The hydrogenation of SBS catalyzed by Ru/TPPTS complex was performed in polyether modified ammonium salt ionic liquid biphasic system. It has been observed that the hydrogenation degree can be increased by addition of 'promoter ligand' TPP. Under the optimized conditions of T = 150degreesC, t = 12 h, P = 5.0 MPa, Ru/TPPTS/TPP = 1:5:2, the hydrogenation degree of the polybutadiene segments of SBS was 89%. In addition, no hydrogenation takes place on the benzene ring. The Ru catalyst immobilized in ionic liquid can be recovered simply by phase separation and recycled three times without significant changes in the catalytic activity. (C) 2004 Elsevier B.V. All rights reserved.