Hydrogenation of 2-butyne-1,4-diol to 1,4-butanediol promoted by stainless steel reactor wall has been investigated in supercritical carbon dioxide (scCO(2)) as well as in conventional organic solvents in the absence of catalysts at 50degreesC. scCO(2) was found to be an effective medium at pressures higher than supercritical region (7.3 MPa). The influence of phase behavior, pressure and reaction time has been discussed. The first step hydrogenation of butynediol (Cequivalent toC) to butenediol (C=C) is slower but the second-step hydrogenation of butenediol (C=C) to butanediol (C-C) is faster in scCO(2) compared with the case of ethanol. (C) 2004 Elsevier B.V. All rights reserved.