Catalytic reactions of acetylene have become a subject of renewed interest. However, recent literatures about the synthesis of acrylic acid by acetylene carbonylation were rare to be found. In our research, the yield of acrylic acid is greatly improved to similar to 86% (242.85 g Acrylic acidig Cat..h) by using heterogeneous catalyst Cu(I)Y, against similar to 70% from other reports using complex homogeneous catalyst. Y modified with different valence states copper Were prepared by heating the precursor at various atmospheres and characterized by XRD, BET, XPS and FT-IR. More than one type of copper (Cu2+, CuO, Cu2O, Cu+ or Cu-0) was found on one sample. Moreover, the distribution and the forming process of these types of copper were determined. According to FT-IR using pyridine or CO as probe, Cu+ at site II' not only enhanced the acid strength obviously, but also promoted the formation of the most stable monocarbonyls. Furthermore, the strong acid site and the stable monocarbonyls are beneficial for the acetylene carbonylation. (C) 2016 Elsevier B.V. All rights reserved.