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Metallic elements calcination

As we have already seen, there was throughout this period a steady increase in the materialization of the chemical elements, whether one believed in three, four, or five. In the case of fire the phlogiston concept is certainly in that pattern. But the chief ancestor lies in the even older tradition of the sulphur principle. The sensation of heat is seen as distinct from the particles of fire, which for many chemists, Boyle among them, were responsible for the increase in weight when metals were calcined. There is no problem in finding a source for Rouelle s idea of fire as occurring both fixed and free. [Pg.137]

In contrast to lead, the possible poisoning by metallic elements, derived from the vehicle system, is not easily documented. Many formulations of automotive catalysts contain both base and noble metals, but the detailed effect of such combinations on the particular reactions is rarely known with precision. One study was concerned with the effect of Cu on noble metal oxidation catalysts, since these, placed downstream from Monel NOx catalysts, could accumulate up to 0.15% Cu (100). The introduction of this amount of Cu into a practical catalyst containing 0.35% Pt and Pd in an equiatomic ratio has, after calcination in air, depressed the CO oxidation activity, but enhanced the ethylene oxidation. Formation of a mixed Pt-Cu-oxide phase is thought to underlie this behavior. This particular instance shows an example, when an element introduced into a given catalyst serves as a poison for one reaction, and as a promoter for... [Pg.356]

The reductive/oxidative properties of transitional metal elements in these zeolite catalysts were also examined by TPR and TPO, and it is shown that metallic species in certain cation locations may migrate under calcination, reduction, and reaction conditions [7], The different treatment, e g, coking or even the oxidative regeneration, will produce metallic species of varied oxidation states with different distributions in the molecular sieve structures as exemplified by the above XPS data. The redox properties of these metallic cations exhibit the influence of hydrogen and/or coke molecules, and it is further postulated that the electron transfer with oxygen species are considered responsible for their catalyzed performance in the TPO regeneration processes, as shown in Figure 2. [Pg.220]

Conventional cathode materials such as LCD with a single transition metal element are prepared by a simple solid-phase method, in which cobalt acetate and lithium carbonate are calcined at around 900 °C, and consistent product is easily obtained. For materials with multiple transition metal elements like LMO, on the other hand, it is crucial to obtain product composition that is stoichiometrically precise and to obtain the intended crystal structure. Even slight variations can result in widely divergent characteristics when used as cathode material. Strict control of preparation conditions is thus essential for this class of materials. [Pg.9]

In the early research stages of ammonia synthesis catalyst, Mittasch et al. studied almost all metal elements and their bimetallic alloy in the Periodic Table. Several metals have no or less catal3dic functions themselves. However, the addition of some promoter could increase their activities. The addition of a secondary metal into Fe, Mo, W, Co, Ni, Pd, Pt, Os, Mn enhances their activities. The different ratio between two metals leads to a different activity. It can be concluded from these results that the addition of metals in Vlff or VI groups favors enhancing of iron-based catalyst activity. For example, Fe-Mo (1 1) catalyst has high activity. If the Mo content is less than 80%, the activity decreases after running for a long-time. These catalysts are prepared by calcinations of metal nitrates and ammonium molybdate... [Pg.803]

Fischer-Tropsch synthesis, and oxidation reactions [53, 68, 69]. The mixed oxides of transition metal elements formed upon their calcinations have also shown activity in hydrogenation reactions, e. g., in hydrogenation of acetylene [70,71], nitriles [72], nltrocompoimds [73], and carbonyl groups [74]. [Pg.170]

Zinc smelters use x-ray fluorescence spectrometry to analyze for zinc and many other metals in concentrates, calcines, residues, and trace elements precipitated from solution, such as arsenic, antimony, selenium, tellurium, and tin. X-ray analysis is also used for quaUtative and semiquantitative analysis. Electrolytic smelters rely heavily on AAS and polarography for solutions, residues, and environmental samples. [Pg.410]

MetaUic impurities in beryUium metal were formerly determined by d-c arc emission spectrography, foUowing dissolution of the sample in sulfuric acid and calcination to the oxide (16) and this technique is stUl used to determine less common trace elements in nuclear-grade beryUium. However, the common metallic impurities are more conveniently and accurately determined by d-c plasma emission spectrometry, foUowing dissolution of the sample in a hydrochloric—nitric—hydrofluoric acid mixture. Thermal neutron activation analysis has been used to complement d-c plasma and d-c arc emission spectrometry in the analysis of nuclear-grade beryUium. [Pg.69]

The TEM images of 12 wt.% Co/MgO calcined at 873 K (Catalyst I) before and after reduction are shown in Fig. 1 (a) and (b), respectively. Although Co metal phase was detected in reduced Co/MgO by X-ray diffraction measurements (XRD) [7, 8], no Co metal particle was observed on both catalysts. EDS elemental analysis showed that primary particles contain both Mg and Co elements, whose concentrations were about the same as loaded amounts. Figure 2 shows TEM image of 12 wt.% Co/MgO calcined at 1173 K (Catalyst II). [Pg.518]

The catalysts with metals are previously impregnated with solutions of vanadyl and nickel naphtenates based on the Mitchell method [4], Before hydrothermal deactivation the samples were calcined in air at 600°C. The activity was performed in the conventional MAT test using 5 grams of catalyst, ratio cat/oil 5, stripping time 35 seconds, and reaction temperature 515°C. Elemental analyses to determine the total amount of carbon in the spent catalysts were done by the combustion method using a LECO analyzer. [Pg.145]


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Calcined

Calciner

Calciners

Calcining

Elemental metallic

Elements metals

Elements, metallic

Metallic elements metals

Metals calcination

Metals elemental

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