Catalyst poisoning hydrogen production

In the feed preparation section, those materials are removed from the reactor feed which would either poison the catalyst or which would give rise to compounds detrimental to product quality. Hydrogen sulfide is removed in the DBA tower, and mercaptans are taken out in the caustic wash. The water wash removes traces of caustic and DBA, both of which are serious catalyst poisons. Also, the water wash is used to control the water content of the reactor feed (which has to be kept at a predetermined level to keep the polymerization catalyst properly hydrated) and remove NH3, which would poison the catalyst. Diolefins and oxygen should also be kept out of poly feed for good operation. 

The metals in the FCC feed have many deleterious effects. Nickel causes excess hydrogen production, forcing eventual loss in the conversion or thruput. Both vanadium and sodium destroy catalyst structure, causing losses in activity and selectivity. Solving the undesirable effects of metal poisoning involves several approaches ... 

The similar phenomenon of poisoning in situ of a palladium catalyst by hydrogen which was in this case the product of a reaction was observed by Brill and Watson (37). The reaction studied was the decomposition of formic acid... 

Researchers at Merck Co. [35] who, together with scientists from Solvias, had developed the enantioselective hydrogenation of unprotected enamine amides and esters [36], reported a more recent example of product inhibition. The product amine amide or ester was found to be an inhibitor of the catalyst, and indeed instances of catalyst poisoning by amines have been reported several times (see later). The authors also found an excellent solution to this problem the addition of BOC-anhydride to the hydrogenation reaction neatly reacts away all the amine to form the BOC-protected amine, whereas the enamine was left unreacted (Scheme 44.4). This addition resulted in a remarkable rate enhancement [35]. 

Chlorine (Cl), 6 130-211 9 280. See also Inorganic chlorine XeCl laser addition to fullerene, 12 240-241 analytical methods, 6 202 bleaching agent, 4 50 capacities of facilities, 6 193-198t catalyst poison, 5 257t chemical properties, 6 133-138 diffusion coefficient for dilute gas in water at 20° C, l 67t diffusion coefficient in air at 0° C, l 70t for disinfection, 8 605 economic aspects, 6 188-202 electrolytic preparation/production of, 12 759 16 40 end uses, 6 134-135 in fused quartz manufacture, 22 413 generating from hydrogen chloride, 13 833... 

The term chiral poisoning as a deactivating strategy has been proposed for the asymmetric hydrogenation reaction of dimethyl itaconate catalyzed by CHIRAPHOS-Rh complex (Scheme 8.5). The combination of racemic CHIRAPHOS-Rh complex and (5)-METHOPHOS 6 as a catalyst poison yields the hydrogenated product in 49% ee. (5)-METHOPHOS is believed to bind to the (S. S -CHlRAPHOS-Rh complex preferentially, as the use of enantiopure (R,R)-CHlRAPHOS-Rh complex affords the product with 98% ee. 

The presence of benzo[6]thiophene in commercial naphthalene, its possible contamination with isomeric thienothiophenes 1 and 2, and their ability to poison aromatic hydrogenation catalysts led Maxted and Walker to develop detoxification by a preliminary short hydrogenation, in which thienothiophenes 1 and 2, and benzo[6]-thiophene are adsorbed on the catalyst. This is followed by their hydrogenation products that can easUy be oxidized with hydrogen peroxide or permolybdic acid to nontoxic sulfones subsequent hydrogenation of the aromatic hydrocarbons is then performed as usual. 

The best results are obtained with the PEM electrolyser current density of 1 200 A/m2 under cell voltage of 1 V corresponding to a hydrogen production of 500 NL.fr1.nr2. The results from both electrolysers show sulphur deposition at the cathode. This chemical reduction consumes electrons at the expense of hydrogen production causing sulphur to poison the catalyst and modify the membrane conductivity. 

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