Hydro-demetallation

Hydro-Demetallization (HDM) and -Desulfurization (HDS) of Heavy Oils. The hydrocarbon petroleum fractions contain... 

Pd species. This intermediate undergoes carbonylation, methoxy substitution, and reductive elimination to furnish the Z-configured derivative 193. The resulting Pd(0)-species is reoxidized by oxygen in the presence of iodide ions. On the other hand, the presence of potassium iodide can also equilibrate the ( 2-alkynyl carbamate-Pd-iodide complex to the r/2-alkynyl carbamate-Pd-diiodide complex, which, in turn, causes an anti-attack of the carbamate at the Pdl2-complexed alkyne. Therefore, an antz-vinyl-Pd species results, which ultimately and accordingly leads to the -configured derivative 194. Without carbon monoxide the vinyl-Pd-species suffer a hydro-demetallation. 

Hydrolysis of Organometallic Compounds Hydro-de-metallation or Demetallation... 

Catalytic hydrodemetallation studies with vanadyl naphthenates have been reported by West (1984). The instability of these compounds makes them relatively poor models for mechanistic studies. At typical hydro-treating conditions, a homogeneous noncatalytic demetallation route and a heterogeneous catalytic route contribute to overall metal removal. 

Poisoning is not always bad. There are situations where a catalyst is intentionally poisoned to decrease activity towards an undesirable reaction. In the hydro-desulfurization and -demetallization of a petroleum feedstock the catalyst is presulfided prior to introducing the feed to decrease its activity and minimize cracking reactions that will produce unwanted gases. Another is the use of ammonia to slightly poison a Pt catalyst used in the hydrogenation of fats and oils to decrease undesirable oversaturation. 

A third pathway leads via the quinone imine intermediates 38 to 3-hydro-xycarbazoles 41 (mode C in Scheme 12) [97, 98, 108, 109]. Oxidation of the complexes 36 with manganese dioxide afforded the quinone imines 38, which on treatment with very active manganese dioxide undergo oxidative cyclization to the tricarbonyl(ri" -4b,8a-dihydrocarbazol-3-one)iron complexes 39. Demetalation of 39 with trimethylamine iV-oxide and subsequent aromatization lead to the 3-hydro-xycarbazoles 41. The isomerization providing the aromatic carbazole system is a... 

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