Ruthenium carbonyls as benzo[b]thiophene hydrodesulfurization catalysts inhomogeneous phase

The catalytic activity of mononuclear and polynuclear ruthenium complexes i n the benzo[b]thiophene (BT) hydrodesulfurization (HDS) has been tested in the temperature range between 150 and 170 degrees C under 100 bar of hydrog en. The ruthenium complexes tested are shown to be catalytically active in the hydrogenation of BT to 2,3-dihydrobenzo[b]thiophene (DHBT) and 2-ethylt hiophenol. The best performance was provided by H4Ru4(CO)(8)(PPh3)(4) when working at 170 degrees C: In these conditions BT is hydrogenated to DHBT wi th a conversion of 38.2% after 96 h or 81.2% after 384 h. Ethylbenzene (con version 4.9%) is also formed confirming that a complete HDS of the substrat e (even if in a low amount) may be obtained. The addition of a strong base ((BuOK)-Bu-t) as a co-catalyst changes the chemioselectivity of the reactio n. The mononuclear complexes are less active than the cluster ones. BT is i n fact converted to DHBT up to 19.5% in the presence of Ru(CO)(3)(PPh3)(2) under the same conditions. These data show that this reaction is promoted b y the cooperation of several metal atoms in the catalytic intermediates. (C ) 1999 Elsevier Science S.A. All rights reserved.