Poison polarization

In all of the ethylene polymerization processes, the catalyst is sensitive to feed impurities and is poisoned by most polar compounds. Many of the properties of the polymer are determined by polymerization conditions, but catalyst composition and condition are critical determinants as well. 

Water and polar solvents poisoned the early catalysts used. 

Scheme 11 Catalyst deactivation routes in copolymerizations with polar olefins a P-elimination of a leaving group to afford allylic or dimeric species, b poisoning by N-complexation in the attempted copolymerization of acrylonitrile...

While the human body can remove an excess of any water-soluble vitamin, excesses of fat-soluble vitamins are more serious. Early arctic explorers discovered that the Inuit regarded seal liver and polar bear liver as taboo and must not be eaten. Those explorers who ignored this advice risked retinol poisoning as the livers of both these species are rich in retinol (vitamin A) that can not be excreted. The effects of retinol poisoning are extremely unpleasant. It is for this reason that fortification with fat-soluble vitamins is not likely to be undertaken. 

Dees et al. [66, 67] reported that the sulfur poisoning was due to a large increase in anode interfacial polarization resistance (Rp). They found that total Rp for an Ni-YSZ cermet anode/electrolyte/anode symmetrical cell in 97% H2/3% H2 increased from 0.27 to 0.45 fl/cm2 (an -67% increase) when 100 ppm H2S was introduced into the... 

A long disputed issue of the nature of strongly bound species in this reaction has been recently revived with the vibrational spectroscopy studies of Bewick et al. (30) using EMIRS technique and of Kunimatsu and Kita (31) using polarization modulation IR-reflection-absorption technique. These data indicated the only CO is a strongly bound intermediate. Heitbaum et al. (32) on the other hand advocate COH, and most recently HCO (33), as the poisoning species on the basis of differential electrochemical mass spectroscopy (DEMS). 

In order to increase the selectivity in diene hydrogenation, low-temperature basic additives and the use of less polar solvents may help. In special cases, treatment of the catalysts with the salts of heavy metals (Zn, Cd, Pb) can be the method used to modify the activity and selectivity53. Rh and Ir catalysts could be selectively poisoned with CO-containing hydrogen, in order to saturate 1,3-butadiene to 1-butene without isomerization54. 

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