It is found that nickel oxide alone does not effectively serve as a catalyst but a mixture of nickel oxide–copper salt works very well.The effect of copper salts as promoter on the hydrocarboxylation of acetylene was investigated at 235◦C, 4 MPa of initial total pressure, 1.5 of CO/C2H2 molar ratio and 10 of acetone/H2O volume ratio. As can be seen from Table 2, different copper salts showed varied catalytic activity. The catalytic activity of copper halides(entries 1–6) is significantly higher than that of the other copper salts (entries 7–9). When cupric acetate, cupric nitrate and cupric oxide were used as promoters, large quantities of resinous material were found sticking to the side of the autoclave, and almost no acrylic acid can be detected in the liquid, indicating the occurrence of polymerization of acetylene instead of its decomposition or hydrocarboxylation. It was observed that the employ of CuCl2 as activator also resulted in the formation of resinous material.Among these copper halides, the cupric bromide and cuprous bromide gave the best catalytic activity. For the cuprous bromide, the biggest advantage is that it can be recovered and recycled with the nickel oxide catalyst after reaction, while the cupric bromide is difficult to be separated from the product due to its complete solubility in the liquid. An 80.1% of selectivity to acrylic acid was obtained when using CuI as promoter, but together with a lower STY due to the relative longer contact time to finish a reaction.Cupric halide or cuprous halide has been accepted as the effective catalysts in activating acetylene to give complexes of thefollowing composition