Carbonylation of methanol catalyzed by polymer-protected rhodium colloid

Poly(N-vinyl-2-pyrrolidone)(PVP) protected rhodium colloid (Rh-PVP) was used as a catalyst for methanol carbonylation under elevated temperature (140 degrees C) and high pressure (5.4 MPa). The activity of Rh-PVP colloid catalyst increased while recycled for 6 times totally lasting 56.5 h. During the reaction, the catalyst was still in a colloidal state verified by TEM observation. XPS and IR studies of the catalyst demonstrated that colloidal rhodium metal particles partially changed to [Rh(CO)(2)I-2](-) under the reaction conditions. The rhodium ions in the reaction mixture amounted to 29% of the total charged rhodium after 13 h carbonylation. An additional XPS investigation of the catalyst was carried out; the results showed that oxidative addition of methyl iodide to rhodium colloid caused the transformation of rhodium species from Rh-0 to Rh1+.