 02-based organic oxidations, whether it is mediated by redox active transition metal ions, nonmetal species, metal oxide surfaces, or other species, is fascinatingly complex and represents nearly a field unto itself (7,75). Although initiation, termination, hydroperoxide breakdown, concentration dependent inhibition... 

The general structure of this class of materials can, therefore, be summarized as a fine dispersion of metal oxide in a polymer matrix very similar to plasma polytetrafluoroethylene and in principle any metal should be able to be incorporated. Clearly, if the films are protected from the atmosphere, for metals which form involatile fluorides having a relatively weak metal-fluorine bond strength, it should be possible to produce films having metal atoms dispersed in the matrix. It is expected that these films will have many interesting chemical, optical, electrical and magnetic properties., ... 

For a convenient comparison. Table 1 summarizes the pros and cons for each catalyst tested. Clearly, the sulfated metal oxides are the best choice. 

To summarize, the special bonding characteristics of 7r-acceptor ligands in organotransition metal compounds enable these complexes to coordinate small molecules such as ethylene, CO, and H2 and also provide an electronic buffer system to facilitate changes of metal oxidation state and coordination... 

The behaviour of polarons is of importance for the oxides and similar materials to be discussed in this book, and we summarize some of their properties here, as applied chiefly to transitional-metal oxides. (For more detailed discussions see Mott and Davis (1979, Chap. 3), Austin and Mott (1969a, b), Appel (1968), Emin (1973, 1975) and Mott (1973b). 

The homologous compounds V O2 -1 are derived by the shear operation (121) [0i 1] on rutile. As mentioned above, the arrangement of atomic planes parallel to (121) is. .. ABABAB. .., where A = O and B = MO. After the elimination of an oxygen-only plane A in every n B plane, the arrangement of the atomic planes gives compounds generally expressed as M O2 -1 ( = (n — 1)A + nB). As a typical example. Fig. 2.12 shows an ideal structure of VgOi 1 (n = 6). The structure has been confirmed by X-ray diffraction. In Table 2.1, the shear compounds of the transition metal oxides are summarized. ... 

Side-Chain Alkylation. There is continued interest in the alkylation of toluene with methanol because of the potential of the process in practical application to produce styrene.430 Basic catalysts, specifically, alkali cation-exchanged zeolites, were tested in the transformation. The alkali cation acts as weak Lewis acid site, and the basic sites are the framework oxygen atoms. The base strength and catalytic activity of these materials can be significantly increased by incorporating alkali metal or alkali metal oxide clusters in the zeolite supercages. Results up to 1995 are summarized in a review.430... 

The final choice of the positive to be used in practical lithium ion batteries depends on the specific requirements of a particular developer. The characteristics of the three most common lithium metal oxide electrodes currently exploited in lithium ion technology are summarized in Table 7.3. 

Claus propositions were summarized as three statements in his more widely read paper of 1856 42 (1) If several equivalents of ammonia (from two to six) combine with an equivalent of certain metal chlorides, neutral substances are formed, in which the basic property of ammonia has been destroyed and simultaneously the ammonia can be neither detected by the usual methods nor eliminated by double decomposition . (2) If the chlorine in these compounds is replaced by oxygen, strong bases are obtained, whose saturation capacity is always determined by the oxygen equivalents contained in them but not by the number of equivalents of ammonia present in them . (3) The number of equivalents of ammonia entering into these substances is not a random one as is evident from a number of facts, it is determined by the number of equivalents of water contained in the hydrates of the metal oxides which can enter into such compounds along with the ammonia . 

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