GAS-PHASE HYDROGENOLYSIS MEDIATED BY ACTIVATED CARBON - DEUTERATED BENZENES

Citation
Iwce. Arends et al., GAS-PHASE HYDROGENOLYSIS MEDIATED BY ACTIVATED CARBON - DEUTERATED BENZENES, Recueil des travaux chimiques des Pays-Bas, 115(5), 1996, pp. 271
Citations number
12
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry
ISSN journal
0165-0513
Volume
115
Issue
5
Year of publication
1996
Database
ISI
SICI code
0165-0513(1996)115:5<271:GHMBAC>2.0.ZU;2-Q
Abstract
Hydrogenolyses of hexadeuterobenzene C6D6 and pentadeuterochlorobenzen e C6D5Cl have been studied in flow reactors packed with activated carb on (AC) between 300 degrees and 600 degrees C, with void residence tim es of 4-5 s. At 579 degrees C overall dedeuteration - proceeding in a near statistical manner - was close to 40% in both cases, whereas C6D5 Cl is almost completely dechlorinated to deuterated benzenes at 505 de grees C. On a per-site basis, replacement of Cl by H is ca. 20 times f aster than that of D. These results clearly demonstrate a catalytic ac tivity of AC in both cases of desubstitution, In the absence of AC, te mperatures of 700-900 degrees C are necessary to obtain the same resul t. Then, replacement of Cl and D have almost equal rates, both reactio ns occurring via addition of free H atoms. In the AC-mediated reaction s, the yields of (D) benzenes are quantitative from C6D6, but around 5 0% with C6D5Cl. Apparently the latter compound reacts with bonding of its phenyl group to the AC surface, whereas D --> H substitutions invo lve H transfer to a physisorbed (D) benzene.