For chromium poisoning

There are no specific antidotes for chromium poisoning. Since most human overexposure is by ingestion, gastric lavage is appropriate in some cases. However, emesis should not be induced. Maintaining the proper fluid balance is critical due to impact on the kidney s ability to reabsorb fluid. It is necessary to establish that there is no impairment with breathing due to fluid accumulation in the lungs. Another important step is to decrease the intake of dietary supplements that contain chromium. 

Newly developed alloys have improved properties in many aspects over traditional compositions for interconnect applications. The remaining issues that were discussed in the previous sections, however, require further materials modification and optimization for satisfactory durability and lifetime performance. One approach that has proven to be effective is surface modification of metallic interconnects by application of a protection layer to improve surface and electrical stability, to modify compatibility with adjacent components, and also to mitigate or prevent Cr volatility. It is particularly important on the cathode side due to the oxidizing environment and the susceptibility of SOFC cathodes to chromium poisoning. 

Chromium catalysts are notorious for the difficulty of initiating polymerization after a "turnaround." When process equipment is taken out of service for maintenance, the interior of reactors may be exposed to ambient air. This introduces oxygen and water, severe poisons for chromium catalysts. Even after inert gas (nitrogen) is re-introduced after maintenance activities are completed, trace amounts of poisons adhere to interior surfaces. Diethylzinc is aggressively reactive with water and oxygen and is used to scavenge these poisons from polymerization reactors. When reactors are started up again, polymerization initiates more readily. 

Other examples of the two types of sites behaving differently were provided by the results of poisoning experiments. Polar or other coordinating ligands are usually strong poisons for chromium oxide catalysts,... 

Chromium evaporation is a significant failure mechanism for chromium containing stainless steel Interconnects as it can lead to poisoning of the fuel cell cathode and loss of performance. This failure mechanism is not able to be resolved from the ASR testing, however, careful post-test characterization of the coating microstructure enabled an assessment of the effectiveness of the coating to act as a chromium diffusion barrier. 

In recent years, an interesting but troublesome fact has been revealed, that is, Pt wire reacts with oxygen in air to form Pt02(g) and will be deposited on the three phase boundaries of LSM cathodes [80]. Usually, Pt cathodes are not better than perovskite cathodes so that the electrode activity may be lowered when such Pt will be deposited on cathodes. However, the situation for the chromium poisoning for the LSM cathode is quite different. When Pt is deposited on TPB of LSM cathodes, the cathode performance can be improved or lowered depending on the state of deposited Pt. This disturbs the effects of chromium on the LSM cathodes. This makes it difficult to examine the chromium poisoning in a laboratory scale. 

Figure 5.14 Chromium poisoning for different electrode/electrolyte combinations [65 ].

HTS catalyst consists mainly of magnetite crystals stabilized using chromium oxide. Phosphoms, arsenic, and sulfur are poisons to the catalyst. Low reformer steam to carbon ratios give rise to conditions favoring the formation of iron carbides which catalyze the synthesis of hydrocarbons by the Fisher-Tropsch reaction. Modified iron and iron-free HTS catalysts have been developed to avoid these problems (49,50) and allow operation at steam to carbon ratios as low as 2.7. Kinetic and equiUbrium data for the water gas shift reaction are available in reference 51. 

Metals in the platinum family are recognized for their ability to promote combustion at lowtemperatures. Other catalysts include various oxides of copper, chromium, vanadium, nickel, and cobalt. These catalysts are subject to poisoning, particularly from halogens, halogen and sulfur compounds, zinc, arsenic, lead, mercury, and particulates. It is therefore important that catalyst surfaces be clean and active to ensure optimum performance. 

With this in view, we studied the development of the dehydrofluorination reaction of CF3CH2CI as function of the degree of fluorination of chromium oxide. Moreover, nickel and chromium oxide catalysts were prepared and tested for the dehydrofluorination reaction. Nickel oxide, a basic compound [S], could poison selectively the tes involved during the dehydrofluorination reaction. 

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