| Popis: |
There is a renewed interest in carbon materials as potentially inexpensive and environmentally safe catalysts. While carbon materials have been known as catalysts with modest activity for many years, more recent advances in material science have made possible the synthesis of very high surface area carbon materials. Some of these materials are highly active and selective catalysts for oxidation reaction, dehydrochlorination of alkyl chlorides and selective cleavage of C-C bonds. This work area of coal liquefaction modeling has shown the ability of carbon black and other carbon materials to cleave C-C bonds in model compounds with chemical structure relevant to coal and petroleum resids. A very high selectivity (over 90%) was observed for the cleavage of the bond between a condensed polycyclic aromatic ring and the adjacent aliphatic carbon. This activity has been correlated to the positive surface charge on the carbon catalyst at the reaction temperature. A cation-radical mechanism has been proposed for the reaction, with electron transfer from the polycyclic aromatic ring to the carbon surface as the initial step of the catalysis. The ability of a carbon black transfer an electron from an adsorbed iodine anion to an Fe[sup 3+] cation has been demonstrated by Spiro. Thismore » report describes studies of the catalytic activity of carbon black in selective dehydroxylation and dehalogenation reactions under reductive conditions in the presence of a hydrogen donor. Porous carbons are active catalysts for the oxidative decomposition of halogenated hydrocarbons to CO[sub 2] and HCl. This method, using a reductive medium, would allow for recovery of the carbon and hydrogen part of the molecules, a feature relevant to the effort to recycle waste into useful materials. 13 refs., 1 fig., 2 tabs.« less |
