Mercury chloride, catalyst poison

Lead ores are contaminated with mercury which is poisonous to a vanadium catalyst. Hence, it is first removed by the patented Norwar process by scrubbing with mercuric chloride and recovering mercury by chlorination ... 

Natural gas contains both organic and inorganic sulfur compounds that must be removed to protect both the reforming and downstream methanol synthesis catalysts. Hydrodesulfurization across a cobalt or nickel molybdenum—zinc oxide fixed-bed sequence is the basis for an effective purification system. For high levels of sulfur, bulk removal in a Hquid absorption—stripping system followed by fixed-bed residual clean-up is more practical (see Sulfur REMOVAL AND RECOVERY). Chlorides and mercury may also be found in natural gas, particularly from offshore reservoirs. These poisons can be removed by activated alumina or carbon beds. 

It must be emphasized that high purity syngas is essential for the methanol synthesis catalyst, which is easily poisoned or deactivated by components such as chlorides, sulfur and heavy metals, i.e., mercury. Also, large quantities of inerts, namely, nitrogen and methane, which have no effect on the methanol catalyst, can reduce the overall carbon efficiency which will increase the amount of syngas required per unit make of methanol. 

Mechanistic studies performed with Freeh s pincer catalyst in the Heck reaction excluded catalytic cycles with the involvement of homogeneous palladium(O) species, as indicated by the results obtained from the (recently developed) dibenzyl-test, which is directly applicable under the reactions conditions applied [24aj. Dibenzyl formation was - in contrast to Heck reactions catalyzed by palladium(O) complexes of type [Pd(PR3)2, where Pd /Pd" cycles are operative - not detectable by gas chromatography-mass spectrometry (GC/MS) when reaction mixtures of aryl bromide, olefin, benzyl chloride ( 10 mol% relative to aryl bromide), catalyst, and base were thermally treated. On the other hand, experimental observations, such as quantitative poisoning experiments with metallic mercury and CS2, which were shown to eflfidently inhibit catalysis, as well as analysis of the reaction profiles showed sigmoidal-shaped kinetics with induction periods and hence indicated that palladium nanoparticles are the catalytically active form... 

The poisonings in Minamata were due to mercuric chloride in a river. It had been used as a catalyst in the production of vinyl chloride. The population was poisoned due to the contamination of fish. In Iraq, the mass poisoning was the result of contaminated bread, for which flour accidentially made of grains, which had been treated with methyl mercury, has been used. 

Fishing was officially banned in 1957. It was found that the Chisso Corporation, a petrochemical company and maker of plastics such as polyvinyl chloride, had been discharging heavy-metal waste into the sea. They used mercury compounds as catalysts in their syntheses. It is believed that more than 1400 people were killed and perhaps, 20,000 people were poisoned to a lesser extent. The effects of mercury poisoning are still sometimes referred to as Minamata disease. 

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