Precious metal oxides

Many competitive programs to perfect a metallic anode for chlorine arose. In one, Dow Chemical concentrated on a coating based on cobalt oxide rather than precious metal oxides. This technology was patented (9,10) and developed to the semicommercial state, but the operating characteristics of the cobalt oxide coatings proved inferior to those of the platinum-group metal oxide. 

Cathodic Protection Systems. Metal anodes using either platinum [7440-06 ] metal or precious metal oxide coatings on titanium, niobium [7440-03-17, or tantalum [7440-25-7] substrates are extensively used for impressed current cathodic protection systems. A prime appHcation is the use of platinum-coated titanium anodes for protection of the hulls of marine vessels. The controUed feature of these systems has created an attractive alternative... 

Metal anodes using platinum and precious metal oxide coatings are also incorporated into a variety of designs of impressed current protection for pipeline and deep weU appHcations, as weU as for protection of condenser water boxes in power generating stations (see Pipelines Power generation). 

Anode Applications. Graphite has been used as the primary material for electrolysis of brine (aqueous) and fused-salt electrolytes, both as anode and cathode. Technological advances, however, have resulted in a dimensionally stable anode (DSA) consisting of precious metal oxides deposited on a titanium substrate that has replaced graphite as the primary anode (38—41) (see Alkali and chlorine products). 

It has now gained acceptance as an impressed current anode for cathodic protection and has been in use for this purpose since 1971. The anode consists of a thin film of valve and precious metal oxides baked onto a titanium substrate and when first developed was given the proprietary name dimensionally stable anode , sometimes shortened to DSA. Developments on the composition of the oxide film have taken place since Beer s patent, and this type of anode is now marketed under a number of different trade names. 

Precious metal catalyst, 10 42 Precious-metal oxidation catalyst, 10 102 Precious metals... 

Crucibles must be suitable for the required experimental conditions with respect to their material, capacity and shape. As in the techniques of the chemical laboratory, crucible materials are selected to avoid the possibility of reaction between crucible and sample material. The main materials used are the precious metals, oxide ceramics, quartz and graphite. The size of the crucible is determined by the volume to be weighed. 

In principle, precious metal oxides such as RUO2, Ir02 and Rh203 are thermodynamically unstable under the conditions of H2 evolution since they should be reduced to the metals. In fact, this is not the case, with the exception of Rh203, whose stability depends on the details of the preparation [44, 45]. The reason for this apparent thermodynamic contradiction lies in the electronic conductivity of... 

The modem catalytic converter installed on most automobiles is a washcoat consisting of precious metal oxides, supported on a ceramic monolith. After passage of the... 

These authors suggested that the mechanism of etching is the formation of precious metal oxides (primarily of platinum) under reaction conditions and the subsequent volatilization of these oxides. Although it was noted that the same rate of metal loss and the same gross transformation did not take place in a pure oxygen environment, no attempt was made to reconcile these observations with the etching model. 

Recovery of SCWO products. Examples of valuable products include precious metal oxides, phosphate,paper fillers, iron and aluminum coagulants, and carbon dioxide. 128-130... 

The precious metals are generally introduced in the catalyst by wet chemical methods such as incipient wetness impregnation, typically using aqueous solutions of the precious metal salts, followed by a drying step to remove the water, and then by a caleination step to decompose the precious metal salts. Sometimes, a reduction step is applied to convert the precious metal oxides into the metallic state. Other production procedures are used as well and are described in the patent literature. 

The dimensionally stable anode in this system is composed of an electrically conductive substrate of titanium, having a coating of a defect solid solution containing mixed crystals of precious metal oxides. These substitutional solid solutions are both electrically conductive, electrocatalytic, and dimensionally stable. Within the aforementioned solid-solution host structures the valve metals include titanium, tantalum, niobium, and... 

It is well known that addition of base metal oxides can enhance the catalytic properties of noble metals. Addition of CeOa in three-way catalysts has improved the performance by the ability to store oxygen, promote the water-gas-shift reaction, stabilise the alumina support, suppress strong Rh-ALOa interactions and promote noble metal dispersion [4-5]. Beside the precious metals, oxides of the first row of transition metals are generally active as oxidation catalysts. By promoting Pt and Pd with cobalt oxide it has recently been shown that the activity for oxidation of CO and propene is significantly increased [6-10]. 

Dimensionally Stable Anodes— These anodes are composed of a base metal such as titanium, coated with a precious metal oxide (e.g., ruthenium dioxide). Such anodes can be used instead of Pt or carbon for oxygen evolution counter electrodes in an organic electrosynthesis. They have also found some applications for organic oxidation reactions [61]. 

The specific influence of non-precious metal oxide additives which definitely influence A/F windows will be reported in another study. 

Murrell, L.L., S.J. Tauster and D.R. Anderson, 1991, Laser Raman characterization of surface phase precious metal oxides formed on Ce02, in Catalysis and Automotive Pollution Control II, ed. A. Cmcg (Elsevier, Amsterdam) pp. 275-289. 

Ishihara A, Ohgi Y, Matsuzawa K, Mitsushrma S, Ota K (2010) Progress in non-precious metal oxide-based cathode for polymer electrolyte fuel cells. Electrochim Acta 55(27) 8005-8012... 

Non-precious Metal Oxide-Based Cathode Catalysts 13.4.1 Stability of Group 4 and 5 Metal Oxide-Based Catalysts... 

The type of electrolytic cell commonly used in these marine and offshore applications is a tube within a tube , (but there are a variety of configurations.) A tube within a tube type cell consists of one anode, one cathode, and one bipolar tube with the necessary ancillary hardware to facilitate assembly-see Fig. 1. The outer anode and cathode are manufactured firom seamless titanium pipe. The anode surface is coated with proprietary precious metal oxides, primarily ruthenium and iridium. Seawater enters one end of the cell and passes between the cathode, the anode and bipolar tube annular spaces. When direct current is applied to the cell, sodium hypochlorite results. One cell can produce up to 5.5 kg/day and a maximum of 12 cells can be connected in series for a capacity of 65 kg/day per train. Multiple trains can operate in parallel to produce the required capacity. 

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