Poison compound loading

The plot of at versus poison compounds loading Is shown In Figure 3. It shows that ot is linearly dependent on the pyridine loading and independent of the cracking temperature. The parameter, at, can be expressed for pyridine poisoning as follows ... 

Each precious metal or base metal oxide has unique characteristics, and the correct metal or combination of metals must be selected for each exhaust control appHcation. The metal loading of the supported metal oxide catalysts is typically much greater than for nobel metals, because of the lower inherent activity pet exposed atom of catalyst. This higher overall metal loading, however, can make the system more tolerant of catalyst poisons. Some compounds can quickly poison the limited sites available on the noble metal catalysts (19). 

In addition, chlorine derivatives are important as intermediates in the chemical industry, and there are numerous chlorine-containing pharmaceuticals for which no substitutes are presently available. Furthermore, organochlorine compounds, some very toxic, do occur naturally on a large scale. Clearly, however, we must endeavor to avoid adding unnecessarily to the natural load of toxins as the old adage goes, it is the dose that makes the poison.4 Certainly, problems exist that require an intelligent and chemically informed resolution, but the total ban advocated by some on the use of chlorine and chlorinated compounds is neither necessary nor acceptable. 

Poisoning hy Lead.—When compounds of load are token in sueh quantities as to be destructive to life, tho physical indications which are observed differ with the form of combination of the metallic oxide thus, for instance, the acetate of lead acts as an irritant, but tho carbonate—white lead—has no such sotion, or at beat only a very indecisive one tho same may he observed of the oxide and other compounds of lead, especially those of limited solubility. The general physiological effects already mentioned, are guides which do not fail to pant out the cause when death or violont attacks through the poisonous action of lead follows. 

The industrial application of the Co304 catalyst for ammonia oxidation is complicated by its sensitivity to poisoning action of small amounts of sulfur compounds in the ammonia-air mixture. This phenomenon was studied with the use of radioactive sulfur containing S3s that made it possible to measure very low concentrations of sulfur (168). Poisoning results in decrease both of selectivity and limiting load. A noticeable decrease in selectivity starts at sulfur concentrations in the gas mixture from 0.05 mg/m3. This concentration is many times lower than minimum H2S and S02 concentrations in air detected by smell. 

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