Hydrocarboxylation of acetylene with carbon monoxide to acrylic acid has been carried out using a catalyst system consisting of Pd(OAc)(2). Phosphine ligands and acids under the mild conditions. The effects of acidic promoters, phosphine ligands, water. reaction time and the initial partial pressure of carbon monoxide oil the conversion of acetylene as well as the selectivity to acrylic acid have been investigated Among all ligands as used, only diphenyl-2-pyridylphosphine has a good catalytic activity. Sulfonic acids and trifluoroacetic acid as acidic promoters display an excellent performance. Effects of water and the initial partial pressure of carbon monoxide have also been discussed. Under the optimal reaction conditions, 85% conversion of acetylene and 99% selectivity to acrylic acid as well as 1011 h(-1) TOF have been achieved. Crown Copyright (C) 2009 Published by Elsevier B V All rights reserved.